1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.11 2002/03/26 22:29:54 swa Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/deanimate.c,v $
6 * Purpose : Declares functions to deanimate GIF images on the fly.
8 * Functions declared include: gif_deanimate, buf_free,
9 * buf_copy, buf_getbyte, gif_skip_data_block, and
12 * Copyright : Written by and Copyright (C) 2001 by the the SourceForge
13 * Privoxy team. http://www.privoxy.org/
15 * Based on the GIF file format specification (see
16 * http://tronche.com/computer-graphics/gif/gif89a.html)
17 * and ideas from the Image::DeAnim Perl module by
18 * Ken MacFarlane, <ksm+cpan@universal.dca.net>
20 * This program is free software; you can redistribute it
21 * and/or modify it under the terms of the GNU General
22 * Public License as published by the Free Software
23 * Foundation; either version 2 of the License, or (at
24 * your option) any later version.
26 * This program is distributed in the hope that it will
27 * be useful, but WITHOUT ANY WARRANTY; without even the
28 * implied warranty of MERCHANTABILITY or FITNESS FOR A
29 * PARTICULAR PURPOSE. See the GNU General Public
30 * License for more details.
32 * The GNU General Public License should be included with
33 * this file. If not, you can view it at
34 * http://www.gnu.org/copyleft/gpl.html
35 * or write to the Free Software Foundation, Inc., 59
36 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
39 * $Log: deanimate.c,v $
40 * Revision 1.11 2002/03/26 22:29:54 swa
41 * we have a new homepage!
43 * Revision 1.10 2002/03/24 13:25:43 swa
44 * name change related issues
46 * Revision 1.9 2002/03/13 00:27:04 jongfoster
49 * Revision 1.8 2002/03/09 19:42:47 jongfoster
50 * Fixing more warnings
52 * Revision 1.7 2002/03/08 17:46:04 jongfoster
53 * Fixing int/size_t warnings
55 * Revision 1.6 2002/03/07 03:46:17 oes
56 * Fixed compiler warnings
58 * Revision 1.5 2001/09/10 10:16:06 oes
59 * Silenced compiler warnings
61 * Revision 1.4 2001/07/18 12:28:49 oes
62 * - Added feature for extracting the first frame
64 * - Separated image buffer extension into buf_extend
65 * - Extended gif deanimation to GIF87a (untested!)
68 * Revision 1.3 2001/07/15 13:57:50 jongfoster
69 * Adding #includes string.h and miscutil.h
71 * Revision 1.2 2001/07/13 13:46:20 oes
72 * Introduced GIF deanimation feature
75 **********************************************************************/
84 #include "deanimate.h"
87 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
89 /*********************************************************************
93 * Description : Safely frees a struct binbuffer
96 * 1 : buf = Pointer to the binbuffer to be freed
100 *********************************************************************/
101 void buf_free(struct binbuffer *buf)
103 if (buf == NULL) return;
105 if (buf->buffer != NULL)
115 /*********************************************************************
117 * Function : buf_extend
119 * Description : Ensure that a given binbuffer can hold a given amount
120 * of bytes, by reallocating its buffer if necessary.
121 * Allocate new mem in chunks of 1024 bytes, so we don't
122 * have to realloc() too often.
125 * 1 : buf = Pointer to the binbuffer
126 * 2 : length = Desired minimum size
129 * Returns : 0 on success, 1 on failiure.
131 *********************************************************************/
132 int buf_extend(struct binbuffer *buf, size_t length)
136 if (buf->offset + length > buf->size)
138 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
139 newbuf = (char *)realloc(buf->buffer, buf->size);
148 buf->buffer = newbuf;
157 /*********************************************************************
159 * Function : buf_copy
161 * Description : Safely copies a given amount of bytes from one
162 * struct binbuffer to another, advancing the
163 * offsets appropriately.
166 * 1 : src = Pointer to the source binbuffer
167 * 2 : dst = Pointer to the destination binbuffer
168 * 3 : length = Number of bytes to be copied
170 * Returns : 0 on success, 1 on failiure.
172 *********************************************************************/
173 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
177 * Sanity check: Can't copy more data than we have
179 if (src->offset + length > src->size)
185 * Ensure that dst can hold the new data
187 if (buf_extend(dst, length))
193 * Now that it's safe, memcpy() the desired amount of
194 * data from src to dst and adjust the offsets
196 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
197 src->offset += length;
198 dst->offset += length;
205 /*********************************************************************
207 * Function : buf_getbyte
209 * Description : Safely gets a byte from a given binbuffer at a
213 * 1 : src = Pointer to the source binbuffer
214 * 2 : offset = Offset to the desired byte
216 * Returns : The byte on success, or 0 on failiure
218 *********************************************************************/
219 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
221 if (src->offset + offset < src->size)
223 return (unsigned char)*(src->buffer + src->offset + offset);
233 /*********************************************************************
235 * Function : gif_skip_data_block
237 * Description : Safely advances the offset of a given struct binbuffer
238 * that contains a GIF image and whose offset is
239 * positioned at the start of a data block, behind
243 * 1 : buf = Pointer to the binbuffer
245 * Returns : 0 on success, or 1 on failiure
247 *********************************************************************/
248 int gif_skip_data_block(struct binbuffer *buf)
253 * Data blocks are sequences of chunks, which are headed
254 * by a one-byte length field, with the last chunk having
257 while((c = buf_getbyte(buf, 0)) != '\0')
259 if ((buf->offset += c + 1) >= buf->size - 1)
271 /*********************************************************************
273 * Function : gif_extract_image
275 * Description : Safely extracts an image data block from a given
276 * struct binbuffer that contains a GIF image and whose
277 * offset is positioned at the start of a data block
278 * into a given destination binbuffer.
281 * 1 : src = Pointer to the source binbuffer
282 * 2 : dst = Pointer to the destination binbuffer
284 * Returns : 0 on success, or 1 on failiure
286 *********************************************************************/
287 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
292 * Remember the colormap flag and copy the image head
294 c = buf_getbyte(src, 9);
295 if (buf_copy(src, dst, 10))
301 * If the image has a local colormap, copy it.
305 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
310 if (buf_copy(src, dst, 1)) return 1;
313 * Copy the image chunk by chunk.
315 while((c = buf_getbyte(src, 0)) != '\0')
317 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
319 if (buf_copy(src, dst, 1)) return 1;
322 * Trim and rewind the dst buffer
324 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
325 dst->size = dst->offset;
332 /*********************************************************************
334 * Function : gif_deanimate
336 * Description : Deanimate a given GIF image, i.e. given a GIF with
337 * an (optional) image block and an arbitrary number
338 * of image extension blocks, produce an output GIF with
339 * only one image block that contains the last image
340 * (extenstion) block of the original.
341 * Also strip Comments, Application extenstions, etc.
344 * 1 : src = Pointer to the source binbuffer
345 * 2 : dst = Pointer to the destination binbuffer
346 * 3 : get_first_image = Flag: If set, get the first image
347 * If unset (default), get the last
349 * Returns : 0 on success, or 1 on failiure
351 *********************************************************************/
352 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
355 struct binbuffer *image;
357 if (NULL == src || NULL == dst)
362 c = buf_getbyte(src, 10);
365 * Check & copy GIF header
367 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
373 if (buf_copy(src, dst, 13))
380 * Look for global colormap and copy if found.
384 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
391 * Reserve a buffer for the current image block
393 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
399 * Parse the GIF block by block and copy the relevant
402 while(src->offset < src->size)
404 switch(buf_getbyte(src, 0))
407 * End-of-GIF Marker: Append current image and return
413 * Image block: Extract to current image buffer.
417 if (gif_extract_image(src, image)) goto failed;
418 if (get_first_image) goto write;
422 * Extension block: Look at next byte and decide
425 switch (buf_getbyte(src, 1))
428 * Image extension: Copy extension header and image
429 * to the current image buffer
433 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
434 if (gif_extract_image(src, image)) goto failed;
435 if (get_first_image) goto write;
439 * Application extension: Skip
442 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
446 * Comment extension: Skip
449 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
453 * Plain text extension: Skip
456 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
460 * Ooops, what type of extension is that?
468 * Ooops, what type of block is that?
474 } /* -END- while src */
477 * Either we got here by goto, or because the GIF is
478 * bogus and EOF was reached before an end-of-gif marker
487 * Append the current image to dst and return
491 if (buf_copy(image, dst, image->size)) goto failed;
492 if (buf_extend(dst, 1)) goto failed;
493 *(dst->buffer + dst->offset++) = 0x3b;