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