summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorMichael Drake <michael.drake@codethink.co.uk>2017-04-03 09:23:18 (GMT)
committer Michael Drake <michael.drake@codethink.co.uk>2017-04-05 10:06:23 (GMT)
commit34f3a9a81824dcda5a3e1944d14b0273298ec0c3 (patch)
treeec22c0d6a0ca946ba4bd31cc2c53ec0a9c4714c5
parent86ebd63cc1e9570cf247da26635375e31fc57d40 (diff)
downloadlibnsgif-34f3a9a81824dcda5a3e1944d14b0273298ec0c3.tar.gz
libnsgif-34f3a9a81824dcda5a3e1944d14b0273298ec0c3.tar.bz2
GIF decoding: Remove old LZW decoder and port library to new implementation.
-rw-r--r--include/libnsgif.h2
-rw-r--r--src/Makefile2
-rw-r--r--src/libnsgif.c369
3 files changed, 47 insertions, 326 deletions
diff --git a/include/libnsgif.h b/include/libnsgif.h
index fd92a0a..a819fec 100644
--- a/include/libnsgif.h
+++ b/include/libnsgif.h
@@ -93,6 +93,8 @@ typedef struct gif_bitmap_callback_vt {
/** GIF animation data */
typedef struct gif_animation {
+ /** LZW decode context */
+ void *lzw_ctx;
/** callbacks for bitmap functions */
gif_bitmap_callback_vt bitmap_callbacks;
/** pointer to GIF data */
diff --git a/src/Makefile b/src/Makefile
index 0fa4dc6..cb5d31f 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,4 +1,4 @@
# Sources
-DIR_SOURCES := libnsgif.c
+DIR_SOURCES := libnsgif.c lzw.c
include $(NSBUILD)/Makefile.subdir
diff --git a/src/libnsgif.c b/src/libnsgif.c
index 998f8d7..fffbd94 100644
--- a/src/libnsgif.c
+++ b/src/libnsgif.c
@@ -8,6 +8,7 @@
*/
#include <stdbool.h>
+#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
@@ -15,6 +16,8 @@
#include "libnsgif.h"
#include "utils/log.h"
+#include "lzw.h"
+
/**
*
* \file
@@ -36,9 +39,6 @@
/** Internal flag that a frame is invalid/unprocessed */
#define GIF_INVALID_FRAME -1
-/** Maximum LZW bits available */
-#define GIF_MAX_LZW 12
-
/** Transparent colour */
#define GIF_TRANSPARENT_COLOUR 0x00
@@ -65,313 +65,6 @@
/** standard GIF header size */
#define GIF_STANDARD_HEADER_SIZE 13
-/** LZW parameters */
-struct lzw_s {
- unsigned char buf[4];
- const unsigned char *direct;
- int table[2][(1 << GIF_MAX_LZW)];
- unsigned char stack[(1 << GIF_MAX_LZW) * 2];
- unsigned char *stack_pointer;
-
- int code_size, set_code_size;
-
- int max_code, max_code_size;
-
- int clear_code, end_code;
-
- int curbit, lastbit, last_byte;
-
- int firstcode;
- int oldcode;
-
- bool zero_data_block;
- bool get_done;
-};
-
-
-/* General LZW values. They are shared for all GIFs being decoded, and thus we
- * can't handle progressive decoding efficiently without having the data for
- * each image which would use an extra 10Kb or so per GIF.
- */
-static struct lzw_s lzw_params = {
- .zero_data_block = false,
-};
-
-static struct lzw_s *lzw = &lzw_params;
-
-/**
- * get the next LZW code from the GIF
- *
- * reads codes from the input data stream coping with GIF data sub blocking
- *
- * \param[in] compressed_data LZW compressed data
- * \param[in] compressed_data_len Byte size of compressed_data
- * \param[in,out] compressed_data_pos Current position in compressed_data
- * updated on exit.
- * \param[in] code_size Number of bits in the current LZW code
- * \return The next code to process or error return code
- */
-static int gif_next_code(
- const uint8_t *compressed_data,
- uint32_t compressed_data_len,
- uint32_t *compressed_data_pos,
- int code_size)
-{
- int i, j, end, count, ret;
- uint32_t pos = *compressed_data_pos;
- const unsigned char *b;
- static const int maskTbl[16] = {
- 0x0000, 0x0001, 0x0003, 0x0007, 0x000f, 0x001f, 0x003f, 0x007f,
- 0x00ff, 0x01ff, 0x03ff, 0x07ff, 0x0fff, 0x1fff, 0x3fff, 0x7fff
- };
-
- end = lzw->curbit + code_size;
- if (end >= lzw->lastbit) {
- if (lzw->get_done) {
- return GIF_END_OF_FRAME;
- }
- lzw->buf[0] = lzw->direct[lzw->last_byte - 2];
- lzw->buf[1] = lzw->direct[lzw->last_byte - 1];
-
- /* get the next block */
- lzw->direct = compressed_data + pos;
- if (pos >= compressed_data_len) {
- return GIF_INSUFFICIENT_FRAME_DATA;
- }
-
- count = lzw->direct[0];
- lzw->zero_data_block = (count == 0);
- if ((pos + count) >= compressed_data_len) {
- return GIF_INSUFFICIENT_FRAME_DATA;
- }
-
- if (count == 0) {
- lzw->get_done = true;
- } else {
- if (pos + 3 >= compressed_data_len) {
- return GIF_INSUFFICIENT_FRAME_DATA;
- }
- lzw->direct -= 1;
- lzw->buf[2] = lzw->direct[2];
- lzw->buf[3] = lzw->direct[3];
- }
- pos += count + 1;
-
- /* update our variables */
- lzw->last_byte = 2 + count;
- lzw->curbit = (lzw->curbit - lzw->lastbit) + 16;
- lzw->lastbit = (2 + count) << 3;
- end = lzw->curbit + code_size;
- }
-
- i = lzw->curbit >> 3;
- if (i < 2) {
- b = lzw->buf;
- } else {
- b = lzw->direct;
- }
-
- ret = b[i];
- j = (end >> 3) - 1;
- if (i <= j) {
- ret |= (b[i + 1] << 8);
- if (i < j) {
- ret |= (b[i + 2] << 16);
- }
- }
- ret = (ret >> (lzw->curbit % 8)) & maskTbl[code_size];
- lzw->curbit += code_size;
-
- *compressed_data_pos = pos;
- return ret;
-}
-
-
-/**
- * Clear LZW code dictionary
- *
- * \param[in] compressed_data LZW compressed data
- * \param[in] compressed_data_len Byte size of compressed_data
- * \param[in,out] compressed_data_pos Current position in compressed_data
- * updated on exit.
- * \return GIF_OK or error code.
- */
-static gif_result gif_clear_codes_LZW(
- const uint8_t *compressed_data,
- uint32_t compressed_data_len,
- uint32_t *compressed_data_pos)
-{
- int i;
- int code;
-
- if (lzw->clear_code >= (1 << GIF_MAX_LZW)) {
- lzw->stack_pointer = lzw->stack;
- return GIF_FRAME_DATA_ERROR;
- }
-
- /* initialise our table */
- memset(lzw->table, 0x00, (1 << GIF_MAX_LZW) * 8);
- for (i = 0; i < lzw->clear_code; ++i) {
- lzw->table[1][i] = i;
- }
-
- /* reset LZW parameters */
- lzw->code_size = lzw->set_code_size + 1;
- lzw->max_code_size = lzw->clear_code << 1;
- lzw->max_code = lzw->clear_code + 2;
- lzw->stack_pointer = lzw->stack;
-
- /* process repeated clear codes */
- do {
- code = gif_next_code(compressed_data, compressed_data_len,
- compressed_data_pos, lzw->code_size);
- if (code < 0) {
- return code;
- }
- } while (code == lzw->clear_code);
- lzw->firstcode = lzw->oldcode = code;
-
- *lzw->stack_pointer++ = lzw->firstcode;
-
- return GIF_OK;
-}
-
-
-/**
- * Initialise LZW
- *
- * This initialises a LZW context ready to commence decompression.
- *
- * \param[in] compressed_data LZW compressed data
- * \param[in] compressed_data_len Byte size of compressed_data
- * \param[in,out] compressed_data_pos Current position in compressed_data
- * updated on exit.
- * \param[in] initial_code_size Size of codes used on clearing of code dictionary
- */
-static gif_result gif_initialise_LZW(
- const uint8_t *compressed_data,
- uint32_t compressed_data_len,
- uint32_t *compressed_data_pos,
- int initial_code_size)
-{
- lzw->set_code_size = initial_code_size;
- lzw->code_size = lzw->set_code_size + 1;
- lzw->clear_code = (1 << lzw->set_code_size);
- lzw->end_code = lzw->clear_code + 1;
- lzw->max_code_size = lzw->clear_code << 1;
- lzw->max_code = lzw->clear_code + 2;
- lzw->curbit = lzw->lastbit = 0;
- lzw->last_byte = 2;
- lzw->get_done = false;
- lzw->direct = lzw->buf;
-
- return gif_clear_codes_LZW(compressed_data,
- compressed_data_len,
- compressed_data_pos);
-}
-
-/**
- * fill the LZW stack with decompressed data
- *
- * \param[in] compressed_data LZW compressed data
- * \param[in] compressed_data_len Byte size of compressed_data
- * \param[in,out] compressed_data_pos Current position in compressed_data
- * updated on exit.
- * \return true on sucessful decode of the next LZW code else false.
- */
-static gif_result gif_next_LZW(
- const uint8_t *compressed_data,
- uint32_t compressed_data_len,
- uint32_t *compressed_data_pos)
-{
- int code, incode;
- int block_size;
- int new_code;
-
- code = gif_next_code(compressed_data, compressed_data_len,
- compressed_data_pos, lzw->code_size);
- if (code < 0) {
- return code;
- }
-
- if (code == lzw->clear_code) {
- return gif_clear_codes_LZW(compressed_data,
- compressed_data_len,
- compressed_data_pos);
- }
-
- if (code == lzw->end_code) {
- /* skip to the end of our data so multi-image GIFs work */
- if (lzw->zero_data_block) {
- return GIF_FRAME_DATA_ERROR;
- }
- block_size = 0;
- while (block_size != 1 &&
- *compressed_data_pos < compressed_data_len) {
- block_size = compressed_data[*compressed_data_pos] + 1;
- *compressed_data_pos += block_size;
- }
- return GIF_FRAME_DATA_ERROR;
- }
-
- incode = code;
- if (code >= lzw->max_code) {
- if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2)) {
- return GIF_FRAME_DATA_ERROR;
- }
- *lzw->stack_pointer++ = lzw->firstcode;
- code = lzw->oldcode;
- }
-
- /* The following loop is the most important in the GIF decoding cycle
- * as every single pixel passes through it.
- *
- * Note: our stack is always big enough to hold a complete decompressed
- * chunk.
- */
- while (code >= lzw->clear_code) {
- if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2) ||
- code >= (1 << GIF_MAX_LZW)) {
- return GIF_FRAME_DATA_ERROR;
- }
- *lzw->stack_pointer++ = lzw->table[1][code];
- new_code = lzw->table[0][code];
- if (new_code < lzw->clear_code) {
- code = new_code;
- break;
- }
-
- if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2) ||
- new_code >= (1 << GIF_MAX_LZW)) {
- return GIF_FRAME_DATA_ERROR;
- }
- *lzw->stack_pointer++ = lzw->table[1][new_code];
- code = lzw->table[0][new_code];
- if (code == new_code) {
- return GIF_FRAME_DATA_ERROR;
- }
- }
-
- if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2)) {
- return GIF_FRAME_DATA_ERROR;
- }
- *lzw->stack_pointer++ = lzw->firstcode = lzw->table[1][code];
-
- code = lzw->max_code;
- if (code < (1 << GIF_MAX_LZW)) {
- lzw->table[0][code] = lzw->oldcode;
- lzw->table[1][code] = lzw->firstcode;
- ++lzw->max_code;
- if ((lzw->max_code >= lzw->max_code_size) &&
- (lzw->max_code_size < (1 << GIF_MAX_LZW))) {
- lzw->max_code_size = lzw->max_code_size << 1;
- ++lzw->code_size;
- }
- }
- lzw->oldcode = incode;
- return GIF_OK;
-}
-
/**
* Updates the sprite memory size
@@ -725,7 +418,7 @@ static gif_result gif_initialise_frame(gif_animation *gif)
if (gif_bytes < 1) {
return GIF_INSUFFICIENT_FRAME_DATA;
}
- if (gif_data[0] > GIF_MAX_LZW) {
+ if (gif_data[0] > LZW_CODE_MAX) {
return GIF_DATA_ERROR;
}
@@ -863,7 +556,20 @@ static unsigned int gif_interlaced_line(int height, int y) {
}
-
+static gif_result gif_error_from_lzw(lzw_result l_res)
+{
+ static const gif_result g_res[] = {
+ [LZW_OK] = GIF_OK,
+ [LZW_OK_EOD] = GIF_END_OF_FRAME,
+ [LZW_NO_MEM] = GIF_INSUFFICIENT_MEMORY,
+ [LZW_NO_DATA] = GIF_INSUFFICIENT_FRAME_DATA,
+ [LZW_EOI_CODE] = GIF_FRAME_DATA_ERROR,
+ [LZW_BAD_ICODE] = GIF_FRAME_DATA_ERROR,
+ [LZW_BAD_CODE] = GIF_FRAME_DATA_ERROR,
+ [LZW_BAD_DATA] = GIF_FRAME_DATA_ERROR,
+ };
+ return g_res[l_res];
+}
/**
@@ -878,7 +584,6 @@ gif_internal_decode_frame(gif_animation *gif,
unsigned int frame,
bool clear_image)
{
- gif_result res;
unsigned int index = 0;
unsigned char *gif_data, *gif_end;
int gif_bytes;
@@ -1038,6 +743,10 @@ gif_internal_decode_frame(gif_animation *gif,
/* If we are clearing the image we just clear, if not decode */
if (!clear_image) {
+ lzw_result res;
+ const uint8_t *stack_base;
+ const uint8_t *stack_pos;
+
/* Ensure we have enough data for a 1-byte LZW code size +
* 1-byte gif trailer
*/
@@ -1114,10 +823,11 @@ gif_internal_decode_frame(gif_animation *gif,
gif->buffer_position = (gif_data - gif->gif_data) + 1;
/* Initialise the LZW decoding */
- res = gif_initialise_LZW(gif->gif_data, gif->buffer_size,
- &gif->buffer_position, gif_data[0]);
- if (res != GIF_OK) {
- return res;
+ res = lzw_decode_init(gif->lzw_ctx, gif->gif_data,
+ gif->buffer_size, gif->buffer_position,
+ gif_data[0], &stack_base, &stack_pos);
+ if (res != LZW_OK) {
+ return gif_error_from_lzw(res);
}
/* Decompress the data */
@@ -1135,14 +845,14 @@ gif_internal_decode_frame(gif_animation *gif,
*/
x = width;
while (x > 0) {
- burst_bytes = (lzw->stack_pointer - lzw->stack);
+ burst_bytes = (stack_pos - stack_base);
if (burst_bytes > 0) {
if (burst_bytes > x) {
burst_bytes = x;
}
x -= burst_bytes;
while (burst_bytes-- > 0) {
- colour = *--lzw->stack_pointer;
+ colour = *--stack_pos;
if (((gif->frames[frame].transparency) &&
(colour != gif->frames[frame].transparency_index)) ||
(!gif->frames[frame].transparency)) {
@@ -1151,15 +861,13 @@ gif_internal_decode_frame(gif_animation *gif,
frame_scanline++;
}
} else {
- res = gif_next_LZW(gif->gif_data,
- gif->buffer_size,
- &gif->buffer_position);
- if (res != GIF_OK) {
+ res = lzw_decode(gif->lzw_ctx, &stack_pos);
+ if (res != LZW_OK) {
/* Unexpected end of frame, try to recover */
- if (res == GIF_END_OF_FRAME) {
+ if (res == LZW_OK_EOD) {
return_value = GIF_OK;
} else {
- return_value = res;
+ return_value = gif_error_from_lzw(res);
}
goto gif_decode_frame_exit;
}
@@ -1230,6 +938,14 @@ gif_result gif_initialise(gif_animation *gif, size_t size, unsigned char *data)
gif->buffer_size = size;
gif->gif_data = data;
+ if (gif->lzw_ctx == NULL) {
+ lzw_result res = lzw_context_create(
+ (struct lzw_ctx **)&gif->lzw_ctx);
+ if (res != LZW_OK) {
+ return gif_error_from_lzw(res);
+ }
+ }
+
/* Check for sufficient data to be a GIF (6-byte header + 7-byte
* logical screen descriptor)
*/
@@ -1448,4 +1164,7 @@ void gif_finalise(gif_animation *gif)
gif->local_colour_table = NULL;
free(gif->global_colour_table);
gif->global_colour_table = NULL;
+
+ lzw_context_destroy(gif->lzw_ctx);
+ gif->lzw_ctx = NULL;
}