rle_putcom.c

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/*
 * 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;
}