/*

    File: file_png.c

    Copyright (C) 1998-2007 Christophe GRENIER <grenier@cgsecurity.org>
    Thanks to Holger Klemm for JNG (JPEG Network Graphics) and
    MNG (Multiple-Image Network Graphics) support (2006)
  
    This software 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 of the License, 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; if not, write the Free Software Foundation, Inc., 51
    Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

 */
/*
   MNG (Multiple-image Network Graphics) Format
   http://www.libpng.org/pub/mng/spec/
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include <stdio.h>
#include "types.h"
#include "filegen.h"


static void register_header_check_png(file_stat_t *file_stat);
static int header_check_png(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new);
static void file_check_png(file_recovery_t *file_recovery);

const file_hint_t file_hint_png= {
  .extension="png",
  .description="Portable/JPEG/Multiple-Image Network Graphics",
  .min_header_distance=0,
  .max_filesize=PHOTOREC_MAX_FILE_SIZE,
  .recover=1,
  .enable_by_default=1,
  .register_header_check=&register_header_check_png
};

static const unsigned char png_header[8]= { 0x89, 'P', 'N','G', 0x0d, 0x0a, 0x1a, 0x0a};
static const unsigned char mng_header[8]= { 0x8a, 'M', 'N','G', 0x0d, 0x0a, 0x1a, 0x0a};
static const unsigned char jng_header[8]= { 0x8b, 'J', 'N','G', 0x0d, 0x0a, 0x1a, 0x0a};

static void register_header_check_png(file_stat_t *file_stat)
{
  register_header_check(0, png_header,sizeof(png_header), &header_check_png, file_stat);
  register_header_check(0, mng_header,sizeof(mng_header), &header_check_png, file_stat);
  register_header_check(0, jng_header,sizeof(jng_header), &header_check_png, file_stat);
}

static int header_check_png(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
{
  if(memcmp(buffer,png_header,sizeof(png_header))==0)
  {
    reset_file_recovery(file_recovery_new);
    file_recovery_new->min_filesize=92;
    file_recovery_new->file_check=file_check_png;
    file_recovery_new->extension=file_hint_png.extension;
    return 1;
  }
  if(memcmp(buffer,jng_header,sizeof(jng_header))==0)
  {
    reset_file_recovery(file_recovery_new);
    file_recovery_new->min_filesize=92;
    file_recovery_new->file_check=file_check_png;
    file_recovery_new->extension="jng";
    return 1;
  }
  if(memcmp(buffer,mng_header,sizeof(mng_header))==0)
  {
    reset_file_recovery(file_recovery_new);
    file_recovery_new->min_filesize=92;
    file_recovery_new->file_check=file_check_png;
    file_recovery_new->extension="mng";
    return 1;
  }
  return 0;
}

static void file_check_png(file_recovery_t *file_recovery)
{
  const unsigned char mng_footer[4]= {'M','E','N','D'};
  const unsigned char png_footer[4]= {'I','E','N','D'};
  if(strstr(file_recovery->filename,".mng")!=NULL)
    file_search_footer(file_recovery, mng_footer,sizeof(mng_footer));
  else
    file_search_footer(file_recovery, png_footer,sizeof(png_footer));
  if(file_recovery->file_size>0)
    file_recovery->file_size+=4;
}