1 const char deanimate_rcs[] = "$Id: deanimate.c,v 2.0 2002/06/04 14:34:21 jongfoster Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/src/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 2.0 2002/06/04 14:34:21 jongfoster
41 * Moving source files to src/
43 * Revision 1.12 2002/05/12 21:36:29 jongfoster
44 * Correcting function comments
46 * Revision 1.11 2002/03/26 22:29:54 swa
47 * we have a new homepage!
49 * Revision 1.10 2002/03/24 13:25:43 swa
50 * name change related issues
52 * Revision 1.9 2002/03/13 00:27:04 jongfoster
55 * Revision 1.8 2002/03/09 19:42:47 jongfoster
56 * Fixing more warnings
58 * Revision 1.7 2002/03/08 17:46:04 jongfoster
59 * Fixing int/size_t warnings
61 * Revision 1.6 2002/03/07 03:46:17 oes
62 * Fixed compiler warnings
64 * Revision 1.5 2001/09/10 10:16:06 oes
65 * Silenced compiler warnings
67 * Revision 1.4 2001/07/18 12:28:49 oes
68 * - Added feature for extracting the first frame
70 * - Separated image buffer extension into buf_extend
71 * - Extended gif deanimation to GIF87a (untested!)
74 * Revision 1.3 2001/07/15 13:57:50 jongfoster
75 * Adding #includes string.h and miscutil.h
77 * Revision 1.2 2001/07/13 13:46:20 oes
78 * Introduced GIF deanimation feature
81 **********************************************************************/
90 #include "deanimate.h"
93 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
95 /*********************************************************************
99 * Description : Safely frees a struct binbuffer
102 * 1 : buf = Pointer to the binbuffer to be freed
106 *********************************************************************/
107 void buf_free(struct binbuffer *buf)
109 if (buf == NULL) return;
111 if (buf->buffer != NULL)
121 /*********************************************************************
123 * Function : buf_extend
125 * Description : Ensure that a given binbuffer can hold a given amount
126 * of bytes, by reallocating its buffer if necessary.
127 * Allocate new mem in chunks of 1024 bytes, so we don't
128 * have to realloc() too often.
131 * 1 : buf = Pointer to the binbuffer
132 * 2 : length = Desired minimum size
135 * Returns : 0 on success, 1 on failure.
137 *********************************************************************/
138 int buf_extend(struct binbuffer *buf, size_t length)
142 if (buf->offset + length > buf->size)
144 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
145 newbuf = (char *)realloc(buf->buffer, buf->size);
154 buf->buffer = newbuf;
163 /*********************************************************************
165 * Function : buf_copy
167 * Description : Safely copies a given amount of bytes from one
168 * struct binbuffer to another, advancing the
169 * offsets appropriately.
172 * 1 : src = Pointer to the source binbuffer
173 * 2 : dst = Pointer to the destination binbuffer
174 * 3 : length = Number of bytes to be copied
176 * Returns : 0 on success, 1 on failure.
178 *********************************************************************/
179 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
183 * Sanity check: Can't copy more data than we have
185 if (src->offset + length > src->size)
191 * Ensure that dst can hold the new data
193 if (buf_extend(dst, length))
199 * Now that it's safe, memcpy() the desired amount of
200 * data from src to dst and adjust the offsets
202 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
203 src->offset += length;
204 dst->offset += length;
211 /*********************************************************************
213 * Function : buf_getbyte
215 * Description : Safely gets a byte from a given binbuffer at a
219 * 1 : src = Pointer to the source binbuffer
220 * 2 : offset = Offset to the desired byte
222 * Returns : The byte on success, or 0 on failure
224 *********************************************************************/
225 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
227 if (src->offset + offset < src->size)
229 return (unsigned char)*(src->buffer + src->offset + offset);
239 /*********************************************************************
241 * Function : gif_skip_data_block
243 * Description : Safely advances the offset of a given struct binbuffer
244 * that contains a GIF image and whose offset is
245 * positioned at the start of a data block, behind
249 * 1 : buf = Pointer to the binbuffer
251 * Returns : 0 on success, or 1 on failure
253 *********************************************************************/
254 int gif_skip_data_block(struct binbuffer *buf)
259 * Data blocks are sequences of chunks, which are headed
260 * by a one-byte length field, with the last chunk having
263 while((c = buf_getbyte(buf, 0)) != '\0')
265 if ((buf->offset += c + 1) >= buf->size - 1)
277 /*********************************************************************
279 * Function : gif_extract_image
281 * Description : Safely extracts an image data block from a given
282 * struct binbuffer that contains a GIF image and whose
283 * offset is positioned at the start of a data block
284 * into a given destination binbuffer.
287 * 1 : src = Pointer to the source binbuffer
288 * 2 : dst = Pointer to the destination binbuffer
290 * Returns : 0 on success, or 1 on failure
292 *********************************************************************/
293 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
298 * Remember the colormap flag and copy the image head
300 c = buf_getbyte(src, 9);
301 if (buf_copy(src, dst, 10))
307 * If the image has a local colormap, copy it.
311 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
316 if (buf_copy(src, dst, 1)) return 1;
319 * Copy the image chunk by chunk.
321 while((c = buf_getbyte(src, 0)) != '\0')
323 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
325 if (buf_copy(src, dst, 1)) return 1;
328 * Trim and rewind the dst buffer
330 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
331 dst->size = dst->offset;
338 /*********************************************************************
340 * Function : gif_deanimate
342 * Description : Deanimate a given GIF image, i.e. given a GIF with
343 * an (optional) image block and an arbitrary number
344 * of image extension blocks, produce an output GIF with
345 * only one image block that contains the last image
346 * (extenstion) block of the original.
347 * Also strip Comments, Application extenstions, etc.
350 * 1 : src = Pointer to the source binbuffer
351 * 2 : dst = Pointer to the destination binbuffer
352 * 3 : get_first_image = Flag: If set, get the first image
353 * If unset (default), get the last
355 * Returns : 0 on success, or 1 on failure
357 *********************************************************************/
358 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
361 struct binbuffer *image;
363 if (NULL == src || NULL == dst)
368 c = buf_getbyte(src, 10);
371 * Check & copy GIF header
373 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
379 if (buf_copy(src, dst, 13))
386 * Look for global colormap and copy if found.
390 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
397 * Reserve a buffer for the current image block
399 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
405 * Parse the GIF block by block and copy the relevant
408 while(src->offset < src->size)
410 switch(buf_getbyte(src, 0))
413 * End-of-GIF Marker: Append current image and return
419 * Image block: Extract to current image buffer.
423 if (gif_extract_image(src, image)) goto failed;
424 if (get_first_image) goto write;
428 * Extension block: Look at next byte and decide
431 switch (buf_getbyte(src, 1))
434 * Image extension: Copy extension header and image
435 * to the current image buffer
439 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
440 if (gif_extract_image(src, image)) goto failed;
441 if (get_first_image) goto write;
445 * Application extension: Skip
448 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
452 * Comment extension: Skip
455 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
459 * Plain text extension: Skip
462 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
466 * Ooops, what type of extension is that?
474 * Ooops, what type of block is that?
480 } /* -END- while src */
483 * Either we got here by goto, or because the GIF is
484 * bogus and EOF was reached before an end-of-gif marker
493 * Append the current image to dst and return
497 if (buf_copy(image, dst, image->size)) goto failed;
498 if (buf_extend(dst, 1)) goto failed;
499 *(dst->buffer + dst->offset++) = 0x3b;