--- /dev/null
+const char deanimate_rcs[] = "$Id: $";
+/*********************************************************************
+ *
+ * File : $Source: $
+ *
+ * Purpose : Declares functions to deanimate GIF images on the fly.
+ *
+ * Functions declared include: gif_deanimate, buf_free,
+ * buf_copy, buf_getbyte, gif_skip_data_block, and
+ * gif_extract_image
+ *
+ * Copyright : Written by and Copyright (C) 2001 Andreas S. Oesterhelt
+ * for the SourceForge IJBSWA team. http://ijbswa.sourceforge.net
+ *
+ * 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.
+ *
+ * Revisions :
+ * $Log: $
+ *
+ **********************************************************************/
+\f
+
+#include "config.h"
+#include "project.h"
+#include "deanimate.h"
+
+#include <fcntl.h>
+
+const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
+
+/*********************************************************************
+ *
+ * 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_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 failiure.
+ *
+ *********************************************************************/
+int buf_copy(struct binbuffer *src, struct binbuffer *dst, int length)
+{
+ char *p;
+
+ /*
+ * Sanity check: Can't copy more data than we have
+ */
+ if (src->offset + length > src->size)
+ {
+ return 1;
+ }
+
+ /*
+ * If dst can't hold the new data, get mem first. (In chunks
+ * of 1000 bytes, so we don't have to realloc() too often)
+ */
+ if (dst->offset + length > dst->size)
+ {
+ dst->size = dst->size + length + 1000 - (dst->size + length) % 1000;
+ p = dst->buffer;
+ dst->buffer = (char *)realloc(dst->buffer, dst->size);
+
+ if (dst->buffer == NULL)
+ {
+ free(p);
+ 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 : buf = Pointer to the source binbuffer
+ * 2 : offset = Offset to the desired byte
+ *
+ * Returns : The byte on success, or 0 on failiure
+ *
+ *********************************************************************/
+unsigned char buf_getbyte(struct binbuffer *src, int 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 failiure
+ *
+ *********************************************************************/
+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))
+ {
+ if ((buf->offset += c + 1) >= 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 failiure
+ *
+ *********************************************************************/
+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)
+ {
+ if (buf_copy(src, dst, 3 * (1 << ((c & 0x07) + 1))))
+ {
+ return 1;
+ }
+ }
+ if (buf_copy(src, dst, 1)) return 1;
+
+ /*
+ * Copy the image chunk by chunk.
+ */
+ while(c = buf_getbyte(src, 0))
+ {
+ if (buf_copy(src, dst, c + 1)) return 1;
+ }
+ if (buf_copy(src, dst, 1)) return 1;
+
+ /*
+ * Trim and rewind the dst buffer
+ */
+ dst->buffer = (char *)realloc(dst->buffer, dst->offset);
+ 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
+ * (extenstion) block of the original.
+ * Also strip Comments, Application extenstions, etc.
+ *
+ * Parameters :
+ * 1 : src = Pointer to the source binbuffer
+ * 2 : dst = Pointer to the destination binbuffer
+ *
+ * Returns : 0 on success, or 1 on failiure
+ *
+ *********************************************************************/
+int gif_deanimate(struct binbuffer *src, struct binbuffer *dst)
+{
+ 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))
+ {
+ fprintf(stderr, "This is not a GIF98a!\n");
+ return 1;
+ }
+ else
+ {
+ if (buf_copy(src, dst, 13))
+ {
+ return 1;
+ }
+ }
+
+ /*
+ * Look for global colormap and copy if found.
+ */
+ if(c & 0x80)
+ {
+ if (buf_copy(src, dst, 3 * (1 << ((c & 0x07) + 1))))
+ {
+ return 1;
+ }
+ }
+
+ /*
+ * Reserve a buffer for the current image block
+ */
+ if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
+ {
+ return 1;
+ }
+
+ /*
+ * 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:
+ if (buf_copy(image, dst, image->size) || buf_copy(src, dst, 1))
+ {
+ goto failed;
+ }
+ buf_free(image);
+ return(0);
+
+ /*
+ * Image block: Extract to current image buffer
+ */
+ case 0x2c:
+ image->offset = 0;
+ if (gif_extract_image(src, image))
+ {
+ goto failed;
+ }
+ 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;
+ 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;
+
+}
+
+
+/*
+ Local Variables:
+ tab-width: 3
+ end:
+*/
projects / privoxy.git / commitdiff