rle_putcom.c

/*
 * This software is copyrighted as noted below.  It may be freely copied,
 * modified, and redistributed, provided that the copyright notice is
 * preserved on all copies.
 *
 * There is no warranty or other guarantee of fitness for this software,
 * it is provided solely "as is".  Bug reports or fixes may be sent
 * to the author, who may or may not act on them as he desires.
 *
 * You may not include this software in a program or other software product
 * without supplying the source, or without informing the end-user that the
 * source is available for no extra charge.
 *
 * If you modify this software, you should include a notice giving the
 * name of the person performing the modification, the date of modification,
 * and the reason for such modification.
 */
/*
 * rle_putcom.c - Add a picture comment to the header struct.
 *
 * Author:	Spencer W. Thomas
 * 		Computer Science Dept.
 * 		University of Utah
 * Date:	Mon Feb  2 1987
 * Copyright (c) 1987, University of Utah
 */

#include <stdio.h>
#include "rle.h"

/*****************************************************************
 * TAG( match )
 *
 * Match a name against a test string for "name=value" or "name".
 * If it matches name=value, return pointer to value part, if just
 * name, return pointer to NUL at end of string.  If no match, return NULL.
 *
 * Inputs:
 * 	n:	Name to match.  May also be "name=value" to make it easier
 *		to replace comments.
 *	v:	Test string.
 * Outputs:
 * 	Returns pointer as above.
 * Assumptions:
 *	[None]
 * Algorithm:
 *	[None]
 */
static char *
match( n, v )
register char *n;
register char *v;
{
    for ( ; *n != '\0' && *n != '=' && *n == *v; n++, v++ )
	;
    if (*n == '\0' || *n == '=')
	if ( *v == '\0' )
	    return v;
	else if ( *v == '=' )
	    return ++v;

    return NULL;
}

/*****************************************************************
 * TAG( rle_putcom )
 *
 * Put a comment into the header struct.
 * Inputs:
 * 	value:		Value to add to comments.
 *	the_hdr:	Header struct to add to.
 * Outputs:
 * 	the_hdr:	Modified header struct.
 *	Returns previous value;
 * Assumptions:
 * 	value pointer can be used as is (data is NOT copied).
 * Algorithm:
 * 	Find match if any, else add at end (realloc to make bigger).
 */
CONST_DECL char *
rle_putcom( value, the_hdr )
CONST_DECL char * value;
rle_hdr * the_hdr;
{
    register CONST_DECL char ** cp, ** old_comments;
    CONST_DECL char * v;
    int i;

    if ( the_hdr->comments == NULL )
    {
	the_hdr->comments = (CONST_DECL char **)malloc( 2 * sizeof(char *) );
	the_hdr->comments[0] = value;
	the_hdr->comments[1] = NULL;
    }
    else
    {
	for ( i = 2, cp = the_hdr->comments; *cp != NULL; i++, cp++ )
	    if ( match( value, *cp ) != NULL )
	    {
		v = *cp;
		*cp = value;
		return v;
	    }
	/* Not found */
	/* Can't realloc because somebody else might be pointing to this
	 * comments block.  Of course, if this were true, then the
	 * assignment above would change the comments for two headers.
	 * But at least, that won't crash the program.  Realloc will.
	 * This would work a lot better in C++, where hdr1 = hdr2
	 * could copy the pointers, too.
	 */
	old_comments = the_hdr->comments;
	the_hdr->comments = (CONST_DECL char **)malloc(i * sizeof(char *) );
	the_hdr->comments[--i] = NULL;
	the_hdr->comments[--i] = value;
	for ( i--; i >= 0; i-- )
	    the_hdr->comments[i] = old_comments[i];
    }

    return NULL;
}

/*****************************************************************
 * TAG( rle_delcom )
 *
 * Delete a comment from header struct.
 * Inputs:
 * 	name:		Name of comment to delete.
 *	the_hdr:	Header to delete comment from.
 * Outputs:
 * 	the_hdr:	Modified header struct.
 *	Returns original comment value.
 * Assumptions:
 *	[None]
 * Algorithm:
 *	[None]
 */
CONST_DECL char *
rle_delcom( name, the_hdr )
CONST_DECL char * name;
rle_hdr *the_hdr ;
{
    register CONST_DECL char ** cp;
    CONST_DECL char * v = NULL;

    if ( the_hdr->comments == NULL )
	return NULL;
    else
    {
	for ( cp = the_hdr->comments; *cp != NULL; cp++ )
	    if ( match( name, *cp ) != NULL )
	    {
		v = *cp;
		for ( ; *cp != NULL; cp++ )
		    *cp = cp[1];
		break;
	    }
	/* Not found */
    }

    if ( *the_hdr->comments == NULL )
	the_hdr->comments = NULL;

    return v;
}