/*
 * 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 <limits.h>
#include <assert.h>
#include <stdio.h>

#include "netpbm/mallocvar.h"
#include "netpbm/pm.h"
#include "rle.h"



static const char *
match(const char * const nArg,
      const char * const vArg) {
/*----------------------------------------------------------------------------
  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]
-----------------------------------------------------------------------------*/
    const char * n;
    const char * v;

    for (n = nArg, v = vArg; *n != '\0' && *n != '=' && *n == *v; ++n, ++v)
        ;
    if (*n == '\0' || *n == '=') {
        if (*v == '\0')
            return v;
        else if (*v == '=')
            return ++v;
    }

    return NULL;
}



const char *
rle_putcom(const char * const value,
           rle_hdr *    const hdrP) {
/*----------------------------------------------------------------------------
  Put a comment into the header struct, replacing the existing one
    that has the same key, if there is one.
  Inputs:
   value:      Value to add to comments.
   *hdrP:    Header struct to add to.
  Outputs:
   *hdrP:    Modified header struct.
   Returns previous comment having the same key; NULL if none
  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).
-----------------------------------------------------------------------------*/
    if ( hdrP->comments == NULL) {
        MALLOCARRAY_NOFAIL(hdrP->comments, 2);
        hdrP->comments[0] = value;
        hdrP->comments[1] = NULL;
    } else {
        const char ** cp;
        const char * v;
        const char ** oldComments;
        unsigned int i;

        for (i = 2, cp = hdrP->comments;
             *cp != NULL && i < UINT_MAX;
             ++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.
         */
        oldComments = hdrP->comments;
        MALLOCARRAY(hdrP->comments, i);
        if (hdrP->comments == NULL)
            pm_error("Unable to allocate memory for comments");
        assert(i >= 2);
        hdrP->comments[--i] = NULL;
        hdrP->comments[--i] = value;
        for (; i > 0; --i)
            hdrP->comments[i-1] = oldComments[i-1];
    }

    return NULL;
}