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/* backupfile.c -- make Emacs style backup file names

   Copyright (C) 1990,1991,1992,1993,1995,1997 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 2, or (at your option)

   any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; see the file COPYING.

   If not, write to the Free Software Foundation,

   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Written by David MacKenzie <djm@gnu.ai.mit.edu>.

   Some algorithms adapted from GNU Emacs. */

#if HAVE_CONFIG_H

# include <config.h>

#endif

#include <argmatch.h>

#include <backupfile.h>

#include <stdio.h>

#include <sys/types.h>

#if HAVE_STRING_H

# include <string.h>

#else

# include <strings.h>

#endif

#if HAVE_DIRENT_H

# include <dirent.h>

# define NLENGTH(direct) strlen ((direct)->d_name)

#else

# define dirent direct

# define NLENGTH(direct) ((size_t) (direct)->d_namlen)

# if HAVE_SYS_NDIR_H

#  include <sys/ndir.h>

# endif

# if HAVE_SYS_DIR_H

#  include <sys/dir.h>

# endif

# if HAVE_NDIR_H

#  include <ndir.h>

# endif

#endif

#if CLOSEDIR_VOID

/* Fake a return value. */

# define CLOSEDIR(d) (closedir (d), 0)

#else

# define CLOSEDIR(d) closedir (d)

#endif

#if STDC_HEADERS

# include <stdlib.h>

#else

char *malloc ();

#endif

#if HAVE_DIRENT_H || HAVE_NDIR_H || HAVE_SYS_DIR_H || HAVE_SYS_NDIR_H

# define HAVE_DIR 1

#else

# define HAVE_DIR 0

#endif

#if HAVE_LIMITS_H

# include <limits.h>

#endif

#ifndef CHAR_BIT

#define CHAR_BIT 8

#endif

/* Upper bound on the string length of an integer converted to string.

   302 / 1000 is ceil (log10 (2.0)).  Subtract 1 for the sign bit;

   add 1 for integer division truncation; add 1 more for a minus sign.  */

#define INT_STRLEN_BOUND(t) ((sizeof (t) * CHAR_BIT - 1) * 302 / 1000 + 2)

/* ISDIGIT differs from isdigit, as follows:

   - Its arg may be any int or unsigned int; it need not be an unsigned char.

   - It's guaranteed to evaluate its argument exactly once.

   - It's typically faster.

   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that

   only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless

   it's important to use the locale's definition of `digit' even when the

   host does not conform to Posix.  */

#define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)

#if D_INO_IN_DIRENT

# define REAL_DIR_ENTRY(dp) ((dp)->d_ino != 0)

#else

# define REAL_DIR_ENTRY(dp) 1

#endif

/* Which type of backup file names are generated. */

enum backup_type backup_type = none;

/* The extension added to file names to produce a simple (as opposed

   to numbered) backup file name. */

const char *simple_backup_suffix = ".orig";

static int max_backup_version __BACKUPFILE_P ((const char *, const char *));

static int version_number __BACKUPFILE_P ((const char *, const char *, size_t));

/* Return the name of the new backup file for file FILE,

   allocated with malloc.  Return 0 if out of memory.

   FILE must not end with a '/' unless it is the root directory.

   Do not call this function if backup_type == none. */

char *

find_backup_file_name (file)

     const char *file;

{

  size_t backup_suffix_size_max;

  size_t file_len = strlen (file);

  size_t numbered_suffix_size_max = INT_STRLEN_BOUND (int) + 4;

  char *s;

  const char *suffix = simple_backup_suffix;

  /* Allow room for simple or `.~N~' backups.  */

  backup_suffix_size_max = strlen (simple_backup_suffix) + 1;

  if (HAVE_DIR && backup_suffix_size_max < numbered_suffix_size_max)

    backup_suffix_size_max = numbered_suffix_size_max;

  s = malloc (file_len + backup_suffix_size_max + numbered_suffix_size_max);

  if (s)

    {

      strcpy (s, file);

#if HAVE_DIR

      if (backup_type != simple)

	{

	  int highest_backup;

	  size_t dir_len = base_name (s) - s;

	  strcpy (s + dir_len, ".");

	  highest_backup = max_backup_version (file + dir_len, s);

	  if (! (backup_type == numbered_existing && highest_backup == 0))

	    {

	      char *numbered_suffix = s + (file_len + backup_suffix_size_max);

	      sprintf (numbered_suffix, ".~%d~", highest_backup + 1);

	      suffix = numbered_suffix;

	    }

	  strcpy (s, file);

	}

#endif /* HAVE_DIR */

      addext (s, suffix, '~');

    }

  return s;

}

#if HAVE_DIR

/* Return the number of the highest-numbered backup file for file

   FILE in directory DIR.  If there are no numbered backups

   of FILE in DIR, or an error occurs reading DIR, return 0.

   */

static int

max_backup_version (file, dir)

     const char *file;

     const char *dir;

{

  DIR *dirp;

  struct dirent *dp;

  int highest_version;

  int this_version;

  size_t file_name_length;

  dirp = opendir (dir);

  if (!dirp)

    return 0;

  highest_version = 0;

  file_name_length = strlen (file);

  while ((dp = readdir (dirp)) != 0)

    {

      if (!REAL_DIR_ENTRY (dp) || NLENGTH (dp) < file_name_length + 4)

	continue;

      this_version = version_number (file, dp->d_name, file_name_length);

      if (this_version > highest_version)

	highest_version = this_version;

    }

  if (CLOSEDIR (dirp))

    return 0;

  return highest_version;

}

/* If BACKUP is a numbered backup of BASE, return its version number;

   otherwise return 0.  BASE_LENGTH is the length of BASE.

   */

static int

version_number (base, backup, base_length)

     const char *base;

     const char *backup;

     size_t base_length;

{

  int version;

  const char *p;

  version = 0;

  if (strncmp (base, backup, base_length) == 0

      && backup[base_length] == '.'

      && backup[base_length + 1] == '~')

    {

      for (p = &backup[base_length + 2]; ISDIGIT (*p); ++p)

	version = version * 10 + *p - '0';

      if (p[0] != '~' || p[1])

	version = 0;

    }

  return version;

}

#endif /* HAVE_DIR */

static const char * const backup_args[] =

{

  "never", "simple", "nil", "existing", "t", "numbered", 0

};

static const enum backup_type backup_types[] =

{

  simple, simple, numbered_existing, numbered_existing, numbered, numbered

};

/* Return the type of backup indicated by VERSION.

   Unique abbreviations are accepted. */

enum backup_type

get_version (version)

     const char *version;

{

  int i;

  if (version == 0 || *version == 0)

    return numbered_existing;

  i = argmatch (version, backup_args);

  if (i < 0)

    {

      invalid_arg ("version control type", version, i);

      exit (2);

    }

  return backup_types[i];

}