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/*

    		 Crown Copyright (c) 1997

    This TenDRA(r) Computer Program is subject to Copyright

    owned by the United Kingdom Secretary of State for Defence

    acting through the Defence Evaluation and Research Agency

    (DERA).  It is made available to Recipients with a

    royalty-free licence for its use, reproduction, transfer

    to other parties and amendment for any purpose not excluding

    product development provided that any such use et cetera

    shall be deemed to be acceptance of the following conditions:-

        (1) Its Recipients shall ensure that this Notice is

        reproduced upon any copies or amended versions of it;

        (2) Any amended version of it shall be clearly marked to

        show both the nature of and the organisation responsible

        for the relevant amendment or amendments;

        (3) Its onward transfer from a recipient to another

        party shall be deemed to be that party's acceptance of

        these conditions;

        (4) DERA gives no warranty or assurance as to its

        quality or suitability for any purpose and DERA accepts

        no liability whatsoever in relation to any use to which

        it may be put.

*/

#define calculus_IO_ROUTINES

#include "config.h"

#include "read.h"

#include "calculus.h"

#include "common.h"

#include "error.h"

#include "output.h"

#include "xalloc.h"

/*

    BITMASKS

    This array gives the masks for each bit value.

*/

unsigned long bitmask [ CHAR_BIT ] ;

/*

    INITIALISE MASKS

    This routine initialises the array of bitmasks.  This is done

    dynamically rather than statically in case CHAR_BIT is not 8.

*/

void init_bitmask

    PROTO_Z ()

{

    int i ;

    for ( i = 0 ; i < CHAR_BIT ; i++ ) bitmask [i] = MASK ( i ) ;

    return ;

}

/*

    INPUT FILE

    These variables describe the input file.  There is a one byte input

    buffer.

*/

static FILE *input_file ;

static unsigned long input_buff = 0 ;

static int input_bits = 0 ;

/*

    READ A NUMBER OF BITS

    This routine reads the next n bits from the input file.

*/

static unsigned long read_bits

    PROTO_N ( ( n ) )

    PROTO_T ( int n )

{

    int b = input_bits ;

    unsigned long m = input_buff ;

    unsigned long r = 0 ;

    while ( n ) {

	if ( b == 0 ) {

	    /* Read next byte */

	    int c = getc ( input_file ) ;

	    if ( c == EOF ) {

		error ( ERROR_FATAL, "Premature end of file" ) ;

	    } else {

		m = ( ( ( unsigned long ) c ) & MASK ( CHAR_BIT ) ) ;

	    }

	    b = CHAR_BIT ;

	}

	if ( n >= b ) {

	    r = ( r << b ) | m ;

	    n -= b ;

	    b = 0 ;

	} else {

	    int c = b - n ;

	    r = ( r << n ) | ( m >> c ) ;

	    m &= bitmask [c] ;

	    n = 0 ;

	    b = c ;

	}

    }

    input_bits = b ;

    input_buff = m ;

    return ( r ) ;

}

/*

    READ AN INTEGER

    This routine reads an integer from the input file.  This is encoded

    as a sequence of octal digits with a marker bit for the end of the

    number.

*/

static unsigned long read_int

    PROTO_Z ()

{

    unsigned long r = 0, d ;

    while ( d = read_bits ( 4 ), ( d & 0x08 ) == 0 ) {

	r = ( r << 3 ) | d ;

    }

    r = ( r << 3 ) | ( d & 0x07 ) ;

    return ( r ) ;

}

/*

    READ A STRING

    This routine reads an integer from the input file.  This is encoded

    as the string length followed by the characters comprising the

    string (8 bits each).

*/

static char *read_string

    PROTO_Z ()

{

    unsigned long i, n = read_int () ;

    char *s = xstr ( ( long ) ( n + 1 ) ) ;

    for ( i = 0 ; i < n ; i++ ) {

	s [i] = ( char ) read_bits ( 8 ) ;

    }

    s [n] = 0 ;

    return ( s ) ;

}

/*

    READ A FILENAME

    File names are just strings, however they are buffered to save

    space.

*/

static char *read_filename

    PROTO_Z ()

{

    char *s ;

    static char *last_filename = "????" ;

    if ( read_bits ( 1 ) ) {

	s = last_filename ;

    } else {

	s = read_string () ;

	last_filename = s ;

    }

    return ( s ) ;

}

/*

    AUTOMATICALLY GENERATED DISK READING ROUTINES

    The main disk reading routines are automatically generated.  The

    various macros are used to customise these routines.

*/

#define READ_BITS( N )		( ( unsigned ) read_bits ( N ) )

#define READ_ALIAS()		( ( unsigned ) read_int () )

#define READ_DIM()		( ( unsigned ) read_int () )

#define READ_int()		( ( int ) read_int () )

#define READ_number()		( ( number ) read_int () )

#define READ_string()		read_string ()

#define READ_name_string()	read_filename ()

#define READ_zero_int()		0

#include "read_def.h"

/*

    READ AN INPUT FILE

    This routine reads an algebra from the input file nm.

*/

void read_file

    PROTO_N ( ( nm ) )

    PROTO_T ( char *nm )

{

    char *s ;

    /* Open file */

    crt_line_no = -1 ;

    crt_file_name = nm ;

    input_file = fopen ( nm, "rb" ) ;

    if ( input_file == NULL ) {

	error ( ERROR_SERIOUS, "Can't open input file, '%s'", nm ) ;

	return ;

    }

    init_bitmask () ;

    input_buff = 0 ;

    input_bits = 0 ;

    /* Confirm file header */

    s = READ_string () ;

    if ( !streq ( s, calculus_NAME ) ) {

	error ( ERROR_FATAL, "Invalid file header identifier" ) ;

    }

    s = READ_string () ;

    if ( !streq ( s, calculus_VERSION ) ) {

	error ( ERROR_FATAL, "Invalid file header version, '%s'", s ) ;

    }

    /* Read the algebra */

    algebra->name = READ_string () ;

    algebra->major_no = READ_int () ;

    algebra->minor_no = READ_int () ;

    algebra->types = READ_list_ptr_type () ;

    clear_calculus_alias () ;

    /* Extract lists of primitives etc */

    LOOP_TYPE {

	TYPE_P t = CRT_TYPE ;

	TYPE t0 = DEREF_type ( t ) ;

	switch ( TAG_type ( t0 ) ) {

	    case type_primitive_tag : {

		PRIMITIVE_P p = DEREF_ptr ( type_primitive_prim ( t0 ) ) ;

		CONS_ptr ( p, algebra->primitives, algebra->primitives ) ;

		break ;

	    }

	    case type_ident_tag : {

		IDENTITY_P p = DEREF_ptr ( type_ident_id ( t0 ) ) ;

		CONS_ptr ( p, algebra->identities, algebra->identities ) ;

		break ;

	    }

	    case type_enumeration_tag : {

		ENUM_P p = DEREF_ptr ( type_enumeration_en ( t0 ) ) ;

		CONS_ptr ( p, algebra->enumerations, algebra->enumerations ) ;

		break ;

	    }

	    case type_structure_tag : {

		STRUCTURE_P p = DEREF_ptr ( type_structure_struc ( t0 ) ) ;

		CONS_ptr ( p, algebra->structures, algebra->structures ) ;

		break ;

	    }

	    case type_onion_tag : {

		UNION_P p = DEREF_ptr ( type_onion_un ( t0 ) ) ;

		CONS_ptr ( p, algebra->unions, algebra->unions ) ;

		break ;

	    }

	}

    }

    /* Close file */

    fclose_v ( input_file ) ;

    return ;

}