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https://github.com/netsurf-browser/netsurf
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08177fa581
Add global content list. Better error handling in content code. Improved code documentation. Remove some obsolete functions. Implement debug window listing contents. svn path=/import/netsurf/; revision=951
1012 lines
29 KiB
C
1012 lines
29 KiB
C
/*
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* This file is part of NetSurf, http://netsurf.sourceforge.net/
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* Licensed under the GNU General Public License,
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* http://www.opensource.org/licenses/gpl-license
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* Copyright 2004 Richard Wilson <not_ginger_matt@sourceforge.net>
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include "gifread.h"
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#include "netsurf/utils/log.h"
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#include "oslib/osspriteop.h"
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#include "oslib/osfile.h"
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/* READING GIF FILES
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=================
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The functions provided by this file allow for efficient progressive GIF
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decoding. Whilst the initialisation does not ensure that there is
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sufficient image data to complete the entire frame, it does ensure that
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the information provided is valid. Any subsequent attempts to decode an
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initialised GIF are guaranteed to succeed, and any bytes of the image
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not present are assumed to be totally transparent.
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To begin decoding a GIF, the 'gif' structure must be initialised with
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the 'gif_data' and 'buffer_size' set to their initial values. The
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'buffer_position' should initially be 0, and will be internally updated
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as the decoding commences. The caller should then repeatedly call
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gif_initialise() with the structure until the function returns 1, or
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no more data is avaliable.
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Once the initialisation has begun, the decoder completes the variables
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'frame_count' and 'frame_count_partial'. The former being the total
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number of frames that have been successfully initialised, and the
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latter being the number of frames that a partial amount of data is
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available for. This assists the caller in managing the animation whilst
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decoding is continuing.
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To decode a frame, the caller must use gif_decode_frame() which updates
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the current 'frame_image' to reflect the desired frame. The required
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'background_action' is also updated to reflect how the frame should be
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plotted. The caller must not assume that the current 'frame_image' will
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be valid between calls if initialisation is still occuring, and should
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either always request that the frame is decoded (no processing will
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occur if the 'decoded_frame' has not been invalidated by initialisation)
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or perform the check itself.
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It should be noted that gif_finalise() should always be called, even if
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no frames were initialised.
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[rjw] - Fri 2nd April 2004
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*/
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/* Internal GIF routines
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*/
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static int gif_initialise_sprite(struct gif_animation *gif, unsigned int width, unsigned int height);
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static int gif_initialise_frame(struct gif_animation *gif);
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static unsigned int gif_interlaced_line(int height, int y);
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/* Internal LZW routines
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*/
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static int gif_next_LZW(struct gif_animation *gif);
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static int gif_next_code(struct gif_animation *gif, int code_size);
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#define gif_read_LZW(gif) ((stack_pointer > stack) ? *--stack_pointer : gif_next_LZW(gif))
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/* General LZW values. They are shared for all GIFs being decoded, and
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thus we can't handle progressive decoding efficiently without having
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the data for each image which would use an extra 10Kb or so per GIF.
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*/
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static unsigned char buf[280];
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static int maskTbl[16] = {0x0000, 0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f,
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0x00ff, 0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff};
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static int table[2][(1<< GIF_MAX_LZW)];
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static int stack[(1 << GIF_MAX_LZW) * 2];
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static int *stack_pointer;
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static int code_size, set_code_size;
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static int max_code, max_code_size;
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static int clear_code, end_code;
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static int curbit, lastbit, get_done, last_byte;
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static int return_clear;
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static int zero_data_block = FALSE;
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/* Whether to clear the decoded image rather than plot
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*/
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static int clear_image = FALSE;
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/* Initialises any workspace held by the animation and attempts to decode
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any information that hasn't already been decoded.
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If an error occurs, all previously decoded frames are retained.
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@return GIF_FRAME_DATA_ERROR for GIF frame data error
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GIF_INSUFFICIENT_FRAME_DATA for insufficient data to process
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any more frames
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GIF_INSUFFICIENT_MEMORY for memory error
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GIF_DATA_ERROR for GIF error
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GIF_INSUFFICIENT_DATA for insufficient data to do anything
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0 for successful decoding
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1 for successful decoding (all frames completely read)
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*/
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int gif_initialise(struct gif_animation *gif) {
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unsigned char *gif_data;
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unsigned int index;
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int return_value;
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unsigned int frame;
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/* Check for sufficient data to be a GIF
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*/
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if (gif->buffer_size < 13) return GIF_INSUFFICIENT_DATA;
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/* Get our current processing position
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*/
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gif_data = gif->gif_data + gif->buffer_position;
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/* See if we should initialise the GIF
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*/
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if (gif->buffer_position == 0) {
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/* We want everything to be NULL before we start so we've no chance
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of freeing bad pointers (paranoia)
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*/
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gif->frame_image = NULL;
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gif->frames = NULL;
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gif->local_colour_table = NULL;
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gif->global_colour_table = NULL;
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/* The caller may have been lazy and not reset any values
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*/
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gif->frame_count = 0;
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gif->frame_count_partial = 0;
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gif->decoded_frame = 0xffffffff;
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/* Check we are a GIF
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*/
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if (strncmp(gif_data, "GIF", 3) != 0) {
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// LOG(("Invalid GIF header - should be 'GIF'"));
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return GIF_DATA_ERROR;
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}
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gif_data += 3;
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/* Check we are a GIF type 87a or 89a
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*/
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if ((strncmp(gif_data, "87a", 3) != 0) &&
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(strncmp(gif_data, "89a", 3) != 0)) {
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// LOG(("Unknown GIF format - proceeding anyway"));
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}
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gif_data += 3;
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/* Get our GIF data. Quite often the width/height are lies, so we don't fill them in
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*/
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gif->width = 0; // Can't trust the supplied value
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gif->height = 0; // Can't trust the supplied value
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gif->global_colours = (gif_data[4] & 0x80);
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gif->colour_table_size = (2 << (gif_data[4] & 0x07));
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gif->background_colour = gif_data[5];
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gif->aspect_ratio = gif_data[6];
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gif->dirty_frame = -1;
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gif->loop_count = 1;
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gif_data += 7;
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/* Allocate some data irrespective of whether we've got any colour tables. We
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always get the maximum size in case a GIF is lying to us. It's far better
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to give the wrong colours than to trample over some memory somewhere.
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*/
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gif->global_colour_table = (unsigned int *)calloc(GIF_MAX_COLOURS, sizeof(int));
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gif->local_colour_table = (unsigned int *)calloc(GIF_MAX_COLOURS, sizeof(int));
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if ((gif->global_colour_table == NULL) || (gif->local_colour_table == NULL)) {
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gif_finalise(gif);
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return GIF_INSUFFICIENT_MEMORY;
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}
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/* Set the first colour to a value that will never occur in reality so we
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know if we've processed it
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*/
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gif->global_colour_table[0] = 0xaa000000;
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/* Initialise enough workspace for 4 frame initially
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*/
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if ((gif->frames = (gif_frame *)malloc(sizeof(gif_frame))) == NULL) {
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gif_finalise(gif);
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return GIF_INSUFFICIENT_MEMORY;
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}
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gif->frame_holders = 1;
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/* Initialise the sprite header
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*/
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if ((gif->frame_image = (osspriteop_header *)malloc(sizeof(osspriteop_header))) == NULL) {
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gif_finalise(gif);
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return GIF_INSUFFICIENT_MEMORY;
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}
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gif->frame_image->size = sizeof(osspriteop_header);
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strcpy(gif->frame_image->name, "gif");
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gif->frame_image->left_bit = 0;
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gif->frame_image->right_bit = 31;
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gif->frame_image->width = 0;
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gif->frame_image->height = 0;
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gif->frame_image->image = sizeof(osspriteop_header);
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gif->frame_image->mask = sizeof(osspriteop_header);
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gif->frame_image->mode = (os_mode) 0x301680b5;
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/* Remember we've done this now
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*/
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gif->buffer_position = gif_data - gif->gif_data;
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}
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/* Do the colour map if we haven't already. As the top byte is always 0xff or 0x00
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depending on the transparency we know if it's been filled in.
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*/
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if (gif->global_colour_table[0] == 0xaa000000) {
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/* Check for a global colour map signified by bit 7
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*/
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if (gif->global_colours) {
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if (gif->buffer_size < (gif->colour_table_size * 3 + 12)) {
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return GIF_INSUFFICIENT_DATA;
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}
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// LOG(("Found global colour table with %i entries", gif->colour_table_size));
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for (index = 0; index < gif->colour_table_size; index++) {
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gif->global_colour_table[index] = gif_data[0] | (gif_data[1] << 8) |
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(gif_data[2] << 16) | 0xff000000;
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gif_data += 3;
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}
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gif->buffer_position = (gif_data - gif->gif_data);
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} else {
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// LOG(("No global colour table"));
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/* Create a default colour table with the first two colours as black and white
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*/
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gif->global_colour_table[0] = 0xff000000;
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gif->global_colour_table[1] = 0xffffffff;
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}
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}
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/* Repeatedly try to decode frames
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*/
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while ((return_value = gif_initialise_frame(gif)) == 0);
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/* Update the redraw areas now we know the full data set
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*/
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if (gif->frame_count_partial > 0) {
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/* Set the redraw for the first frame to the maximum frame size
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*/
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gif->frames[0].redraw_required = 0;
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gif->frames[0].redraw_x = 0;
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gif->frames[0].redraw_y = 0;
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gif->frames[0].redraw_width = gif->width;
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gif->frames[0].redraw_height = gif->height;
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/* We now work backwards to update the redraw characteristics of frames
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with clear codes to stop a snowball effect of the redraw areas. It doesn't
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really make much difference for most images, and will not work as well
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(ie will not optimise as well as for a single-pass call, but still works)
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for multiple calls to this routine when decoding progressively.
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*/
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for (frame = gif->frame_count_partial - 1; frame > 0; frame--) {
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if (gif->frames[frame].redraw_required) {
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if (gif->frames[frame].redraw_x > gif->frames[frame - 1].redraw_x) {
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gif->frames[frame].redraw_width +=
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(gif->frames[frame].redraw_x - gif->frames[frame - 1].redraw_x);
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gif->frames[frame].redraw_x = gif->frames[frame - 1].redraw_x;
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}
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if (gif->frames[frame].redraw_y > gif->frames[frame - 1].redraw_y) {
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gif->frames[frame].redraw_height +=
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(gif->frames[frame].redraw_y - gif->frames[frame - 1].redraw_y);
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gif->frames[frame].redraw_y = gif->frames[frame - 1].redraw_y;
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}
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if ((gif->frames[frame - 1].redraw_x + gif->frames[frame - 1].redraw_width) >
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(gif->frames[frame].redraw_x + gif->frames[frame].redraw_width)) {
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gif->frames[frame].redraw_width =
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(gif->frames[frame - 1].redraw_x + gif->frames[frame - 1].redraw_width) -
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gif->frames[frame].redraw_x;
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}
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if ((gif->frames[frame - 1].redraw_y + gif->frames[frame - 1].redraw_height) >
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(gif->frames[frame].redraw_y + gif->frames[frame].redraw_height)) {
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gif->frames[frame].redraw_height =
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(gif->frames[frame - 1].redraw_y + gif->frames[frame - 1].redraw_height) -
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gif->frames[frame].redraw_y;
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}
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}
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}
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}
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/* If there was a memory error tell the caller
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*/
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if ((return_value == GIF_INSUFFICIENT_MEMORY) ||
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(return_value == GIF_DATA_ERROR)) {
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return return_value;
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}
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/* If we didn't have some frames then a GIF_INSUFFICIENT_DATA becomes a
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GIF_INSUFFICIENT_FRAME_DATA
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*/
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if ((return_value == GIF_INSUFFICIENT_DATA) && (gif->frame_count_partial > 0)) {
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return_value = GIF_INSUFFICIENT_FRAME_DATA;
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}
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/* Return how many we got
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*/
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return return_value;
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}
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/** Updates the sprite memory size
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@return -3 for a memory error
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0 for success
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*/
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static int gif_initialise_sprite(struct gif_animation *gif, unsigned int width, unsigned int height) {
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struct osspriteop_header *buffer;
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unsigned int max_width;
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unsigned int max_height;
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unsigned int frame_bytes;
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/* Check if we've changed
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*/
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if ((width <= gif->width) && (height <= gif->height)) return 0;
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/* Get our maximum values
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*/
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max_width = (width > gif->width) ? width : gif->width;
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max_height = (height > gif->height) ? height : gif->height;
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frame_bytes = max_width * max_height * 4 + sizeof(osspriteop_header);
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/* Allocate some more memory
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*/
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if ((buffer = (osspriteop_header *)realloc(gif->frame_image, frame_bytes)) == NULL) {
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return GIF_INSUFFICIENT_MEMORY;
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}
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gif->frame_image = buffer;
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/* Update the sizes
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*/
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gif->width = max_width;
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gif->height = max_height;
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/* Update our sprite image
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*/
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buffer->size = frame_bytes;
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buffer->width = max_width - 1;
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buffer->height = max_height - 1;
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/* Invalidate our currently decoded image
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*/
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gif->decoded_frame = 0xffffffff;
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return 0;
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}
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/* Attempts to initialise the next frame
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@return -4 for insufficient data to process the entire frame
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-3 for a memory error
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-2 for a data error
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-1 for insufficient data to process anything
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0 for success
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1 for success (GIF terminator found)
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*/
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int gif_initialise_frame(struct gif_animation *gif) {
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unsigned int frame;
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gif_frame *temp_buf;
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unsigned char *gif_data, *gif_end;
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int gif_bytes;
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unsigned int flags = 0;
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unsigned int background_action;
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unsigned int width, height, offset_x, offset_y;
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unsigned int extension_size, colour_table_size;
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unsigned int block_size;
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unsigned int more_images;
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unsigned int first_image;
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/* Get the frame to decode and our data position
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*/
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frame = gif->frame_count;
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/* Get our buffer position etc.
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*/
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gif_data = (unsigned char *)(gif->gif_data + gif->buffer_position);
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gif_end = (unsigned char *)(gif->gif_data + gif->buffer_size);
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gif_bytes = (gif_end - gif_data);
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/* Check we have enough data for at least the header, or if we've finished
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*/
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if ((gif_bytes > 0) && (gif_data[0] == 0x3b)) return 1;
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if (gif_bytes < 11) return -1;
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/* We could theoretically get some junk data that gives us millions of frames, so
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we ensure that we don't have a silly number
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*/
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if (frame > 4096) return GIF_DATA_ERROR;
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/* Get some memory to store our pointers in etc.
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*/
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if (gif->frame_holders <= frame) {
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/* Allocate more memory
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*/
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if ((temp_buf = (gif_frame *)realloc(gif->frames,
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(frame + 1) * sizeof(gif_frame))) == NULL) {
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return GIF_INSUFFICIENT_MEMORY;
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}
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gif->frames = temp_buf;
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/* Remember we allocated it
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*/
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gif->frame_holders = frame + 1;
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}
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/* Store our frame pointer. We would do it when allocating except we
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start off with one frame allocated so we can always use realloc.
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*/
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gif->frames[frame].frame_pointer = gif->buffer_position;
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gif->frames[frame].frame_delay = 100; // Paranoia
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gif->frames[frame].redraw_required = 0; // Paranoia
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/* Invalidate any previous decoding we have of this frame
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*/
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if (gif->decoded_frame == frame) gif->decoded_frame = 0xffffffff;
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/* We pretend to initialise the frames, but really we just skip over all
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the data contained within. This is all basically a cut down version of
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gif_decode_frame that doesn't have any of the LZW bits in it.
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*/
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more_images = 1;
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first_image = 1;
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while (more_images != 0) {
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/* Ensure we have some data
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*/
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if ((gif_end - gif_data) < 10) return GIF_INSUFFICIENT_FRAME_DATA;
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/* Decode the extensions
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*/
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background_action = 0;
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while (gif_data[0] == 0x21) {
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/* Get the extension size
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*/
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extension_size = gif_data[2];
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/* Check we've enough data for the extension then header
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*/
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if ((gif_end - gif_data) < (int)(extension_size + 13)) return GIF_INSUFFICIENT_FRAME_DATA;
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/* Graphic control extension - store the frame delay.
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*/
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if (gif_data[1] == 0xf9) {
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gif->frames[frame].frame_delay = gif_data[4] | (gif_data[5] << 8);
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background_action = ((gif_data[3] & 0x1c) >> 2);
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more_images = ((gif->frames[frame].frame_delay) == 0);
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/* Application extension - handle NETSCAPE2.0 looping
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*/
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} else if ((gif_data[1] == 0xff) &&
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(gif_data[2] == 0x0b) &&
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(strncmp(gif_data + 3, "NETSCAPE2.0", 11) == 0) &&
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(gif_data[14] == 0x03) &&
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(gif_data[15] == 0x01)) {
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gif->loop_count = gif_data[16] | (gif_data[17] << 8);
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}
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/* Move to the first sub-block
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*/
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gif_data += 2;
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/* Skip all the sub-blocks
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*/
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while (gif_data[0] != 0x00) {
|
|
gif_data += gif_data[0] + 1;
|
|
if ((gif_end - gif_data) < 10) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
}
|
|
gif_data++;
|
|
}
|
|
|
|
/* We must have at least one image descriptor
|
|
*/
|
|
if (gif_data[0] != 0x2c) return GIF_FRAME_DATA_ERROR;
|
|
|
|
/* Do some simple boundary checking
|
|
*/
|
|
offset_x = gif_data[1] | (gif_data[2] << 8);
|
|
offset_y = gif_data[3] | (gif_data[4] << 8);
|
|
width = gif_data[5] | (gif_data[6] << 8);
|
|
height = gif_data[7] | (gif_data[8] << 8);
|
|
|
|
/* Set up the redraw characteristics. We have to check for extending the area
|
|
due to multi-image frames.
|
|
*/
|
|
if (first_image == 0) {
|
|
if (gif->frames[frame].redraw_x > offset_x) {
|
|
gif->frames[frame].redraw_width += (gif->frames[frame].redraw_x - offset_x);
|
|
gif->frames[frame].redraw_x = offset_x;
|
|
}
|
|
if (gif->frames[frame].redraw_y > offset_y) {
|
|
gif->frames[frame].redraw_height += (gif->frames[frame].redraw_y - offset_y);
|
|
gif->frames[frame].redraw_y = offset_y;
|
|
}
|
|
if ((offset_x + width) > (gif->frames[frame].redraw_x + gif->frames[frame].redraw_width)) {
|
|
gif->frames[frame].redraw_width = (offset_x + width) - gif->frames[frame].redraw_x;
|
|
}
|
|
if ((offset_y + height) > (gif->frames[frame].redraw_y + gif->frames[frame].redraw_height)) {
|
|
gif->frames[frame].redraw_height = (offset_y + height) - gif->frames[frame].redraw_y;
|
|
}
|
|
} else {
|
|
first_image = 0;
|
|
gif->frames[frame].redraw_x = offset_x;
|
|
gif->frames[frame].redraw_y = offset_y;
|
|
gif->frames[frame].redraw_width = width;
|
|
gif->frames[frame].redraw_height = height;
|
|
}
|
|
|
|
/* if we are clearing the background then we need to redraw enough to cover the previous
|
|
frame too
|
|
*/
|
|
if (((background_action == 2) || (background_action == 3)) && (frame > 0)) {
|
|
gif->frames[frame].redraw_required = 1;
|
|
}
|
|
|
|
/* Boundary checking - shouldn't ever happen except with junk data
|
|
*/
|
|
if (gif_initialise_sprite(gif, (offset_x + width), (offset_y + height))) {
|
|
return GIF_INSUFFICIENT_MEMORY;
|
|
}
|
|
|
|
/* Decode the flags
|
|
*/
|
|
flags = gif_data[9];
|
|
colour_table_size = 2 << (flags & 0x07);
|
|
|
|
/* Move our data onwards and remember we've got a bit of this frame
|
|
*/
|
|
gif_data += 10;
|
|
gif_bytes = (gif_end - gif_data);
|
|
gif->frame_count_partial = frame + 1;
|
|
|
|
/* Skip the local colour table
|
|
*/
|
|
if (flags & 0x80) {
|
|
gif_data += 3 * colour_table_size;
|
|
if ((gif_bytes = (gif_end - gif_data)) < 0) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
}
|
|
|
|
/* Ensure we have a correct code size
|
|
*/
|
|
if (gif_data[0] > GIF_MAX_LZW) return GIF_DATA_ERROR;
|
|
|
|
/* Move our data onwards
|
|
*/
|
|
gif_data++;
|
|
if (--gif_bytes < 0) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
|
|
/* Repeatedly skip blocks until we get a zero block or run out of data
|
|
*/
|
|
block_size = 0;
|
|
while (block_size != 1) {
|
|
/* Skip the block data
|
|
*/
|
|
block_size = gif_data[0] + 1;
|
|
if ((gif_bytes -= block_size) < 0) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
gif_data += block_size;
|
|
}
|
|
|
|
/* Check for end of data
|
|
*/
|
|
if ((gif_bytes < 1) || (gif_data[0] == 0x3b)) more_images = 0;
|
|
}
|
|
|
|
/* Check if we've finished
|
|
*/
|
|
if (gif_bytes < 1) {
|
|
return GIF_INSUFFICIENT_FRAME_DATA;
|
|
} else {
|
|
gif->buffer_position = gif_data - gif->gif_data;
|
|
gif->frame_count = frame + 1;
|
|
if (gif_data[0] == 0x3b) return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
|
|
/** Decodes a GIF frame.
|
|
|
|
@return GIF_FRAME_DATA_ERROR for GIF frame data error
|
|
GIF_INSUFFICIENT_FRAME_DATA for insufficient data to complete the frame
|
|
GIF_DATA_ERROR for GIF error (invalid frame header)
|
|
GIF_INSUFFICIENT_DATA for insufficient data to do anything
|
|
0 for successful decoding
|
|
*/
|
|
int gif_decode_frame(struct gif_animation *gif, unsigned int frame) {
|
|
unsigned int index = 0;
|
|
unsigned char *gif_data;
|
|
unsigned char *gif_end;
|
|
int gif_bytes;
|
|
unsigned int width, height, offset_x, offset_y;
|
|
unsigned int flags, colour_table_size, interlace;
|
|
unsigned int *colour_table;
|
|
unsigned int *frame_data = 0; // Set to 0 for no warnings
|
|
unsigned int *frame_scanline;
|
|
unsigned int extension_size;
|
|
unsigned int background_action;
|
|
int transparency_index = -1;
|
|
unsigned int save_buffer_position;
|
|
unsigned int return_value = 0;
|
|
unsigned int x, y, decode_y, burst_bytes;
|
|
unsigned int block_size;
|
|
register int colour;
|
|
unsigned int more_images;
|
|
|
|
/* Ensure we have a frame to decode
|
|
*/
|
|
if (frame > gif->frame_count_partial) return GIF_INSUFFICIENT_DATA;
|
|
if ((!clear_image) && (frame == gif->decoded_frame)) return 0;
|
|
|
|
/* If the previous frame was dirty, remove it
|
|
*/
|
|
if (!clear_image) {
|
|
if (gif->decoded_frame == gif->dirty_frame) {
|
|
clear_image = TRUE;
|
|
if (frame != 0) gif_decode_frame(gif, gif->dirty_frame);
|
|
clear_image = FALSE;
|
|
}
|
|
gif->dirty_frame = -1;
|
|
}
|
|
|
|
/* Get the start of our frame data and the end of the GIF data
|
|
*/
|
|
gif_data = gif->gif_data + gif->frames[frame].frame_pointer;
|
|
gif_end = gif->gif_data + gif->buffer_size;
|
|
gif_bytes = (gif_end - gif_data);
|
|
|
|
/* Check we have enough data for the header
|
|
*/
|
|
if (gif_bytes < 9) return GIF_INSUFFICIENT_DATA;
|
|
|
|
/* Clear the previous frame totally. We can't just pretend we've got a smaller
|
|
sprite and clear what we need as some frames have multiple images which would
|
|
produce errors.
|
|
*/
|
|
frame_data = (unsigned int*)((char *)gif->frame_image + sizeof(osspriteop_header));
|
|
if (!clear_image) {
|
|
if ((frame == 0) || (gif->decoded_frame == 0xffffffff)) {
|
|
memset((char*)frame_data, 0x00, gif->width * gif->height * sizeof(int));
|
|
}
|
|
gif->decoded_frame = frame;
|
|
}
|
|
|
|
/* Save the buffer position
|
|
*/
|
|
save_buffer_position = gif->buffer_position;
|
|
gif->buffer_position = gif_data - gif->gif_data;
|
|
|
|
/* We've got to do this more than one time if we've got multiple images
|
|
*/
|
|
more_images = 1;
|
|
while (more_images != 0) {
|
|
background_action = 0;
|
|
|
|
/* Ensure we have some data
|
|
*/
|
|
gif_data = gif->gif_data + gif->buffer_position;
|
|
if ((gif_end - gif_data) < 10) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
|
|
/* Decode the extensions
|
|
*/
|
|
while (gif_data[0] == 0x21) {
|
|
|
|
/* Get the extension size
|
|
*/
|
|
extension_size = gif_data[2];
|
|
|
|
/* Check we've enough data for the extension then header
|
|
*/
|
|
if ((gif_end - gif_data) < (int)(extension_size + 13)) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
|
|
/* Graphic control extension - store the frame delay.
|
|
*/
|
|
if (gif_data[1] == 0xf9) {
|
|
flags = gif_data[3];
|
|
if (flags & 0x01) transparency_index = gif_data[6];
|
|
background_action = ((flags & 0x1c) >> 2);
|
|
more_images = ((gif_data[4] | (gif_data[5] << 8)) == 0);
|
|
}
|
|
/* Move to the first sub-block
|
|
*/
|
|
gif_data += 2;
|
|
|
|
/* Skip all the sub-blocks
|
|
*/
|
|
while (gif_data[0] != 0x00) {
|
|
gif_data += gif_data[0] + 1;
|
|
if ((gif_end - gif_data) < 10) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
}
|
|
gif_data++;
|
|
}
|
|
|
|
/* Decode the header
|
|
*/
|
|
if (gif_data[0] != 0x2c) return GIF_DATA_ERROR;
|
|
offset_x = gif_data[1] | (gif_data[2] << 8);
|
|
offset_y = gif_data[3] | (gif_data[4] << 8);
|
|
width = gif_data[5] | (gif_data[6] << 8);
|
|
height = gif_data[7] | (gif_data[8] << 8);
|
|
|
|
/* Boundary checking - shouldn't ever happen except unless the data has been
|
|
modified since initialisation.
|
|
*/
|
|
if ((offset_x + width > gif->width) || (offset_y + height > gif->height)) {
|
|
return GIF_DATA_ERROR;
|
|
}
|
|
|
|
/* Decode the flags
|
|
*/
|
|
flags = gif_data[9];
|
|
colour_table_size = 2 << (flags & 0x07);
|
|
interlace = flags & 0x40;
|
|
|
|
/* Move through our data
|
|
*/
|
|
gif_data += 10;
|
|
gif_bytes = (int)(gif_end - gif_data);
|
|
|
|
/* Set up the colour table
|
|
*/
|
|
if (flags & 0x80) {
|
|
if (gif_bytes < (int)(3 * colour_table_size)) return GIF_INSUFFICIENT_FRAME_DATA;
|
|
colour_table = gif->local_colour_table;
|
|
if (!clear_image) {
|
|
for (index = 0; index < colour_table_size; index++) {
|
|
colour_table[index] = gif_data[0] | (gif_data[1] << 8) |
|
|
(gif_data[2] << 16) | 0xff000000;
|
|
gif_data += 3;
|
|
}
|
|
} else {
|
|
gif_data += 3 * colour_table_size;
|
|
}
|
|
gif_bytes = (int)(gif_end - gif_data);
|
|
} else {
|
|
colour_table = gif->global_colour_table;
|
|
}
|
|
|
|
/* If we are clearing the image we just clear, if not decode
|
|
*/
|
|
if (!clear_image) {
|
|
/* Set our dirty status
|
|
*/
|
|
if ((background_action == 2) || (background_action == 3)) {
|
|
gif->dirty_frame = frame;
|
|
}
|
|
|
|
/* Initialise the LZW decoding
|
|
*/
|
|
set_code_size = gif_data[0];
|
|
gif->buffer_position = (gif_data - gif->gif_data) + 1;
|
|
|
|
/* Set our code variables
|
|
*/
|
|
code_size = set_code_size + 1;
|
|
clear_code = (1 << set_code_size);
|
|
end_code = clear_code + 1;
|
|
max_code_size = clear_code << 1;
|
|
max_code = clear_code + 2;
|
|
curbit = lastbit = 0;
|
|
last_byte = 2;
|
|
get_done = 0;
|
|
return_clear = 1;
|
|
stack_pointer = stack;
|
|
|
|
/* Decompress the data
|
|
*/
|
|
for (y = 0; y < height; y++) {
|
|
if (interlace) {
|
|
decode_y = gif_interlaced_line(height, y) + offset_y;
|
|
} else {
|
|
decode_y = y + offset_y;
|
|
}
|
|
frame_scanline = frame_data + offset_x + (decode_y * gif->width);
|
|
|
|
/* Rather than decoding pixel by pixel, we try to burst out streams
|
|
of data to remove the need for end-of data checks every pixel.
|
|
*/
|
|
x = width;
|
|
while (x-- > 0) {
|
|
/* Do the first pixel to get the stack of some sort
|
|
*/
|
|
if ((colour = gif_read_LZW(gif)) >= 0) {
|
|
if (colour != transparency_index) {
|
|
*frame_scanline = colour_table[colour];
|
|
}
|
|
frame_scanline++;
|
|
} else {
|
|
return_value = GIF_INSUFFICIENT_FRAME_DATA;
|
|
goto gif_decode_frame_exit;
|
|
}
|
|
|
|
/* Try to burst some bytes out
|
|
*/
|
|
burst_bytes = (stack_pointer - stack);
|
|
if (burst_bytes > x) burst_bytes = x;
|
|
x -= burst_bytes;
|
|
while (burst_bytes-- > 0) {
|
|
if ((colour = *--stack_pointer) != transparency_index) {
|
|
*frame_scanline = colour_table[colour];
|
|
}
|
|
frame_scanline++;
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
/* Clear our frame
|
|
*/
|
|
if ((background_action == 2) || (background_action == 3)) {
|
|
for (y = 0; y < height; y++) {
|
|
frame_scanline = frame_data + offset_x + ((offset_y + y) * gif->width);
|
|
memset(frame_scanline, 0x00, width * 4);
|
|
}
|
|
}
|
|
|
|
/* Repeatedly skip blocks until we get a zero block or run out of data
|
|
*/
|
|
gif_bytes = gif->buffer_size - gif->buffer_position;
|
|
gif_data = gif->gif_data + gif->buffer_size;
|
|
block_size = 0;
|
|
while (block_size != 1) {
|
|
/* Skip the block data
|
|
*/
|
|
block_size = gif_data[0] + 1;
|
|
if ((gif_bytes -= block_size) < 0) {
|
|
return_value = GIF_INSUFFICIENT_FRAME_DATA;
|
|
goto gif_decode_frame_exit;
|
|
}
|
|
gif_data += block_size;
|
|
}
|
|
}
|
|
gif_decode_frame_exit:
|
|
|
|
/* Check for end of data
|
|
*/
|
|
gif_bytes = gif->buffer_size - gif->buffer_position;
|
|
if ((gif_bytes < 1) || (gif_data[0] == 0x3b)) more_images = 0;
|
|
gif->buffer_position++;
|
|
}
|
|
|
|
/* Restore the buffer position
|
|
*/
|
|
gif->buffer_position = save_buffer_position;
|
|
|
|
/* Success!
|
|
*/
|
|
return return_value;
|
|
|
|
}
|
|
|
|
static unsigned int gif_interlaced_line(int height, int y) {
|
|
if ((y << 3) < height) return (y << 3);
|
|
y -= ((height + 7) >> 3);
|
|
if ((y << 3) < (height - 4)) return (y << 3) + 4;
|
|
y -= ((height + 3) >> 3);
|
|
if ((y << 2) < (height - 2)) return (y << 2) + 2;
|
|
y -= ((height + 1) >> 2);
|
|
return (y << 1) + 1;
|
|
}
|
|
|
|
/* Releases any workspace held by the animation
|
|
*/
|
|
void gif_finalise(struct gif_animation *gif) {
|
|
/* Release all our memory blocks
|
|
*/
|
|
free(gif->frame_image);
|
|
gif->frame_image = NULL;
|
|
free(gif->frames);
|
|
gif->frames = NULL;
|
|
free(gif->local_colour_table);
|
|
gif->local_colour_table = NULL;
|
|
free(gif->global_colour_table);
|
|
gif->global_colour_table = NULL;
|
|
}
|
|
|
|
|
|
static int gif_next_LZW(struct gif_animation *gif) {
|
|
static int firstcode, oldcode;
|
|
int code, incode;
|
|
unsigned int i, block_size;
|
|
|
|
while ((code = gif_next_code(gif, code_size)) >= 0) {
|
|
if (code == clear_code) {
|
|
/* Check we have a valid clear code
|
|
*/
|
|
if (clear_code >= (1 << GIF_MAX_LZW)) return -2;
|
|
|
|
/* Initialise our table
|
|
*/
|
|
memset(table, 0x00, (1 << GIF_MAX_LZW) * 8);
|
|
for (i = 0; i < (unsigned int)clear_code; ++i) {
|
|
table[1][i] = i;
|
|
}
|
|
|
|
/* Update our LZW parameters
|
|
*/
|
|
code_size = set_code_size + 1;
|
|
max_code_size = clear_code << 1;
|
|
max_code = clear_code + 2;
|
|
stack_pointer = stack;
|
|
do {
|
|
firstcode = oldcode = gif_next_code(gif, code_size);
|
|
} while (firstcode == clear_code);
|
|
return firstcode;
|
|
}
|
|
|
|
if (code == end_code) {
|
|
/* Skip to the end of our data so multi-image GIFs work
|
|
*/
|
|
if (zero_data_block) return -2;
|
|
block_size = 0;
|
|
while (block_size != 1) {
|
|
block_size = gif->gif_data[gif->buffer_position] + 1;
|
|
gif->buffer_position += block_size;
|
|
}
|
|
return -2;
|
|
}
|
|
|
|
/* Fill the stack with some data
|
|
*/
|
|
incode = code;
|
|
|
|
if (code >= max_code) {
|
|
*stack_pointer++ = firstcode;
|
|
code = oldcode;
|
|
}
|
|
|
|
while (code >= clear_code) {
|
|
*stack_pointer++ = table[1][code];
|
|
if (code == table[0][code]) return(code);
|
|
if (((char *)stack_pointer - (char *)stack) >= (int)sizeof(stack)) return(code);
|
|
code = table[0][code];
|
|
}
|
|
|
|
*stack_pointer++ = firstcode = table[1][code];
|
|
|
|
if ((code = max_code) < (1 << GIF_MAX_LZW)) {
|
|
table[0][code] = oldcode;
|
|
table[1][code] = firstcode;
|
|
++max_code;
|
|
if ((max_code >= max_code_size) && (max_code_size < (1 << GIF_MAX_LZW))) {
|
|
max_code_size = max_code_size << 1;
|
|
++code_size;
|
|
}
|
|
}
|
|
|
|
oldcode = incode;
|
|
|
|
if (stack_pointer > stack) return *--stack_pointer;
|
|
}
|
|
return code;
|
|
}
|
|
|
|
|
|
static int gif_next_code(struct gif_animation *gif, int code_size) {
|
|
int i, j, end, count;
|
|
long ret;
|
|
unsigned char *gif_data;
|
|
|
|
if (return_clear) {
|
|
return_clear = 0;
|
|
return clear_code;
|
|
}
|
|
|
|
end = curbit + code_size;
|
|
if (end >= lastbit) {
|
|
if (get_done) return -1;
|
|
buf[0] = buf[last_byte - 2];
|
|
buf[1] = buf[last_byte - 1];
|
|
|
|
/* Get the next block
|
|
*/
|
|
gif_data = gif->gif_data + gif->buffer_position;
|
|
zero_data_block = ((count = gif_data[0]) == 0);
|
|
if ((gif->buffer_position + count) >= gif->buffer_size) return -1;
|
|
if (count == 0) {
|
|
get_done = 1;
|
|
} else {
|
|
memcpy(&buf[2], gif_data + 1, count);
|
|
}
|
|
gif->buffer_position += count + 1;
|
|
|
|
/* Update our variables
|
|
*/
|
|
last_byte = 2 + count;
|
|
curbit = (curbit - lastbit) + 16;
|
|
lastbit = (2 + count) << 3;
|
|
end = curbit + code_size;
|
|
}
|
|
|
|
j = end >> 3;
|
|
i = curbit >> 3;
|
|
if (i == j) {
|
|
ret = (long)buf[i];
|
|
} else if (i + 1 == j) {
|
|
ret = (long)buf[i] | ((long)buf[i+1] << 8);
|
|
} else {
|
|
ret = (long)buf[i] | ((long)buf[i+1] << 8) | ((long)buf[i+2] << 16);
|
|
}
|
|
|
|
ret = (ret >> (curbit % 8)) & maskTbl[code_size];
|
|
curbit += code_size;
|
|
return (int)ret;
|
|
}
|