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https://github.com/netsurf-browser/netsurf
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[project @ 2006-01-01 23:54:37 by rjw]
Optimisation of GIF reading. svn path=/import/netsurf/; revision=1931
This commit is contained in:
Richard Wilson
parent
086046e4a3
commit
a88d14018f
137
image/gifread.c
137
image/gifread.c
@ -65,6 +65,7 @@ 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 void gif_init_LZW(struct gif_animation *gif);
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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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@ -79,12 +80,14 @@ static int maskTbl[16] = {0x0000, 0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f
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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 *stack_end;
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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 curbit, lastbit, last_byte;
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static int firstcode, oldcode;
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static bool zero_data_block = false;
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static bool get_done;
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/* Whether to clear the decoded image rather than plot
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*/
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@ -551,8 +554,10 @@ int gif_decode_frame(struct gif_animation *gif, unsigned int frame) {
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/* Ensure we have a frame to decode
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*/
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if (frame > gif->frame_count_partial) return GIF_INSUFFICIENT_DATA;
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if ((!clear_image) && ((int)frame == gif->decoded_frame)) return 0;
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if (frame > gif->frame_count_partial)
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return GIF_INSUFFICIENT_DATA;
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if ((!clear_image) && ((int)frame == gif->decoded_frame))
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return 0;
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/* If the previous frame was dirty, remove it
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*/
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@ -561,7 +566,8 @@ int gif_decode_frame(struct gif_animation *gif, unsigned int frame) {
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gif->dirty_frame = -1;
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if (gif->decoded_frame == gif->dirty_frame) {
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clear_image = true;
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if (frame != 0) gif_decode_frame(gif, gif->dirty_frame);
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if (frame != 0)
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gif_decode_frame(gif, gif->dirty_frame);
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clear_image = false;
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}
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gif->dirty_frame = -1;
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@ -719,9 +725,8 @@ int gif_decode_frame(struct gif_animation *gif, unsigned int frame) {
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max_code = clear_code + 2;
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curbit = lastbit = 0;
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last_byte = 2;
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get_done = 0;
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return_clear = 1;
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stack_pointer = stack;
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get_done = false;
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gif_init_LZW(gif);
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/* Decompress the data
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*/
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@ -840,41 +845,50 @@ void gif_finalise(struct gif_animation *gif) {
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gif->global_colour_table = NULL;
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}
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static int gif_next_LZW(struct gif_animation *gif) {
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static int firstcode, oldcode;
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int code, incode;
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unsigned int i, block_size;
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while ((code = gif_next_code(gif, code_size)) >= 0) {
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if (code == clear_code) {
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/* Check we have a valid clear code
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/**
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* Initialise LZW decoding
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*/
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if (clear_code >= (1 << GIF_MAX_LZW)) return -2;
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void gif_init_LZW(struct gif_animation *gif) {
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int i;
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/* Initialise our table
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*/
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memset(table, 0x00, (1 << GIF_MAX_LZW) * 8);
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for (i = 0; i < (unsigned int)clear_code; ++i) {
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table[1][i] = i;
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if (clear_code >= (1 << GIF_MAX_LZW)) {
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stack_pointer = stack;
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*stack_pointer++ = -2;
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}
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/* Update our LZW parameters
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*/
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/* initialise our table */
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memset(table, 0x00, (1 << GIF_MAX_LZW) * 8);
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for (i = 0; i < clear_code; ++i)
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table[1][i] = i;
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/* update our LZW parameters */
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code_size = set_code_size + 1;
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max_code_size = clear_code << 1;
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max_code = clear_code + 2;
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stack_pointer = stack;
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stack_end = (int *)((char *)stack + sizeof(stack));
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do {
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firstcode = oldcode = gif_next_code(gif, code_size);
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} while (firstcode == clear_code);
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return firstcode;
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*stack_pointer++ =firstcode;
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}
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static int gif_next_LZW(struct gif_animation *gif) {
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int code, incode;
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int block_size;
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int stack_remaining;
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while ((code = gif_next_code(gif, code_size)) >= 0) {
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if (code == clear_code) {
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gif_init_LZW(gif);
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return *--stack_pointer;
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}
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if (code == end_code) {
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/* Skip to the end of our data so multi-image GIFs work
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*/
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if (zero_data_block) return -2;
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/* skip to the end of our data so multi-image GIFs work */
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if (zero_data_block)
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return -2;
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block_size = 0;
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while (block_size != 1) {
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block_size = gif->gif_data[gif->buffer_position] + 1;
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@ -883,19 +897,30 @@ static int gif_next_LZW(struct gif_animation *gif) {
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return -2;
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}
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/* Fill the stack with some data
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*/
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/* fill the stack with some data */
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incode = code;
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if (code >= max_code) {
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*stack_pointer++ = firstcode;
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code = oldcode;
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}
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stack_remaining = (stack_end - stack_pointer) / sizeof(int);
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/* flush out odd number of words */
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if ((code >= clear_code) && (stack_remaining & 1)) {
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*stack_pointer++ = table[1][code];
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if ((code == table[0][code]) || (--stack_remaining <= 0))
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return code;
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code = table[0][code];
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}
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stack_remaining = stack_remaining >> 1;
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while (code >= clear_code) {
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*stack_pointer++ = table[1][code];
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if (code == table[0][code]) return(code);
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if (((char *)stack_pointer - (char *)stack) >= (int)sizeof(stack)) return(code);
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code = table[0][code];
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if (code < clear_code)
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break;
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*stack_pointer++ = table[1][code];
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if ((code == table[0][code]) || (--stack_remaining <= 0))
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return code;
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code = table[0][code];
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}
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@ -910,45 +935,38 @@ static int gif_next_LZW(struct gif_animation *gif) {
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++code_size;
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}
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}
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oldcode = incode;
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if (stack_pointer > stack) return *--stack_pointer;
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if (stack_pointer > stack)
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return *--stack_pointer;
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}
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return code;
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}
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static int gif_next_code(struct gif_animation *gif, int code_size) {
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int i, j, end, count;
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long ret;
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unsigned int ret;
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unsigned char *gif_data;
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if (return_clear) {
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return_clear = 0;
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return clear_code;
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}
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end = curbit + code_size;
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if (end >= lastbit) {
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if (get_done) return -1;
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if (get_done)
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return -1;
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buf[0] = buf[last_byte - 2];
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buf[1] = buf[last_byte - 1];
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/* Get the next block
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*/
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/* get the next block */
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gif_data = gif->gif_data + gif->buffer_position;
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zero_data_block = ((count = gif_data[0]) == 0);
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if ((gif->buffer_position + count) >= gif->buffer_size) return -1;
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if (count == 0) {
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get_done = 1;
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} else {
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if ((gif->buffer_position + count) >= gif->buffer_size)
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return -1;
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if (count == 0)
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get_done = true;
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else
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memcpy(&buf[2], gif_data + 1, count);
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}
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gif->buffer_position += count + 1;
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/* Update our variables
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*/
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/* update our variables */
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last_byte = 2 + count;
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curbit = (curbit - lastbit) + 16;
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lastbit = (2 + count) << 3;
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@ -957,13 +975,12 @@ static int gif_next_code(struct gif_animation *gif, int code_size) {
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j = end >> 3;
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i = curbit >> 3;
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if (i == j) {
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ret = (long)buf[i];
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} else if (i + 1 == j) {
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ret = (long)buf[i] | ((long)buf[i+1] << 8);
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} else {
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ret = (long)buf[i] | ((long)buf[i+1] << 8) | ((long)buf[i+2] << 16);
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}
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if (i == j)
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ret = buf[i];
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else if (i + 1 == j)
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ret = buf[i] | (buf[i+1] << 8);
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else
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ret = buf[i] | (buf[i+1] << 8) | (buf[i+2] << 16);
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ret = (ret >> (curbit % 8)) & maskTbl[code_size];
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curbit += code_size;
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