217 lines
8.1 KiB
C
217 lines
8.1 KiB
C
/*
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File: file_gif.c
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Copyright (C) 1998-2007 Christophe GRENIER <grenier@cgsecurity.org>
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This software is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write the Free Software Foundation, Inc., 51
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Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#if !defined(SINGLE_FORMAT) || defined(SINGLE_FORMAT_gif)
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#ifdef HAVE_STRING_H
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#include <string.h>
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#endif
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#include <stdio.h>
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#include "types.h"
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#include "filegen.h"
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#include "log.h"
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/*@ requires valid_register_header_check(file_stat); */
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static void register_header_check_gif(file_stat_t *file_stat);
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static data_check_t data_check_gif2(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery);
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const file_hint_t file_hint_gif= {
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.extension="gif",
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.description="Graphic Interchange Format",
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.max_filesize=PHOTOREC_MAX_FILE_SIZE,
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.recover=1,
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.enable_by_default=1,
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.register_header_check=®ister_header_check_gif
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};
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/*@
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@ requires file_recovery->file_check == &file_check_gif;
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@ requires valid_file_check_param(file_recovery);
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@ ensures valid_file_check_result(file_recovery);
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@ assigns *file_recovery->handle, errno, file_recovery->file_size;
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@ assigns Frama_C_entropy_source;
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@*/
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static void file_check_gif(file_recovery_t *file_recovery)
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{
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const char gif_footer[2]= {0x00, 0x3b};
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char buffer[2];
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/* file_recovery->calculated_file_size is always >= */
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if(file_recovery->calculated_file_size < 2 ||
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my_fseek(file_recovery->handle, file_recovery->calculated_file_size-2, SEEK_SET)<0 ||
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fread(buffer, 2, 1, file_recovery->handle)!=1)
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{
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file_recovery->file_size=0;
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return;
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}
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#ifdef __FRAMAC__
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Frama_C_make_unknown(&buffer, sizeof(buffer));
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#endif
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if(memcmp(buffer, gif_footer, sizeof(gif_footer))!=0)
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{
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file_recovery->file_size=0;
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return;
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}
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file_recovery->file_size=file_recovery->calculated_file_size;
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}
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/*@
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@ requires file_recovery->data_check==&data_check_gif;
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@ requires valid_data_check_param(buffer, buffer_size, file_recovery);
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@ ensures valid_data_check_result(\result, file_recovery);
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@ assigns file_recovery->calculated_file_size, file_recovery->data_check;
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@*/
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static data_check_t data_check_gif(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
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{
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if(file_recovery->calculated_file_size + buffer_size/2 >= file_recovery->file_size &&
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file_recovery->calculated_file_size + 1 < file_recovery->file_size + buffer_size/2)
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{
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const unsigned int i=file_recovery->calculated_file_size + buffer_size/2 - file_recovery->file_size;
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/*@ assert 0 <= i < buffer_size - 1; */
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#ifdef DEBUG_GIF
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log_info("data_check_gif calculated_file_size=0x%llx: 0x%02x\n",
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(long long unsigned)file_recovery->calculated_file_size, buffer[i]);
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#endif
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switch(buffer[i])
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{
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case 0x21:
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/* Plain Text Extension 21 01 ... */
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/* Graphic Control Extension 21 f9 04 XX XX XX XX 00 */
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/* Comment Extension 21 fe ... */
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/* Application Extension 21 ff */
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file_recovery->calculated_file_size+=2;
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if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
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return DC_STOP;
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/*@ assert file_recovery->calculated_file_size < PHOTOREC_MAX_FILE_SIZE; */
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file_recovery->data_check=&data_check_gif2;
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return data_check_gif2(buffer, buffer_size, file_recovery);
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case 0x2c:
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if(i + 20 < buffer_size)
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{
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unsigned int j=10+1;
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/* 1 Image Descriptor id=0x2c
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* 4: NW corner
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* 4: width, heigth,
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* 1: is a local color table present ? */
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if(((buffer[i+9]>>7)&0x1)>0)
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{
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/* local color table */
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j+=3<<((buffer[i+9]&7)+1);
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}
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file_recovery->calculated_file_size+=j;
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/* 1: Start of image - LZW minimum code size */
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/* Table Based Image Data */
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if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
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return DC_STOP;
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file_recovery->data_check=&data_check_gif2;
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return data_check_gif2(buffer, buffer_size, file_recovery);
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}
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return DC_CONTINUE;
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case 0x3b:
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/* Trailer */
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file_recovery->calculated_file_size++;
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return DC_STOP;
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default:
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return DC_ERROR;
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}
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}
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return DC_CONTINUE;
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}
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/*@
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@ requires file_recovery->data_check==&data_check_gif2;
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@ requires valid_data_check_param(buffer, buffer_size, file_recovery);
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@ ensures valid_data_check_result(\result, file_recovery);
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@ assigns file_recovery->calculated_file_size, file_recovery->data_check;
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@*/
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static data_check_t data_check_gif2(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
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{
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/*@ loop assigns file_recovery->calculated_file_size, file_recovery->data_check; */
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while(file_recovery->calculated_file_size + buffer_size/2 >= file_recovery->file_size &&
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file_recovery->calculated_file_size + 1 < file_recovery->file_size + buffer_size/2)
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{
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const unsigned int i=file_recovery->calculated_file_size + buffer_size/2 - file_recovery->file_size;
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/*@ assert 0 <= i < buffer_size - 1; */
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#ifdef DEBUG_GIF
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log_info("data_check_gif2 calculated_file_size=0x%llx\n",
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(long long unsigned)file_recovery->calculated_file_size);
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#endif
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file_recovery->calculated_file_size+=(uint64_t)1+buffer[i];
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if(file_recovery->calculated_file_size >= PHOTOREC_MAX_FILE_SIZE)
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return DC_STOP;
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/*@ assert file_recovery->calculated_file_size < PHOTOREC_MAX_FILE_SIZE; */
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if(buffer[i]==0)
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{
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file_recovery->data_check=&data_check_gif;
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return data_check_gif(buffer, buffer_size, file_recovery);
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}
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}
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return DC_CONTINUE;
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}
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/*@
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@ requires buffer_size >= 6+7+(3<<8)+1;
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@ requires separation: \separated(&file_hint_gif, buffer+(..), file_recovery, file_recovery_new);
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@ requires valid_header_check_param(buffer, buffer_size, safe_header_only, file_recovery, file_recovery_new);
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@ ensures valid_header_check_result(\result, file_recovery_new);
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@ ensures (\result == 1) ==> file_recovery_new->file_size == 0;
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@ ensures (\result == 1) ==> (file_recovery_new->extension == file_hint_gif.extension);
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@ ensures (\result == 1) ==> (file_recovery_new->time == 0);
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@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->calculated_file_size >= 6+7);
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@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->data_check == &data_check_gif);
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@ ensures (\result == 1 && file_recovery_new->blocksize>=2) ==> (file_recovery_new->file_check == &file_check_gif);
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@ assigns *file_recovery_new;
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@*/
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static int header_check_gif(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)
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{
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uint64_t offset;
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offset=6; /* Header */
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offset+=7; /* Logical Screen Descriptor */
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if((buffer[10]>>7)&0x1)
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{
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/* Global Color Table */
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offset+=3<<((buffer[10]&7)+1);
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}
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if(offset < buffer_size && buffer[offset]!=0x21 && buffer[offset]!=0x2c)
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return 0;
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reset_file_recovery(file_recovery_new);
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file_recovery_new->extension=file_hint_gif.extension;
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file_recovery_new->min_filesize=42;
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if(file_recovery_new->blocksize < 2)
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return 1;
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file_recovery_new->calculated_file_size=offset;
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file_recovery_new->file_check=&file_check_gif;
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file_recovery_new->data_check=&data_check_gif;
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return 1;
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}
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static void register_header_check_gif(file_stat_t *file_stat)
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{
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static const unsigned char gif_header[6]= { 'G','I','F','8','7','a'};
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static const unsigned char gif_header2[6]= { 'G','I','F','8','9','a'};
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register_header_check(0, gif_header,sizeof(gif_header), &header_check_gif, file_stat);
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#ifndef __FRAMAC__
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register_header_check(0, gif_header2,sizeof(gif_header2), &header_check_gif, file_stat);
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#endif
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}
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#endif
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