486 lines
12 KiB
C
486 lines
12 KiB
C
const char deanimate_rcs[] = "$Id: deanimate.c,v 1.21 2011/09/04 11:10:56 fabiankeil Exp $";
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/*********************************************************************
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*
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* File : $Source: /cvsroot/ijbswa/current/deanimate.c,v $
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*
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* Purpose : Declares functions to manipulate binary images on the
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* fly. High-level functions include:
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* - Deanimation of GIF images
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*
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* Functions declared include: gif_deanimate, buf_free,
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* buf_copy, buf_getbyte, gif_skip_data_block
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* and gif_extract_image
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*
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* Copyright : Written by and Copyright (C) 2001 - 2004, 2006 by the
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* SourceForge Privoxy team. http://www.privoxy.org/
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*
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* Based on the GIF file format specification (see
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* http://tronche.com/computer-graphics/gif/gif89a.html)
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* and ideas from the Image::DeAnim Perl module by
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* Ken MacFarlane, <ksm+cpan@universal.dca.net>
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*
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* This program is free software; you can redistribute it
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* and/or modify it under the terms of the GNU General
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* Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will
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* be useful, but WITHOUT ANY WARRANTY; without even the
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* implied warranty of MERCHANTABILITY or FITNESS FOR A
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* PARTICULAR PURPOSE. See the GNU General Public
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* License for more details.
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*
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* The GNU General Public License should be included with
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* this file. If not, you can view it at
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* http://www.gnu.org/copyleft/gpl.html
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* or write to the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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**********************************************************************/
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#include "config.h"
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#include <string.h>
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#include <fcntl.h>
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#include "errlog.h"
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#include "project.h"
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#include "deanimate.h"
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#include "miscutil.h"
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const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
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/*********************************************************************
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*
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* Function : buf_free
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*
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* Description : Safely frees a struct binbuffer
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*
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* Parameters :
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* 1 : buf = Pointer to the binbuffer to be freed
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*
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* Returns : N/A
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*
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*********************************************************************/
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void buf_free(struct binbuffer *buf)
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{
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if (buf == NULL) return;
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if (buf->buffer != NULL)
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{
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free(buf->buffer);
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}
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free(buf);
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}
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/*********************************************************************
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*
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* Function : buf_extend
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*
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* Description : Ensure that a given binbuffer can hold a given amount
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* of bytes, by reallocating its buffer if necessary.
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* Allocate new mem in chunks of 1024 bytes, so we don't
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* have to realloc() too often.
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*
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* Parameters :
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* 1 : buf = Pointer to the binbuffer
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* 2 : length = Desired minimum size
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*
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*
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* Returns : 0 on success, 1 on failure.
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*
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*********************************************************************/
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static int buf_extend(struct binbuffer *buf, size_t length)
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{
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char *newbuf;
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if (buf->offset + length > buf->size)
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{
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buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
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newbuf = (char *)realloc(buf->buffer, buf->size);
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if (newbuf == NULL)
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{
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freez(buf->buffer);
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return 1;
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}
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else
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{
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buf->buffer = newbuf;
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return 0;
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}
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}
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return 0;
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}
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/*********************************************************************
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*
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* Function : buf_copy
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*
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* Description : Safely copies a given amount of bytes from one
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* struct binbuffer to another, advancing the
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* offsets appropriately.
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*
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* Parameters :
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* 1 : src = Pointer to the source binbuffer
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* 2 : dst = Pointer to the destination binbuffer
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* 3 : length = Number of bytes to be copied
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*
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* Returns : 0 on success, 1 on failure.
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*
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*********************************************************************/
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static int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
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{
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/*
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* Sanity check: Can't copy more data than we have
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*/
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if (src->offset + length > src->size)
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{
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return 1;
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}
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/*
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* Ensure that dst can hold the new data
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*/
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if (buf_extend(dst, length))
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{
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return 1;
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}
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/*
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* Now that it's safe, memcpy() the desired amount of
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* data from src to dst and adjust the offsets
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*/
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memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
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src->offset += length;
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dst->offset += length;
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return 0;
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}
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/*********************************************************************
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*
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* Function : buf_getbyte
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*
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* Description : Safely gets a byte from a given binbuffer at a
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* given offset
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*
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* Parameters :
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* 1 : src = Pointer to the source binbuffer
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* 2 : offset = Offset to the desired byte
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*
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* Returns : The byte on success, or 0 on failure
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*
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*********************************************************************/
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static unsigned char buf_getbyte(const struct binbuffer *src, size_t offset)
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{
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if (src->offset + offset < src->size)
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{
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return (unsigned char)*(src->buffer + src->offset + offset);
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}
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else
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{
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return '\0';
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}
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}
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/*********************************************************************
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*
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* Function : gif_skip_data_block
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*
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* Description : Safely advances the offset of a given struct binbuffer
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* that contains a GIF image and whose offset is
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* positioned at the start of a data block, behind
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* that block.
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*
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* Parameters :
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* 1 : buf = Pointer to the binbuffer
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*
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* Returns : 0 on success, or 1 on failure
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*
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*********************************************************************/
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static int gif_skip_data_block(struct binbuffer *buf)
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{
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unsigned char c;
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/*
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* Data blocks are sequences of chunks, which are headed
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* by a one-byte length field, with the last chunk having
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* zero length.
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*/
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while((c = buf_getbyte(buf, 0)) != '\0')
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{
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buf->offset += (size_t)c + 1;
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if (buf->offset >= buf->size - 1)
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{
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return 1;
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}
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}
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buf->offset++;
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return 0;
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}
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/*********************************************************************
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*
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* Function : gif_extract_image
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*
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* Description : Safely extracts an image data block from a given
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* struct binbuffer that contains a GIF image and whose
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* offset is positioned at the start of a data block
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* into a given destination binbuffer.
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*
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* Parameters :
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* 1 : src = Pointer to the source binbuffer
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* 2 : dst = Pointer to the destination binbuffer
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*
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* Returns : 0 on success, or 1 on failure
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*
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*********************************************************************/
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static int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
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{
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unsigned char c;
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/*
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* Remember the colormap flag and copy the image head
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*/
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c = buf_getbyte(src, 9);
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if (buf_copy(src, dst, 10))
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{
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return 1;
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}
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/*
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* If the image has a local colormap, copy it.
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*/
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if (c & 0x80)
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{
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int map_length = 3 * (1 << ((c & 0x07) + 1));
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if (map_length <= 0)
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{
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log_error(LOG_LEVEL_DEANIMATE,
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"colormap length = %d (%c)?", map_length, c);
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return 1;
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}
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if (buf_copy(src, dst, (size_t)map_length))
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{
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return 1;
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}
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}
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if (buf_copy(src, dst, 1)) return 1;
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/*
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* Copy the image chunk by chunk.
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*/
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while((c = buf_getbyte(src, 0)) != '\0')
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{
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if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
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}
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if (buf_copy(src, dst, 1)) return 1;
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/*
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* Trim and rewind the dst buffer
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*/
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if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
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dst->size = dst->offset;
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dst->offset = 0;
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return(0);
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}
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/*********************************************************************
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*
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* Function : gif_deanimate
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*
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* Description : Deanimate a given GIF image, i.e. given a GIF with
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* an (optional) image block and an arbitrary number
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* of image extension blocks, produce an output GIF with
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* only one image block that contains the last image
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* (extenstion) block of the original.
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* Also strip Comments, Application extenstions, etc.
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*
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* Parameters :
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* 1 : src = Pointer to the source binbuffer
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* 2 : dst = Pointer to the destination binbuffer
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* 3 : get_first_image = Flag: If set, get the first image
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* If unset (default), get the last
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*
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* Returns : 0 on success, or 1 on failure
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*
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*********************************************************************/
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int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
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{
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unsigned char c;
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struct binbuffer *image;
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if (NULL == src || NULL == dst)
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{
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return 1;
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}
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c = buf_getbyte(src, 10);
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/*
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* Check & copy GIF header
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*/
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if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
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{
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return 1;
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}
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else
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{
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if (buf_copy(src, dst, 13))
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{
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return 1;
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}
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}
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/*
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* Look for global colormap and copy if found.
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*/
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if(c & 0x80)
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{
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int map_length = 3 * (1 << ((c & 0x07) + 1));
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if (map_length <= 0)
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{
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log_error(LOG_LEVEL_DEANIMATE,
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"colormap length = %d (%c)?", map_length, c);
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return 1;
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}
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if (buf_copy(src, dst, (size_t)map_length))
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{
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return 1;
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}
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}
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/*
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* Reserve a buffer for the current image block
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*/
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if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
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{
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return 1;
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}
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/*
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* Parse the GIF block by block and copy the relevant
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* parts to dst
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*/
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while(src->offset < src->size)
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{
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switch(buf_getbyte(src, 0))
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{
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/*
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* End-of-GIF Marker: Append current image and return
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*/
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case 0x3b:
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goto write;
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/*
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* Image block: Extract to current image buffer.
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*/
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case 0x2c:
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image->offset = 0;
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if (gif_extract_image(src, image)) goto failed;
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if (get_first_image) goto write;
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continue;
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/*
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* Extension block: Look at next byte and decide
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*/
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case 0x21:
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switch (buf_getbyte(src, 1))
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{
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/*
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* Image extension: Copy extension header and image
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* to the current image buffer
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*/
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case 0xf9:
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image->offset = 0;
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if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
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if (gif_extract_image(src, image)) goto failed;
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if (get_first_image) goto write;
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continue;
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/*
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* Application extension: Skip
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*/
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case 0xff:
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if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
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continue;
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/*
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* Comment extension: Skip
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*/
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case 0xfe:
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if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
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continue;
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/*
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* Plain text extension: Skip
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*/
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case 0x01:
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if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
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continue;
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/*
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* Ooops, what type of extension is that?
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*/
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default:
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goto failed;
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}
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/*
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* Ooops, what type of block is that?
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*/
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default:
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goto failed;
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}
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} /* -END- while src */
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/*
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* Either we got here by goto, or because the GIF is
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* bogus and EOF was reached before an end-of-gif marker
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* was found.
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*/
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failed:
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buf_free(image);
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return 1;
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/*
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* Append the current image to dst and return
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*/
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write:
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if (buf_copy(image, dst, image->size)) goto failed;
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if (buf_extend(dst, 1)) goto failed;
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*(dst->buffer + dst->offset++) = 0x3b;
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buf_free(image);
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return 0;
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}
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/*
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Local Variables:
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tab-width: 3
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end:
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*/
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