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authorMichael Drake <tlsa@netsurf-browser.org>2017-02-06 19:58:09 (GMT)
committer Michael Drake <tlsa@netsurf-browser.org>2017-02-06 20:32:57 (GMT)
commitce45f8bc146aac4ce08554112ddeb52cf37848de (patch)
tree72950b02910e60fb5be1517d9807875ef3e1a852
parent3db59ff9dd4257f9ee0a7c027b508bef32c2f2e3 (diff)
downloadlibnsgif-ce45f8bc146aac4ce08554112ddeb52cf37848de.tar.gz
libnsgif-ce45f8bc146aac4ce08554112ddeb52cf37848de.tar.bz2
Don't pass gif structure into lzw decoder.
-rw-r--r--src/libnsgif.c128
1 files changed, 78 insertions, 50 deletions
diff --git a/src/libnsgif.c b/src/libnsgif.c
index fe91111..f8fa4ef 100644
--- a/src/libnsgif.c
+++ b/src/libnsgif.c
@@ -68,7 +68,7 @@
/** LZW parameters */
struct lzw_s {
unsigned char buf[4];
- unsigned char *direct;
+ const unsigned char *direct;
int table[2][(1 << GIF_MAX_LZW)];
unsigned char stack[(1 << GIF_MAX_LZW) * 2];
unsigned char *stack_pointer;
@@ -104,14 +104,22 @@ static struct lzw_s *lzw = &lzw_params;
*
* reads codes from the input data stream coping with GIF data sub blocking
*
- * \param gif The GIF context
- * \param code_size The number of bitsin the current LZW code
+ * \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(gif_animation *gif, int code_size)
+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;
- unsigned char *b;
+ 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
@@ -126,28 +134,28 @@ static int gif_next_code(gif_animation *gif, int code_size)
lzw->buf[1] = lzw->direct[lzw->last_byte - 1];
/* get the next block */
- lzw->direct = gif->gif_data + gif->buffer_position;
- if (gif->buffer_position >= gif->buffer_size) {
+ 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 ((gif->buffer_position + count) >= gif->buffer_size) {
+ if ((pos + count) >= compressed_data_len) {
return GIF_INSUFFICIENT_FRAME_DATA;
}
if (count == 0) {
lzw->get_done = true;
} else {
- if (gif->buffer_position + 3 >= gif->buffer_size) {
+ 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];
}
- gif->buffer_position += count + 1;
+ pos += count + 1;
/* update our variables */
lzw->last_byte = 2 + count;
@@ -174,6 +182,7 @@ static int gif_next_code(gif_animation *gif, int code_size)
ret = (ret >> (lzw->curbit % 8)) & maskTbl[code_size];
lzw->curbit += code_size;
+ *compressed_data_pos = pos;
return ret;
}
@@ -181,10 +190,16 @@ static int gif_next_code(gif_animation *gif, int code_size)
/**
* Clear LZW code dictionary
*
- * \param gif The GIF context.
+ * \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(gif_animation *gif)
+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;
@@ -208,7 +223,8 @@ static gif_result gif_clear_codes_LZW(gif_animation *gif)
/* process repeated clear codes */
do {
- code = gif_next_code(gif, lzw->code_size);
+ code = gif_next_code(compressed_data, compressed_data_len,
+ compressed_data_pos, lzw->code_size);
if (code < 0) {
return code;
}
@@ -226,9 +242,17 @@ static gif_result gif_clear_codes_LZW(gif_animation *gif)
*
* This initialises a LZW context ready to commence decompression.
*
- * \param initial_code_size The size of codes used on clearing of 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.
+ * \param[in] initial_code_size Size of codes used on clearing of code dictionary
*/
-static gif_result gif_initialise_LZW(gif_animation *gif, int initial_code_size)
+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;
@@ -241,56 +265,59 @@ static gif_result gif_initialise_LZW(gif_animation *gif, int initial_code_size)
lzw->get_done = false;
lzw->direct = lzw->buf;
- return gif_clear_codes_LZW(gif);
+ return gif_clear_codes_LZW(compressed_data,
+ compressed_data_len,
+ compressed_data_pos);
}
/**
* fill the LZW stack with decompressed data
*
- * \param gif The GIF context.
+ * \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 bool gif_next_LZW(gif_animation *gif)
+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(gif, lzw->code_size);
+ code = gif_next_code(compressed_data, compressed_data_len,
+ compressed_data_pos, lzw->code_size);
if (code < 0) {
- gif->current_error = code;
- return false;
+ return code;
}
if (code == lzw->clear_code) {
- gif->current_error = gif_clear_codes_LZW(gif);
- if (gif->current_error != GIF_OK) {
- return false;
- }
- return true;
+ 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) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
block_size = 0;
while (block_size != 1 &&
- gif->buffer_position < gif->buffer_size) {
- block_size = gif->gif_data[gif->buffer_position] + 1;
- gif->buffer_position += block_size;
+ *compressed_data_pos < compressed_data_len) {
+ block_size = compressed_data[*compressed_data_pos] + 1;
+ *compressed_data_pos += block_size;
}
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
incode = code;
if (code >= lzw->max_code) {
if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2)) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
*lzw->stack_pointer++ = lzw->firstcode;
code = lzw->oldcode;
@@ -305,8 +332,7 @@ static bool gif_next_LZW(gif_animation *gif)
while (code >= lzw->clear_code) {
if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2) ||
code >= (1 << GIF_MAX_LZW)) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
*lzw->stack_pointer++ = lzw->table[1][code];
new_code = lzw->table[0][code];
@@ -317,20 +343,17 @@ static bool gif_next_LZW(gif_animation *gif)
if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2) ||
new_code >= (1 << GIF_MAX_LZW)) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
*lzw->stack_pointer++ = lzw->table[1][new_code];
code = lzw->table[0][new_code];
if (code == new_code) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
}
if (lzw->stack_pointer >= lzw->stack + ((1 << GIF_MAX_LZW) * 2)) {
- gif->current_error = GIF_FRAME_DATA_ERROR;
- return false;
+ return GIF_FRAME_DATA_ERROR;
}
*lzw->stack_pointer++ = lzw->firstcode = lzw->table[1][code];
@@ -346,7 +369,7 @@ static bool gif_next_LZW(gif_animation *gif)
}
}
lzw->oldcode = incode;
- return true;
+ return GIF_OK;
}
@@ -855,6 +878,7 @@ 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;
@@ -1091,9 +1115,10 @@ gif_internal_decode_frame(gif_animation *gif,
gif->buffer_position = (gif_data - gif->gif_data) + 1;
/* Initialise the LZW decoding */
- gif->current_error = gif_initialise_LZW(gif, gif_data[0]);
- if (gif->current_error != GIF_OK) {
- return gif->current_error;
+ res = gif_initialise_LZW(gif->gif_data, gif->buffer_size,
+ &gif->buffer_position, gif_data[0]);
+ if (res != GIF_OK) {
+ return res;
}
/* Decompress the data */
@@ -1127,12 +1152,15 @@ gif_internal_decode_frame(gif_animation *gif,
frame_scanline++;
}
} else {
- if (!gif_next_LZW(gif)) {
+ res = gif_next_LZW(gif->gif_data,
+ gif->buffer_size,
+ &gif->buffer_position);
+ if (res != GIF_OK) {
/* Unexpected end of frame, try to recover */
- if (gif->current_error == GIF_END_OF_FRAME) {
+ if (res == GIF_END_OF_FRAME) {
return_value = GIF_OK;
} else {
- return_value = gif->current_error;
+ return_value = res;
}
goto gif_decode_frame_exit;
}