1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.10 2002/03/24 13:25:43 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 1.10 2002/03/24 13:25:43 swa
41 * name change related issues
43 * Revision 1.9 2002/03/13 00:27:04 jongfoster
46 * Revision 1.8 2002/03/09 19:42:47 jongfoster
47 * Fixing more warnings
49 * Revision 1.7 2002/03/08 17:46:04 jongfoster
50 * Fixing int/size_t warnings
52 * Revision 1.6 2002/03/07 03:46:17 oes
53 * Fixed compiler warnings
55 * Revision 1.5 2001/09/10 10:16:06 oes
56 * Silenced compiler warnings
58 * Revision 1.4 2001/07/18 12:28:49 oes
59 * - Added feature for extracting the first frame
61 * - Separated image buffer extension into buf_extend
62 * - Extended gif deanimation to GIF87a (untested!)
65 * Revision 1.3 2001/07/15 13:57:50 jongfoster
66 * Adding #includes string.h and miscutil.h
68 * Revision 1.2 2001/07/13 13:46:20 oes
69 * Introduced GIF deanimation feature
72 **********************************************************************/
81 #include "deanimate.h"
84 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
86 /*********************************************************************
90 * Description : Safely frees a struct binbuffer
93 * 1 : buf = Pointer to the binbuffer to be freed
97 *********************************************************************/
98 void buf_free(struct binbuffer *buf)
100 if (buf == NULL) return;
102 if (buf->buffer != NULL)
112 /*********************************************************************
114 * Function : buf_extend
116 * Description : Ensure that a given binbuffer can hold a given amount
117 * of bytes, by reallocating its buffer if necessary.
118 * Allocate new mem in chunks of 1024 bytes, so we don't
119 * have to realloc() too often.
122 * 1 : buf = Pointer to the binbuffer
123 * 2 : length = Desired minimum size
126 * Returns : 0 on success, 1 on failiure.
128 *********************************************************************/
129 int buf_extend(struct binbuffer *buf, size_t length)
133 if (buf->offset + length > buf->size)
135 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
136 newbuf = (char *)realloc(buf->buffer, buf->size);
145 buf->buffer = newbuf;
154 /*********************************************************************
156 * Function : buf_copy
158 * Description : Safely copies a given amount of bytes from one
159 * struct binbuffer to another, advancing the
160 * offsets appropriately.
163 * 1 : src = Pointer to the source binbuffer
164 * 2 : dst = Pointer to the destination binbuffer
165 * 3 : length = Number of bytes to be copied
167 * Returns : 0 on success, 1 on failiure.
169 *********************************************************************/
170 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
174 * Sanity check: Can't copy more data than we have
176 if (src->offset + length > src->size)
182 * Ensure that dst can hold the new data
184 if (buf_extend(dst, length))
190 * Now that it's safe, memcpy() the desired amount of
191 * data from src to dst and adjust the offsets
193 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
194 src->offset += length;
195 dst->offset += length;
202 /*********************************************************************
204 * Function : buf_getbyte
206 * Description : Safely gets a byte from a given binbuffer at a
210 * 1 : buf = Pointer to the source binbuffer
211 * 2 : offset = Offset to the desired byte
213 * Returns : The byte on success, or 0 on failiure
215 *********************************************************************/
216 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
218 if (src->offset + offset < src->size)
220 return (unsigned char)*(src->buffer + src->offset + offset);
230 /*********************************************************************
232 * Function : gif_skip_data_block
234 * Description : Safely advances the offset of a given struct binbuffer
235 * that contains a GIF image and whose offset is
236 * positioned at the start of a data block, behind
240 * 1 : buf = Pointer to the binbuffer
242 * Returns : 0 on success, or 1 on failiure
244 *********************************************************************/
245 int gif_skip_data_block(struct binbuffer *buf)
250 * Data blocks are sequences of chunks, which are headed
251 * by a one-byte length field, with the last chunk having
254 while((c = buf_getbyte(buf, 0)) != '\0')
256 if ((buf->offset += c + 1) >= buf->size - 1)
268 /*********************************************************************
270 * Function : gif_extract_image
272 * Description : Safely extracts an image data block from a given
273 * struct binbuffer that contains a GIF image and whose
274 * offset is positioned at the start of a data block
275 * into a given destination binbuffer.
278 * 1 : src = Pointer to the source binbuffer
279 * 2 : dst = Pointer to the destination binbuffer
281 * Returns : 0 on success, or 1 on failiure
283 *********************************************************************/
284 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
289 * Remember the colormap flag and copy the image head
291 c = buf_getbyte(src, 9);
292 if (buf_copy(src, dst, 10))
298 * If the image has a local colormap, copy it.
302 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
307 if (buf_copy(src, dst, 1)) return 1;
310 * Copy the image chunk by chunk.
312 while((c = buf_getbyte(src, 0)) != '\0')
314 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
316 if (buf_copy(src, dst, 1)) return 1;
319 * Trim and rewind the dst buffer
321 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
322 dst->size = dst->offset;
329 /*********************************************************************
331 * Function : gif_deanimate
333 * Description : Deanimate a given GIF image, i.e. given a GIF with
334 * an (optional) image block and an arbitrary number
335 * of image extension blocks, produce an output GIF with
336 * only one image block that contains the last image
337 * (extenstion) block of the original.
338 * Also strip Comments, Application extenstions, etc.
341 * 1 : src = Pointer to the source binbuffer
342 * 2 : dst = Pointer to the destination binbuffer
343 * 3 : get_first_image = Flag: If set, get the first image
344 * If unset (default), get the last
346 * Returns : 0 on success, or 1 on failiure
348 *********************************************************************/
349 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
352 struct binbuffer *image;
354 if (NULL == src || NULL == dst)
359 c = buf_getbyte(src, 10);
362 * Check & copy GIF header
364 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
370 if (buf_copy(src, dst, 13))
377 * Look for global colormap and copy if found.
381 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
388 * Reserve a buffer for the current image block
390 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
396 * Parse the GIF block by block and copy the relevant
399 while(src->offset < src->size)
401 switch(buf_getbyte(src, 0))
404 * End-of-GIF Marker: Append current image and return
410 * Image block: Extract to current image buffer.
414 if (gif_extract_image(src, image)) goto failed;
415 if (get_first_image) goto write;
419 * Extension block: Look at next byte and decide
422 switch (buf_getbyte(src, 1))
425 * Image extension: Copy extension header and image
426 * to the current image buffer
430 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
431 if (gif_extract_image(src, image)) goto failed;
432 if (get_first_image) goto write;
436 * Application extension: Skip
439 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
443 * Comment extension: Skip
446 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
450 * Plain text extension: Skip
453 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
457 * Ooops, what type of extension is that?
465 * Ooops, what type of block is that?
471 } /* -END- while src */
474 * Either we got here by goto, or because the GIF is
475 * bogus and EOF was reached before an end-of-gif marker
484 * Append the current image to dst and return
488 if (buf_copy(image, dst, image->size)) goto failed;
489 if (buf_extend(dst, 1)) goto failed;
490 *(dst->buffer + dst->offset++) = 0x3b;