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/* vi:set ts=8 sts=4 sw=4:
 *
 * Handling of regular expressions: vim_regcomp(), vim_regexec(), vim_regsub()
 *
 * NOTICE:
 *
 * This is NOT the original regular expression code as written by Henry
 * Spencer.  This code has been modified specifically for use with the VIM
 * editor, and should not be used separately from Vim.  If you want a good
 * regular expression library, get the original code.  The copyright notice
 * that follows is from the original.
 *
 * END NOTICE
 *
 *      Copyright (c) 1986 by University of Toronto.
 *      Written by Henry Spencer.  Not derived from licensed software.
 *
 *      Permission is granted to anyone to use this software for any
 *      purpose on any computer system, and to redistribute it freely,
 *      subject to the following restrictions:
 *
 *      1. The author is not responsible for the consequences of use of
 *              this software, no matter how awful, even if they arise
 *              from defects in it.
 *
 *      2. The origin of this software must not be misrepresented, either
 *              by explicit claim or by omission.
 *
 *      3. Altered versions must be plainly marked as such, and must not
 *              be misrepresented as being the original software.
 *
 * Beware that some of this code is subtly aware of the way operator
 * precedence is structured in regular expressions.  Serious changes in
 * regular-expression syntax might require a total rethink.
 *
 * Changes have been made by Tony Andrews, Olaf 'Rhialto' Seibert, Robert
 * Webb, Ciaran McCreesh and Bram Moolenaar.
 * Named character class support added by Walter Briscoe (1998 Jul 01)
 */

#include "vim.h"

#undef DEBUG

/*
 * The "internal use only" fields in regexp.h are present to pass info from
 * compile to execute that permits the execute phase to run lots faster on
 * simple cases.  They are:
 *
 * regstart     char that must begin a match; NUL if none obvious; Can be a
 *              multi-byte character.
 * reganch      is the match anchored (at beginning-of-line only)?
 * regmust      string (pointer into program) that match must include, or NULL
 * regmlen      length of regmust string
 * regflags     RF_ values or'ed together
 *
 * Regstart and reganch permit very fast decisions on suitable starting points
 * for a match, cutting down the work a lot.  Regmust permits fast rejection
 * of lines that cannot possibly match.  The regmust tests are costly enough
 * that vim_regcomp() supplies a regmust only if the r.e. contains something
 * potentially expensive (at present, the only such thing detected is * or +
 * at the start of the r.e., which can involve a lot of backup).  Regmlen is
 * supplied because the test in vim_regexec() needs it and vim_regcomp() is
 * computing it anyway.
 */

/*
 * Structure for regexp "program".  This is essentially a linear encoding
 * of a nondeterministic finite-state machine (aka syntax charts or
 * "railroad normal form" in parsing technology).  Each node is an opcode
 * plus a "next" pointer, possibly plus an operand.  "Next" pointers of
 * all nodes except BRANCH and BRACES_COMPLEX implement concatenation; a "next"
 * pointer with a BRANCH on both ends of it is connecting two alternatives.
 * (Here we have one of the subtle syntax dependencies: an individual BRANCH
 * (as opposed to a collection of them) is never concatenated with anything
 * because of operator precedence).  The "next" pointer of a BRACES_COMPLEX
 * node points to the node after the stuff to be repeated.
 * The operand of some types of node is a literal string; for others, it is a
 * node leading into a sub-FSM.  In particular, the operand of a BRANCH node
 * is the first node of the branch.
 * (NB this is *not* a tree structure: the tail of the branch connects to the
 * thing following the set of BRANCHes.)
 *
 * pattern      is coded like:
 *
 *                        +-----------------+
 *                        |                 V
 * <aa>\|<bb>   BRANCH <aa> BRANCH <bb> --> END
 *                   |      ^    |          ^
 *                   +------+    +----------+
 *
 *
 *                     +------------------+
 *                     V                  |
 * <aa>*        BRANCH BRANCH <aa> --> BACK BRANCH --> NOTHING --> END
 *                   |      |               ^                      ^
 *                   |      +---------------+                      |
 *                   +---------------------------------------------+
 *
 *
 *                     +----------------------+
 *                     V                      |
 * <aa>\+       BRANCH <aa> --> BRANCH --> BACK  BRANCH --> NOTHING --> END
 *                   |               |           ^                      ^
 *                   |               +-----------+                      |
 *                   +--------------------------------------------------+
 *
 *
 *                                      +-------------------------+
 *                                      V                         |
 * <aa>\{}      BRANCH BRACE_LIMITS --> BRACE_COMPLEX <aa> --> BACK  END
 *                   |                              |                ^
 *                   |                              +----------------+
 *                   +-----------------------------------------------+
 *
 *
 * <aa>\@!<bb>  BRANCH NOMATCH <aa> --> END  <bb> --> END
 *                   |       |                ^       ^
 *                   |       +----------------+       |
 *                   +--------------------------------+
 *
 *                                                    +---------+
 *                                                    |         V
 * \z[abc]      BRANCH BRANCH  a  BRANCH  b  BRANCH  c  BRANCH  NOTHING --> END
 *                   |      |          |          |     ^                   ^
 *                   |      |          |          +-----+                   |
 *                   |      |          +----------------+                   |
 *                   |      +---------------------------+                   |
 *                   +------------------------------------------------------+
 *
 * They all start with a BRANCH for "\|" alternatives, even when there is only
 * one alternative.
 */

/*
 * The opcodes are:
 */

/* definition   number             opnd?    meaning */
#define END             0        /*      End of program or NOMATCH operand. */
#define BOL             1       /*      Match "" at beginning of line. */
#define EOL             2       /*      Match "" at end of line. */
#define BRANCH          3       /* node Match this alternative, or the
                                 *      next... */
#define BACK            4       /*      Match "", "next" ptr points backward. */
#define EXACTLY         5       /* str  Match this string. */
#define NOTHING         6       /*      Match empty string. */
#define STAR            7       /* node Match this (simple) thing 0 or more
                                 *      times. */
#define PLUS            8       /* node Match this (simple) thing 1 or more
                                 *      times. */
#define MATCH           9       /* node match the operand zero-width */
#define NOMATCH         10      /* node check for no match with operand */
#define BEHIND          11      /* node look behind for a match with operand */
#define NOBEHIND        12      /* node look behind for no match with operand */
#define SUBPAT          13      /* node match the operand here */
#define BRACE_SIMPLE    14      /* node Match this (simple) thing between m and
                                 *      n times (\{m,n\}). */
#define BOW             15      /*      Match "" after [^a-zA-Z0-9_] */
#define EOW             16      /*      Match "" at    [^a-zA-Z0-9_] */
#define BRACE_LIMITS    17      /* nr nr  define the min & max for BRACE_SIMPLE
                                 *      and BRACE_COMPLEX. */
#define NEWL            18      /*      Match line-break */
#define BHPOS           19      /*      End position for BEHIND or NOBEHIND */


/* character classes: 20-48 normal, 50-78 include a line-break */
#define ADD_NL          30
#define FIRST_NL        ANY + ADD_NL
#define ANY             20      /*      Match any one character. */
#define ANYOF           21      /* str  Match any character in this string. */
#define ANYBUT          22      /* str  Match any character not in this
                                 *      string. */
#define IDENT           23      /*      Match identifier char */
#define SIDENT          24      /*      Match identifier char but no digit */
#define KWORD           25      /*      Match keyword char */
#define SKWORD          26      /*      Match word char but no digit */
#define FNAME           27      /*      Match file name char */
#define SFNAME          28      /*      Match file name char but no digit */
#define PRINT           29      /*      Match printable char */
#define SPRINT          30      /*      Match printable char but no digit */
#define WHITE           31      /*      Match whitespace char */
#define NWHITE          32      /*      Match non-whitespace char */
#define DIGIT           33      /*      Match digit char */
#define NDIGIT          34      /*      Match non-digit char */
#define HEX             35      /*      Match hex char */
#define NHEX            36      /*      Match non-hex char */
#define OCTAL           37      /*      Match octal char */
#define NOCTAL          38      /*      Match non-octal char */
#define WORD            39      /*      Match word char */
#define NWORD           40      /*      Match non-word char */
#define HEAD            41      /*      Match head char */
#define NHEAD           42      /*      Match non-head char */
#define ALPHA           43      /*      Match alpha char */
#define NALPHA          44      /*      Match non-alpha char */
#define LOWER           45      /*      Match lowercase char */
#define NLOWER          46      /*      Match non-lowercase char */
#define UPPER           47      /*      Match uppercase char */
#define NUPPER          48      /*      Match non-uppercase char */
#define LAST_NL         NUPPER + ADD_NL
#define WITH_NL(op)     ((op) >= FIRST_NL && (op) <= LAST_NL)

#define MOPEN           80  /* -89       Mark this point in input as start of
                                 *       \( subexpr.  MOPEN + 0 marks start of
                                 *       match. */
#define MCLOSE          90  /* -99       Analogous to MOPEN.  MCLOSE + 0 marks
                                 *       end of match. */
#define BACKREF         100 /* -109 node Match same string again \1-\9 */

#ifdef FEAT_SYN_HL
# define ZOPEN          110 /* -119      Mark this point in input as start of
                                 *       \z( subexpr. */
# define ZCLOSE         120 /* -129      Analogous to ZOPEN. */
# define ZREF           130 /* -139 node Match external submatch \z1-\z9 */
#endif

#define BRACE_COMPLEX   140 /* -149 node Match nodes between m & n times */

#define NOPEN           150     /*      Mark this point in input as start of
                                        \%( subexpr. */
#define NCLOSE          151     /*      Analogous to NOPEN. */

#define MULTIBYTECODE   200     /* mbc  Match one multi-byte character */
#define RE_BOF          201     /*      Match "" at beginning of file. */
#define RE_EOF          202     /*      Match "" at end of file. */
#define CURSOR          203     /*      Match location of cursor. */

#define RE_LNUM         204     /* nr cmp  Match line number */
#define RE_COL          205     /* nr cmp  Match column number */
#define RE_VCOL         206     /* nr cmp  Match virtual column number */

#define RE_MARK         207     /* mark cmp  Match mark position */
#define RE_VISUAL       208     /*      Match Visual area */

/*
 * Magic characters have a special meaning, they don't match literally.
 * Magic characters are negative.  This separates them from literal characters
 * (possibly multi-byte).  Only ASCII characters can be Magic.
 */
#define Magic(x)        ((int)(x) - 256)
#define un_Magic(x)     ((x) + 256)
#define is_Magic(x)     ((x) < 0)

static int no_Magic __ARGS((int x));
static int toggle_Magic __ARGS((int x));

    static int
no_Magic(x)
    int         x;
{
    if (is_Magic(x))
        return un_Magic(x);
    return x;
}

    static int
toggle_Magic(x)
    int         x;
{
    if (is_Magic(x))
        return un_Magic(x);
    return Magic(x);
}

/*
 * The first byte of the regexp internal "program" is actually this magic
 * number; the start node begins in the second byte.  It's used to catch the
 * most severe mutilation of the program by the caller.
 */

#define REGMAGIC        0234

/*
 * Opcode notes:
 *
 * BRANCH       The set of branches constituting a single choice are hooked
 *              together with their "next" pointers, since precedence prevents
 *              anything being concatenated to any individual branch.  The
 *              "next" pointer of the last BRANCH in a choice points to the
 *              thing following the whole choice.  This is also where the
 *              final "next" pointer of each individual branch points; each
 *              branch starts with the operand node of a BRANCH node.
 *
 * BACK         Normal "next" pointers all implicitly point forward; BACK
 *              exists to make loop structures possible.
 *
 * STAR,PLUS    '=', and complex '*' and '+', are implemented as circular
 *              BRANCH structures using BACK.  Simple cases (one character
 *              per match) are implemented with STAR and PLUS for speed
 *              and to minimize recursive plunges.
 *
 * BRACE_LIMITS This is always followed by a BRACE_SIMPLE or BRACE_COMPLEX
 *              node, and defines the min and max limits to be used for that
 *              node.
 *
 * MOPEN,MCLOSE ...are numbered at compile time.
 * ZOPEN,ZCLOSE ...ditto
 */

/*
 * A node is one char of opcode followed by two chars of "next" pointer.
 * "Next" pointers are stored as two 8-bit bytes, high order first.  The
 * value is a positive offset from the opcode of the node containing it.
 * An operand, if any, simply follows the node.  (Note that much of the
 * code generation knows about this implicit relationship.)
 *
 * Using two bytes for the "next" pointer is vast overkill for most things,
 * but allows patterns to get big without disasters.
 */
#define OP(p)           ((int)*(p))
#define NEXT(p)         (((*((p) + 1) & 0377) << 8) + (*((p) + 2) & 0377))
#define OPERAND(p)      ((p) + 3)
/* Obtain an operand that was stored as four bytes, MSB first. */
#define OPERAND_MIN(p)  (((long)(p)[3] << 24) + ((long)(p)[4] << 16) \
                        + ((long)(p)[5] << 8) + (long)(p)[6])
/* Obtain a second operand stored as four bytes. */
#define OPERAND_MAX(p)  OPERAND_MIN((p) + 4)
/* Obtain a second single-byte operand stored after a four bytes operand. */
#define OPERAND_CMP(p)  (p)[7]

/*
 * Utility definitions.
 */
#define UCHARAT(p)      ((int)*(char_u *)(p))

/* Used for an error (down from) vim_regcomp(): give the error message, set
 * rc_did_emsg and return NULL */
#define EMSG_RET_NULL(m) return (EMSG(m), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG_M_RET_NULL(m, c) return (EMSG2((m), (c) ? "" : "\\"), rc_did_emsg = TRUE, (void *)NULL)
#define EMSG_RET_FAIL(m) return (EMSG(m), rc_did_emsg = TRUE, FAIL)
#define EMSG_ONE_RET_NULL EMSG_M_RET_NULL(_("E369: invalid item in %s%%[]"), reg_magic == MAGIC_ALL)

#define MAX_LIMIT       (32767L << 16L)

static int re_multi_type __ARGS((int));
static int cstrncmp __ARGS((char_u *s1, char_u *s2, int *n));
static char_u *cstrchr __ARGS((char_u *, int));

#ifdef DEBUG
static void     regdump __ARGS((char_u *, regprog_T *));
static char_u   *regprop __ARGS((char_u *));
#endif

#define NOT_MULTI       0
#define MULTI_ONE       1
#define MULTI_MULT      2
/*
 * Return NOT_MULTI if c is not a "multi" operator.
 * Return MULTI_ONE if c is a single "multi" operator.
 * Return MULTI_MULT if c is a multi "multi" operator.
 */
    static int
re_multi_type(c)
    int c;
{
    if (c == Magic('@') || c == Magic('=') || c == Magic('?'))
        return MULTI_ONE;
    if (c == Magic('*') || c == Magic('+') || c == Magic('{'))
        return MULTI_MULT;
    return NOT_MULTI;
}

/*
 * Flags to be passed up and down.
 */
#define HASWIDTH        0x1     /* Known never to match null string. */
#define SIMPLE          0x2     /* Simple enough to be STAR/PLUS operand. */
#define SPSTART         0x4     /* Starts with * or +. */
#define HASNL           0x8     /* Contains some \n. */
#define HASLOOKBH       0x10    /* Contains "\@<=" or "\@<!". */
#define WORST           0        /* Worst case. */

/*
 * When regcode is set to this value, code is not emitted and size is computed
 * instead.
 */
#define JUST_CALC_SIZE  ((char_u *) -1)

static char_u           *reg_prev_sub = NULL;

#if defined(EXITFREE) || defined(PROTO)
    void
free_regexp_stuff()
{
    vim_free(reg_prev_sub);
}
#endif

/*
 * REGEXP_INRANGE contains all characters which are always special in a []
 * range after '\'.
 * REGEXP_ABBR contains all characters which act as abbreviations after '\'.
 * These are:
 *  \n  - New line (NL).
 *  \r  - Carriage Return (CR).
 *  \t  - Tab (TAB).
 *  \e  - Escape (ESC).
 *  \b  - Backspace (Ctrl_H).
 *  \d  - Character code in decimal, eg \d123
 *  \o  - Character code in octal, eg \o80
 *  \x  - Character code in hex, eg \x4a
 *  \u  - Multibyte character code, eg \u20ac
 *  \U  - Long multibyte character code, eg \U12345678
 */
static char_u REGEXP_INRANGE[] = "]^-n\\";
static char_u REGEXP_ABBR[] = "nrtebdoxuU";

static int      backslash_trans __ARGS((int c));
static int      get_char_class __ARGS((char_u **pp));
static int      get_equi_class __ARGS((char_u **pp));
static void     reg_equi_class __ARGS((int c));
static int      get_coll_element __ARGS((char_u **pp));
static char_u   *skip_anyof __ARGS((char_u *p));
static void     init_class_tab __ARGS((void));

/*
 * Translate '\x' to its control character, except "\n", which is Magic.
 */
    static int
backslash_trans(c)
    int         c;
{
    switch (c)
    {
        case 'r':   return CAR;
        case 't':   return TAB;
        case 'e':   return ESC;
        case 'b':   return BS;
    }
    return c;
}

/*
 * Check for a character class name "[:name:]".  "pp" points to the '['.
 * Returns one of the CLASS_ items. CLASS_NONE means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
    static int
get_char_class(pp)
    char_u      **pp;
{
    static const char *(class_names[]) =
    {
        "alnum:]",
#define CLASS_ALNUM 0
        "alpha:]",
#define CLASS_ALPHA 1
        "blank:]",
#define CLASS_BLANK 2
        "cntrl:]",
#define CLASS_CNTRL 3
        "digit:]",
#define CLASS_DIGIT 4
        "graph:]",
#define CLASS_GRAPH 5
        "lower:]",
#define CLASS_LOWER 6
        "print:]",
#define CLASS_PRINT 7
        "punct:]",
#define CLASS_PUNCT 8
        "space:]",
#define CLASS_SPACE 9
        "upper:]",
#define CLASS_UPPER 10
        "xdigit:]",
#define CLASS_XDIGIT 11
        "tab:]",
#define CLASS_TAB 12
        "return:]",
#define CLASS_RETURN 13
        "backspace:]",
#define CLASS_BACKSPACE 14
        "escape:]",
#define CLASS_ESCAPE 15
    };
#define CLASS_NONE 99
    int i;

    if ((*pp)[1] == ':')
    {
        for (i = 0; i < sizeof(class_names) / sizeof(*class_names); ++i)
            if (STRNCMP(*pp + 2, class_names[i], STRLEN(class_names[i])) == 0)
            {
                *pp += STRLEN(class_names[i]) + 2;
                return i;
            }
    }
    return CLASS_NONE;
}

/*
 * Specific version of character class functions.
 * Using a table to keep this fast.
 */
static short    class_tab[256];

#define     RI_DIGIT    0x01
#define     RI_HEX      0x02
#define     RI_OCTAL    0x04
#define     RI_WORD     0x08
#define     RI_HEAD     0x10
#define     RI_ALPHA    0x20
#define     RI_LOWER    0x40
#define     RI_UPPER    0x80
#define     RI_WHITE    0x100

    static void
init_class_tab()
{
    int         i;
    static int  done = FALSE;

    if (done)
        return;

    for (i = 0; i < 256; ++i)
    {
        if (i >= '0' && i <= '7')
            class_tab[i] = RI_DIGIT + RI_HEX + RI_OCTAL + RI_WORD;
        else if (i >= '8' && i <= '9')
            class_tab[i] = RI_DIGIT + RI_HEX + RI_WORD;
        else if (i >= 'a' && i <= 'f')
            class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
#ifdef EBCDIC
        else if ((i >= 'g' && i <= 'i') || (i >= 'j' && i <= 'r')
                                                    || (i >= 's' && i <= 'z'))
#else
        else if (i >= 'g' && i <= 'z')
#endif
            class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_LOWER;
        else if (i >= 'A' && i <= 'F')
            class_tab[i] = RI_HEX + RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
#ifdef EBCDIC
        else if ((i >= 'G' && i <= 'I') || ( i >= 'J' && i <= 'R')
                                                    || (i >= 'S' && i <= 'Z'))
#else
        else if (i >= 'G' && i <= 'Z')
#endif
            class_tab[i] = RI_WORD + RI_HEAD + RI_ALPHA + RI_UPPER;
        else if (i == '_')
            class_tab[i] = RI_WORD + RI_HEAD;
        else
            class_tab[i] = 0;
    }
    class_tab[' '] |= RI_WHITE;
    class_tab['\t'] |= RI_WHITE;
    done = TRUE;
}

#ifdef FEAT_MBYTE
# define ri_digit(c)    (c < 0x100 && (class_tab[c] & RI_DIGIT))
# define ri_hex(c)      (c < 0x100 && (class_tab[c] & RI_HEX))
# define ri_octal(c)    (c < 0x100 && (class_tab[c] & RI_OCTAL))
# define ri_word(c)     (c < 0x100 && (class_tab[c] & RI_WORD))
# define ri_head(c)     (c < 0x100 && (class_tab[c] & RI_HEAD))
# define ri_alpha(c)    (c < 0x100 && (class_tab[c] & RI_ALPHA))
# define ri_lower(c)    (c < 0x100 && (class_tab[c] & RI_LOWER))
# define ri_upper(c)    (c < 0x100 && (class_tab[c] & RI_UPPER))
# define ri_white(c)    (c < 0x100 && (class_tab[c] & RI_WHITE))
#else
# define ri_digit(c)    (class_tab[c] & RI_DIGIT)
# define ri_hex(c)      (class_tab[c] & RI_HEX)
# define ri_octal(c)    (class_tab[c] & RI_OCTAL)
# define ri_word(c)     (class_tab[c] & RI_WORD)
# define ri_head(c)     (class_tab[c] & RI_HEAD)
# define ri_alpha(c)    (class_tab[c] & RI_ALPHA)
# define ri_lower(c)    (class_tab[c] & RI_LOWER)
# define ri_upper(c)    (class_tab[c] & RI_UPPER)
# define ri_white(c)    (class_tab[c] & RI_WHITE)
#endif

/* flags for regflags */
#define RF_ICASE    1   /* ignore case */
#define RF_NOICASE  2   /* don't ignore case */
#define RF_HASNL    4   /* can match a NL */
#define RF_ICOMBINE 8   /* ignore combining characters */
#define RF_LOOKBH   16  /* uses "\@<=" or "\@<!" */

/*
 * Global work variables for vim_regcomp().
 */

static char_u   *regparse;      /* Input-scan pointer. */
static int      prevchr_len;    /* byte length of previous char */
static int      num_complex_braces; /* Complex \{...} count */
static int      regnpar;        /* () count. */
#ifdef FEAT_SYN_HL
static int      regnzpar;       /* \z() count. */
static int      re_has_z;       /* \z item detected */
#endif
static char_u   *regcode;       /* Code-emit pointer, or JUST_CALC_SIZE */
static long     regsize;        /* Code size. */
static char_u   had_endbrace[NSUBEXP];  /* flags, TRUE if end of () found */
static unsigned regflags;       /* RF_ flags for prog */
static long     brace_min[10];  /* Minimums for complex brace repeats */
static long     brace_max[10];  /* Maximums for complex brace repeats */
static int      brace_count[10]; /* Current counts for complex brace repeats */
#if defined(FEAT_SYN_HL) || defined(PROTO)
static int      had_eol;        /* TRUE when EOL found by vim_regcomp() */
#endif
static int      one_exactly = FALSE;    /* only do one char for EXACTLY */

static int      reg_magic;      /* magicness of the pattern: */
#define MAGIC_NONE      1       /* "\V" very unmagic */
#define MAGIC_OFF       2       /* "\M" or 'magic' off */
#define MAGIC_ON        3       /* "\m" or 'magic' */
#define MAGIC_ALL       4       /* "\v" very magic */

static int      reg_string;     /* matching with a string instead of a buffer
                                   line */
static int      reg_strict;     /* "[abc" is illegal */

/*
 * META contains all characters that may be magic, except '^' and '$'.
 */

#ifdef EBCDIC
static char_u META[] = "%&()*+.123456789<=>?@ACDFHIKLMOPSUVWX[_acdfhiklmnopsuvwxz{|~";
#else
/* META[] is used often enough to justify turning it into a table. */
static char_u META_flags[] = {
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/*                 %  &     (  )  *  +        .    */
    0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 1, 0,
/*     1  2  3  4  5  6  7  8  9        <  =  >  ? */
    0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1,
/*  @  A     C  D     F     H  I     K  L  M     O */
    1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1,
/*  P        S     U  V  W  X     Z  [           _ */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 1,
/*     a     c  d     f     h  i     k  l  m  n  o */
    0, 1, 0, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1,
/*  p        s     u  v  w  x     z  {  |     ~    */
    1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1
};
#endif

static int      curchr;

/* arguments for reg() */
#define REG_NOPAREN     0        /* toplevel reg() */
#define REG_PAREN       1       /* \(\) */
#define REG_ZPAREN      2       /* \z(\) */
#define REG_NPAREN      3       /* \%(\) */

/*
 * Forward declarations for vim_regcomp()'s friends.
 */
static void     initchr __ARGS((char_u *));
static int      getchr __ARGS((void));
static void     skipchr_keepstart __ARGS((void));
static int      peekchr __ARGS((void));
static void     skipchr __ARGS((void));
static void     ungetchr __ARGS((void));
static int      gethexchrs __ARGS((int maxinputlen));
static int      getoctchrs __ARGS((void));
static int      getdecchrs __ARGS((void));
static int      coll_get_char __ARGS((void));
static void     regcomp_start __ARGS((char_u *expr, int flags));
static char_u   *reg __ARGS((int, int *));
static char_u   *regbranch __ARGS((int *flagp));
static char_u   *regconcat __ARGS((int *flagp));
static char_u   *regpiece __ARGS((int *));
static char_u   *regatom __ARGS((int *));
static char_u   *regnode __ARGS((int));
#ifdef FEAT_MBYTE
static int      use_multibytecode __ARGS((int c));
#endif
static int      prog_magic_wrong __ARGS((void));
static char_u   *regnext __ARGS((char_u *));
static void     regc __ARGS((int b));
#ifdef FEAT_MBYTE
static void     regmbc __ARGS((int c));
#else
# define regmbc(c) regc(c)
#endif
static void     reginsert __ARGS((int, char_u *));
static void     reginsert_limits __ARGS((int, long, long, char_u *));
static char_u   *re_put_long __ARGS((char_u *pr, long_u val));
static int      read_limits __ARGS((long *, long *));
static void     regtail __ARGS((char_u *, char_u *));
static void     regoptail __ARGS((char_u *, char_u *));

/*
 * Return TRUE if compiled regular expression "prog" can match a line break.
 */
    int
re_multiline(prog)
    regprog_T *prog;
{
    return (prog->regflags & RF_HASNL);
}

/*
 * Return TRUE if compiled regular expression "prog" looks before the start
 * position (pattern contains "\@<=" or "\@<!").
 */
    int
re_lookbehind(prog)
    regprog_T *prog;
{
    return (prog->regflags & RF_LOOKBH);
}

/*
 * Check for an equivalence class name "[=a=]".  "pp" points to the '['.
 * Returns a character representing the class. Zero means that no item was
 * recognized.  Otherwise "pp" is advanced to after the item.
 */
    static int
get_equi_class(pp)
    char_u      **pp;
{
    int         c;
    int         l = 1;
    char_u      *p = *pp;

    if (p[1] == '=')
    {
#ifdef FEAT_MBYTE
        if (has_mbyte)
            l = (*mb_ptr2len)(p + 2);
#endif
        if (p[l + 2] == '=' && p[l + 3] == ']')
        {
#ifdef FEAT_MBYTE
            if (has_mbyte)
                c = mb_ptr2char(p + 2);
            else
#endif
                c = p[2];
            *pp += l + 4;
            return c;
        }
    }
    return 0;
}

/*
 * Produce the bytes for equivalence class "c".
 * Currently only handles latin1, latin9 and utf-8.
 */
    static void
reg_equi_class(c)
    int     c;
{
#ifdef FEAT_MBYTE
    if (enc_utf8 || STRCMP(p_enc, "latin1") == 0
                                         || STRCMP(p_enc, "iso-8859-15") == 0)
#endif
    {
        switch (c)
        {
            case 'A': case '\300': case '\301': case '\302':
            case '\303': case '\304': case '\305':
                      regmbc('A'); regmbc('\300'); regmbc('\301');
                      regmbc('\302'); regmbc('\303'); regmbc('\304');
                      regmbc('\305');
                      return;
            case 'C': case '\307':
                      regmbc('C'); regmbc('\307');
                      return;
            case 'E': case '\310': case '\311': case '\312': case '\313':
                      regmbc('E'); regmbc('\310'); regmbc('\311');
                      regmbc('\312'); regmbc('\313');
                      return;
            case 'I': case '\314': case '\315': case '\316': case '\317':
                      regmbc('I'); regmbc('\314'); regmbc('\315');
                      regmbc('\316'); regmbc('\317');
                      return;
            case 'N': case '\321':
                      regmbc('N'); regmbc('\321');
                      return;
            case 'O': case '\322': case '\323': case '\324': case '\325':
            case '\326':
                      regmbc('O'); regmbc('\322'); regmbc('\323');
                      regmbc('\324'); regmbc('\325'); regmbc('\326');
                      return;
            case 'U': case '\331': case '\332': case '\333': case '\334':
                      regmbc('U'); regmbc('\331'); regmbc('\332');
                      regmbc('\333'); regmbc('\334');
                      return;
            case 'Y': case '\335':
                      regmbc('Y'); regmbc('\335');
                      return;
            case 'a': case '\340': case '\341': case '\342':
            case '\343': case '\344': case '\345':
                      regmbc('a'); regmbc('\340'); regmbc('\341');
                      regmbc('\342'); regmbc('\343'); regmbc('\344');
                      regmbc('\345');
                      return;
            case 'c': case '\347':
                      regmbc('c'); regmbc('\347');
                      return;
            case 'e': case '\350': case '\351': case '\352': case '\353':
                      regmbc('e'); regmbc('\350'); regmbc('\351');
                      regmbc('\352'); regmbc('\353');
                      return;
            case 'i': case '\354': case '\355': case '\356': case '\357':
                      regmbc('i'); regmbc('\354'); regmbc('\355');
                      regmbc('\356'); regmbc('\357');
                      return;
            case 'n': case '\361':
                      regmbc('n'); regmbc('\361');
                      return;
            case 'o': case '\362': case '\363': case '\364': case '\365':
            case '\366':
                      regmbc('o'); regmbc('\362'); regmbc('\363');
                      regmbc('\364'); regmbc('\365'); regmbc('\366');
                      return;
            case 'u': case '\371': case '\372': case '\373': case '\374':
                      regmbc('u'); regmbc('\371'); regmbc('\372');
                      regmbc('\373'); regmbc('\374');
                      return;
            case 'y': case '\375': case '\377':
                      regmbc('y'); regmbc('\375'); regmbc('\377');
                      return;
        }
    }
    regmbc(c);
}

/*
 * Check for a collating element "[.a.]".  "pp" points to the '['.
 * Returns a character. Zero means that no item was recognized.  Otherwise
 * "pp" is advanced to after the item.
 * Currently only single characters are recognized!
 */
    static int
get_coll_element(pp)
    char_u      **pp;
{
    int         c;
    int         l = 1;
    char_u      *p = *pp;

    if (p[1] == '.')
    {
#ifdef FEAT_MBYTE
        if (has_mbyte)
            l = (*mb_ptr2len)(p + 2);
#endif
        if (p[l + 2] == '.' && p[l + 3] == ']')
        {
#ifdef FEAT_MBYTE
            if (has_mbyte)
                c = mb_ptr2char(p + 2);
            else
#endif
                c = p[2];
            *pp += l + 4;
            return c;
        }
    }
    return 0;
}


/*
 * Skip over a "[]" range.
 * "p" must point to the character after the '['.
 * The returned pointer is on the matching ']', or the terminating NUL.
 */
    static char_u *
skip_anyof(p)
    char_u      *p;
{
    int         cpo_lit;        /* 'cpoptions' contains 'l' flag */
    int         cpo_bsl;        /* 'cpoptions' contains '\' flag */
#ifdef FEAT_MBYTE
    int         l;
#endif

    cpo_lit = vim_strchr(p_cpo, CPO_LITERAL) != NULL;
    cpo_bsl = vim_strchr(p_cpo, CPO_BACKSL) != NULL;

    if (*p == '^')      /* Complement of range. */
        ++p;
    if (*p == ']' || *p == '-')
        ++p;
    while (*p != NUL && *p != ']')
    {
#ifdef FEAT_MBYTE
        if (has_mbyte && (l = (*mb_ptr2len)(p)) > 1)
            p += l;
        else
#endif
            if (*p == '-')
            {
                ++p;
                if (*p != ']' && *p != NUL)
                    mb_ptr_adv(p);
            }
        else if (*p == '\\'
                && !cpo_bsl
                && (vim_strchr(REGEXP_INRANGE, p[1]) != NULL
                    || (!cpo_lit && vim_strchr(REGEXP_ABBR, p[1]) != NULL)))
            p += 2;
        else if (*p == '[')
        {
            if (get_char_class(&p) == CLASS_NONE
                    && get_equi_class(&p) == 0
                    && get_coll_element(&p) == 0)
                ++p; /* It was not a class name */
        }
        else
            ++p;
    }

    return p;
}

/*
 * Skip past regular expression.
 * Stop at end of "startp" or where "dirc" is found ('/', '?', etc).
 * Take care of characters with a backslash in front of it.
 * Skip strings inside [ and ].
 * When "newp" is not NULL and "dirc" is '?', make an allocated copy of the
 * expression and change "\?" to "?".  If "*newp" is not NULL the expression
 * is changed in-place.
 */
    char_u *
skip_regexp(startp, dirc, magic, newp)
    char_u      *startp;
    int         dirc;
    int         magic;
    char_u      **newp;
{
    int         mymagic;
    char_u      *p = startp;

    if (magic)
        mymagic = MAGIC_ON;
    else
        mymagic = MAGIC_OFF;

    for (; p[0] != NUL; mb_ptr_adv(p))
    {
        if (p[0] == dirc)       /* found end of regexp */
            break;
        if ((p[0] == '[' && mymagic >= MAGIC_ON)
                || (p[0] == '\\' && p[1] == '[' && mymagic <= MAGIC_OFF))
        {
            p = skip_anyof(p + 1);
            if (p[0] == NUL)
                break;
        }
        else if (p[0] == '\\' && p[1] != NUL)
        {
            if (dirc == '?' && newp != NULL && p[1] == '?')
            {
                /* change "\?" to "?", make a copy first. */
                if (*newp == NULL)
                {
                    *newp = vim_strsave(startp);
                    if (*newp != NULL)
                        p = *newp + (p - startp);
                }
                if (*newp != NULL)
                    mch_memmove(p, p + 1, STRLEN(p));
                else
                    ++p;
            }
            else
                ++p;    /* skip next character */
            if (*p == 'v')
                mymagic = MAGIC_ALL;
            else if (*p == 'V')
                mymagic = MAGIC_NONE;
        }
    }
    return p;
}

/*
 * vim_regcomp() - compile a regular expression into internal code
 * Returns the program in allocated space.  Returns NULL for an error.
 *
 * We can't allocate space until we know how big the compiled form will be,
 * but we can't compile it (and thus know how big it is) until we've got a
 * place to put the code.  So we cheat:  we compile it twice, once with code
 * generation turned off and size counting turned on, and once "for real".
 * This also means that we don't allocate space until we are sure that the
 * thing really will compile successfully, and we never have to move the
 * code and thus invalidate pointers into it.  (Note that it has to be in
 * one piece because vim_free() must be able to free it all.)
 *
 * Whether upper/lower case is to be ignored is decided when executing the
 * program, it does not matter here.
 *
 * Beware that the optimization-preparation code in here knows about some
 * of the structure of the compiled regexp.
 * "re_flags": RE_MAGIC and/or RE_STRING.
 */
    regprog_T *
vim_regcomp(expr, re_flags)
    char_u      *expr;
    int         re_flags;
{
    regprog_T   *r;
    char_u      *scan;
    char_u      *longest;
    int         len;
    int         flags;

    if (expr == NULL)
        EMSG_RET_NULL(_(e_null));

    init_class_tab();

    /*
     * First pass: determine size, legality.
     */
    regcomp_start(expr, re_flags);
    regcode = JUST_CALC_SIZE;
    regc(REGMAGIC);
    if (reg(REG_NOPAREN, &flags) == NULL)
        return NULL;

    /* Small enough for pointer-storage convention? */
#ifdef SMALL_MALLOC             /* 16 bit storage allocation */
    if (regsize >= 65536L - 256L)
        EMSG_RET_NULL(_("E339: Pattern too long"));
#endif

    /* Allocate space. */
    r = (regprog_T *)lalloc(sizeof(regprog_T) + regsize, TRUE);
    if (r == NULL)
        return NULL;

    /*
     * Second pass: emit code.
     */
    regcomp_start(expr, re_flags);
    regcode = r->program;
    regc(REGMAGIC);
    if (reg(REG_NOPAREN, &flags) == NULL)
    {
        vim_free(r);
        return NULL;
    }

    /* Dig out information for optimizations. */
    r->regstart = NUL;          /* Worst-case defaults. */
    r->reganch = 0;
    r->regmust = NULL;
    r->regmlen = 0;
    r->regflags = regflags;
    if (flags & HASNL)
        r->regflags |= RF_HASNL;
    if (flags & HASLOOKBH)
        r->regflags |= RF_LOOKBH;
#ifdef FEAT_SYN_HL
    /* Remember whether this pattern has any \z specials in it. */
    r->reghasz = re_has_z;
#endif
    scan = r->program + 1;      /* First BRANCH. */
    if (OP(regnext(scan)) == END)   /* Only one top-level choice. */
    {
        scan = OPERAND(scan);

        /* Starting-point info. */
        if (OP(scan) == BOL || OP(scan) == RE_BOF)
        {
            r->reganch++;
            scan = regnext(scan);
        }

        if (OP(scan) == EXACTLY)
        {
#ifdef FEAT_MBYTE
            if (has_mbyte)
                r->regstart = (*mb_ptr2char)(OPERAND(scan));
            else
#endif
                r->regstart = *OPERAND(scan);
        }
        else if ((OP(scan) == BOW
                    || OP(scan) == EOW
                    || OP(scan) == NOTHING
                    || OP(scan) == MOPEN + 0 || OP(scan) == NOPEN
                    || OP(scan) == MCLOSE + 0 || OP(scan) == NCLOSE)
                 && OP(regnext(scan)) == EXACTLY)
        {
#ifdef FEAT_MBYTE
            if (has_mbyte)
                r->regstart = (*mb_ptr2char)(OPERAND(regnext(scan)));
            else
#endif
                r->regstart = *OPERAND(regnext(scan));
        }

        /*
         * If there's something expensive in the r.e., find the longest
         * literal string that must appear and make it the regmust.  Resolve
         * ties in favor of later strings, since the regstart check works
         * with the beginning of the r.e. and avoiding duplication
         * strengthens checking.  Not a strong reason, but sufficient in the
         * absence of others.
         */
        /*
         * When the r.e. starts with BOW, it is faster to look for a regmust
         * first. Used a lot for "#" and "*" commands. (Added by mool).
         */
        if ((flags & SPSTART || OP(scan) == BOW || OP(scan) == EOW)
                                                          && !(flags & HASNL))
        {
            longest = NULL;
            len = 0;
            for (; scan != NULL; scan = regnext(scan))
                if (OP(scan) == EXACTLY && STRLEN(OPERAND(scan)) >= (size_t)len)
                {
                    longest = OPERAND(scan);
                    len = (int)STRLEN(OPERAND(scan));
                }
            r->regmust = longest;
            r->regmlen = len;
        }
    }
#ifdef DEBUG
    regdump(expr, r);
#endif
    return r;
}

/*
 * Setup to parse the regexp.  Used once to get the length and once to do it.
 */
    static void
regcomp_start(expr, re_flags)
    char_u      *expr;
    int         re_flags;           /* see vim_regcomp() */
{
    initchr(expr);
    if (re_flags & RE_MAGIC)
        reg_magic = MAGIC_ON;
    else
        reg_magic = MAGIC_OFF;
    reg_string = (re_flags & RE_STRING);
    reg_strict = (re_flags & RE_STRICT);

    num_complex_braces = 0;
    regnpar = 1;
    vim_memset(had_endbrace, 0, sizeof(had_endbrace));
#ifdef FEAT_SYN_HL
    regnzpar = 1;
    re_has_z = 0;
#endif
    regsize = 0L;
    regflags = 0;
#if defined(FEAT_SYN_HL) || defined(PROTO)
    had_eol = FALSE;
#endif
}

#if defined(FEAT_SYN_HL) || defined(PROTO)
/*
 * Check if during the previous call to vim_regcomp the EOL item "$" has been
 * found.  This is messy, but it works fine.
 */
    int
vim_regcomp_had_eol()
{
    return had_eol;
}
#endif

/*
 * reg - regular expression, i.e. main body or parenthesized thing
 *
 * Caller must absorb opening parenthesis.
 *
 * Combining parenthesis handling with the base level of regular expression
 * is a trifle forced, but the need to tie the tails of the branches to what
 * follows makes it hard to avoid.
 */
    static char_u *
reg(paren, flagp)
    int         paren;  /* REG_NOPAREN, REG_PAREN, REG_NPAREN or REG_ZPAREN */
    int         *flagp;
{
    char_u      *ret;
    char_u      *br;
    char_u      *ender;
    int         parno = 0;
    int         flags;

    *flagp = HASWIDTH;          /* Tentatively. */

#ifdef FEAT_SYN_HL
    if (paren == REG_ZPAREN)
    {
        /* Make a ZOPEN node. */
        if (regnzpar >= NSUBEXP)
            EMSG_RET_NULL(_("E50: Too many \\z("));
        parno = regnzpar;
        regnzpar++;
        ret = regnode(ZOPEN + parno);
    }
    else
#endif
        if (paren == REG_PAREN)
    {
        /* Make a MOPEN node. */
        if (regnpar >= NSUBEXP)
            EMSG_M_RET_NULL(_("E51: Too many %s("), reg_magic == MAGIC_ALL);
        parno = regnpar;
        ++regnpar;
        ret = regnode(MOPEN + parno);
    }
    else if (paren == REG_NPAREN)
    {
        /* Make a NOPEN node. */
        ret = regnode(NOPEN);
    }
    else
        ret = NULL;

    /* Pick up the branches, linking them together. */
    br = regbranch(&flags);
    if (br == NULL)
        return NULL;
    if (ret != NULL)
        regtail(ret, br);       /* [MZ]OPEN -> first. */
    else
        ret = br;
    /* If one of the branches can be zero-width, the whole thing can.
     * If one of the branches has * at start or matches a line-break, the
     * whole thing can. */
    if (!(flags & HASWIDTH))
        *flagp &= ~HASWIDTH;
    *flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
    while (peekchr() == Magic('|'))
    {
        skipchr();
        br = regbranch(&flags);
        if (br == NULL)
            return NULL;
        regtail(ret, br);       /* BRANCH -> BRANCH. */
        if (!(flags & HASWIDTH))
            *flagp &= ~HASWIDTH;
        *flagp |= flags & (SPSTART | HASNL | HASLOOKBH);
    }

    /* Make a closing node, and hook it on the end. */
    ender = regnode(
#ifdef FEAT_SYN_HL
            paren == REG_ZPAREN ? ZCLOSE + parno :
#endif
            paren == REG_PAREN ? MCLOSE + parno :
            paren == REG_NPAREN ? NCLOSE : END);
    regtail(ret, ender);

    /* Hook the tails of the branches to the closing node. */
    for (br = ret; br != NULL; br = regnext(br))
        regoptail(br, ender);

    /* Check for proper termination. */
    if (paren != REG_NOPAREN && getchr() != Magic(')'))
    {
#ifdef FEAT_SYN_HL
        if (paren == REG_ZPAREN)
            EMSG_RET_NULL(_("E52: Unmatched \\z("));
        else
#endif
            if (paren == REG_NPAREN)
            EMSG_M_RET_NULL(_("E53: Unmatched %s%%("), reg_magic == MAGIC_ALL);
        else
            EMSG_M_RET_NULL(_("E54: Unmatched %s("), reg_magic == MAGIC_ALL);
    }
    else if (paren == REG_NOPAREN && peekchr() != NUL)
    {
        if (curchr == Magic(')'))
            EMSG_M_RET_NULL(_("E55: Unmatched %s)"), reg_magic == MAGIC_ALL);
        else
            EMSG_RET_NULL(_(e_trailing));       /* "Can't happen". */
        /* NOTREACHED */
    }
    /*
     * Here we set the flag allowing back references to this set of
     * parentheses.
     */
    if (paren == REG_PAREN)
        had_endbrace[parno] = TRUE;     /* have seen the close paren */
    return ret;
}

/*
 * regbranch - one alternative of an | operator
 *
 * Implements the & operator.
 */
    static char_u *
regbranch(flagp)
    int         *flagp;
{
    char_u      *ret;
    char_u      *chain = NULL;
    char_u      *latest;
    int         flags;

    *flagp = WORST | HASNL;             /* Tentatively. */

    ret = regnode(BRANCH);
    for (;;)
    {
        latest = regconcat(&flags);
        if (latest == NULL)
            return NULL;
        /* If one of the branches has width, the whole thing has.  If one of
         * the branches anchors at start-of-line, the whole thing does.
         * If one of the branches uses look-behind, the whole thing does. */
        *flagp |= flags & (HASWIDTH | SPSTART | HASLOOKBH);
        /* If one of the branches doesn't match a line-break, the whole thing
         * doesn't. */
        *flagp &= ~HASNL | (flags & HASNL);
        if (chain != NULL)
            regtail(chain, latest);
        if (peekchr() != Magic('&'))
            break;
        skipchr();
        regtail(latest, regnode(END)); /* operand ends */
        reginsert(MATCH, latest);
        chain = latest;
    }

    return ret;
}

/*
 * regbranch - one alternative of an | or & operator
 *
 * Implements the concatenation operator.
 */
    static char_u *
regconcat(flagp)
    int         *flagp;
{
    char_u      *first = NULL;
    char_u      *chain = NULL;
    char_u      *latest;
    int         flags;
    int         cont = TRUE;

    *flagp = WORST;             /* Tentatively. */

    while (cont)
    {
        switch (peekchr())
        {
            case NUL:
            case Magic('|'):
            case Magic('&'):
            case Magic(')'):
                            cont = FALSE;
                            break;
            case Magic('Z'):
#ifdef FEAT_MBYTE
                            regflags |= RF_ICOMBINE;
#endif
                            skipchr_keepstart();
                            break;
            case Magic('c'):
                            regflags |= RF_ICASE;
                            skipchr_keepstart();
                            break;
            case Magic('C'):
                            regflags |= RF_NOICASE;
                            skipchr_keepstart();
                            break;
            case Magic('v'):
                            reg_magic = MAGIC_ALL;
                            skipchr_keepstart();
                            curchr = -1;
                            break;
            case Magic('m'):
                            reg_magic = MAGIC_ON;
                            skipchr_keepstart();
                            curchr = -1;
                            break;
            case Magic('M'):
                            reg_magic = MAGIC_OFF;
                            skipchr_keepstart();
                            curchr = -1;
                            break;
            case Magic('V'):
                            reg_magic = MAGIC_NONE;
                            skipchr_keepstart();
                            curchr = -1;
                            break;
            default:
                            latest = regpiece(&flags);
                            if (latest == NULL)
                                return NULL;
                            *flagp |= flags & (HASWIDTH | HASNL | HASLOOKBH);
                            if (chain == NULL)  /* First piece. */
                                *flagp |= flags & SPSTART;
                            else
                                regtail(chain, latest);
                            chain = latest;
                            if (first == NULL)
                                first = latest;
                            break;
        }
    }
    if (first == NULL)          /* Loop ran zero times. */
        first = regnode(NOTHING);
    return first;
}

/*
 * regpiece - something followed by possible [*+=]
 *
 * Note that the branching code sequences used for = and the general cases
 * of * and + are somewhat optimized:  they use the same NOTHING node as
 * both the endmarker for their branch list and the body of the last branch.
 * It might seem that this node could be dispensed with entirely, but the
 * endmarker role is not redundant.
 */
    static char_u *
regpiece(flagp)
    int             *flagp;
{
    char_u          *ret;
    int             op;
    char_u          *next;
    int             flags;
    long            minval;
    long            maxval;

    ret = regatom(&flags);
    if (ret == NULL)
        return NULL;

    op = peekchr();
    if (re_multi_type(op) == NOT_MULTI)
    {
        *flagp = flags;
        return ret;
    }
    /* default flags */
    *flagp = (WORST | SPSTART | (flags & (HASNL | HASLOOKBH)));

    skipchr();
    switch (op)
    {
        case Magic('*'):
            if (flags & SIMPLE)
                reginsert(STAR, ret);
            else
            {
                /* Emit x* as (x&|), where & means "self". */
                reginsert(BRANCH, ret); /* Either x */
                regoptail(ret, regnode(BACK));  /* and loop */
                regoptail(ret, ret);    /* back */
                regtail(ret, regnode(BRANCH));  /* or */
                regtail(ret, regnode(NOTHING)); /* null. */
            }
            break;

        case Magic('+'):
            if (flags & SIMPLE)
                reginsert(PLUS, ret);
            else
            {
                /* Emit x+ as x(&|), where & means "self". */
                next = regnode(BRANCH); /* Either */
                regtail(ret, next);
                regtail(regnode(BACK), ret);    /* loop back */
                regtail(next, regnode(BRANCH)); /* or */
                regtail(ret, regnode(NOTHING)); /* null. */
            }
            *flagp = (WORST | HASWIDTH | (flags & (HASNL | HASLOOKBH)));
            break;

        case Magic('@'):
            {
                int     lop = END;

                switch (no_Magic(getchr()))
                {
                    case '=': lop = MATCH; break;                 /* \@= */
                    case '!': lop = NOMATCH; break;               /* \@! */
                    case '>': lop = SUBPAT; break;                /* \@> */
                    case '<': switch (no_Magic(getchr()))
                              {
                                  case '=': lop = BEHIND; break;   /* \@<= */
                                  case '!': lop = NOBEHIND; break; /* \@<! */
                              }
                }
                if (lop == END)
                    EMSG_M_RET_NULL(_("E59: invalid character after %s@"),
                                                      reg_magic == MAGIC_ALL);
                /* Look behind must match with behind_pos. */
                if (lop == BEHIND || lop == NOBEHIND)
                {
                    regtail(ret, regnode(BHPOS));
                    *flagp |= HASLOOKBH;
                }
                regtail(ret, regnode(END)); /* operand ends */
                reginsert(lop, ret);
                break;
            }

        case Magic('?'):
        case Magic('='):
            /* Emit x= as (x|) */
            reginsert(BRANCH, ret);             /* Either x */
            regtail(ret, regnode(BRANCH));      /* or */
            next = regnode(NOTHING);            /* null. */
            regtail(ret, next);
            regoptail(ret, next);
            break;

        case Magic('{'):
            if (!read_limits(&minval, &maxval))
                return NULL;
            if (flags & SIMPLE)
            {
                reginsert(BRACE_SIMPLE, ret);
                reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
            }
            else
            {
                if (num_complex_braces >= 10)
                    EMSG_M_RET_NULL(_("E60: Too many complex %s{...}s"),
                                                      reg_magic == MAGIC_ALL);
                reginsert(BRACE_COMPLEX + num_complex_braces, ret);
                regoptail(ret, regnode(BACK));
                regoptail(ret, ret);
                reginsert_limits(BRACE_LIMITS, minval, maxval, ret);
                ++num_complex_braces;
            }
            if (minval > 0 && maxval > 0)
                *flagp = (HASWIDTH | (flags & (HASNL | HASLOOKBH)));
            break;
    }
    if (re_multi_type(peekchr()) != NOT_MULTI)
    {
        /* Can't have a multi follow a multi. */
        if (peekchr() == Magic('*'))
            sprintf((char *)IObuff, _("E61: Nested %s*"),
                                            reg_magic >= MAGIC_ON ? "" : "\\");
        else
            sprintf((char *)IObuff, _("E62: Nested %s%c"),
                reg_magic == MAGIC_ALL ? "" : "\\", no_Magic(peekchr()));
        EMSG_RET_NULL(IObuff);
    }

    return ret;
}

/*
 * regatom - the lowest level
 *
 * Optimization:  gobbles an entire sequence of ordinary characters so that
 * it can turn them into a single node, which is smaller to store and
 * faster to run.  Don't do this when one_exactly is set.
 */
    static char_u *
regatom(flagp)
    int            *flagp;
{
    char_u          *ret;
    int             flags;
    int             cpo_lit;        /* 'cpoptions' contains 'l' flag */
    int             cpo_bsl;        /* 'cpoptions' contains '\' flag */
    int             c;
    static char_u   *classchars = (char_u *)".iIkKfFpPsSdDxXoOwWhHaAlLuU";
    static int      classcodes[] = {ANY, IDENT, SIDENT, KWORD, SKWORD,
                                    FNAME, SFNAME, PRINT, SPRINT,
                                    WHITE, NWHITE, DIGIT, NDIGIT,
                                    HEX, NHEX, OCTAL, NOCTAL,
                                    WORD, NWORD, HEAD, NHEAD,
                                    ALPHA, NALPHA, LOWER, NLOWER,
                                    UPPER, NUPPER
                                    };
    char_u          *p;
    int             extra = 0;

    *flagp = WORST;             /* Tentatively. */
    cpo_lit = vim_strchr(p_cpo, CPO_LITERAL) != NULL;
    cpo_bsl = vim_strchr(p_cpo, CPO_BACKSL) != NULL;

    c = getchr();
    switch (c)
    {
      case Magic('^'):
        ret = regnode(BOL);
        break;

      case Magic('$'):
        ret = regnode(EOL);
#if defined(FEAT_SYN_HL) || defined(PROTO)
        had_eol = TRUE;
#endif
        break;

      case Magic('<'):
        ret = regnode(BOW);
        break;

      case Magic('>'):
        ret = regnode(EOW);
        break;

      case Magic('_'):
        c = no_Magic(getchr());
        if (c == '^')           /* "\_^" is start-of-line */
        {
            ret = regnode(BOL);
            break;
        }
        if (c == '$')           /* "\_$" is end-of-line */
        {
            ret = regnode(EOL);
#if defined(FEAT_SYN_HL) || defined(PROTO)
            had_eol = TRUE;
#endif
            break;
        }

        extra = ADD_NL;
        *flagp |= HASNL;

        /* "\_[" is character range plus newline */
        if (c == '[')
            goto collection;

        /* "\_x" is character class plus newline */
        /*FALLTHROUGH*/

        /*
         * Character classes.
         */
      case Magic('.'):
      case Magic('i'):
      case Magic('I'):
      case Magic('k'):
      case Magic('K'):
      case Magic('f'):
      case Magic('F'):
      case Magic('p'):
      case Magic('P'):
      case Magic('s'):
      case Magic('S'):
      case Magic('d'):
      case Magic('D'):
      case Magic('x'):
      case Magic('X'):
      case Magic('o'):
      case Magic('O'):
      case Magic('w'):
      case Magic('W'):
      case Magic('h'):
      case Magic('H'):
      case Magic('a'):
      case Magic('A'):
      case Magic('l'):
      case Magic('L'):
      case Magic('u'):
      case Magic('U'):
        p = vim_strchr(classchars, no_Magic(c));
        if (p == NULL)
            EMSG_RET_NULL(_("E63: invalid use of \\_"));
#ifdef FEAT_MBYTE
        /* When '.' is followed by a composing char ignore the dot, so that
         * the composing char is matched here. */
        if (enc_utf8 && c == Magic('.') && utf_iscomposing(peekchr()))
        {
            c = getchr();
            goto do_multibyte;
        }
#endif
        ret = regnode(classcodes[p - classchars] + extra);
        *flagp |= HASWIDTH | SIMPLE;
        break;

      case Magic('n'):
        if (reg_string)
        {
            /* In a string "\n" matches a newline character. */
            ret = regnode(EXACTLY);
            regc(NL);
            regc(NUL);
            *flagp |= HASWIDTH | SIMPLE;
        }
        else
        {
            /* In buffer text "\n" matches the end of a line. */
            ret = regnode(NEWL);
            *flagp |= HASWIDTH | HASNL;
        }
        break;

      case Magic('('):
        if (one_exactly)
            EMSG_ONE_RET_NULL;
        ret = reg(REG_PAREN, &flags);
        if (ret == NULL)
            return NULL;
        *flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
        break;

      case NUL:
      case Magic('|'):
      case Magic('&'):
      case Magic(')'):
        EMSG_RET_NULL(_(e_internal));   /* Supposed to be caught earlier. */
        /* NOTREACHED */

      case Magic('='):
      case Magic('?'):
      case Magic('+'):
      case Magic('@'):
      case Magic('{'):
      case Magic('*'):
        c = no_Magic(c);
        sprintf((char *)IObuff, _("E64: %s%c follows nothing"),
                (c == '*' ? reg_magic >= MAGIC_ON : reg_magic == MAGIC_ALL)
                ? "" : "\\", c);
        EMSG_RET_NULL(IObuff);
        /* NOTREACHED */

      case Magic('~'):          /* previous substitute pattern */
            if (reg_prev_sub != NULL)
            {
                char_u      *lp;

                ret = regnode(EXACTLY);
                lp = reg_prev_sub;
                while (*lp != NUL)
                    regc(*lp++);
                regc(NUL);
                if (*reg_prev_sub != NUL)
                {
                    *flagp |= HASWIDTH;
                    if ((lp - reg_prev_sub) == 1)
                        *flagp |= SIMPLE;
                }
            }
            else
                EMSG_RET_NULL(_(e_nopresub));
            break;

      case Magic('1'):
      case Magic('2'):
      case Magic('3'):
      case Magic('4'):
      case Magic('5'):
      case Magic('6'):
      case Magic('7'):
      case Magic('8'):
      case Magic('9'):
            {
                int                 refnum;

                refnum = c - Magic('0');
                /*
                 * Check if the back reference is legal. We must have seen the
                 * close brace.
                 * TODO: Should also check that we don't refer to something
                 * that is repeated (+*=): what instance of the repetition
                 * should we match?
                 */
                if (!had_endbrace[refnum])
                {
                    /* Trick: check if "@<=" or "@<!" follows, in which case
                     * the \1 can appear before the referenced match. */
                    for (p = regparse; *p != NUL; ++p)
                        if (p[0] == '@' && p[1] == '<'
                                              && (p[2] == '!' || p[2] == '='))
                            break;
                    if (*p == NUL)
                        EMSG_RET_NULL(_("E65: Illegal back reference"));
                }
                ret = regnode(BACKREF + refnum);
            }
            break;

      case Magic('z'):
        {
            c = no_Magic(getchr());
            switch (c)
            {
#ifdef FEAT_SYN_HL
                case '(': if (reg_do_extmatch != REX_SET)
                              EMSG_RET_NULL(_("E66: \\z( not allowed here"));
                          if (one_exactly)
                              EMSG_ONE_RET_NULL;
                          ret = reg(REG_ZPAREN, &flags);
                          if (ret == NULL)
                              return NULL;
                          *flagp |= flags & (HASWIDTH|SPSTART|HASNL|HASLOOKBH);
                          re_has_z = REX_SET;
                          break;

                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9': if (reg_do_extmatch != REX_USE)
                              EMSG_RET_NULL(_("E67: \\z1 et al. not allowed here"));
                          ret = regnode(ZREF + c - '0');
                          re_has_z = REX_USE;
                          break;
#endif

                case 's': ret = regnode(MOPEN + 0);
                          break;

                case 'e': ret = regnode(MCLOSE + 0);
                          break;

                default:  EMSG_RET_NULL(_("E68: Invalid character after \\z"));
            }
        }
        break;

      case Magic('%'):
        {
            c = no_Magic(getchr());
            switch (c)
            {
                /* () without a back reference */
                case '(':
                    if (one_exactly)
                        EMSG_ONE_RET_NULL;
                    ret = reg(REG_NPAREN, &flags);
                    if (ret == NULL)
                        return NULL;
                    *flagp |= flags & (HASWIDTH | SPSTART | HASNL | HASLOOKBH);
                    break;

                /* Catch \%^ and \%$ regardless of where they appear in the
                 * pattern -- regardless of whether or not it makes sense. */
                case '^':
                    ret = regnode(RE_BOF);
                    break;

                case '$':
                    ret = regnode(RE_EOF);
                    break;

                case '#':
                    ret = regnode(CURSOR);
                    break;

                case 'V':
                    ret = regnode(RE_VISUAL);
                    break;

                /* \%[abc]: Emit as a list of branches, all ending at the last
                 * branch which matches nothing. */
                case '[':
                          if (one_exactly)      /* doesn't nest */
                              EMSG_ONE_RET_NULL;
                          {
                              char_u    *lastbranch;
                              char_u    *lastnode = NULL;
                              char_u    *br;

                              ret = NULL;
                              while ((c = getchr()) != ']')
                              {
                                  if (c == NUL)
                                      EMSG_M_RET_NULL(_("E69: Missing ] after %s%%["),
                                                      reg_magic == MAGIC_ALL);
                                  br = regnode(BRANCH);
                                  if (ret == NULL)
                                      ret = br;
                                  else
                                      regtail(lastnode, br);

                                  ungetchr();
                                  one_exactly = TRUE;
                                  lastnode = regatom(flagp);
                                  one_exactly = FALSE;
                                  if (lastnode == NULL)
                                      return NULL;
                              }
                              if (ret == NULL)
                                  EMSG_M_RET_NULL(_("E70: Empty %s%%[]"),
                                                      reg_magic == MAGIC_ALL);
                              lastbranch = regnode(BRANCH);
                              br = regnode(NOTHING);
                              if (ret != JUST_CALC_SIZE)
                              {
                                  regtail(lastnode, br);
                                  regtail(lastbranch, br);
                                  /* connect all branches to the NOTHING
                                   * branch at the end */
                                  for (br = ret; br != lastnode; )
                                  {
                                      if (OP(br) == BRANCH)
                                      {
                                          regtail(br, lastbranch);
                                          br = OPERAND(br);
                                      }
                                      else
                                          br = regnext(br);
                                  }
                              }
                              *flagp &= ~HASWIDTH;
                              break;
                          }

                case 'd':   /* %d123 decimal */
                case 'o':   /* %o123 octal */
                case 'x':   /* %xab hex 2 */
                case 'u':   /* %uabcd hex 4 */
                case 'U':   /* %U1234abcd hex 8 */
                          {
                              int i;

                              switch (c)
                              {
                                  case 'd': i = getdecchrs(); break;
                                  case 'o': i = getoctchrs(); break;
                                  case 'x': i = gethexchrs(2); break;
                                  case 'u': i = gethexchrs(4); break;
                                  case 'U': i = gethexchrs(8); break;
                                  default:  i = -1; break;
                              }

                              if (i < 0)
                                  EMSG_M_RET_NULL(
                                        _("E678: Invalid character after %s%%[dxouU]"),
                                        reg_magic == MAGIC_ALL);
#ifdef FEAT_MBYTE
                              if (use_multibytecode(i))
                                  ret = regnode(MULTIBYTECODE);
                              else
#endif
                                  ret = regnode(EXACTLY);
                              if (i == 0)
                                  regc(0x0a);
                              else
#ifdef FEAT_MBYTE
                                  regmbc(i);
#else
                                  regc(i);
#endif
                              regc(NUL);
                              *flagp |= HASWIDTH;
                              break;
                          }

                default:
                          if (VIM_ISDIGIT(c) || c == '<' || c == '>'
                                                                 || c == '\'')
                          {
                              long_u    n = 0;
                              int       cmp;

                              cmp = c;
                              if (cmp == '<' || cmp == '>')
                                  c = getchr();
                              while (VIM_ISDIGIT(c))
                              {
                                  n = n * 10 + (c - '0');
                                  c = getchr();
                              }
                              if (c == '\'' && n == 0)
                              {
                                  /* "\%'m", "\%<'m" and "\%>'m": Mark */
                                  c = getchr();
                                  ret = regnode(RE_MARK);
                                  if (ret == JUST_CALC_SIZE)
                                      regsize += 2;
                                  else
                                  {
                                      *regcode++ = c;
                                      *regcode++ = cmp;
                                  }
                                  break;
                              }
                              else if (c == 'l' || c == 'c' || c == 'v')
                              {
                                  if (c == 'l')
                                      ret = regnode(RE_LNUM);
                                  else if (c == 'c')
                                      ret = regnode(RE_COL);
                                  else
                                      ret = regnode(RE_VCOL);
                                  if (ret == JUST_CALC_SIZE)
                                      regsize += 5;
                                  else
                                  {
                                      /* put the number and the optional
                                       * comparator after the opcode */
                                      regcode = re_put_long(regcode, n);
                                      *regcode++ = cmp;
                                  }
                                  break;
                              }
                          }

                          EMSG_M_RET_NULL(_("E71: Invalid character after %s%%"),
                                                      reg_magic == MAGIC_ALL);
            }
        }
        break;

      case Magic('['):
collection:
        {
            char_u      *lp;

            /*
             * If there is no matching ']', we assume the '[' is a normal
             * character.  This makes 'incsearch' and ":help [" work.
             */
            lp = skip_anyof(regparse);
            if (*lp == ']')     /* there is a matching ']' */
            {
                int     startc = -1;    /* > 0 when next '-' is a range */
                int     endc;

                /*
                 * In a character class, different parsing rules apply.
                 * Not even \ is special anymore, nothing is.
                 */
                if (*regparse == '^')       /* Complement of range. */
                {
                    ret = regnode(ANYBUT + extra);
                    regparse++;
                }
                else
                    ret = regnode(ANYOF + extra);

                /* At the start ']' and '-' mean the literal character. */
                if (*regparse == ']' || *regparse == '-')
                {
                    startc = *regparse;
                    regc(*regparse++);
                }

                while (*regparse != NUL && *regparse != ']')
                {
                    if (*regparse == '-')
                    {
                        ++regparse;
                        /* The '-' is not used for a range at the end and
                         * after or before a '\n'. */
                        if (*regparse == ']' || *regparse == NUL
                                || startc == -1
                                || (regparse[0] == '\\' && regparse[1] == 'n'))
                        {
                            regc('-');
                            startc = '-';       /* [--x] is a range */
                        }
                        else
                        {
                            /* Also accept "a-[.z.]" */
                            endc = 0;
                            if (*regparse == '[')
                                endc = get_coll_element(&regparse);
                            if (endc == 0)
                            {
#ifdef FEAT_MBYTE
                                if (has_mbyte)
                                    endc = mb_ptr2char_adv(&regparse);
                                else
#endif
                                    endc = *regparse++;
                            }

                            /* Handle \o40, \x20 and \u20AC style sequences */
                            if (endc == '\\' && !cpo_lit && !cpo_bsl)
                                endc = coll_get_char();

                            if (startc > endc)
                                EMSG_RET_NULL(_(e_invrange));
#ifdef FEAT_MBYTE
                            if (has_mbyte && ((*mb_char2len)(startc) > 1
                                                 || (*mb_char2len)(endc) > 1))
                            {
                                /* Limit to a range of 256 chars */
                                if (endc > startc + 256)
                                    EMSG_RET_NULL(_(e_invrange));
                                while (++startc <= endc)
                                    regmbc(startc);
                            }
                            else
#endif
                            {
#ifdef EBCDIC
                                int     alpha_only = FALSE;

                                /* for alphabetical range skip the gaps
                                 * 'i'-'j', 'r'-'s', 'I'-'J' and 'R'-'S'.  */
                                if (isalpha(startc) && isalpha(endc))
                                    alpha_only = TRUE;
#endif
                                while (++startc <= endc)
#ifdef EBCDIC
                                    if (!alpha_only || isalpha(startc))
#endif
                                        regc(startc);
                            }
                            startc = -1;
                        }
                    }
                    /*
                     * Only "\]", "\^", "\]" and "\\" are special in Vi.  Vim
                     * accepts "\t", "\e", etc., but only when the 'l' flag in
                     * 'cpoptions' is not included.
                     * Posix doesn't recognize backslash at all.
                     */
                    else if (*regparse == '\\'
                            && !cpo_bsl
                            && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
                                || (!cpo_lit
                                    && vim_strchr(REGEXP_ABBR,
                                                       regparse[1]) != NULL)))
                    {
                        regparse++;
                        if (*regparse == 'n')
                        {
                            /* '\n' in range: also match NL */
                            if (ret != JUST_CALC_SIZE)
                            {
                                if (*ret == ANYBUT)
                                    *ret = ANYBUT + ADD_NL;
                                else if (*ret == ANYOF)
                                    *ret = ANYOF + ADD_NL;
                                /* else: must have had a \n already */
                            }
                            *flagp |= HASNL;
                            regparse++;
                            startc = -1;
                        }
                        else if (*regparse == 'd'
                                || *regparse == 'o'
                                || *regparse == 'x'
                                || *regparse == 'u'
                                || *regparse == 'U')
                        {
                            startc = coll_get_char();
                            if (startc == 0)
                                regc(0x0a);
                            else
#ifdef FEAT_MBYTE
                                regmbc(startc);
#else
                                regc(startc);
#endif
                        }
                        else
                        {
                            startc = backslash_trans(*regparse++);
                            regc(startc);
                        }
                    }
                    else if (*regparse == '[')
                    {
                        int c_class;
                        int cu;

                        c_class = get_char_class(&regparse);
                        startc = -1;
                        /* Characters assumed to be 8 bits! */
                        switch (c_class)
                        {
                            case CLASS_NONE:
                                c_class = get_equi_class(&regparse);
                                if (c_class != 0)
                                {
                                    /* produce equivalence class */
                                    reg_equi_class(c_class);
                                }
                                else if ((c_class =
                                            get_coll_element(&regparse)) != 0)
                                {
                                    /* produce a collating element */
                                    regmbc(c_class);
                                }
                                else
                                {
                                    /* literal '[', allow [[-x] as a range */
                                    startc = *regparse++;
                                    regc(startc);
                                }
                                break;
                            case CLASS_ALNUM:
                                for (cu = 1; cu <= 255; cu++)
                                    if (isalnum(cu))
                                        regc(cu);
                                break;
                            case CLASS_ALPHA:
                                for (cu = 1; cu <= 255; cu++)
                                    if (isalpha(cu))
                                        regc(cu);
                                break;
                            case CLASS_BLANK:
                                regc(' ');
                                regc('\t');
                                break;
                            case CLASS_CNTRL:
                                for (cu = 1; cu <= 255; cu++)
                                    if (iscntrl(cu))
                                        regc(cu);
                                break;
                            case CLASS_DIGIT:
                                for (cu = 1; cu <= 255; cu++)
                                    if (VIM_ISDIGIT(cu))
                                        regc(cu);
                                break;
                            case CLASS_GRAPH:
                                for (cu = 1; cu <= 255; cu++)
                                    if (isgraph(cu))
                                        regc(cu);
                                break;
                            case CLASS_LOWER:
                                for (cu = 1; cu <= 255; cu++)
                                    if (islower(cu))
                                        regc(cu);
                                break;
                            case CLASS_PRINT:
                                for (cu = 1; cu <= 255; cu++)
                                    if (vim_isprintc(cu))
                                        regc(cu);
                                break;
                            case CLASS_PUNCT:
                                for (cu = 1; cu <= 255; cu++)
                                    if (ispunct(cu))
                                        regc(cu);
                                break;
                            case CLASS_SPACE:
                                for (cu = 9; cu <= 13; cu++)
                                    regc(cu);
                                regc(' ');
                                break;
                            case CLASS_UPPER:
                                for (cu = 1; cu <= 255; cu++)
                                    if (isupper(cu))
                                        regc(cu);
                                break;
                            case CLASS_XDIGIT:
                                for (cu = 1; cu <= 255; cu++)
                                    if (vim_isxdigit(cu))
                                        regc(cu);
                                break;
                            case CLASS_TAB:
                                regc('\t');
                                break;
                            case CLASS_RETURN:
                                regc('\r');
                                break;
                            case CLASS_BACKSPACE:
                                regc('\b');
                                break;
                            case CLASS_ESCAPE:
                                regc('\033');
                                break;
                        }
                    }
                    else
                    {
#ifdef FEAT_MBYTE
                        if (has_mbyte)
                        {
                            int len;

                            /* produce a multibyte character, including any
                             * following composing characters */
                            startc = mb_ptr2char(regparse);
                            len = (*mb_ptr2len)(regparse);
                            if (enc_utf8 && utf_char2len(startc) != len)
                                startc = -1;    /* composing chars */
                            while (--len >= 0)
                                regc(*regparse++);
                        }
                        else
#endif
                        {
                            startc = *regparse++;
                            regc(startc);
                        }
                    }
                }
                regc(NUL);
                prevchr_len = 1;        /* last char was the ']' */
                if (*regparse != ']')
                    EMSG_RET_NULL(_(e_toomsbra));       /* Cannot happen? */
                skipchr();          /* let's be friends with the lexer again */
                *flagp |= HASWIDTH | SIMPLE;
                break;
            }
            else if (reg_strict)
                EMSG_M_RET_NULL(_("E769: Missing ] after %s["),
                                                       reg_magic > MAGIC_OFF);
        }
        /* FALLTHROUGH */

      default:
        {
            int         len;

#ifdef FEAT_MBYTE
            /* A multi-byte character is handled as a separate atom if it's
             * before a multi and when it's a composing char. */
            if (use_multibytecode(c))
            {
do_multibyte:
                ret = regnode(MULTIBYTECODE);
                regmbc(c);
                *flagp |= HASWIDTH | SIMPLE;
                break;
            }
#endif

            ret = regnode(EXACTLY);

            /*
             * Append characters as long as:
             * - there is no following multi, we then need the character in
             *   front of it as a single character operand
             * - not running into a Magic character
             * - "one_exactly" is not set
             * But always emit at least one character.  Might be a Multi,
             * e.g., a "[" without matching "]".
             */
            for (len = 0; c != NUL && (len == 0
                        || (re_multi_type(peekchr()) == NOT_MULTI
                            && !one_exactly
                            && !is_Magic(c))); ++len)
            {
                c = no_Magic(c);
#ifdef FEAT_MBYTE
                if (has_mbyte)
                {
                    regmbc(c);
                    if (enc_utf8)
                    {
                        int     l;

                        /* Need to get composing character too. */
                        for (;;)
                        {
                            l = utf_ptr2len(regparse);
                            if (!UTF_COMPOSINGLIKE(regparse, regparse + l))
                                break;
                            regmbc(utf_ptr2char(regparse));
                            skipchr();
                        }
                    }
                }
                else
#endif
                    regc(c);
                c = getchr();
            }
            ungetchr();

            regc(NUL);
            *flagp |= HASWIDTH;
            if (len == 1)
                *flagp |= SIMPLE;
        }
        break;
    }

    return ret;
}

#ifdef FEAT_MBYTE
/*
 * Return TRUE if MULTIBYTECODE should be used instead of EXACTLY for
 * character "c".
 */
    static int
use_multibytecode(c)
    int c;
{
    return has_mbyte && (*mb_char2len)(c) > 1
                     && (re_multi_type(peekchr()) != NOT_MULTI
                             || (enc_utf8 && utf_iscomposing(c)));
}
#endif

/*
 * emit a node
 * Return pointer to generated code.
 */
    static char_u *
regnode(op)
    int         op;
{
    char_u  *ret;

    ret = regcode;
    if (ret == JUST_CALC_SIZE)
        regsize += 3;
    else
    {
        *regcode++ = op;
        *regcode++ = NUL;               /* Null "next" pointer. */
        *regcode++ = NUL;
    }
    return ret;
}

/*
 * Emit (if appropriate) a byte of code
 */
    static void
regc(b)
    int         b;
{
    if (regcode == JUST_CALC_SIZE)
        regsize++;
    else
        *regcode++ = b;
}

#ifdef FEAT_MBYTE
/*
 * Emit (if appropriate) a multi-byte character of code
 */
    static void
regmbc(c)
    int         c;
{
    if (regcode == JUST_CALC_SIZE)
        regsize += (*mb_char2len)(c);
    else
        regcode += (*mb_char2bytes)(c, regcode);
}
#endif

/*
 * reginsert - insert an operator in front of already-emitted operand
 *
 * Means relocating the operand.
 */
    static void
reginsert(op, opnd)
    int         op;
    char_u     *opnd;
{
    char_u      *src;
    char_u      *dst;
    char_u      *place;

    if (regcode == JUST_CALC_SIZE)
    {
        regsize += 3;
        return;
    }
    src = regcode;
    regcode += 3;
    dst = regcode;
    while (src > opnd)
        *--dst = *--src;

    place = opnd;               /* Op node, where operand used to be. */
    *place++ = op;
    *place++ = NUL;
    *place = NUL;
}

/*
 * reginsert_limits - insert an operator in front of already-emitted operand.
 * The operator has the given limit values as operands.  Also set next pointer.
 *
 * Means relocating the operand.
 */
    static void
reginsert_limits(op, minval, maxval, opnd)
    int         op;
    long        minval;
    long        maxval;
    char_u      *opnd;
{
    char_u      *src;
    char_u      *dst;
    char_u      *place;

    if (regcode == JUST_CALC_SIZE)
    {
        regsize += 11;
        return;
    }
    src = regcode;
    regcode += 11;
    dst = regcode;
    while (src > opnd)
        *--dst = *--src;

    place = opnd;               /* Op node, where operand used to be. */
    *place++ = op;
    *place++ = NUL;
    *place++ = NUL;
    place = re_put_long(place, (long_u)minval);
    place = re_put_long(place, (long_u)maxval);
    regtail(opnd, place);
}

/*
 * Write a long as four bytes at "p" and return pointer to the next char.
 */
    static char_u *
re_put_long(p, val)
    char_u      *p;
    long_u      val;
{
    *p++ = (char_u) ((val >> 24) & 0377);
    *p++ = (char_u) ((val >> 16) & 0377);
    *p++ = (char_u) ((val >> 8) & 0377);
    *p++ = (char_u) (val & 0377);
    return p;
}

/*
 * regtail - set the next-pointer at the end of a node chain
 */
    static void
regtail(p, val)
    char_u      *p;
    char_u      *val;
{
    char_u      *scan;
    char_u      *temp;
    int         offset;

    if (p == JUST_CALC_SIZE)
        return;

    /* Find last node. */
    scan = p;
    for (;;)
    {
        temp = regnext(scan);
        if (temp == NULL)
            break;
        scan = temp;
    }

    if (OP(scan) == BACK)
        offset = (int)(scan - val);
    else
        offset = (int)(val - scan);
    *(scan + 1) = (char_u) (((unsigned)offset >> 8) & 0377);
    *(scan + 2) = (char_u) (offset & 0377);
}

/*
 * regoptail - regtail on item after a BRANCH; nop if none
 */
    static void
regoptail(p, val)
    char_u      *p;
    char_u      *val;
{
    /* When op is neither BRANCH nor BRACE_COMPLEX0-9, it is "operandless" */
    if (p == NULL || p == JUST_CALC_SIZE
            || (OP(p) != BRANCH
                && (OP(p) < BRACE_COMPLEX || OP(p) > BRACE_COMPLEX + 9)))
        return;
    regtail(OPERAND(p), val);
}

/*
 * getchr() - get the next character from the pattern. We know about
 * magic and such, so therefore we need a lexical analyzer.
 */

/* static int       curchr; */
static int      prevprevchr;
static int      prevchr;
static int      nextchr;    /* used for ungetchr() */
/*
 * Note: prevchr is sometimes -1 when we are not at the start,
 * eg in /[ ^I]^ the pattern was never found even if it existed, because ^ was
 * taken to be magic -- webb
 */
static int      at_start;       /* True when on the first character */
static int      prev_at_start;  /* True when on the second character */

    static void
initchr(str)
    char_u *str;
{
    regparse = str;
    prevchr_len = 0;
    curchr = prevprevchr = prevchr = nextchr = -1;
    at_start = TRUE;
    prev_at_start = FALSE;
}

    static int
peekchr()
{
    static int  after_slash = FALSE;

    if (curchr == -1)
    {
        switch (curchr = regparse[0])
        {
        case '.':
        case '[':
        case '~':
            /* magic when 'magic' is on */
            if (reg_magic >= MAGIC_ON)
                curchr = Magic(curchr);
            break;
        case '(':
        case ')':
        case '{':
        case '%':
        case '+':
        case '=':
        case '?':
        case '@':
        case '!':
        case '&':
        case '|':
        case '<':
        case '>':
        case '#':       /* future ext. */
        case '"':       /* future ext. */
        case '\'':      /* future ext. */
        case ',':       /* future ext. */
        case '-':       /* future ext. */
        case ':':       /* future ext. */
        case ';':       /* future ext. */
        case '`':       /* future ext. */
        case '/':       /* Can't be used in / command */
            /* magic only after "\v" */
            if (reg_magic == MAGIC_ALL)
                curchr = Magic(curchr);
            break;
        case '*':
            /* * is not magic as the very first character, eg "?*ptr", when
             * after '^', eg "/^*ptr" and when after "\(", "\|", "\&".  But
             * "\(\*" is not magic, thus must be magic if "after_slash" */
            if (reg_magic >= MAGIC_ON
                    && !at_start
                    && !(prev_at_start && prevchr == Magic('^'))
                    && (after_slash
                        || (prevchr != Magic('(')
                            && prevchr != Magic('&')
                            && prevchr != Magic('|'))))
                curchr = Magic('*');
            break;
        case '^':
            /* '^' is only magic as the very first character and if it's after
             * "\(", "\|", "\&' or "\n" */
            if (reg_magic >= MAGIC_OFF
                    && (at_start
                        || reg_magic == MAGIC_ALL
                        || prevchr == Magic('(')
                        || prevchr == Magic('|')
                        || prevchr == Magic('&')
                        || prevchr == Magic('n')
                        || (no_Magic(prevchr) == '('
                            && prevprevchr == Magic('%'))))
            {
                curchr = Magic('^');
                at_start = TRUE;
                prev_at_start = FALSE;
            }
            break;
        case '$':
            /* '$' is only magic as the very last char and if it's in front of
             * either "\|", "\)", "\&", or "\n" */
            if (reg_magic >= MAGIC_OFF)
            {
                char_u *p = regparse + 1;

                /* ignore \c \C \m and \M after '$' */
                while (p[0] == '\\' && (p[1] == 'c' || p[1] == 'C'
                                || p[1] == 'm' || p[1] == 'M' || p[1] == 'Z'))
                    p += 2;
                if (p[0] == NUL
                        || (p[0] == '\\'
                            && (p[1] == '|' || p[1] == '&' || p[1] == ')'
                                || p[1] == 'n'))
                        || reg_magic == MAGIC_ALL)
                    curchr = Magic('$');
            }
            break;
        case '\\':
            {
                int c = regparse[1];

                if (c == NUL)
                    curchr = '\\';      /* trailing '\' */
                else if (
#ifdef EBCDIC
                        vim_strchr(META, c)
#else
                        c <= '~' && META_flags[c]
#endif
                        )
                {
                    /*
                     * META contains everything that may be magic sometimes,
                     * except ^ and $ ("\^" and "\$" are only magic after
                     * "\v").  We now fetch the next character and toggle its
                     * magicness.  Therefore, \ is so meta-magic that it is
                     * not in META.
                     */
                    curchr = -1;
                    prev_at_start = at_start;
                    at_start = FALSE;   /* be able to say "/\*ptr" */
                    ++regparse;
                    ++after_slash;
                    peekchr();
                    --regparse;
                    --after_slash;
                    curchr = toggle_Magic(curchr);
                }
                else if (vim_strchr(REGEXP_ABBR, c))
                {
                    /*
                     * Handle abbreviations, like "\t" for TAB -- webb
                     */
                    curchr = backslash_trans(c);
                }
                else if (reg_magic == MAGIC_NONE && (c == '$' || c == '^'))
                    curchr = toggle_Magic(c);
                else
                {
                    /*
                     * Next character can never be (made) magic?
                     * Then backslashing it won't do anything.
                     */
#ifdef FEAT_MBYTE
                    if (has_mbyte)
                        curchr = (*mb_ptr2char)(regparse + 1);
                    else
#endif
                        curchr = c;
                }
                break;
            }

#ifdef FEAT_MBYTE
        default:
            if (has_mbyte)
                curchr = (*mb_ptr2char)(regparse);
#endif
        }
    }

    return curchr;
}

/*
 * Eat one lexed character.  Do this in a way that we can undo it.
 */
    static void
skipchr()
{
    /* peekchr() eats a backslash, do the same here */
    if (*regparse == '\\')
        prevchr_len = 1;
    else
        prevchr_len = 0;
    if (regparse[prevchr_len] != NUL)
    {
#ifdef FEAT_MBYTE
        if (enc_utf8)
            prevchr_len += utf_char2len(mb_ptr2char(regparse + prevchr_len));
        else if (has_mbyte)
            prevchr_len += (*mb_ptr2len)(regparse + prevchr_len);
        else
#endif
            ++prevchr_len;
    }
    regparse += prevchr_len;
    prev_at_start = at_start;
    at_start = FALSE;
    prevprevchr = prevchr;
    prevchr = curchr;
    curchr = nextchr;       /* use previously unget char, or -1 */
    nextchr = -1;
}

/*
 * Skip a character while keeping the value of prev_at_start for at_start.
 * prevchr and prevprevchr are also kept.
 */
    static void
skipchr_keepstart()
{
    int as = prev_at_start;
    int pr = prevchr;
    int prpr = prevprevchr;

    skipchr();
    at_start = as;
    prevchr = pr;
    prevprevchr = prpr;
}

    static int
getchr()
{
    int chr = peekchr();

    skipchr();
    return chr;
}

/*
 * put character back.  Works only once!
 */
    static void
ungetchr()
{
    nextchr = curchr;
    curchr = prevchr;
    prevchr = prevprevchr;
    at_start = prev_at_start;
    prev_at_start = FALSE;

    /* Backup regparse, so that it's at the same position as before the
     * getchr(). */
    regparse -= prevchr_len;
}

/*
 * Get and return the value of the hex string at the current position.
 * Return -1 if there is no valid hex number.
 * The position is updated:
 *     blahblah\%x20asdf
 *         before-^ ^-after
 * The parameter controls the maximum number of input characters. This will be
 * 2 when reading a \%x20 sequence and 4 when reading a \%u20AC sequence.
 */
    static int
gethexchrs(maxinputlen)
    int         maxinputlen;
{
    int         nr = 0;
    int         c;
    int         i;

    for (i = 0; i < maxinputlen; ++i)
    {
        c = regparse[0];
        if (!vim_isxdigit(c))
            break;
        nr <<= 4;
        nr |= hex2nr(c);
        ++regparse;
    }

    if (i == 0)
        return -1;
    return nr;
}

/*
 * get and return the value of the decimal string immediately after the
 * current position. Return -1 for invalid.  Consumes all digits.
 */
    static int
getdecchrs()
{
    int         nr = 0;
    int         c;
    int         i;

    for (i = 0; ; ++i)
    {
        c = regparse[0];
        if (c < '0' || c > '9')
            break;
        nr *= 10;
        nr += c - '0';
        ++regparse;
    }

    if (i == 0)
        return -1;
    return nr;
}

/*
 * get and return the value of the octal string immediately after the current
 * position. Return -1 for invalid, or 0-255 for valid. Smart enough to handle
 * numbers > 377 correctly (for example, 400 is treated as 40) and doesn't
 * treat 8 or 9 as recognised characters. Position is updated:
 *     blahblah\%o210asdf
 *         before-^  ^-after
 */
    static int
getoctchrs()
{
    int         nr = 0;
    int         c;
    int         i;

    for (i = 0; i < 3 && nr < 040; ++i)
    {
        c = regparse[0];
        if (c < '0' || c > '7')
            break;
        nr <<= 3;
        nr |= hex2nr(c);
        ++regparse;
    }

    if (i == 0)
        return -1;
    return nr;
}

/*
 * Get a number after a backslash that is inside [].
 * When nothing is recognized return a backslash.
 */
    static int
coll_get_char()
{
    int     nr = -1;

    switch (*regparse++)
    {
        case 'd': nr = getdecchrs(); break;
        case 'o': nr = getoctchrs(); break;
        case 'x': nr = gethexchrs(2); break;
        case 'u': nr = gethexchrs(4); break;
        case 'U': nr = gethexchrs(8); break;
    }
    if (nr < 0)
    {
        /* If getting the number fails be backwards compatible: the character
         * is a backslash. */
        --regparse;
        nr = '\\';
    }
    return nr;
}

/*
 * read_limits - Read two integers to be taken as a minimum and maximum.
 * If the first character is '-', then the range is reversed.
 * Should end with 'end'.  If minval is missing, zero is default, if maxval is
 * missing, a very big number is the default.
 */
    static int
read_limits(minval, maxval)
    long        *minval;
    long        *maxval;
{
    int         reverse = FALSE;
    char_u      *first_char;
    long        tmp;

    if (*regparse == '-')
    {
        /* Starts with '-', so reverse the range later */
        regparse++;
        reverse = TRUE;
    }
    first_char = regparse;
    *minval = getdigits(&regparse);
    if (*regparse == ',')           /* There is a comma */
    {
        if (vim_isdigit(*++regparse))
            *maxval = getdigits(&regparse);
        else
            *maxval = MAX_LIMIT;
    }
    else if (VIM_ISDIGIT(*first_char))
        *maxval = *minval;          /* It was \{n} or \{-n} */
    else
        *maxval = MAX_LIMIT;        /* It was \{} or \{-} */
    if (*regparse == '\\')
        regparse++;     /* Allow either \{...} or \{...\} */
    if (*regparse != '}')
    {
        sprintf((char *)IObuff, _("E554: Syntax error in %s{...}"),
                                          reg_magic == MAGIC_ALL ? "" : "\\");
        EMSG_RET_FAIL(IObuff);
    }

    /*
     * Reverse the range if there was a '-', or make sure it is in the right
     * order otherwise.
     */
    if ((!reverse && *minval > *maxval) || (reverse && *minval < *maxval))
    {
        tmp = *minval;
        *minval = *maxval;
        *maxval = tmp;
    }
    skipchr();          /* let's be friends with the lexer again */
    return OK;
}

/*
 * vim_regexec and friends
 */

/*
 * Global work variables for vim_regexec().
 */

/* The current match-position is remembered with these variables: */
static linenr_T reglnum;        /* line number, relative to first line */
static char_u   *regline;       /* start of current line */
static char_u   *reginput;      /* current input, points into "regline" */

static int      need_clear_subexpr;     /* subexpressions still need to be
                                         * cleared */
#ifdef FEAT_SYN_HL
static int      need_clear_zsubexpr = FALSE;    /* extmatch subexpressions
                                                 * still need to be cleared */
#endif

/*
 * Structure used to save the current input state, when it needs to be
 * restored after trying a match.  Used by reg_save() and reg_restore().
 * Also stores the length of "backpos".
 */
typedef struct
{
    union
    {
        char_u  *ptr;   /* reginput pointer, for single-line regexp */
        lpos_T  pos;    /* reginput pos, for multi-line regexp */
    } rs_u;
    int         rs_len;
} regsave_T;

/* struct to save start/end pointer/position in for \(\) */
typedef struct
{
    union
    {
        char_u  *ptr;
        lpos_T  pos;
    } se_u;
} save_se_T;

static char_u   *reg_getline __ARGS((linenr_T lnum));
static long     vim_regexec_both __ARGS((char_u *line, colnr_T col));
static long     regtry __ARGS((regprog_T *prog, colnr_T col));
static void     cleanup_subexpr __ARGS((void));
#ifdef FEAT_SYN_HL
static void     cleanup_zsubexpr __ARGS((void));
#endif
static void     reg_nextline __ARGS((void));
static void     reg_save __ARGS((regsave_T *save, garray_T *gap));
static void     reg_restore __ARGS((regsave_T *save, garray_T *gap));
static int      reg_save_equal __ARGS((regsave_T *save));
static void     save_se_multi __ARGS((save_se_T *savep, lpos_T *posp));
static void     save_se_one __ARGS((save_se_T *savep, char_u **pp));

/* Save the sub-expressions before attempting a match. */
#define save_se(savep, posp, pp) \
    REG_MULTI ? save_se_multi((savep), (posp)) : save_se_one((savep), (pp))

/* After a failed match restore the sub-expressions. */
#define restore_se(savep, posp, pp) { \
    if (REG_MULTI) \
        *(posp) = (savep)->se_u.pos; \
    else \
        *(pp) = (savep)->se_u.ptr; }

static int      re_num_cmp __ARGS((long_u val, char_u *scan));
static int      regmatch __ARGS((char_u *prog));
static int      regrepeat __ARGS((char_u *p, long maxcount));

#ifdef DEBUG
int             regnarrate = 0;
#endif

/*
 * Internal copy of 'ignorecase'.  It is set at each call to vim_regexec().
 * Normally it gets the value of "rm_ic" or "rmm_ic", but when the pattern
 * contains '\c' or '\C' the value is overruled.
 */
static int      ireg_ic;

#ifdef FEAT_MBYTE
/*
 * Similar to ireg_ic, but only for 'combining' characters.  Set with \Z flag
 * in the regexp.  Defaults to false, always.
 */
static int      ireg_icombine;
#endif

/*
 * Copy of "rmm_maxcol": maximum column to search for a match.  Zero when
 * there is no maximum.
 */
static colnr_T  ireg_maxcol;

/*
 * Sometimes need to save a copy of a line.  Since alloc()/free() is very
 * slow, we keep one allocated piece of memory and only re-allocate it when
 * it's too small.  It's freed in vim_regexec_both() when finished.
 */
static char_u   *reg_tofree;
static unsigned reg_tofreelen;

/*
 * These variables are set when executing a regexp to speed up the execution.
 * Which ones are set depends on whether a single-line or multi-line match is
 * done:
 *                      single-line             multi-line
 * reg_match            &regmatch_T             NULL
 * reg_mmatch           NULL                    &regmmatch_T
 * reg_startp           reg_match->startp       <invalid>
 * reg_endp             reg_match->endp         <invalid>
 * reg_startpos         <invalid>               reg_mmatch->startpos
 * reg_endpos           <invalid>               reg_mmatch->endpos
 * reg_win              NULL                    window in which to search
 * reg_buf              <invalid>               buffer in which to search
 * reg_firstlnum        <invalid>               first line in which to search
 * reg_maxline          0                        last line nr
 * reg_line_lbr         FALSE or TRUE           FALSE
 */
static regmatch_T       *reg_match;
static regmmatch_T      *reg_mmatch;
static char_u           **reg_startp = NULL;
static char_u           **reg_endp = NULL;
static lpos_T           *reg_startpos = NULL;
static lpos_T           *reg_endpos = NULL;
static win_T            *reg_win;
static buf_T            *reg_buf;
static linenr_T         reg_firstlnum;
static linenr_T         reg_maxline;
static int              reg_line_lbr;       /* "\n" in string is line break */

/* Values for rs_state in regitem_T. */
typedef enum regstate_E
{
    RS_NOPEN = 0        /* NOPEN and NCLOSE */
    , RS_MOPEN          /* MOPEN + [0-9] */
    , RS_MCLOSE         /* MCLOSE + [0-9] */
#ifdef FEAT_SYN_HL
    , RS_ZOPEN          /* ZOPEN + [0-9] */
    , RS_ZCLOSE         /* ZCLOSE + [0-9] */
#endif
    , RS_BRANCH         /* BRANCH */
    , RS_BRCPLX_MORE    /* BRACE_COMPLEX and trying one more match */
    , RS_BRCPLX_LONG    /* BRACE_COMPLEX and trying longest match */
    , RS_BRCPLX_SHORT   /* BRACE_COMPLEX and trying shortest match */
    , RS_NOMATCH        /* NOMATCH */
    , RS_BEHIND1        /* BEHIND / NOBEHIND matching rest */
    , RS_BEHIND2        /* BEHIND / NOBEHIND matching behind part */
    , RS_STAR_LONG      /* STAR/PLUS/BRACE_SIMPLE longest match */
    , RS_STAR_SHORT     /* STAR/PLUS/BRACE_SIMPLE shortest match */
} regstate_T;

/*
 * When there are alternatives a regstate_T is put on the regstack to remember
 * what we are doing.
 * Before it may be another type of item, depending on rs_state, to remember
 * more things.
 */
typedef struct regitem_S
{
    regstate_T  rs_state;       /* what we are doing, one of RS_ above */
    char_u      *rs_scan;       /* current node in program */
    union
    {
        save_se_T  sesave;
        regsave_T  regsave;
    } rs_un;                    /* room for saving reginput */
    short       rs_no;          /* submatch nr */
} regitem_T;

static regitem_T *regstack_push __ARGS((regstate_T state, char_u *scan));
static void regstack_pop __ARGS((char_u **scan));

/* used for BEHIND and NOBEHIND matching */
typedef struct regbehind_S
{
    regsave_T   save_after;
    regsave_T   save_behind;
} regbehind_T;

/* used for STAR, PLUS and BRACE_SIMPLE matching */
typedef struct regstar_S
{
    int         nextb;          /* next byte */
    int         nextb_ic;       /* next byte reverse case */
    long        count;
    long        minval;
    long        maxval;
} regstar_T;

/* used to store input position when a BACK was encountered, so that we now if
 * we made any progress since the last time. */
typedef struct backpos_S
{
    char_u      *bp_scan;       /* "scan" where BACK was encountered */
    regsave_T   bp_pos;         /* last input position */
} backpos_T;

/*
 * regstack and backpos are used by regmatch().  They are kept over calls to
 * avoid invoking malloc() and free() often.
 */
static garray_T regstack;       /* stack with regitem_T items, sometimes
                                   preceded by regstar_T or regbehind_T. */
static garray_T backpos;        /* table with backpos_T for BACK */

/*
 * Get pointer to the line "lnum", which is relative to "reg_firstlnum".
 */
    static char_u *
reg_getline(lnum)
    linenr_T    lnum;
{
    /* when looking behind for a match/no-match lnum is negative.  But we
     * can't go before line 1 */
    if (reg_firstlnum + lnum < 1)
        return NULL;
    if (lnum > reg_maxline)
        /* Must have matched the "\n" in the last line. */
        return (char_u *)"";
    return ml_get_buf(reg_buf, reg_firstlnum + lnum, FALSE);
}

static regsave_T behind_pos;

#ifdef FEAT_SYN_HL
static char_u   *reg_startzp[NSUBEXP];  /* Workspace to mark beginning */
static char_u   *reg_endzp[NSUBEXP];    /*   and end of \z(...\) matches */
static lpos_T   reg_startzpos[NSUBEXP]; /* idem, beginning pos */
static lpos_T   reg_endzpos[NSUBEXP];   /* idem, end pos */
#endif

/* TRUE if using multi-line regexp. */
#define REG_MULTI       (reg_match == NULL)

/*
 * Match a regexp against a string.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return TRUE if there is a match, FALSE if not.
 */
    int
vim_regexec(rmp, line, col)
    regmatch_T  *rmp;
    char_u      *line;  /* string to match against */
    colnr_T     col;    /* column to start looking for match */
{
    reg_match = rmp;
    reg_mmatch = NULL;
    reg_maxline = 0;
    reg_line_lbr = FALSE;
    reg_win = NULL;
    ireg_ic = rmp->rm_ic;
#ifdef FEAT_MBYTE
    ireg_icombine = FALSE;
#endif
    ireg_maxcol = 0;
    return (vim_regexec_both(line, col) != 0);
}

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) \
        || defined(FIND_REPLACE_DIALOG) || defined(PROTO)
/*
 * Like vim_regexec(), but consider a "\n" in "line" to be a line break.
 */
    int
vim_regexec_nl(rmp, line, col)
    regmatch_T  *rmp;
    char_u      *line;  /* string to match against */
    colnr_T     col;    /* column to start looking for match */
{
    reg_match = rmp;
    reg_mmatch = NULL;
    reg_maxline = 0;
    reg_line_lbr = TRUE;
    reg_win = NULL;
    ireg_ic = rmp->rm_ic;
#ifdef FEAT_MBYTE
    ireg_icombine = FALSE;
#endif
    ireg_maxcol = 0;
    return (vim_regexec_both(line, col) != 0);
}
#endif

/*
 * Match a regexp against multiple lines.
 * "rmp->regprog" is a compiled regexp as returned by vim_regcomp().
 * Uses curbuf for line count and 'iskeyword'.
 *
 * Return zero if there is no match.  Return number of lines contained in the
 * match otherwise.
 */
    long
vim_regexec_multi(rmp, win, buf, lnum, col)
    regmmatch_T *rmp;
    win_T       *win;           /* window in which to search or NULL */
    buf_T       *buf;           /* buffer in which to search */
    linenr_T    lnum;           /* nr of line to start looking for match */
    colnr_T     col;            /* column to start looking for match */
{
    long        r;
    buf_T       *save_curbuf = curbuf;

    reg_match = NULL;
    reg_mmatch = rmp;
    reg_buf = buf;
    reg_win = win;
    reg_firstlnum = lnum;
    reg_maxline = reg_buf->b_ml.ml_line_count - lnum;
    reg_line_lbr = FALSE;
    ireg_ic = rmp->rmm_ic;
#ifdef FEAT_MBYTE
    ireg_icombine = FALSE;
#endif
    ireg_maxcol = rmp->rmm_maxcol;

    /* Need to switch to buffer "buf" to make vim_iswordc() work. */
    curbuf = buf;
    r = vim_regexec_both(NULL, col);
    curbuf = save_curbuf;

    return r;
}

/*
 * Match a regexp against a string ("line" points to the string) or multiple
 * lines ("line" is NULL, use reg_getline()).
 */
    static long
vim_regexec_both(line, col)
    char_u      *line;
    colnr_T     col;            /* column to start looking for match */
{
    regprog_T   *prog;
    char_u      *s;
    long        retval = 0L;

    reg_tofree = NULL;

    /* Init the regstack empty.  Use an item size of 1 byte, since we push
     * different things onto it.  Use a large grow size to avoid reallocating
     * it too often. */
    ga_init2(&regstack, 1, 10000);

    /* Init the backpos table empty. */
    ga_init2(&backpos, sizeof(backpos_T), 10);

    if (REG_MULTI)
    {
        prog = reg_mmatch->regprog;
        line = reg_getline((linenr_T)0);
        reg_startpos = reg_mmatch->startpos;
        reg_endpos = reg_mmatch->endpos;
    }
    else
    {
        prog = reg_match->regprog;
        reg_startp = reg_match->startp;
        reg_endp = reg_match->endp;
    }

    /* Be paranoid... */
    if (prog == NULL || line == NULL)
    {
        EMSG(_(e_null));
        goto theend;
    }

    /* Check validity of program. */
    if (prog_magic_wrong())
        goto theend;

    /* If the start column is past the maximum column: no need to try. */
    if (ireg_maxcol > 0 && col >= ireg_maxcol)
        goto theend;

    /* If pattern contains "\c" or "\C": overrule value of ireg_ic */
    if (prog->regflags & RF_ICASE)
        ireg_ic = TRUE;
    else if (prog->regflags & RF_NOICASE)
        ireg_ic = FALSE;

#ifdef FEAT_MBYTE
    /* If pattern contains "\Z" overrule value of ireg_icombine */
    if (prog->regflags & RF_ICOMBINE)
        ireg_icombine = TRUE;
#endif

    /* If there is a "must appear" string, look for it. */
    if (prog->regmust != NULL)
    {
        int c;

#ifdef FEAT_MBYTE
        if (has_mbyte)
            c = (*mb_ptr2char)(prog->regmust);
        else
#endif
            c = *prog->regmust;
        s = line + col;

        /*
         * This is used very often, esp. for ":global".  Use three versions of
         * the loop to avoid overhead of conditions.
         */
        if (!ireg_ic
#ifdef FEAT_MBYTE
                && !has_mbyte
#endif
                )
            while ((s = vim_strbyte(s, c)) != NULL)
            {
                if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
                    break;              /* Found it. */
                ++s;
            }
#ifdef FEAT_MBYTE
        else if (!ireg_ic || (!enc_utf8 && mb_char2len(c) > 1))
            while ((s = vim_strchr(s, c)) != NULL)
            {
                if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
                    break;              /* Found it. */
                mb_ptr_adv(s);
            }
#endif
        else
            while ((s = cstrchr(s, c)) != NULL)
            {
                if (cstrncmp(s, prog->regmust, &prog->regmlen) == 0)
                    break;              /* Found it. */
                mb_ptr_adv(s);
            }
        if (s == NULL)          /* Not present. */
            goto theend;
    }

    regline = line;
    reglnum = 0;

    /* Simplest case: Anchored match need be tried only once. */
    if (prog->reganch)
    {
        int     c;

#ifdef FEAT_MBYTE
        if (has_mbyte)
            c = (*mb_ptr2char)(regline + col);
        else
#endif
            c = regline[col];
        if (prog->regstart == NUL
                || prog->regstart == c
                || (ireg_ic && ((
#ifdef FEAT_MBYTE
                        (enc_utf8 && utf_fold(prog->regstart) == utf_fold(c)))
                        || (c < 255 && prog->regstart < 255 &&
#endif
                            TOLOWER_LOC(prog->regstart) == TOLOWER_LOC(c)))))
            retval = regtry(prog, col);
        else
            retval = 0;
    }
    else
    {
        /* Messy cases:  unanchored match. */
        while (!got_int)
        {
            if (prog->regstart != NUL)
            {
                /* Skip until the char we know it must start with.
                 * Used often, do some work to avoid call overhead. */
                if (!ireg_ic
#ifdef FEAT_MBYTE
                            && !has_mbyte
#endif
                            )
                    s = vim_strbyte(regline + col, prog->regstart);
                else
                    s = cstrchr(regline + col, prog->regstart);
                if (s == NULL)
                {
                    retval = 0;
                    break;
                }
                col = (int)(s - regline);
            }

            /* Check for maximum column to try. */
            if (ireg_maxcol > 0 && col >= ireg_maxcol)
            {
                retval = 0;
                break;
            }

            retval = regtry(prog, col);
            if (retval > 0)
                break;

            /* if not currently on the first line, get it again */
            if (reglnum != 0)
            {
                reglnum = 0;
                regline = reg_getline((linenr_T)0);
            }
            if (regline[col] == NUL)
                break;
#ifdef FEAT_MBYTE
            if (has_mbyte)
                col += (*mb_ptr2len)(regline + col);
            else
#endif
                ++col;
        }
    }

theend:
    vim_free(reg_tofree);
    ga_clear(&regstack);
    ga_clear(&backpos);

    return retval;
}

#ifdef FEAT_SYN_HL
static reg_extmatch_T *make_extmatch __ARGS((void));

/*
 * Create a new extmatch and mark it as referenced once.
 */
    static reg_extmatch_T *
make_extmatch()
{
    reg_extmatch_T      *em;

    em = (reg_extmatch_T *)alloc_clear((unsigned)sizeof(reg_extmatch_T));
    if (em != NULL)
        em->refcnt = 1;
    return em;
}

/*
 * Add a reference to an extmatch.
 */
    reg_extmatch_T *
ref_extmatch(em)
    reg_extmatch_T      *em;
{
    if (em != NULL)
        em->refcnt++;
    return em;
}

/*
 * Remove a reference to an extmatch.  If there are no references left, free
 * the info.
 */
    void
unref_extmatch(em)
    reg_extmatch_T      *em;
{
    int i;

    if (em != NULL && --em->refcnt <= 0)
    {
        for (i = 0; i < NSUBEXP; ++i)
            vim_free(em->matches[i]);
        vim_free(em);
    }
}
#endif

/*
 * regtry - try match of "prog" with at regline["col"].
 * Returns 0 for failure, number of lines contained in the match otherwise.
 */
    static long
regtry(prog, col)
    regprog_T   *prog;
    colnr_T     col;
{
    reginput = regline + col;
    need_clear_subexpr = TRUE;
#ifdef FEAT_SYN_HL
    /* Clear the external match subpointers if necessary. */
    if (prog->reghasz == REX_SET)
        need_clear_zsubexpr = TRUE;
#endif

    if (regmatch(prog->program + 1) == 0)
        return 0;

    cleanup_subexpr();
    if (REG_MULTI)
    {
        if (reg_startpos[0].lnum < 0)
        {
            reg_startpos[0].lnum = 0;
            reg_startpos[0].col = col;
        }
        if (reg_endpos[0].lnum < 0)
        {
            reg_endpos[0].lnum = reglnum;
            reg_endpos[0].col = (int)(reginput - regline);
        }
        else
            /* Use line number of "\ze". */
            reglnum = reg_endpos[0].lnum;
    }
    else
    {
        if (reg_startp[0] == NULL)
            reg_startp[0] = regline + col;
        if (reg_endp[0] == NULL)
            reg_endp[0] = reginput;
    }
#ifdef FEAT_SYN_HL
    /* Package any found \z(...\) matches for export. Default is none. */
    unref_extmatch(re_extmatch_out);
    re_extmatch_out = NULL;

    if (prog->reghasz == REX_SET)
    {
        int             i;

        cleanup_zsubexpr();
        re_extmatch_out = make_extmatch();
        for (i = 0; i < NSUBEXP; i++)
        {
            if (REG_MULTI)
            {
                /* Only accept single line matches. */
                if (reg_startzpos[i].lnum >= 0
                        && reg_endzpos[i].lnum == reg_startzpos[i].lnum)
                    re_extmatch_out->matches[i] =
                        vim_strnsave(reg_getline(reg_startzpos[i].lnum)
                                                       + reg_startzpos[i].col,
                                   reg_endzpos[i].col - reg_startzpos[i].col);
            }
            else
            {
                if (reg_startzp[i] != NULL && reg_endzp[i] != NULL)
                    re_extmatch_out->matches[i] =
                            vim_strnsave(reg_startzp[i],
                                        (int)(reg_endzp[i] - reg_startzp[i]));
            }
        }
    }
#endif
    return 1 + reglnum;
}

#ifdef FEAT_MBYTE
static int reg_prev_class __ARGS((void));

/*
 * Get class of previous character.
 */
    static int
reg_prev_class()
{
    if (reginput > regline)
        return mb_get_class(reginput - 1
                                     - (*mb_head_off)(regline, reginput - 1));
    return -1;
}

#endif
#define ADVANCE_REGINPUT() mb_ptr_adv(reginput)

/*
 * The arguments from BRACE_LIMITS are stored here.  They are actually local
 * to regmatch(), but they are here to reduce the amount of stack space used
 * (it can be called recursively many times).
 */
static long     bl_minval;
static long     bl_maxval;

/*
 * regmatch - main matching routine
 *
 * Conceptually the strategy is simple: Check to see whether the current node
 * matches, push an item onto the regstack and loop to see whether the rest
 * matches, and then act accordingly.  In practice we make some effort to
 * avoid using the regstack, in particular by going through "ordinary" nodes
 * (that don't need to know whether the rest of the match failed) by a nested
 * loop.
 *
 * Returns TRUE when there is a match.  Leaves reginput and reglnum just after
 * the last matched character.
 * Returns FALSE when there is no match.  Leaves reginput and reglnum in an
 * undefined state!
 */
    static int
regmatch(scan)
    char_u      *scan;          /* Current node. */
{
  char_u        *next;          /* Next node. */
  int           op;
  int           c;
  regitem_T     *rp;
  int           no;
  int           status;         /* one of the RA_ values: */
#define RA_FAIL         1       /* something failed, abort */
#define RA_CONT         2       /* continue in inner loop */
#define RA_BREAK        3       /* break inner loop */
#define RA_MATCH        4       /* successful match */
#define RA_NOMATCH      5       /* didn't match */

  /* Init the regstack and backpos table empty.  They are initialized and
   * freed in vim_regexec_both() to reduce malloc()/free() calls. */
  regstack.ga_len = 0;
  backpos.ga_len = 0;

  /*
   * Repeat until "regstack" is empty.
   */
  for (;;)
  {
    /* Some patterns my cause a long time to match, even though they are not
     * illegal.  E.g., "\([a-z]\+\)\+Q".  Allow breaking them with CTRL-C. */
    fast_breakcheck();

#ifdef DEBUG
    if (scan != NULL && regnarrate)
    {
        mch_errmsg(regprop(scan));
        mch_errmsg("(\n");
    }
#endif

    /*
     * Repeat for items that can be matched sequentially, without using the
     * regstack.
     */
    for (;;)
    {
        if (got_int || scan == NULL)
        {
            status = RA_FAIL;
            break;
        }
        status = RA_CONT;

#ifdef DEBUG
        if (regnarrate)
        {
            mch_errmsg(regprop(scan));
            mch_errmsg("...\n");
# ifdef FEAT_SYN_HL
            if (re_extmatch_in != NULL)
            {
                int i;

                mch_errmsg(_("External submatches:\n"));
                for (i = 0; i < NSUBEXP; i++)
                {
                    mch_errmsg("    \"");
                    if (re_extmatch_in->matches[i] != NULL)
                        mch_errmsg(re_extmatch_in->matches[i]);
                    mch_errmsg("\"\n");
                }
            }
# endif
        }
#endif
        next = regnext(scan);

        op = OP(scan);
        /* Check for character class with NL added. */
        if (!reg_line_lbr && WITH_NL(op) && REG_MULTI
                                && *reginput == NUL && reglnum <= reg_maxline)
        {
            reg_nextline();
        }
        else if (reg_line_lbr && WITH_NL(op) && *reginput == '\n')
        {
            ADVANCE_REGINPUT();
        }
        else
        {
          if (WITH_NL(op))
              op -= ADD_NL;
#ifdef FEAT_MBYTE
          if (has_mbyte)
              c = (*mb_ptr2char)(reginput);
          else
#endif
              c = *reginput;
          switch (op)
          {
          case BOL:
            if (reginput != regline)
                status = RA_NOMATCH;
            break;

          case EOL:
            if (c != NUL)
                status = RA_NOMATCH;
            break;

          case RE_BOF:
            /* Passing -1 to the getline() function provided for the search
             * should always return NULL if the current line is the first
             * line of the file. */
            if (reglnum != 0 || reginput != regline
                        || (REG_MULTI && reg_getline((linenr_T)-1) != NULL))
                status = RA_NOMATCH;
            break;

          case RE_EOF:
            if (reglnum != reg_maxline || c != NUL)
                status = RA_NOMATCH;
            break;

          case CURSOR:
            /* Check if the buffer is in a window and compare the
             * reg_win->w_cursor position to the match position. */
            if (reg_win == NULL
                    || (reglnum + reg_firstlnum != reg_win->w_cursor.lnum)
                    || ((colnr_T)(reginput - regline) != reg_win->w_cursor.col))
                status = RA_NOMATCH;
            break;

          case RE_MARK:
            /* Compare the mark position to the match position.  NOTE: Always
             * uses the current buffer. */
            {
                int     mark = OPERAND(scan)[0];
                int     cmp = OPERAND(scan)[1];
                pos_T   *pos;

                pos = getmark(mark, FALSE);
                if (pos == NULL              /* mark doesn't exist */
                        || pos->lnum <= 0    /* mark isn't set (in curbuf) */
                        || (pos->lnum == reglnum + reg_firstlnum
                                ? (pos->col == (colnr_T)(reginput - regline)
                                    ? (cmp == '<' || cmp == '>')
                                    : (pos->col < (colnr_T)(reginput - regline)
                                        ? cmp != '>'
                                        : cmp != '<'))
                                : (pos->lnum < reglnum + reg_firstlnum
                                    ? cmp != '>'
                                    : cmp != '<')))
                    status = RA_NOMATCH;
            }
            break;

          case RE_VISUAL:
#ifdef FEAT_VISUAL
            /* Check if the buffer is the current buffer. and whether the
             * position is inside the Visual area. */
            if (reg_buf != curbuf || VIsual.lnum == 0)
                status = RA_NOMATCH;
            else
            {
                pos_T       top, bot;
                linenr_T    lnum;
                colnr_T     col;
                win_T       *wp = reg_win == NULL ? curwin : reg_win;
                int         mode;

                if (VIsual_active)
                {
                    if (lt(VIsual, wp->w_cursor))
                    {
                        top = VIsual;
                        bot = wp->w_cursor;
                    }
                    else
                    {
                        top = wp->w_cursor;
                        bot = VIsual;
                    }
                    mode = VIsual_mode;
                }
                else
                {
                    if (lt(curbuf->b_visual.vi_start, curbuf->b_visual.vi_end))
                    {
                        top = curbuf->b_visual.vi_start;
                        bot = curbuf->b_visual.vi_end;
                    }
                    else
                    {
                        top = curbuf->b_visual.vi_end;
                        bot = curbuf->b_visual.vi_start;
                    }
                    mode = curbuf->b_visual.vi_mode;
                }
                lnum = reglnum + reg_firstlnum;
                col = (colnr_T)(reginput - regline);
                if (lnum < top.lnum || lnum > bot.lnum)
                    status = RA_NOMATCH;
                else if (mode == 'v')
                {
                    if ((lnum == top.lnum && col < top.col)
                            || (lnum == bot.lnum
                                         && col >= bot.col + (*p_sel != 'e')))
                        status = RA_NOMATCH;
                }
                else if (mode == Ctrl_V)
                {
                    colnr_T         start, end;
                    colnr_T         start2, end2;
                    colnr_T         cols;

                    getvvcol(wp, &top, &start, NULL, &end);
                    getvvcol(wp, &bot, &start2, NULL, &end2);
                    if (start2 < start)
                        start = start2;
                    if (end2 > end)
                        end = end2;
                    if (top.col == MAXCOL || bot.col == MAXCOL)
                        end = MAXCOL;
                    cols = win_linetabsize(wp,
                                      regline, (colnr_T)(reginput - regline));
                    if (cols < start || cols > end - (*p_sel == 'e'))
                        status = RA_NOMATCH;
                }
            }
#else
            status = RA_NOMATCH;
#endif
            break;

          case RE_LNUM:
            if (!REG_MULTI || !re_num_cmp((long_u)(reglnum + reg_firstlnum),
                                                                        scan))
                status = RA_NOMATCH;
            break;

          case RE_COL:
            if (!re_num_cmp((long_u)(reginput - regline) + 1, scan))
                status = RA_NOMATCH;
            break;

          case RE_VCOL:
            if (!re_num_cmp((long_u)win_linetabsize(
                            reg_win == NULL ? curwin : reg_win,
                            regline, (colnr_T)(reginput - regline)) + 1, scan))
                status = RA_NOMATCH;
            break;

          case BOW:     /* \<word; reginput points to w */
            if (c == NUL)       /* Can't match at end of line */
                status = RA_NOMATCH;
#ifdef FEAT_MBYTE
            else if (has_mbyte)
            {
                int this_class;

                /* Get class of current and previous char (if it exists). */
                this_class = mb_get_class(reginput);
                if (this_class <= 1)
                    status = RA_NOMATCH;  /* not on a word at all */
                else if (reg_prev_class() == this_class)
                    status = RA_NOMATCH;  /* previous char is in same word */
            }
#endif
            else
            {
                if (!vim_iswordc(c)
                        || (reginput > regline && vim_iswordc(reginput[-1])))
                    status = RA_NOMATCH;
            }
            break;

          case EOW:     /* word\>; reginput points after d */
            if (reginput == regline)    /* Can't match at start of line */
                status = RA_NOMATCH;
#ifdef FEAT_MBYTE
            else if (has_mbyte)
            {
                int this_class, prev_class;

                /* Get class of current and previous char (if it exists). */
                this_class = mb_get_class(reginput);
                prev_class = reg_prev_class();
                if (this_class == prev_class
                        || prev_class == 0 || prev_class == 1)
                    status = RA_NOMATCH;
            }
#endif
            else
            {
                if (!vim_iswordc(reginput[-1])
                        || (reginput[0] != NUL && vim_iswordc(c)))
                    status = RA_NOMATCH;
            }
            break; /* Matched with EOW */

          case ANY:
            if (c == NUL)
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case IDENT:
            if (!vim_isIDc(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case SIDENT:
            if (VIM_ISDIGIT(*reginput) || !vim_isIDc(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case KWORD:
            if (!vim_iswordp(reginput))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case SKWORD:
            if (VIM_ISDIGIT(*reginput) || !vim_iswordp(reginput))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case FNAME:
            if (!vim_isfilec(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case SFNAME:
            if (VIM_ISDIGIT(*reginput) || !vim_isfilec(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case PRINT:
            if (ptr2cells(reginput) != 1)
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case SPRINT:
            if (VIM_ISDIGIT(*reginput) || ptr2cells(reginput) != 1)
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case WHITE:
            if (!vim_iswhite(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NWHITE:
            if (c == NUL || vim_iswhite(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case DIGIT:
            if (!ri_digit(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NDIGIT:
            if (c == NUL || ri_digit(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case HEX:
            if (!ri_hex(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NHEX:
            if (c == NUL || ri_hex(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case OCTAL:
            if (!ri_octal(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NOCTAL:
            if (c == NUL || ri_octal(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case WORD:
            if (!ri_word(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NWORD:
            if (c == NUL || ri_word(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case HEAD:
            if (!ri_head(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NHEAD:
            if (c == NUL || ri_head(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case ALPHA:
            if (!ri_alpha(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NALPHA:
            if (c == NUL || ri_alpha(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case LOWER:
            if (!ri_lower(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NLOWER:
            if (c == NUL || ri_lower(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case UPPER:
            if (!ri_upper(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case NUPPER:
            if (c == NUL || ri_upper(c))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

          case EXACTLY:
            {
                int     len;
                char_u  *opnd;

                opnd = OPERAND(scan);
                /* Inline the first byte, for speed. */
                if (*opnd != *reginput
                        && (!ireg_ic || (
#ifdef FEAT_MBYTE
                            !enc_utf8 &&
#endif
                            TOLOWER_LOC(*opnd) != TOLOWER_LOC(*reginput))))
                    status = RA_NOMATCH;
                else if (*opnd == NUL)
                {
                    /* match empty string always works; happens when "~" is
                     * empty. */
                }
                else if (opnd[1] == NUL
#ifdef FEAT_MBYTE
                            && !(enc_utf8 && ireg_ic)
#endif
                        )
                    ++reginput;         /* matched a single char */
                else
                {
                    len = (int)STRLEN(opnd);
                    /* Need to match first byte again for multi-byte. */
                    if (cstrncmp(opnd, reginput, &len) != 0)
                        status = RA_NOMATCH;
#ifdef FEAT_MBYTE
                    /* Check for following composing character. */
                    else if (enc_utf8
                               && UTF_COMPOSINGLIKE(reginput, reginput + len))
                    {
                        /* raaron: This code makes a composing character get
                         * ignored, which is the correct behavior (sometimes)
                         * for voweled Hebrew texts. */
                        if (!ireg_icombine)
                            status = RA_NOMATCH;
                    }
#endif
                    else
                        reginput += len;
                }
            }
            break;

          case ANYOF:
          case ANYBUT:
            if (c == NUL)
                status = RA_NOMATCH;
            else if ((cstrchr(OPERAND(scan), c) == NULL) == (op == ANYOF))
                status = RA_NOMATCH;
            else
                ADVANCE_REGINPUT();
            break;

#ifdef FEAT_MBYTE
          case MULTIBYTECODE:
            if (has_mbyte)
            {
                int     i, len;
                char_u  *opnd;
                int     opndc = 0, inpc;

                opnd = OPERAND(scan);
                /* Safety check (just in case 'encoding' was changed since
                 * compiling the program). */
                if ((len = (*mb_ptr2len)(opnd)) < 2)
                {
                    status = RA_NOMATCH;
                    break;
                }
                if (enc_utf8)
                    opndc = mb_ptr2char(opnd);
                if (enc_utf8 && utf_iscomposing(opndc))
                {
                    /* When only a composing char is given match at any
                     * position where that composing char appears. */
                    status = RA_NOMATCH;
                    for (i = 0; reginput[i] != NUL; i += utf_char2len(inpc))
                    {
                        inpc = mb_ptr2char(reginput + i);
                        if (!utf_iscomposing(inpc))
                        {
                            if (i > 0)
                                break;
                        }
                        else if (opndc == inpc)
                        {
                            /* Include all following composing chars. */
                            len = i + mb_ptr2len(reginput + i);
                            status = RA_MATCH;
                            break;
                        }
                    }
                }
                else
                    for (i = 0; i < len; ++i)
                        if (opnd[i] != reginput[i])
                        {
                            status = RA_NOMATCH;
                            break;
                        }
                reginput += len;
            }
            else
                status = RA_NOMATCH;
            break;
#endif

          case NOTHING:
            break;

          case BACK:
            {
                int             i;
                backpos_T       *bp;

                /*
                 * When we run into BACK we need to check if we don't keep
                 * looping without matching any input.  The second and later
                 * times a BACK is encountered it fails if the input is still
                 * at the same position as the previous time.
                 * The positions are stored in "backpos" and found by the
                 * current value of "scan", the position in the RE program.
                 */
                bp = (backpos_T *)backpos.ga_data;
                for (i = 0; i < backpos.ga_len; ++i)
                    if (bp[i].bp_scan == scan)
                        break;
                if (i == backpos.ga_len)
                {
                    /* First time at this BACK, make room to store the pos. */
                    if (ga_grow(&backpos, 1) == FAIL)
                        status = RA_FAIL;
                    else
                    {
                        /* get "ga_data" again, it may have changed */
                        bp = (backpos_T *)backpos.ga_data;
                        bp[i].bp_scan = scan;
                        ++backpos.ga_len;
                    }
                }
                else if (reg_save_equal(&bp[i].bp_pos))
                    /* Still at same position as last time, fail. */
                    status = RA_NOMATCH;

                if (status != RA_FAIL && status != RA_NOMATCH)
                    reg_save(&bp[i].bp_pos, &backpos);
            }
            break;

          case MOPEN + 0:   /* Match start: \zs */
          case MOPEN + 1:   /* \( */
          case MOPEN + 2:
          case MOPEN + 3:
          case MOPEN + 4:
          case MOPEN + 5:
          case MOPEN + 6:
          case MOPEN + 7:
          case MOPEN + 8:
          case MOPEN + 9:
            {
                no = op - MOPEN;
                cleanup_subexpr();
                rp = regstack_push(RS_MOPEN, scan);
                if (rp == NULL)
                    status = RA_FAIL;
                else
                {
                    rp->rs_no = no;
                    save_se(&rp->rs_un.sesave, &reg_startpos[no],
                                                             &reg_startp[no]);
                    /* We simply continue and handle the result when done. */
                }
            }
            break;

          case NOPEN:       /* \%( */
          case NCLOSE:      /* \) after \%( */
                if (regstack_push(RS_NOPEN, scan) == NULL)
                    status = RA_FAIL;
                /* We simply continue and handle the result when done. */
                break;

#ifdef FEAT_SYN_HL
          case ZOPEN + 1:
          case ZOPEN + 2:
          case ZOPEN + 3:
          case ZOPEN + 4:
          case ZOPEN + 5:
          case ZOPEN + 6:
          case ZOPEN + 7:
          case ZOPEN + 8:
          case ZOPEN + 9:
            {
                no = op - ZOPEN;
                cleanup_zsubexpr();
                rp = regstack_push(RS_ZOPEN, scan);
                if (rp == NULL)
                    status = RA_FAIL;
                else
                {
                    rp->rs_no = no;
                    save_se(&rp->rs_un.sesave, &reg_startzpos[no],
                                                             &reg_startzp[no]);
                    /* We simply continue and handle the result when done. */
                }
            }
            break;
#endif

          case MCLOSE + 0:  /* Match end: \ze */
          case MCLOSE + 1:  /* \) */
          case MCLOSE + 2:
          case MCLOSE + 3:
          case MCLOSE + 4:
          case MCLOSE + 5:
          case MCLOSE + 6:
          case MCLOSE + 7:
          case MCLOSE + 8:
          case MCLOSE + 9:
            {
                no = op - MCLOSE;
                cleanup_subexpr();
                rp = regstack_push(RS_MCLOSE, scan);
                if (rp == NULL)
                    status = RA_FAIL;
                else
                {
                    rp->rs_no = no;
                    save_se(&rp->rs_un.sesave, &reg_endpos[no], &reg_endp[no]);
                    /* We simply continue and handle the result when done. */
                }
            }
            break;

#ifdef FEAT_SYN_HL
          case ZCLOSE + 1:  /* \) after \z( */
          case ZCLOSE + 2:
          case ZCLOSE + 3:
          case ZCLOSE + 4:
          case ZCLOSE + 5:
          case ZCLOSE + 6:
          case ZCLOSE + 7:
          case ZCLOSE + 8:
          case ZCLOSE + 9:
            {
                no = op - ZCLOSE;
                cleanup_zsubexpr();
                rp = regstack_push(RS_ZCLOSE, scan);
                if (rp == NULL)
                    status = RA_FAIL;
                else
                {
                    rp->rs_no = no;
                    save_se(&rp->rs_un.sesave, &reg_endzpos[no],
                                                              &reg_endzp[no]);
                    /* We simply continue and handle the result when done. */
                }
            }
            break;
#endif

          case BACKREF + 1:
          case BACKREF + 2:
          case BACKREF + 3:
          case BACKREF + 4:
          case BACKREF + 5:
          case BACKREF + 6:
          case BACKREF + 7:
          case BACKREF + 8:
          case BACKREF + 9:
            {
                int             len;
                linenr_T        clnum;
                colnr_T         ccol;
                char_u          *p;

                no = op - BACKREF;
                cleanup_subexpr();
                if (!REG_MULTI)         /* Single-line regexp */
                {
                    if (reg_endp[no] == NULL)
                    {
                        /* Backref was not set: Match an empty string. */
                        len = 0;
                    }
                    else
                    {
                        /* Compare current input with back-ref in the same
                         * line. */
                        len = (int)(reg_endp[no] - reg_startp[no]);
                        if (cstrncmp(reg_startp[no], reginput, &len) != 0)
                            status = RA_NOMATCH;
                    }
                }
                else                            /* Multi-line regexp */
                {
                    if (reg_endpos[no].lnum < 0)
                    {
                        /* Backref was not set: Match an empty string. */
                        len = 0;
                    }
                    else
                    {
                        if (reg_startpos[no].lnum == reglnum
                                && reg_endpos[no].lnum == reglnum)
                        {
                            /* Compare back-ref within the current line. */
                            len = reg_endpos[no].col - reg_startpos[no].col;
                            if (cstrncmp(regline + reg_startpos[no].col,
                                                          reginput, &len) != 0)
                                status = RA_NOMATCH;
                        }
                        else
                        {
                            /* Messy situation: Need to compare between two
                             * lines. */
                            ccol = reg_startpos[no].col;
                            clnum = reg_startpos[no].lnum;
                            for (;;)
                            {
                                /* Since getting one line may invalidate
                                 * the other, need to make copy.  Slow! */
                                if (regline != reg_tofree)
                                {
                                    len = (int)STRLEN(regline);
                                    if (reg_tofree == NULL
                                                 || len >= (int)reg_tofreelen)
                                    {
                                        len += 50;      /* get some extra */
                                        vim_free(reg_tofree);
                                        reg_tofree = alloc(len);
                                        if (reg_tofree == NULL)
                                        {
                                            status = RA_FAIL; /* outof memory!*/
                                            break;
                                        }
                                        reg_tofreelen = len;
                                    }
                                    STRCPY(reg_tofree, regline);
                                    reginput = reg_tofree
                                                       + (reginput - regline);
                                    regline = reg_tofree;
                                }

                                /* Get the line to compare with. */
                                p = reg_getline(clnum);
                                if (clnum == reg_endpos[no].lnum)
                                    len = reg_endpos[no].col - ccol;
                                else
                                    len = (int)STRLEN(p + ccol);

                                if (cstrncmp(p + ccol, reginput, &len) != 0)
                                {
                                    status = RA_NOMATCH;  /* doesn't match */
                                    break;
                                }
                                if (clnum == reg_endpos[no].lnum)
                                    break;              /* match and at end! */
                                if (reglnum >= reg_maxline)
                                {
                                    status = RA_NOMATCH;  /* text too short */
                                    break;
                                }

                                /* Advance to next line. */
                                reg_nextline();
                                ++clnum;
                                ccol = 0;
                                if (got_int)
                                {
                                    status = RA_FAIL;
                                    break;
                                }
                            }

                            /* found a match!  Note that regline may now point
                             * to a copy of the line, that should not matter. */
                        }
                    }
                }

                /* Matched the backref, skip over it. */
                reginput += len;
            }
            break;

#ifdef FEAT_SYN_HL
          case ZREF + 1:
          case ZREF + 2:
          case ZREF + 3:
          case ZREF + 4:
          case ZREF + 5:
          case ZREF + 6:
          case ZREF + 7:
          case ZREF + 8:
          case ZREF + 9:
            {
                int     len;

                cleanup_zsubexpr();
                no = op - ZREF;
                if (re_extmatch_in != NULL
                        && re_extmatch_in->matches[no] != NULL)
                {
                    len = (int)STRLEN(re_extmatch_in->matches[no]);
                    if (cstrncmp(re_extmatch_in->matches[no],
                                                          reginput, &len) != 0)
                        status = RA_NOMATCH;
                    else
                        reginput += len;
                }
                else
                {
                    /* Backref was not set: Match an empty string. */
                }
            }
            break;
#endif

          case BRANCH:
            {
                if (OP(next) != BRANCH) /* No choice. */
                    next = OPERAND(scan);       /* Avoid recursion. */
                else
                {
                    rp = regstack_push(RS_BRANCH, scan);
                    if (rp == NULL)
                        status = RA_FAIL;
                    else
                        status = RA_BREAK;      /* rest is below */
                }
            }
            break;

          case BRACE_LIMITS:
            {
                if (OP(next) == BRACE_SIMPLE)
                {
                    bl_minval = OPERAND_MIN(scan);
                    bl_maxval = OPERAND_MAX(scan);
                }
                else if (OP(next) >= BRACE_COMPLEX
                        && OP(next) < BRACE_COMPLEX + 10)
                {
                    no = OP(next) - BRACE_COMPLEX;
                    brace_min[no] = OPERAND_MIN(scan);
                    brace_max[no] = OPERAND_MAX(scan);
                    brace_count[no] = 0;
                }
                else
                {
                    EMSG(_(e_internal));            /* Shouldn't happen */
                    status = RA_FAIL;
                }
            }
            break;

          case BRACE_COMPLEX + 0:
          case BRACE_COMPLEX + 1:
          case BRACE_COMPLEX + 2:
          case BRACE_COMPLEX + 3:
          case BRACE_COMPLEX + 4:
          case BRACE_COMPLEX + 5:
          case BRACE_COMPLEX + 6:
          case BRACE_COMPLEX + 7:
          case BRACE_COMPLEX + 8:
          case BRACE_COMPLEX + 9:
            {
                no = op - BRACE_COMPLEX;
                ++brace_count[no];

                /* If not matched enough times yet, try one more */
                if (brace_count[no] <= (brace_min[no] <= brace_max[no]
                                             ? brace_min[no] : brace_max[no]))
                {
                    rp = regstack_push(RS_BRCPLX_MORE, scan);
                    if (rp == NULL)
                        status = RA_FAIL;
                    else
                    {
                        rp->rs_no = no;
                        reg_save(&rp->rs_un.regsave, &backpos);
                        next = OPERAND(scan);
                        /* We continue and handle the result when done. */
                    }
                    break;
                }

                /* If matched enough times, may try matching some more */
                if (brace_min[no] <= brace_max[no])
                {
                    /* Range is the normal way around, use longest match */
                    if (brace_count[no] <= brace_max[no])
                    {
                        rp = regstack_push(RS_BRCPLX_LONG, scan);
                        if (rp == NULL)
                            status = RA_FAIL;
                        else
                        {
                            rp->rs_no = no;
                            reg_save(&rp->rs_un.regsave, &backpos);
                            next = OPERAND(scan);
                            /* We continue and handle the result when done. */
                        }
                    }
                }
                else
                {
                    /* Range is backwards, use shortest match first */
                    if (brace_count[no] <= brace_min[no])
                    {
                        rp = regstack_push(RS_BRCPLX_SHORT, scan);
                        if (rp == NULL)
                            status = RA_FAIL;
                        else
                        {
                            reg_save(&rp->rs_un.regsave, &backpos);
                            /* We continue and handle the result when done. */
                        }
                    }
                }
            }
            break;

          case BRACE_SIMPLE:
          case STAR:
          case PLUS:
            {
                regstar_T       rst;

                /*
                 * Lookahead to avoid useless match attempts when we know
                 * what character comes next.
                 */
                if (OP(next) == EXACTLY)
                {
                    rst.nextb = *OPERAND(next);
                    if (ireg_ic)
                    {
                        if (isupper(rst.nextb))
                            rst.nextb_ic = TOLOWER_LOC(rst.nextb);
                        else
                            rst.nextb_ic = TOUPPER_LOC(rst.nextb);
                    }
                    else
                        rst.nextb_ic = rst.nextb;
                }
                else
                {
                    rst.nextb = NUL;
                    rst.nextb_ic = NUL;
                }
                if (op != BRACE_SIMPLE)
                {
                    rst.minval = (op == STAR) ? 0 : 1;
                    rst.maxval = MAX_LIMIT;
                }
                else
                {
                    rst.minval = bl_minval;
                    rst.maxval = bl_maxval;
                }

                /*
                 * When maxval > minval, try matching as much as possible, up
                 * to maxval.  When maxval < minval, try matching at least the
                 * minimal number (since the range is backwards, that's also
                 * maxval!).
                 */
                rst.count = regrepeat(OPERAND(scan), rst.maxval);
                if (got_int)
                {
                    status = RA_FAIL;
                    break;
                }
                if (rst.minval <= rst.maxval
                          ? rst.count >= rst.minval : rst.count >= rst.maxval)
                {
                    /* It could match.  Prepare for trying to match what
                     * follows.  The code is below.  Parameters are stored in
                     * a regstar_T on the regstack. */
                    if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
                    {
                        EMSG(_(e_maxmempat));
                        status = RA_FAIL;
                    }
                    else if (ga_grow(&regstack, sizeof(regstar_T)) == FAIL)
                        status = RA_FAIL;
                    else
                    {
                        regstack.ga_len += sizeof(regstar_T);
                        rp = regstack_push(rst.minval <= rst.maxval
                                        ? RS_STAR_LONG : RS_STAR_SHORT, scan);
                        if (rp == NULL)
                            status = RA_FAIL;
                        else
                        {
                            *(((regstar_T *)rp) - 1) = rst;
                            status = RA_BREAK;      /* skip the restore bits */
                        }
                    }
                }
                else
                    status = RA_NOMATCH;

            }
            break;

          case NOMATCH:
          case MATCH:
          case SUBPAT:
            rp = regstack_push(RS_NOMATCH, scan);
            if (rp == NULL)
                status = RA_FAIL;
            else
            {
                rp->rs_no = op;
                reg_save(&rp->rs_un.regsave, &backpos);
                next = OPERAND(scan);
                /* We continue and handle the result when done. */
            }
            break;

          case BEHIND:
          case NOBEHIND:
            /* Need a bit of room to store extra positions. */
            if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
            {
                EMSG(_(e_maxmempat));
                status = RA_FAIL;
            }
            else if (ga_grow(&regstack, sizeof(regbehind_T)) == FAIL)
                status = RA_FAIL;
            else
            {
                regstack.ga_len += sizeof(regbehind_T);
                rp = regstack_push(RS_BEHIND1, scan);
                if (rp == NULL)
                    status = RA_FAIL;
                else
                {
                    rp->rs_no = op;
                    reg_save(&rp->rs_un.regsave, &backpos);
                    /* First try if what follows matches.  If it does then we
                     * check the behind match by looping. */
                }
            }
            break;

          case BHPOS:
            if (REG_MULTI)
            {
                if (behind_pos.rs_u.pos.col != (colnr_T)(reginput - regline)
                        || behind_pos.rs_u.pos.lnum != reglnum)
                    status = RA_NOMATCH;
            }
            else if (behind_pos.rs_u.ptr != reginput)
                status = RA_NOMATCH;
            break;

          case NEWL:
            if ((c != NUL || !REG_MULTI || reglnum > reg_maxline
                             || reg_line_lbr) && (c != '\n' || !reg_line_lbr))
                status = RA_NOMATCH;
            else if (reg_line_lbr)
                ADVANCE_REGINPUT();
            else
                reg_nextline();
            break;

          case END:
            status = RA_MATCH;  /* Success! */
            break;

          default:
            EMSG(_(e_re_corr));
#ifdef DEBUG
            printf("Illegal op code %d\n", op);
#endif
            status = RA_FAIL;
            break;
          }
        }

        /* If we can't continue sequentially, break the inner loop. */
        if (status != RA_CONT)
            break;

        /* Continue in inner loop, advance to next item. */
        scan = next;

    } /* end of inner loop */

    /*
     * If there is something on the regstack execute the code for the state.
     * If the state is popped then loop and use the older state.
     */
    while (regstack.ga_len > 0 && status != RA_FAIL)
    {
        rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
        switch (rp->rs_state)
        {
          case RS_NOPEN:
            /* Result is passed on as-is, simply pop the state. */
            regstack_pop(&scan);
            break;

          case RS_MOPEN:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
                restore_se(&rp->rs_un.sesave, &reg_startpos[rp->rs_no],
                                                  &reg_startp[rp->rs_no]);
            regstack_pop(&scan);
            break;

#ifdef FEAT_SYN_HL
          case RS_ZOPEN:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
                restore_se(&rp->rs_un.sesave, &reg_startzpos[rp->rs_no],
                                                 &reg_startzp[rp->rs_no]);
            regstack_pop(&scan);
            break;
#endif

          case RS_MCLOSE:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
                restore_se(&rp->rs_un.sesave, &reg_endpos[rp->rs_no],
                                                    &reg_endp[rp->rs_no]);
            regstack_pop(&scan);
            break;

#ifdef FEAT_SYN_HL
          case RS_ZCLOSE:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
                restore_se(&rp->rs_un.sesave, &reg_endzpos[rp->rs_no],
                                                   &reg_endzp[rp->rs_no]);
            regstack_pop(&scan);
            break;
#endif

          case RS_BRANCH:
            if (status == RA_MATCH)
                /* this branch matched, use it */
                regstack_pop(&scan);
            else
            {
                if (status != RA_BREAK)
                {
                    /* After a non-matching branch: try next one. */
                    reg_restore(&rp->rs_un.regsave, &backpos);
                    scan = rp->rs_scan;
                }
                if (scan == NULL || OP(scan) != BRANCH)
                {
                    /* no more branches, didn't find a match */
                    status = RA_NOMATCH;
                    regstack_pop(&scan);
                }
                else
                {
                    /* Prepare to try a branch. */
                    rp->rs_scan = regnext(scan);
                    reg_save(&rp->rs_un.regsave, &backpos);
                    scan = OPERAND(scan);
                }
            }
            break;

          case RS_BRCPLX_MORE:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
            {
                reg_restore(&rp->rs_un.regsave, &backpos);
                --brace_count[rp->rs_no];       /* decrement match count */
            }
            regstack_pop(&scan);
            break;

          case RS_BRCPLX_LONG:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
            {
                /* There was no match, but we did find enough matches. */
                reg_restore(&rp->rs_un.regsave, &backpos);
                --brace_count[rp->rs_no];
                /* continue with the items after "\{}" */
                status = RA_CONT;
            }
            regstack_pop(&scan);
            if (status == RA_CONT)
                scan = regnext(scan);
            break;

          case RS_BRCPLX_SHORT:
            /* Pop the state.  Restore pointers when there is no match. */
            if (status == RA_NOMATCH)
                /* There was no match, try to match one more item. */
                reg_restore(&rp->rs_un.regsave, &backpos);
            regstack_pop(&scan);
            if (status == RA_NOMATCH)
            {
                scan = OPERAND(scan);
                status = RA_CONT;
            }
            break;

          case RS_NOMATCH:
            /* Pop the state.  If the operand matches for NOMATCH or
             * doesn't match for MATCH/SUBPAT, we fail.  Otherwise backup,
             * except for SUBPAT, and continue with the next item. */
            if (status == (rp->rs_no == NOMATCH ? RA_MATCH : RA_NOMATCH))
                status = RA_NOMATCH;
            else
            {
                status = RA_CONT;
                if (rp->rs_no != SUBPAT)        /* zero-width */
                    reg_restore(&rp->rs_un.regsave, &backpos);
            }
            regstack_pop(&scan);
            if (status == RA_CONT)
                scan = regnext(scan);
            break;

          case RS_BEHIND1:
            if (status == RA_NOMATCH)
            {
                regstack_pop(&scan);
                regstack.ga_len -= sizeof(regbehind_T);
            }
            else
            {
                /* The stuff after BEHIND/NOBEHIND matches.  Now try if
                 * the behind part does (not) match before the current
                 * position in the input.  This must be done at every
                 * position in the input and checking if the match ends at
                 * the current position. */

                /* save the position after the found match for next */
                reg_save(&(((regbehind_T *)rp) - 1)->save_after, &backpos);

                /* start looking for a match with operand at the current
                 * position.  Go back one character until we find the
                 * result, hitting the start of the line or the previous
                 * line (for multi-line matching).
                 * Set behind_pos to where the match should end, BHPOS
                 * will match it.  Save the current value. */
                (((regbehind_T *)rp) - 1)->save_behind = behind_pos;
                behind_pos = rp->rs_un.regsave;

                rp->rs_state = RS_BEHIND2;

                reg_restore(&rp->rs_un.regsave, &backpos);
                scan = OPERAND(rp->rs_scan);
            }
            break;

          case RS_BEHIND2:
            /*
             * Looping for BEHIND / NOBEHIND match.
             */
            if (status == RA_MATCH && reg_save_equal(&behind_pos))
            {
                /* found a match that ends where "next" started */
                behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
                if (rp->rs_no == BEHIND)
                    reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
                                                                    &backpos);
                else
                    /* But we didn't want a match. */
                    status = RA_NOMATCH;
                regstack_pop(&scan);
                regstack.ga_len -= sizeof(regbehind_T);
            }
            else
            {
                /* No match: Go back one character.  May go to previous
                 * line once. */
                no = OK;
                if (REG_MULTI)
                {
                    if (rp->rs_un.regsave.rs_u.pos.col == 0)
                    {
                        if (rp->rs_un.regsave.rs_u.pos.lnum
                                        < behind_pos.rs_u.pos.lnum
                                || reg_getline(
                                        --rp->rs_un.regsave.rs_u.pos.lnum)
                                                                  == NULL)
                            no = FAIL;
                        else
                        {
                            reg_restore(&rp->rs_un.regsave, &backpos);
                            rp->rs_un.regsave.rs_u.pos.col =
                                                 (colnr_T)STRLEN(regline);
                        }
                    }
                    else
                        --rp->rs_un.regsave.rs_u.pos.col;
                }
                else
                {
                    if (rp->rs_un.regsave.rs_u.ptr == regline)
                        no = FAIL;
                    else
                        --rp->rs_un.regsave.rs_u.ptr;
                }
                if (no == OK)
                {
                    /* Advanced, prepare for finding match again. */
                    reg_restore(&rp->rs_un.regsave, &backpos);
                    scan = OPERAND(rp->rs_scan);
                }
                else
                {
                    /* Can't advance.  For NOBEHIND that's a match. */
                    behind_pos = (((regbehind_T *)rp) - 1)->save_behind;
                    if (rp->rs_no == NOBEHIND)
                    {
                        reg_restore(&(((regbehind_T *)rp) - 1)->save_after,
                                                                    &backpos);
                        status = RA_MATCH;
                    }
                    else
                        status = RA_NOMATCH;
                    regstack_pop(&scan);
                    regstack.ga_len -= sizeof(regbehind_T);
                }
            }
            break;

          case RS_STAR_LONG:
          case RS_STAR_SHORT:
            {
                regstar_T           *rst = ((regstar_T *)rp) - 1;

                if (status == RA_MATCH)
                {
                    regstack_pop(&scan);
                    regstack.ga_len -= sizeof(regstar_T);
                    break;
                }

                /* Tried once already, restore input pointers. */
                if (status != RA_BREAK)
                    reg_restore(&rp->rs_un.regsave, &backpos);

                /* Repeat until we found a position where it could match. */
                for (;;)
                {
                    if (status != RA_BREAK)
                    {
                        /* Tried first position already, advance. */
                        if (rp->rs_state == RS_STAR_LONG)
                        {
                            /* Trying for longest match, but couldn't or
                             * didn't match -- back up one char. */
                            if (--rst->count < rst->minval)
                                break;
                            if (reginput == regline)
                            {
                                /* backup to last char of previous line */
                                --reglnum;
                                regline = reg_getline(reglnum);
                                /* Just in case regrepeat() didn't count
                                 * right. */
                                if (regline == NULL)
                                    break;
                                reginput = regline + STRLEN(regline);
                                fast_breakcheck();
                            }
                            else
                                mb_ptr_back(regline, reginput);
                        }
                        else
                        {
                            /* Range is backwards, use shortest match first.
                             * Careful: maxval and minval are exchanged!
                             * Couldn't or didn't match: try advancing one
                             * char. */
                            if (rst->count == rst->minval
                                  || regrepeat(OPERAND(rp->rs_scan), 1L) == 0)
                                break;
                            ++rst->count;
                        }
                        if (got_int)
                            break;
                    }
                    else
                        status = RA_NOMATCH;

                    /* If it could match, try it. */
                    if (rst->nextb == NUL || *reginput == rst->nextb
                                             || *reginput == rst->nextb_ic)
                    {
                        reg_save(&rp->rs_un.regsave, &backpos);
                        scan = regnext(rp->rs_scan);
                        status = RA_CONT;
                        break;
                    }
                }
                if (status != RA_CONT)
                {
                    /* Failed. */
                    regstack_pop(&scan);
                    regstack.ga_len -= sizeof(regstar_T);
                    status = RA_NOMATCH;
                }
            }
            break;
        }

        /* If we want to continue the inner loop or didn't pop a state
         * continue matching loop */
        if (status == RA_CONT || rp == (regitem_T *)
                             ((char *)regstack.ga_data + regstack.ga_len) - 1)
            break;
    }

    /* May need to continue with the inner loop, starting at "scan". */
    if (status == RA_CONT)
        continue;

    /*
     * If the regstack is empty or something failed we are done.
     */
    if (regstack.ga_len == 0 || status == RA_FAIL)
    {
        if (scan == NULL)
        {
            /*
             * We get here only if there's trouble -- normally "case END" is
             * the terminating point.
             */
            EMSG(_(e_re_corr));
#ifdef DEBUG
            printf("Premature EOL\n");
#endif
        }
        if (status == RA_FAIL)
            got_int = TRUE;
        return (status == RA_MATCH);
    }

  } /* End of loop until the regstack is empty. */

  /* NOTREACHED */
}

/*
 * Push an item onto the regstack.
 * Returns pointer to new item.  Returns NULL when out of memory.
 */
    static regitem_T *
regstack_push(state, scan)
    regstate_T  state;
    char_u      *scan;
{
    regitem_T   *rp;

    if ((long)((unsigned)regstack.ga_len >> 10) >= p_mmp)
    {
        EMSG(_(e_maxmempat));
        return NULL;
    }
    if (ga_grow(&regstack, sizeof(regitem_T)) == FAIL)
        return NULL;

    rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len);
    rp->rs_state = state;
    rp->rs_scan = scan;

    regstack.ga_len += sizeof(regitem_T);
    return rp;
}

/*
 * Pop an item from the regstack.
 */
    static void
regstack_pop(scan)
    char_u      **scan;
{
    regitem_T   *rp;

    rp = (regitem_T *)((char *)regstack.ga_data + regstack.ga_len) - 1;
    *scan = rp->rs_scan;

    regstack.ga_len -= sizeof(regitem_T);
}

/*
 * regrepeat - repeatedly match something simple, return how many.
 * Advances reginput (and reglnum) to just after the matched chars.
 */
    static int
regrepeat(p, maxcount)
    char_u      *p;
    long        maxcount;   /* maximum number of matches allowed */
{
    long        count = 0;
    char_u      *scan;
    char_u      *opnd;
    int         mask;
    int         testval = 0;

    scan = reginput;        /* Make local copy of reginput for speed. */
    opnd = OPERAND(p);
    switch (OP(p))
    {
      case ANY:
      case ANY + ADD_NL:
        while (count < maxcount)
        {
            /* Matching anything means we continue until end-of-line (or
             * end-of-file for ANY + ADD_NL), only limited by maxcount. */
            while (*scan != NUL && count < maxcount)
            {
                ++count;
                mb_ptr_adv(scan);
            }
            if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                         || reg_line_lbr || count == maxcount)
                break;
            ++count;            /* count the line-break */
            reg_nextline();
            scan = reginput;
            if (got_int)
                break;
        }
        break;

      case IDENT:
      case IDENT + ADD_NL:
        testval = TRUE;
        /*FALLTHROUGH*/
      case SIDENT:
      case SIDENT + ADD_NL:
        while (count < maxcount)
        {
            if (vim_isIDc(*scan) && (testval || !VIM_ISDIGIT(*scan)))
            {
                mb_ptr_adv(scan);
            }
            else if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
            else
                break;
            ++count;
        }
        break;

      case KWORD:
      case KWORD + ADD_NL:
        testval = TRUE;
        /*FALLTHROUGH*/
      case SKWORD:
      case SKWORD + ADD_NL:
        while (count < maxcount)
        {
            if (vim_iswordp(scan) && (testval || !VIM_ISDIGIT(*scan)))
            {
                mb_ptr_adv(scan);
            }
            else if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
            else
                break;
            ++count;
        }
        break;

      case FNAME:
      case FNAME + ADD_NL:
        testval = TRUE;
        /*FALLTHROUGH*/
      case SFNAME:
      case SFNAME + ADD_NL:
        while (count < maxcount)
        {
            if (vim_isfilec(*scan) && (testval || !VIM_ISDIGIT(*scan)))
            {
                mb_ptr_adv(scan);
            }
            else if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
            else
                break;
            ++count;
        }
        break;

      case PRINT:
      case PRINT + ADD_NL:
        testval = TRUE;
        /*FALLTHROUGH*/
      case SPRINT:
      case SPRINT + ADD_NL:
        while (count < maxcount)
        {
            if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
            else if (ptr2cells(scan) == 1 && (testval || !VIM_ISDIGIT(*scan)))
            {
                mb_ptr_adv(scan);
            }
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
            else
                break;
            ++count;
        }
        break;

      case WHITE:
      case WHITE + ADD_NL:
        testval = mask = RI_WHITE;
do_class:
        while (count < maxcount)
        {
#ifdef FEAT_MBYTE
            int         l;
#endif
            if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
#ifdef FEAT_MBYTE
            else if (has_mbyte && (l = (*mb_ptr2len)(scan)) > 1)
            {
                if (testval != 0)
                    break;
                scan += l;
            }
#endif
            else if ((class_tab[*scan] & mask) == testval)
                ++scan;
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
            else
                break;
            ++count;
        }
        break;

      case NWHITE:
      case NWHITE + ADD_NL:
        mask = RI_WHITE;
        goto do_class;
      case DIGIT:
      case DIGIT + ADD_NL:
        testval = mask = RI_DIGIT;
        goto do_class;
      case NDIGIT:
      case NDIGIT + ADD_NL:
        mask = RI_DIGIT;
        goto do_class;
      case HEX:
      case HEX + ADD_NL:
        testval = mask = RI_HEX;
        goto do_class;
      case NHEX:
      case NHEX + ADD_NL:
        mask = RI_HEX;
        goto do_class;
      case OCTAL:
      case OCTAL + ADD_NL:
        testval = mask = RI_OCTAL;
        goto do_class;
      case NOCTAL:
      case NOCTAL + ADD_NL:
        mask = RI_OCTAL;
        goto do_class;
      case WORD:
      case WORD + ADD_NL:
        testval = mask = RI_WORD;
        goto do_class;
      case NWORD:
      case NWORD + ADD_NL:
        mask = RI_WORD;
        goto do_class;
      case HEAD:
      case HEAD + ADD_NL:
        testval = mask = RI_HEAD;
        goto do_class;
      case NHEAD:
      case NHEAD + ADD_NL:
        mask = RI_HEAD;
        goto do_class;
      case ALPHA:
      case ALPHA + ADD_NL:
        testval = mask = RI_ALPHA;
        goto do_class;
      case NALPHA:
      case NALPHA + ADD_NL:
        mask = RI_ALPHA;
        goto do_class;
      case LOWER:
      case LOWER + ADD_NL:
        testval = mask = RI_LOWER;
        goto do_class;
      case NLOWER:
      case NLOWER + ADD_NL:
        mask = RI_LOWER;
        goto do_class;
      case UPPER:
      case UPPER + ADD_NL:
        testval = mask = RI_UPPER;
        goto do_class;
      case NUPPER:
      case NUPPER + ADD_NL:
        mask = RI_UPPER;
        goto do_class;

      case EXACTLY:
        {
            int     cu, cl;

            /* This doesn't do a multi-byte character, because a MULTIBYTECODE
             * would have been used for it. */
            if (ireg_ic)
            {
                cu = TOUPPER_LOC(*opnd);
                cl = TOLOWER_LOC(*opnd);
                while (count < maxcount && (*scan == cu || *scan == cl))
                {
                    count++;
                    scan++;
                }
            }
            else
            {
                cu = *opnd;
                while (count < maxcount && *scan == cu)
                {
                    count++;
                    scan++;
                }
            }
            break;
        }

#ifdef FEAT_MBYTE
      case MULTIBYTECODE:
        {
            int         i, len, cf = 0;

            /* Safety check (just in case 'encoding' was changed since
             * compiling the program). */
            if ((len = (*mb_ptr2len)(opnd)) > 1)
            {
                if (ireg_ic && enc_utf8)
                    cf = utf_fold(utf_ptr2char(opnd));
                while (count < maxcount)
                {
                    for (i = 0; i < len; ++i)
                        if (opnd[i] != scan[i])
                            break;
                    if (i < len && (!ireg_ic || !enc_utf8
                                        || utf_fold(utf_ptr2char(scan)) != cf))
                        break;
                    scan += len;
                    ++count;
                }
            }
        }
        break;
#endif

      case ANYOF:
      case ANYOF + ADD_NL:
        testval = TRUE;
        /*FALLTHROUGH*/

      case ANYBUT:
      case ANYBUT + ADD_NL:
        while (count < maxcount)
        {
#ifdef FEAT_MBYTE
            int len;
#endif
            if (*scan == NUL)
            {
                if (!REG_MULTI || !WITH_NL(OP(p)) || reglnum > reg_maxline
                                                              || reg_line_lbr)
                    break;
                reg_nextline();
                scan = reginput;
                if (got_int)
                    break;
            }
            else if (reg_line_lbr && *scan == '\n' && WITH_NL(OP(p)))
                ++scan;
#ifdef FEAT_MBYTE
            else if (has_mbyte && (len = (*mb_ptr2len)(scan)) > 1)
            {
                if ((cstrchr(opnd, (*mb_ptr2char)(scan)) == NULL) == testval)
                    break;
                scan += len;
            }
#endif
            else
            {
                if ((cstrchr(opnd, *scan) == NULL) == testval)
                    break;
                ++scan;
            }
            ++count;
        }
        break;

      case NEWL:
        while (count < maxcount
                && ((*scan == NUL && reglnum <= reg_maxline && !reg_line_lbr
                            && REG_MULTI) || (*scan == '\n' && reg_line_lbr)))
        {
            count++;
            if (reg_line_lbr)
                ADVANCE_REGINPUT();
            else
                reg_nextline();
            scan = reginput;
            if (got_int)
                break;
        }
        break;

      default:                  /* Oh dear.  Called inappropriately. */
        EMSG(_(e_re_corr));
#ifdef DEBUG
        printf("Called regrepeat with op code %d\n", OP(p));
#endif
        break;
    }

    reginput = scan;

    return (int)count;
}

/*
 * regnext - dig the "next" pointer out of a node
 */
    static char_u *
regnext(p)
    char_u  *p;
{
    int     offset;

    if (p == JUST_CALC_SIZE)
        return NULL;

    offset = NEXT(p);
    if (offset == 0)
        return NULL;

    if (OP(p) == BACK)
        return p - offset;
    else
        return p + offset;
}

/*
 * Check the regexp program for its magic number.
 * Return TRUE if it's wrong.
 */
    static int
prog_magic_wrong()
{
    if (UCHARAT(REG_MULTI
                ? reg_mmatch->regprog->program
                : reg_match->regprog->program) != REGMAGIC)
    {
        EMSG(_(e_re_corr));
        return TRUE;
    }
    return FALSE;
}

/*
 * Cleanup the subexpressions, if this wasn't done yet.
 * This construction is used to clear the subexpressions only when they are
 * used (to increase speed).
 */
    static void
cleanup_subexpr()
{
    if (need_clear_subexpr)
    {
        if (REG_MULTI)
        {
            /* Use 0xff to set lnum to -1 */
            vim_memset(reg_startpos, 0xff, sizeof(lpos_T) * NSUBEXP);
            vim_memset(reg_endpos, 0xff, sizeof(lpos_T) * NSUBEXP);
        }
        else
        {
            vim_memset(reg_startp, 0, sizeof(char_u *) * NSUBEXP);
            vim_memset(reg_endp, 0, sizeof(char_u *) * NSUBEXP);
        }
        need_clear_subexpr = FALSE;
    }
}

#ifdef FEAT_SYN_HL
    static void
cleanup_zsubexpr()
{
    if (need_clear_zsubexpr)
    {
        if (REG_MULTI)
        {
            /* Use 0xff to set lnum to -1 */
            vim_memset(reg_startzpos, 0xff, sizeof(lpos_T) * NSUBEXP);
            vim_memset(reg_endzpos, 0xff, sizeof(lpos_T) * NSUBEXP);
        }
        else
        {
            vim_memset(reg_startzp, 0, sizeof(char_u *) * NSUBEXP);
            vim_memset(reg_endzp, 0, sizeof(char_u *) * NSUBEXP);
        }
        need_clear_zsubexpr = FALSE;
    }
}
#endif

/*
 * Advance reglnum, regline and reginput to the next line.
 */
    static void
reg_nextline()
{
    regline = reg_getline(++reglnum);
    reginput = regline;
    fast_breakcheck();
}

/*
 * Save the input line and position in a regsave_T.
 */
    static void
reg_save(save, gap)
    regsave_T   *save;
    garray_T    *gap;
{
    if (REG_MULTI)
    {
        save->rs_u.pos.col = (colnr_T)(reginput - regline);
        save->rs_u.pos.lnum = reglnum;
    }
    else
        save->rs_u.ptr = reginput;
    save->rs_len = gap->ga_len;
}

/*
 * Restore the input line and position from a regsave_T.
 */
    static void
reg_restore(save, gap)
    regsave_T   *save;
    garray_T    *gap;
{
    if (REG_MULTI)
    {
        if (reglnum != save->rs_u.pos.lnum)
        {
            /* only call reg_getline() when the line number changed to save
             * a bit of time */
            reglnum = save->rs_u.pos.lnum;
            regline = reg_getline(reglnum);
        }
        reginput = regline + save->rs_u.pos.col;
    }
    else
        reginput = save->rs_u.ptr;
    gap->ga_len = save->rs_len;
}

/*
 * Return TRUE if current position is equal to saved position.
 */
    static int
reg_save_equal(save)
    regsave_T   *save;
{
    if (REG_MULTI)
        return reglnum == save->rs_u.pos.lnum
                                  && reginput == regline + save->rs_u.pos.col;
    return reginput == save->rs_u.ptr;
}

/*
 * Tentatively set the sub-expression start to the current position (after
 * calling regmatch() they will have changed).  Need to save the existing
 * values for when there is no match.
 * Use se_save() to use pointer (save_se_multi()) or position (save_se_one()),
 * depending on REG_MULTI.
 */
    static void
save_se_multi(savep, posp)
    save_se_T   *savep;
    lpos_T      *posp;
{
    savep->se_u.pos = *posp;
    posp->lnum = reglnum;
    posp->col = (colnr_T)(reginput - regline);
}

    static void
save_se_one(savep, pp)
    save_se_T   *savep;
    char_u      **pp;
{
    savep->se_u.ptr = *pp;
    *pp = reginput;
}

/*
 * Compare a number with the operand of RE_LNUM, RE_COL or RE_VCOL.
 */
    static int
re_num_cmp(val, scan)
    long_u      val;
    char_u      *scan;
{
    long_u  n = OPERAND_MIN(scan);

    if (OPERAND_CMP(scan) == '>')
        return val > n;
    if (OPERAND_CMP(scan) == '<')
        return val < n;
    return val == n;
}


#ifdef DEBUG

/*
 * regdump - dump a regexp onto stdout in vaguely comprehensible form
 */
    static void
regdump(pattern, r)
    char_u      *pattern;
    regprog_T   *r;
{
    char_u  *s;
    int     op = EXACTLY;       /* Arbitrary non-END op. */
    char_u  *next;
    char_u  *end = NULL;

    printf("\r\nregcomp(%s):\r\n", pattern);

    s = r->program + 1;
    /*
     * Loop until we find the END that isn't before a referred next (an END
     * can also appear in a NOMATCH operand).
     */
    while (op != END || s <= end)
    {
        op = OP(s);
        printf("%2d%s", (int)(s - r->program), regprop(s)); /* Where, what. */
        next = regnext(s);
        if (next == NULL)       /* Next ptr. */
            printf("(0)");
        else
            printf("(%d)", (int)((s - r->program) + (next - s)));
        if (end < next)
            end = next;
        if (op == BRACE_LIMITS)
        {
            /* Two short ints */
            printf(" minval %ld, maxval %ld", OPERAND_MIN(s), OPERAND_MAX(s));
            s += 8;
        }
        s += 3;
        if (op == ANYOF || op == ANYOF + ADD_NL
                || op == ANYBUT || op == ANYBUT + ADD_NL
                || op == EXACTLY)
        {
            /* Literal string, where present. */
            while (*s != NUL)
                printf("%c", *s++);
            s++;
        }
        printf("\r\n");
    }

    /* Header fields of interest. */
    if (r->regstart != NUL)
        printf("start `%s' 0x%x; ", r->regstart < 256
                ? (char *)transchar(r->regstart)
                : "multibyte", r->regstart);
    if (r->reganch)
        printf("anchored; ");
    if (r->regmust != NULL)
        printf("must have \"%s\"", r->regmust);
    printf("\r\n");
}

/*
 * regprop - printable representation of opcode
 */
    static char_u *
regprop(op)
    char_u         *op;
{
    char_u          *p;
    static char_u   buf[50];

    (void) strcpy(buf, ":");

    switch (OP(op))
    {
      case BOL:
        p = "BOL";
        break;
      case EOL:
        p = "EOL";
        break;
      case RE_BOF:
        p = "BOF";
        break;
      case RE_EOF:
        p = "EOF";
        break;
      case CURSOR:
        p = "CURSOR";
        break;
      case RE_VISUAL:
        p = "RE_VISUAL";
        break;
      case RE_LNUM:
        p = "RE_LNUM";
        break;
      case RE_MARK:
        p = "RE_MARK";
        break;
      case RE_COL:
        p = "RE_COL";
        break;
      case RE_VCOL:
        p = "RE_VCOL";
        break;
      case BOW:
        p = "BOW";
        break;
      case EOW:
        p = "EOW";
        break;
      case ANY:
        p = "ANY";
        break;
      case ANY + ADD_NL:
        p = "ANY+NL";
        break;
      case ANYOF:
        p = "ANYOF";
        break;
      case ANYOF + ADD_NL:
        p = "ANYOF+NL";
        break;
      case ANYBUT:
        p = "ANYBUT";
        break;
      case ANYBUT + ADD_NL:
        p = "ANYBUT+NL";
        break;
      case IDENT:
        p = "IDENT";
        break;
      case IDENT + ADD_NL:
        p = "IDENT+NL";
        break;
      case SIDENT:
        p = "SIDENT";
        break;
      case SIDENT + ADD_NL:
        p = "SIDENT+NL";
        break;
      case KWORD:
        p = "KWORD";
        break;
      case KWORD + ADD_NL:
        p = "KWORD+NL";
        break;
      case SKWORD:
        p = "SKWORD";
        break;
      case SKWORD + ADD_NL:
        p = "SKWORD+NL";
        break;
      case FNAME:
        p = "FNAME";
        break;
      case FNAME + ADD_NL:
        p = "FNAME+NL";
        break;
      case SFNAME:
        p = "SFNAME";
        break;
      case SFNAME + ADD_NL:
        p = "SFNAME+NL";
        break;
      case PRINT:
        p = "PRINT";
        break;
      case PRINT + ADD_NL:
        p = "PRINT+NL";
        break;
      case SPRINT:
        p = "SPRINT";
        break;
      case SPRINT + ADD_NL:
        p = "SPRINT+NL";
        break;
      case WHITE:
        p = "WHITE";
        break;
      case WHITE + ADD_NL:
        p = "WHITE+NL";
        break;
      case NWHITE:
        p = "NWHITE";
        break;
      case NWHITE + ADD_NL:
        p = "NWHITE+NL";
        break;
      case DIGIT:
        p = "DIGIT";
        break;
      case DIGIT + ADD_NL:
        p = "DIGIT+NL";
        break;
      case NDIGIT:
        p = "NDIGIT";
        break;
      case NDIGIT + ADD_NL:
        p = "NDIGIT+NL";
        break;
      case HEX:
        p = "HEX";
        break;
      case HEX + ADD_NL:
        p = "HEX+NL";
        break;
      case NHEX:
        p = "NHEX";
        break;
      case NHEX + ADD_NL:
        p = "NHEX+NL";
        break;
      case OCTAL:
        p = "OCTAL";
        break;
      case OCTAL + ADD_NL:
        p = "OCTAL+NL";
        break;
      case NOCTAL:
        p = "NOCTAL";
        break;
      case NOCTAL + ADD_NL:
        p = "NOCTAL+NL";
        break;
      case WORD:
        p = "WORD";
        break;
      case WORD + ADD_NL:
        p = "WORD+NL";
        break;
      case NWORD:
        p = "NWORD";
        break;
      case NWORD + ADD_NL:
        p = "NWORD+NL";
        break;
      case HEAD:
        p = "HEAD";
        break;
      case HEAD + ADD_NL:
        p = "HEAD+NL";
        break;
      case NHEAD:
        p = "NHEAD";
        break;
      case NHEAD + ADD_NL:
        p = "NHEAD+NL";
        break;
      case ALPHA:
        p = "ALPHA";
        break;
      case ALPHA + ADD_NL:
        p = "ALPHA+NL";
        break;
      case NALPHA:
        p = "NALPHA";
        break;
      case NALPHA + ADD_NL:
        p = "NALPHA+NL";
        break;
      case LOWER:
        p = "LOWER";
        break;
      case LOWER + ADD_NL:
        p = "LOWER+NL";
        break;
      case NLOWER:
        p = "NLOWER";
        break;
      case NLOWER + ADD_NL:
        p = "NLOWER+NL";
        break;
      case UPPER:
        p = "UPPER";
        break;
      case UPPER + ADD_NL:
        p = "UPPER+NL";
        break;
      case NUPPER:
        p = "NUPPER";
        break;
      case NUPPER + ADD_NL:
        p = "NUPPER+NL";
        break;
      case BRANCH:
        p = "BRANCH";
        break;
      case EXACTLY:
        p = "EXACTLY";
        break;
      case NOTHING:
        p = "NOTHING";
        break;
      case BACK:
        p = "BACK";
        break;
      case END:
        p = "END";
        break;
      case MOPEN + 0:
        p = "MATCH START";
        break;
      case MOPEN + 1:
      case MOPEN + 2:
      case MOPEN + 3:
      case MOPEN + 4:
      case MOPEN + 5:
      case MOPEN + 6:
      case MOPEN + 7:
      case MOPEN + 8:
      case MOPEN + 9:
        sprintf(buf + STRLEN(buf), "MOPEN%d", OP(op) - MOPEN);
        p = NULL;
        break;
      case MCLOSE + 0:
        p = "MATCH END";
        break;
      case MCLOSE + 1:
      case MCLOSE + 2:
      case MCLOSE + 3:
      case MCLOSE + 4:
      case MCLOSE + 5:
      case MCLOSE + 6:
      case MCLOSE + 7:
      case MCLOSE + 8:
      case MCLOSE + 9:
        sprintf(buf + STRLEN(buf), "MCLOSE%d", OP(op) - MCLOSE);
        p = NULL;
        break;
      case BACKREF + 1:
      case BACKREF + 2:
      case BACKREF + 3:
      case BACKREF + 4:
      case BACKREF + 5:
      case BACKREF + 6:
      case BACKREF + 7:
      case BACKREF + 8:
      case BACKREF + 9:
        sprintf(buf + STRLEN(buf), "BACKREF%d", OP(op) - BACKREF);
        p = NULL;
        break;
      case NOPEN:
        p = "NOPEN";
        break;
      case NCLOSE:
        p = "NCLOSE";
        break;
#ifdef FEAT_SYN_HL
      case ZOPEN + 1:
      case ZOPEN + 2:
      case ZOPEN + 3:
      case ZOPEN + 4:
      case ZOPEN + 5:
      case ZOPEN + 6:
      case ZOPEN + 7:
      case ZOPEN + 8:
      case ZOPEN + 9:
        sprintf(buf + STRLEN(buf), "ZOPEN%d", OP(op) - ZOPEN);
        p = NULL;
        break;
      case ZCLOSE + 1:
      case ZCLOSE + 2:
      case ZCLOSE + 3:
      case ZCLOSE + 4:
      case ZCLOSE + 5:
      case ZCLOSE + 6:
      case ZCLOSE + 7:
      case ZCLOSE + 8:
      case ZCLOSE + 9:
        sprintf(buf + STRLEN(buf), "ZCLOSE%d", OP(op) - ZCLOSE);
        p = NULL;
        break;
      case ZREF + 1:
      case ZREF + 2:
      case ZREF + 3:
      case ZREF + 4:
      case ZREF + 5:
      case ZREF + 6:
      case ZREF + 7:
      case ZREF + 8:
      case ZREF + 9:
        sprintf(buf + STRLEN(buf), "ZREF%d", OP(op) - ZREF);
        p = NULL;
        break;
#endif
      case STAR:
        p = "STAR";
        break;
      case PLUS:
        p = "PLUS";
        break;
      case NOMATCH:
        p = "NOMATCH";
        break;
      case MATCH:
        p = "MATCH";
        break;
      case BEHIND:
        p = "BEHIND";
        break;
      case NOBEHIND:
        p = "NOBEHIND";
        break;
      case SUBPAT:
        p = "SUBPAT";
        break;
      case BRACE_LIMITS:
        p = "BRACE_LIMITS";
        break;
      case BRACE_SIMPLE:
        p = "BRACE_SIMPLE";
        break;
      case BRACE_COMPLEX + 0:
      case BRACE_COMPLEX + 1:
      case BRACE_COMPLEX + 2:
      case BRACE_COMPLEX + 3:
      case BRACE_COMPLEX + 4:
      case BRACE_COMPLEX + 5:
      case BRACE_COMPLEX + 6:
      case BRACE_COMPLEX + 7:
      case BRACE_COMPLEX + 8:
      case BRACE_COMPLEX + 9:
        sprintf(buf + STRLEN(buf), "BRACE_COMPLEX%d", OP(op) - BRACE_COMPLEX);
        p = NULL;
        break;
#ifdef FEAT_MBYTE
      case MULTIBYTECODE:
        p = "MULTIBYTECODE";
        break;
#endif
      case NEWL:
        p = "NEWL";
        break;
      default:
        sprintf(buf + STRLEN(buf), "corrupt %d", OP(op));
        p = NULL;
        break;
    }
    if (p != NULL)
        (void) strcat(buf, p);
    return buf;
}
#endif

#ifdef FEAT_MBYTE
static void mb_decompose __ARGS((int c, int *c1, int *c2, int *c3));

typedef struct
{
    int a, b, c;
} decomp_T;


/* 0xfb20 - 0xfb4f */
static decomp_T decomp_table[0xfb4f-0xfb20+1] =
{
    {0x5e2,0,0},                /* 0xfb20       alt ayin */
    {0x5d0,0,0},                /* 0xfb21       alt alef */
    {0x5d3,0,0},                /* 0xfb22       alt dalet */
    {0x5d4,0,0},                /* 0xfb23       alt he */
    {0x5db,0,0},                /* 0xfb24       alt kaf */
    {0x5dc,0,0},                /* 0xfb25       alt lamed */
    {0x5dd,0,0},                /* 0xfb26       alt mem-sofit */
    {0x5e8,0,0},                /* 0xfb27       alt resh */
    {0x5ea,0,0},                /* 0xfb28       alt tav */
    {'+', 0, 0},                /* 0xfb29       alt plus */
    {0x5e9, 0x5c1, 0},          /* 0xfb2a       shin+shin-dot */
    {0x5e9, 0x5c2, 0},          /* 0xfb2b       shin+sin-dot */
    {0x5e9, 0x5c1, 0x5bc},      /* 0xfb2c       shin+shin-dot+dagesh */
    {0x5e9, 0x5c2, 0x5bc},      /* 0xfb2d       shin+sin-dot+dagesh */
    {0x5d0, 0x5b7, 0},          /* 0xfb2e       alef+patah */
    {0x5d0, 0x5b8, 0},          /* 0xfb2f       alef+qamats */
    {0x5d0, 0x5b4, 0},          /* 0xfb30       alef+hiriq */
    {0x5d1, 0x5bc, 0},          /* 0xfb31       bet+dagesh */
    {0x5d2, 0x5bc, 0},          /* 0xfb32       gimel+dagesh */
    {0x5d3, 0x5bc, 0},          /* 0xfb33       dalet+dagesh */
    {0x5d4, 0x5bc, 0},          /* 0xfb34       he+dagesh */
    {0x5d5, 0x5bc, 0},          /* 0xfb35       vav+dagesh */
    {0x5d6, 0x5bc, 0},          /* 0xfb36       zayin+dagesh */
    {0xfb37, 0, 0},             /* 0xfb37 -- UNUSED */
    {0x5d8, 0x5bc, 0},          /* 0xfb38       tet+dagesh */
    {0x5d9, 0x5bc, 0},          /* 0xfb39       yud+dagesh */
    {0x5da, 0x5bc, 0},          /* 0xfb3a       kaf sofit+dagesh */
    {0x5db, 0x5bc, 0},          /* 0xfb3b       kaf+dagesh */
    {0x5dc, 0x5bc, 0},          /* 0xfb3c       lamed+dagesh */
    {0xfb3d, 0, 0},             /* 0xfb3d -- UNUSED */
    {0x5de, 0x5bc, 0},          /* 0xfb3e       mem+dagesh */
    {0xfb3f, 0, 0},             /* 0xfb3f -- UNUSED */
    {0x5e0, 0x5bc, 0},          /* 0xfb40       nun+dagesh */
    {0x5e1, 0x5bc, 0},          /* 0xfb41       samech+dagesh */
    {0xfb42, 0, 0},             /* 0xfb42 -- UNUSED */
    {0x5e3, 0x5bc, 0},          /* 0xfb43       pe sofit+dagesh */
    {0x5e4, 0x5bc,0},           /* 0xfb44       pe+dagesh */
    {0xfb45, 0, 0},             /* 0xfb45 -- UNUSED */
    {0x5e6, 0x5bc, 0},          /* 0xfb46       tsadi+dagesh */
    {0x5e7, 0x5bc, 0},          /* 0xfb47       qof+dagesh */
    {0x5e8, 0x5bc, 0},          /* 0xfb48       resh+dagesh */
    {0x5e9, 0x5bc, 0},          /* 0xfb49       shin+dagesh */
    {0x5ea, 0x5bc, 0},          /* 0xfb4a       tav+dagesh */
    {0x5d5, 0x5b9, 0},          /* 0xfb4b       vav+holam */
    {0x5d1, 0x5bf, 0},          /* 0xfb4c       bet+rafe */
    {0x5db, 0x5bf, 0},          /* 0xfb4d       kaf+rafe */
    {0x5e4, 0x5bf, 0},          /* 0xfb4e       pe+rafe */
    {0x5d0, 0x5dc, 0}           /* 0xfb4f       alef-lamed */
};

    static void
mb_decompose(c, c1, c2, c3)
    int c, *c1, *c2, *c3;
{
    decomp_T d;

    if (c >= 0x4b20 && c <= 0xfb4f)
    {
        d = decomp_table[c - 0xfb20];
        *c1 = d.a;
        *c2 = d.b;
        *c3 = d.c;
    }
    else
    {
        *c1 = c;
        *c2 = *c3 = 0;
    }
}
#endif

/*
 * Compare two strings, ignore case if ireg_ic set.
 * Return 0 if strings match, non-zero otherwise.
 * Correct the length "*n" when composing characters are ignored.
 */
    static int
cstrncmp(s1, s2, n)
    char_u      *s1, *s2;
    int         *n;
{
    int         result;

    if (!ireg_ic)
        result = STRNCMP(s1, s2, *n);
    else
        result = MB_STRNICMP(s1, s2, *n);

#ifdef FEAT_MBYTE
    /* if it failed and it's utf8 and we want to combineignore: */
    if (result != 0 && enc_utf8 && ireg_icombine)
    {
        char_u  *str1, *str2;
        int     c1, c2, c11, c12;
        int     junk;

        /* we have to handle the strcmp ourselves, since it is necessary to
         * deal with the composing characters by ignoring them: */
        str1 = s1;
        str2 = s2;
        c1 = c2 = 0;
        while ((int)(str1 - s1) < *n)
        {
            c1 = mb_ptr2char_adv(&str1);
            c2 = mb_ptr2char_adv(&str2);

            /* decompose the character if necessary, into 'base' characters
             * because I don't care about Arabic, I will hard-code the Hebrew
             * which I *do* care about!  So sue me... */
            if (c1 != c2 && (!ireg_ic || utf_fold(c1) != utf_fold(c2)))
            {
                /* decomposition necessary? */
                mb_decompose(c1, &c11, &junk, &junk);
                mb_decompose(c2, &c12, &junk, &junk);
                c1 = c11;
                c2 = c12;
                if (c11 != c12 && (!ireg_ic || utf_fold(c11) != utf_fold(c12)))
                    break;
            }
        }
        result = c2 - c1;
        if (result == 0)
            *n = (int)(str2 - s2);
    }
#endif

    return result;
}

/*
 * cstrchr: This function is used a lot for simple searches, keep it fast!
 */
    static char_u *
cstrchr(s, c)
    char_u      *s;
    int         c;
{
    char_u      *p;
    int         cc;

    if (!ireg_ic
#ifdef FEAT_MBYTE
            || (!enc_utf8 && mb_char2len(c) > 1)
#endif
            )
        return vim_strchr(s, c);

    /* tolower() and toupper() can be slow, comparing twice should be a lot
     * faster (esp. when using MS Visual C++!).
     * For UTF-8 need to use folded case. */
#ifdef FEAT_MBYTE
    if (enc_utf8 && c > 0x80)
        cc = utf_fold(c);
    else
#endif
         if (isupper(c))
        cc = TOLOWER_LOC(c);
    else if (islower(c))
        cc = TOUPPER_LOC(c);
    else
        return vim_strchr(s, c);

#ifdef FEAT_MBYTE
    if (has_mbyte)
    {
        for (p = s; *p != NUL; p += (*mb_ptr2len)(p))
        {
            if (enc_utf8 && c > 0x80)
            {
                if (utf_fold(utf_ptr2char(p)) == cc)
                    return p;
            }
            else if (*p == c || *p == cc)
                return p;
        }
    }
    else
#endif
        /* Faster version for when there are no multi-byte characters. */
        for (p = s; *p != NUL; ++p)
            if (*p == c || *p == cc)
                return p;

    return NULL;
}

/***************************************************************
 *                    regsub stuff                             *
 ***************************************************************/

/* This stuff below really confuses cc on an SGI -- webb */
#ifdef __sgi
# undef __ARGS
# define __ARGS(x)  ()
#endif

/*
 * We should define ftpr as a pointer to a function returning a pointer to
 * a function returning a pointer to a function ...
 * This is impossible, so we declare a pointer to a function returning a
 * pointer to a function returning void. This should work for all compilers.
 */
typedef void (*(*fptr_T) __ARGS((int *, int)))();

static fptr_T do_upper __ARGS((int *, int));
static fptr_T do_Upper __ARGS((int *, int));
static fptr_T do_lower __ARGS((int *, int));
static fptr_T do_Lower __ARGS((int *, int));

static int vim_regsub_both __ARGS((char_u *source, char_u *dest, int copy, int magic, int backslash));

    static fptr_T
do_upper(d, c)
    int         *d;
    int         c;
{
    *d = MB_TOUPPER(c);

    return (fptr_T)NULL;
}

    static fptr_T
do_Upper(d, c)
    int         *d;
    int         c;
{
    *d = MB_TOUPPER(c);

    return (fptr_T)do_Upper;
}

    static fptr_T
do_lower(d, c)
    int         *d;
    int         c;
{
    *d = MB_TOLOWER(c);

    return (fptr_T)NULL;
}

    static fptr_T
do_Lower(d, c)
    int         *d;
    int         c;
{
    *d = MB_TOLOWER(c);

    return (fptr_T)do_Lower;
}

/*
 * regtilde(): Replace tildes in the pattern by the old pattern.
 *
 * Short explanation of the tilde: It stands for the previous replacement
 * pattern.  If that previous pattern also contains a ~ we should go back a
 * step further...  But we insert the previous pattern into the current one
 * and remember that.
 * This still does not handle the case where "magic" changes.  So require the
 * user to keep his hands off of "magic".
 *
 * The tildes are parsed once before the first call to vim_regsub().
 */
    char_u *
regtilde(source, magic)
    char_u      *source;
    int         magic;
{
    char_u      *newsub = source;
    char_u      *tmpsub;
    char_u      *p;
    int         len;
    int         prevlen;

    for (p = newsub; *p; ++p)
    {
        if ((*p == '~' && magic) || (*p == '\\' && *(p + 1) == '~' && !magic))
        {
            if (reg_prev_sub != NULL)
            {
                /* length = len(newsub) - 1 + len(prev_sub) + 1 */
                prevlen = (int)STRLEN(reg_prev_sub);
                tmpsub = alloc((unsigned)(STRLEN(newsub) + prevlen));
                if (tmpsub != NULL)
                {
                    /* copy prefix */
                    len = (int)(p - newsub);    /* not including ~ */
                    mch_memmove(tmpsub, newsub, (size_t)len);
                    /* interpret tilde */
                    mch_memmove(tmpsub + len, reg_prev_sub, (size_t)prevlen);
                    /* copy postfix */
                    if (!magic)
                        ++p;                    /* back off \ */
                    STRCPY(tmpsub + len + prevlen, p + 1);

                    if (newsub != source)       /* already allocated newsub */
                        vim_free(newsub);
                    newsub = tmpsub;
                    p = newsub + len + prevlen;
                }
            }
            else if (magic)
                STRCPY(p, p + 1);               /* remove '~' */
            else
                STRCPY(p, p + 2);               /* remove '\~' */
            --p;
        }
        else
        {
            if (*p == '\\' && p[1])             /* skip escaped characters */
                ++p;
#ifdef FEAT_MBYTE
            if (has_mbyte)
                p += (*mb_ptr2len)(p) - 1;
#endif
        }
    }

    vim_free(reg_prev_sub);
    if (newsub != source)       /* newsub was allocated, just keep it */
        reg_prev_sub = newsub;
    else                        /* no ~ found, need to save newsub  */
        reg_prev_sub = vim_strsave(newsub);
    return newsub;
}

#ifdef FEAT_EVAL
static int can_f_submatch = FALSE;      /* TRUE when submatch() can be used */

/* These pointers are used instead of reg_match and reg_mmatch for
 * reg_submatch().  Needed for when the substitution string is an expression
 * that contains a call to substitute() and submatch(). */
static regmatch_T       *submatch_match;
static regmmatch_T      *submatch_mmatch;
#endif

#if defined(FEAT_MODIFY_FNAME) || defined(FEAT_EVAL) || defined(PROTO)
/*
 * vim_regsub() - perform substitutions after a vim_regexec() or
 * vim_regexec_multi() match.
 *
 * If "copy" is TRUE really copy into "dest".
 * If "copy" is FALSE nothing is copied, this is just to find out the length
 * of the result.
 *
 * If "backslash" is TRUE, a backslash will be removed later, need to double
 * them to keep them, and insert a backslash before a CR to avoid it being
 * replaced with a line break later.
 *
 * Note: The matched text must not change between the call of
 * vim_regexec()/vim_regexec_multi() and vim_regsub()!  It would make the back
 * references invalid!
 *
 * Returns the size of the replacement, including terminating NUL.
 */
    int
vim_regsub(rmp, source, dest, copy, magic, backslash)
    regmatch_T  *rmp;
    char_u      *source;
    char_u      *dest;
    int         copy;
    int         magic;
    int         backslash;
{
    reg_match = rmp;
    reg_mmatch = NULL;
    reg_maxline = 0;
    return vim_regsub_both(source, dest, copy, magic, backslash);
}
#endif

    int
vim_regsub_multi(rmp, lnum, source, dest, copy, magic, backslash)
    regmmatch_T *rmp;
    linenr_T    lnum;
    char_u      *source;
    char_u      *dest;
    int         copy;
    int         magic;
    int         backslash;
{
    reg_match = NULL;
    reg_mmatch = rmp;
    reg_buf = curbuf;           /* always works on the current buffer! */
    reg_firstlnum = lnum;
    reg_maxline = curbuf->b_ml.ml_line_count - lnum;
    return vim_regsub_both(source, dest, copy, magic, backslash);
}

    static int
vim_regsub_both(source, dest, copy, magic, backslash)
    char_u      *source;
    char_u      *dest;
    int         copy;
    int         magic;
    int         backslash;
{
    char_u      *src;
    char_u      *dst;
    char_u      *s;
    int         c;
    int         cc;
    int         no = -1;
    fptr_T      func = (fptr_T)NULL;
    linenr_T    clnum = 0;      /* init for GCC */
    int         len = 0;        /* init for GCC */
#ifdef FEAT_EVAL
    static char_u *eval_result = NULL;
#endif

    /* Be paranoid... */
    if (source == NULL || dest == NULL)
    {
        EMSG(_(e_null));
        return 0;
    }
    if (prog_magic_wrong())
        return 0;
    src = source;
    dst = dest;

    /*
     * When the substitute part starts with "\=" evaluate it as an expression.
     */
    if (source[0] == '\\' && source[1] == '='
#ifdef FEAT_EVAL
            && !can_f_submatch      /* can't do this recursively */
#endif
            )
    {
#ifdef FEAT_EVAL
        /* To make sure that the length doesn't change between checking the
         * length and copying the string, and to speed up things, the
         * resulting string is saved from the call with "copy" == FALSE to the
         * call with "copy" == TRUE. */
        if (copy)
        {
            if (eval_result != NULL)
            {
                STRCPY(dest, eval_result);
                dst += STRLEN(eval_result);
                vim_free(eval_result);
                eval_result = NULL;
            }
        }
        else
        {
            linenr_T    save_reg_maxline;
            win_T       *save_reg_win;
            int         save_ireg_ic;

            vim_free(eval_result);

            /* The expression may contain substitute(), which calls us
             * recursively.  Make sure submatch() gets the text from the first
             * level.  Don't need to save "reg_buf", because
             * vim_regexec_multi() can't be called recursively. */
            submatch_match = reg_match;
            submatch_mmatch = reg_mmatch;
            save_reg_maxline = reg_maxline;
            save_reg_win = reg_win;
            save_ireg_ic = ireg_ic;
            can_f_submatch = TRUE;

            eval_result = eval_to_string(source + 2, NULL, TRUE);
            if (eval_result != NULL)
            {
                for (s = eval_result; *s != NUL; mb_ptr_adv(s))
                {
                    /* Change NL to CR, so that it becomes a line break.
                     * Skip over a backslashed character. */
                    if (*s == NL)
                        *s = CAR;
                    else if (*s == '\\' && s[1] != NUL)
                        ++s;
                }

                dst += STRLEN(eval_result);
            }

            reg_match = submatch_match;
            reg_mmatch = submatch_mmatch;
            reg_maxline = save_reg_maxline;
            reg_win = save_reg_win;
            ireg_ic = save_ireg_ic;
            can_f_submatch = FALSE;
        }
#endif
    }
    else
      while ((c = *src++) != NUL)
      {
        if (c == '&' && magic)
            no = 0;
        else if (c == '\\' && *src != NUL)
        {
            if (*src == '&' && !magic)
            {
                ++src;
                no = 0;
            }
            else if ('0' <= *src && *src <= '9')
            {
                no = *src++ - '0';
            }
            else if (vim_strchr((char_u *)"uUlLeE", *src))
            {
                switch (*src++)
                {
                case 'u':   func = (fptr_T)do_upper;
                            continue;
                case 'U':   func = (fptr_T)do_Upper;
                            continue;
                case 'l':   func = (fptr_T)do_lower;
                            continue;
                case 'L':   func = (fptr_T)do_Lower;
                            continue;
                case 'e':
                case 'E':   func = (fptr_T)NULL;
                            continue;
                }
            }
        }
        if (no < 0)           /* Ordinary character. */
        {
            if (c == K_SPECIAL && src[0] != NUL && src[1] != NUL)
            {
                /* Copy a special key as-is. */
                if (copy)
                {
                    *dst++ = c;
                    *dst++ = *src++;
                    *dst++ = *src++;
                }
                else
                {
                    dst += 3;
                    src += 2;
                }
                continue;
            }

            if (c == '\\' && *src != NUL)
            {
                /* Check for abbreviations -- webb */
                switch (*src)
                {
                    case 'r':   c = CAR;        ++src;  break;
                    case 'n':   c = NL;         ++src;  break;
                    case 't':   c = TAB;        ++src;  break;
                 /* Oh no!  \e already has meaning in subst pat :-( */
                 /* case 'e':   c = ESC;        ++src;  break; */
                    case 'b':   c = Ctrl_H;     ++src;  break;

                    /* If "backslash" is TRUE the backslash will be removed
                     * later.  Used to insert a literal CR. */
                    default:    if (backslash)
                                {
                                    if (copy)
                                        *dst = '\\';
                                    ++dst;
                                }
                                c = *src++;
                }
            }
#ifdef FEAT_MBYTE
            else if (has_mbyte)
                c = mb_ptr2char(src - 1);
#endif

            /* Write to buffer, if copy is set. */
            if (func == (fptr_T)NULL)   /* just copy */
                cc = c;
            else
                /* Turbo C complains without the typecast */
                func = (fptr_T)(func(&cc, c));

#ifdef FEAT_MBYTE
            if (has_mbyte)
            {
                src += mb_ptr2len(src - 1) - 1;
                if (copy)
                    mb_char2bytes(cc, dst);
                dst += mb_char2len(cc) - 1;
            }
            else
#endif
                if (copy)
                    *dst = cc;
            dst++;
        }
        else
        {
            if (REG_MULTI)
            {
                clnum = reg_mmatch->startpos[no].lnum;
                if (clnum < 0 || reg_mmatch->endpos[no].lnum < 0)
                    s = NULL;
                else
                {
                    s = reg_getline(clnum) + reg_mmatch->startpos[no].col;
                    if (reg_mmatch->endpos[no].lnum == clnum)
                        len = reg_mmatch->endpos[no].col
                                               - reg_mmatch->startpos[no].col;
                    else
                        len = (int)STRLEN(s);
                }
            }
            else
            {
                s = reg_match->startp[no];
                if (reg_match->endp[no] == NULL)
                    s = NULL;
                else
                    len = (int)(reg_match->endp[no] - s);
            }
            if (s != NULL)
            {
                for (;;)
                {
                    if (len == 0)
                    {
                        if (REG_MULTI)
                        {
                            if (reg_mmatch->endpos[no].lnum == clnum)
                                break;
                            if (copy)
                                *dst = CAR;
                            ++dst;
                            s = reg_getline(++clnum);
                            if (reg_mmatch->endpos[no].lnum == clnum)
                                len = reg_mmatch->endpos[no].col;
                            else
                                len = (int)STRLEN(s);
                        }
                        else
                            break;
                    }
                    else if (*s == NUL) /* we hit NUL. */
                    {
                        if (copy)
                            EMSG(_(e_re_damg));
                        goto exit;
                    }
                    else
                    {
                        if (backslash && (*s == CAR || *s == '\\'))
                        {
                            /*
                             * Insert a backslash in front of a CR, otherwise
                             * it will be replaced by a line break.
                             * Number of backslashes will be halved later,
                             * double them here.
                             */
                            if (copy)
                            {
                                dst[0] = '\\';
                                dst[1] = *s;
                            }
                            dst += 2;
                        }
                        else
                        {
#ifdef FEAT_MBYTE
                            if (has_mbyte)
                                c = mb_ptr2char(s);
                            else
#endif
                                c = *s;

                            if (func == (fptr_T)NULL)   /* just copy */
                                cc = c;
                            else
                                /* Turbo C complains without the typecast */
                                func = (fptr_T)(func(&cc, c));

#ifdef FEAT_MBYTE
                            if (has_mbyte)
                            {
                                int l = mb_ptr2len(s) - 1;

                                s += l;
                                len -= l;
                                if (copy)
                                    mb_char2bytes(cc, dst);
                                dst += mb_char2len(cc) - 1;
                            }
                            else
#endif
                                if (copy)
                                    *dst = cc;
                            dst++;
                        }

                        ++s;
                        --len;
                    }
                }
            }
            no = -1;
        }
      }
    if (copy)
        *dst = NUL;

exit:
    return (int)((dst - dest) + 1);
}

#ifdef FEAT_EVAL
/*
 * Used for the submatch() function: get the string from the n'th submatch in
 * allocated memory.
 * Returns NULL when not in a ":s" command and for a non-existing submatch.
 */
    char_u *
reg_submatch(no)
    int         no;
{
    char_u      *retval = NULL;
    char_u      *s;
    int         len;
    int         round;
    linenr_T    lnum;

    if (!can_f_submatch || no < 0)
        return NULL;

    if (submatch_match == NULL)
    {
        /*
         * First round: compute the length and allocate memory.
         * Second round: copy the text.
         */
        for (round = 1; round <= 2; ++round)
        {
            lnum = submatch_mmatch->startpos[no].lnum;
            if (lnum < 0 || submatch_mmatch->endpos[no].lnum < 0)
                return NULL;

            s = reg_getline(lnum) + submatch_mmatch->startpos[no].col;
            if (s == NULL)  /* anti-crash check, cannot happen? */
                break;
            if (submatch_mmatch->endpos[no].lnum == lnum)
            {
                /* Within one line: take form start to end col. */
                len = submatch_mmatch->endpos[no].col
                                          - submatch_mmatch->startpos[no].col;
                if (round == 2)
                    vim_strncpy(retval, s, len);
                ++len;
            }
            else
            {
                /* Multiple lines: take start line from start col, middle
                 * lines completely and end line up to end col. */
                len = (int)STRLEN(s);
                if (round == 2)
                {
                    STRCPY(retval, s);
                    retval[len] = '\n';
                }
                ++len;
                ++lnum;
                while (lnum < submatch_mmatch->endpos[no].lnum)
                {
                    s = reg_getline(lnum++);
                    if (round == 2)
                        STRCPY(retval + len, s);
                    len += (int)STRLEN(s);
                    if (round == 2)
                        retval[len] = '\n';
                    ++len;
                }
                if (round == 2)
                    STRNCPY(retval + len, reg_getline(lnum),
                                             submatch_mmatch->endpos[no].col);
                len += submatch_mmatch->endpos[no].col;
                if (round == 2)
                    retval[len] = NUL;
                ++len;
            }

            if (retval == NULL)
            {
                retval = lalloc((long_u)len, TRUE);
                if (retval == NULL)
                    return NULL;
            }
        }
    }
    else
    {
        if (submatch_match->endp[no] == NULL)
            retval = NULL;
        else
        {
            s = submatch_match->startp[no];
            retval = vim_strnsave(s, (int)(submatch_match->endp[no] - s));
        }
    }

    return retval;
}
#endif