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update libnsgif

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for improved lzw decode
This commit is contained in:
John Cupitt 2021-04-24 18:57:20 +01:00
parent 83c4e56cfb
commit cc1020ae55
4 changed files with 1058 additions and 1056 deletions
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1953
libvips/foreign/libnsgif/libnsgif.c
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File diff suppressed because it is too large Load Diff

97
libvips/foreign/libnsgif/lzw.c
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@ -224,18 +224,39 @@ static inline lzw_result lzw__read_code(
/**
* Clear LZW code table.
* Handle clear code.
*
* \param[in] ctx LZW reading context, updated.
* \param[in] ctx LZW reading context, updated.
* \param[out] code_out Returns next code after a clear code.
* \return LZW_OK or error code.
*/
static inline void lzw__clear_table(
struct lzw_ctx *ctx)
static inline lzw_result lzw__handle_clear(
struct lzw_ctx *ctx,
uint32_t *code_out)
{
uint32_t code;
/* Reset table building context */
ctx->code_size = ctx->initial_code_size;
ctx->code_max = (1 << ctx->initial_code_size) - 1;
ctx->table_size = ctx->eoi_code + 1;
/* There might be a sequence of clear codes, so process them all */
do {
lzw_result res = lzw__read_code(&ctx->input,
ctx->code_size, &code);
if (res != LZW_OK) {
return res;
}
} while (code == ctx->clear_code);
/* The initial code must be from the initial table. */
if (code > ctx->clear_code) {
return LZW_BAD_ICODE;
}
*code_out = code;
return LZW_OK;
}
@ -248,6 +269,8 @@ lzw_result lzw_decode_init(
uint8_t minimum_code_size)
{
struct lzw_table_entry *table = ctx->table;
lzw_result res;
uint32_t code;
if (minimum_code_size >= LZW_CODE_MAX) {
return LZW_BAD_ICODE;
@ -276,8 +299,19 @@ lzw_result lzw_decode_init(
table[i].count = 1;
}
lzw__clear_table(ctx);
ctx->prev_code = ctx->clear_code;
res = lzw__handle_clear(ctx, &code);
if (res != LZW_OK) {
return res;
}
/* Store details of this code as "previous code" to the context. */
ctx->prev_code_first = ctx->table[code].first;
ctx->prev_code_count = ctx->table[code].count;
ctx->prev_code = code;
/* Add code to context for immediate output. */
ctx->output_code = code;
ctx->output_left = 1;
return LZW_OK;
}
@ -345,31 +379,27 @@ static inline lzw_result lzw__decode(struct lzw_ctx *ctx,
return LZW_BAD_CODE;
} else if (code == ctx->clear_code) {
lzw__clear_table(ctx);
} else {
if (ctx->prev_code == ctx->clear_code) {
if (code > ctx->clear_code) {
return LZW_BAD_ICODE;
}
} else if (ctx->table_size < LZW_TABLE_ENTRY_MAX) {
uint32_t size = ctx->table_size;
lzw__table_add_entry(ctx, (code < size) ?
ctx->table[code].first :
ctx->prev_code_first);
/* Ensure code size is increased, if needed. */
if (size == ctx->code_max &&
ctx->code_size < LZW_CODE_MAX) {
ctx->code_size++;
ctx->code_max = (1 << ctx->code_size) - 1;
}
res = lzw__handle_clear(ctx, &code);
if (res != LZW_OK) {
return res;
}
*used += write_pixels(ctx, output, length, *used, code,
ctx->table[code].count);
} else if (ctx->table_size < LZW_TABLE_ENTRY_MAX) {
uint32_t size = ctx->table_size;
lzw__table_add_entry(ctx, (code < size) ?
ctx->table[code].first :
ctx->prev_code_first);
/* Ensure code size is increased, if needed. */
if (size == ctx->code_max && ctx->code_size < LZW_CODE_MAX) {
ctx->code_size++;
ctx->code_max = (1 << ctx->code_size) - 1;
}
}
*used += write_pixels(ctx, output, length, *used, code,
ctx->table[code].count);
/* Store details of this code as "previous code" to the context. */
ctx->prev_code_first = ctx->table[code].first;
ctx->prev_code_count = ctx->table[code].count;
@ -432,20 +462,9 @@ static inline uint32_t lzw__write_pixels(struct lzw_ctx *ctx,
return count;
}
/* Exported function, documented in lzw.h */
lzw_result lzw_decode(struct lzw_ctx *ctx,
const uint8_t *restrict* const restrict data,
uint32_t *restrict used)
{
*used = 0;
*data = ctx->stack_base;
return lzw__decode(ctx, ctx->stack_base, sizeof(ctx->stack_base),
lzw__write_pixels, used);
}
/* Exported function, documented in lzw.h */
lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
const uint8_t ** const data,
const uint8_t *restrict *const restrict data,
uint32_t *restrict used)
{
*used = 0;

17
libvips/foreign/libnsgif/lzw.h
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@ -76,21 +76,6 @@ lzw_result lzw_decode_init(
uint32_t compressed_data_pos,
uint8_t minimum_code_size);
/**
* Read a single LZW code and write into lzw context owned output buffer.
*
* Ensure anything in output is used before calling this, as anything
* on the there before this call will be trampled.
*
* \param[in] ctx LZW reading context, updated.
* \param[out] data Returns pointer to array of output values.
* \param[out] used Returns the number of values written to data.
* \return LZW_OK on success, or appropriate error code otherwise.
*/
lzw_result lzw_decode(struct lzw_ctx *ctx,
const uint8_t *restrict *const restrict data,
uint32_t *restrict used);
/**
* Read input codes until end of lzw context owned output buffer.
*
@ -103,7 +88,7 @@ lzw_result lzw_decode(struct lzw_ctx *ctx,
* \return LZW_OK on success, or appropriate error code otherwise.
*/
lzw_result lzw_decode_continuous(struct lzw_ctx *ctx,
const uint8_t ** const data,
const uint8_t *restrict *const restrict data,
uint32_t *restrict used);
/**

47
libvips/foreign/libnsgif/patches/no-input-modify.patch
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@ -1,23 +1,13 @@
--- libnsgif-orig.c 2021-02-28 14:10:41.818557190 +0000
+++ libnsgif.c 2021-02-28 14:11:55.942285930 +0000
@@ -435,20 +435,15 @@
block_size = gif_data[0] + 1;
/* Check if the frame data runs off the end of the file */
if ((int)(gif_bytes - block_size) < 0) {
- /* Try to recover by signaling the end of the gif.
- * Once we get garbage data, there is no logical way to
- * determine where the next frame is. It's probably
- * better to partially load the gif than not at all.
- */
- if (gif_bytes >= 2) {
- gif_data[0] = 0;
- gif_data[1] = GIF_TRAILER;
- gif_bytes = 1;
- ++gif_data;
- break;
- } else {
- return GIF_INSUFFICIENT_FRAME_DATA;
- }
--- libnsgif.c.orig 2021-04-24 18:33:02.757323861 +0100
+++ libnsgif.c 2021-04-24 18:35:14.659860190 +0100
@@ -424,20 +424,15 @@
block_size = gif_data[0] + 1;
/* Check if the frame data runs off the end of the file */
if ((int)(gif_bytes - block_size) < 0) {
- /* Try to recover by signaling the end of the gif.
- * Once we get garbage data, there is no logical way to
- * determine where the next frame is. It's probably
- * better to partially load the gif than not at all.
+ /* jcupitt 15/9/19
+ *
+ * There was code here to set a TRAILER tag. But this
@ -25,8 +15,17 @@
+ * libvips, where buffers can be mmaped read only files.
+ *
+ * Instead, just signal insufficient frame data.
+ */
*/
- if (gif_bytes >= 2) {
- gif_data[0] = 0;
- gif_data[1] = GIF_TRAILER;
- gif_bytes = 1;
- ++gif_data;
- break;
- } else {
- return GIF_INSUFFICIENT_FRAME_DATA;
- }
+ return GIF_INSUFFICIENT_FRAME_DATA;
} else {
gif_bytes -= block_size;
gif_data += block_size;
} else {
gif_bytes -= block_size;
gif_data += block_size;