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Decoder support for new empty meta-block format.

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This change enforces the new 16MB limit on the
size of the meta-blocks and adds support for
empty meta-blocks with optional ignored metadata.
This commit is contained in:
Zoltan Szabadka 2015-04-22 14:25:08 +02:00
parent f393bff2e3
commit a81f2ef433
2 changed files with 52 additions and 17 deletions
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67
dec/decode.c
View File

@ -86,26 +86,40 @@ static BROTLI_INLINE int DecodeVarLenUint8(BrotliBitReader* br) {
return 0;
}
static void DecodeMetaBlockLength(BrotliBitReader* br,
int* meta_block_length,
int* input_end,
int* is_uncompressed) {
static int DecodeMetaBlockLength(BrotliBitReader* br,
int* meta_block_length,
int* input_end,
int* is_metadata,
int* is_uncompressed) {
int size_nibbles;
int i;
*input_end = (int)BrotliReadBits(br, 1);
*meta_block_length = 0;
*is_uncompressed = 0;
*is_metadata = 0;
if (*input_end && BrotliReadBits(br, 1)) {
return;
return 1;
}
size_nibbles = (int)BrotliReadBits(br, 2) + 4;
if (size_nibbles == 7) {
*is_metadata = 1;
/* Verify reserved bit. */
if (BrotliReadBits(br, 1) != 0) {
return 0;
}
size_nibbles = 2 * (int)BrotliReadBits(br, 2);
if (size_nibbles == 0) {
return 1;
}
}
for (i = 0; i < size_nibbles; ++i) {
*meta_block_length |= (int)BrotliReadBits(br, 4) << (i * 4);
}
++(*meta_block_length);
if (!*input_end) {
if (!*input_end && !*is_metadata) {
*is_uncompressed = (int)BrotliReadBits(br, 1);
}
return 1;
}
/* Decodes the next Huffman code from bit-stream. */
@ -375,13 +389,6 @@ static int TranslateShortCodes(int code, int* ringbuffer, int index) {
return val;
}
static void MoveToFront(uint8_t* v, uint8_t index) {
uint8_t value = v[index];
uint8_t i = index;
for (; i; --i) v[i] = v[i - 1];
v[0] = value;
}
static void InverseMoveToFrontTransform(uint8_t* v, int v_len) {
uint8_t mtf[256];
int i;
@ -390,8 +397,12 @@ static void InverseMoveToFrontTransform(uint8_t* v, int v_len) {
}
for (i = 0; i < v_len; ++i) {
uint8_t index = v[i];
v[i] = mtf[index];
if (index) MoveToFront(mtf, index);
uint8_t value = mtf[index];
v[i] = value;
for (; index; --index) {
mtf[index] = mtf[index - 1];
}
mtf[0] = value;
}
}
@ -971,9 +982,20 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
break;
}
BROTLI_LOG_UINT(pos);
DecodeMetaBlockLength(br, &s->meta_block_remaining_len,
&s->input_end, &s->is_uncompressed);
if (!DecodeMetaBlockLength(br,
&s->meta_block_remaining_len,
&s->input_end,
&s->is_metadata,
&s->is_uncompressed)) {
result = BROTLI_RESULT_ERROR;
break;
}
BROTLI_LOG_UINT(s->meta_block_remaining_len);
if (s->is_metadata) {
BrotliSetBitPos(br, (s->br.bit_pos_ + 7) & (uint32_t)(~7UL));
s->state = BROTLI_STATE_METADATA;
break;
}
if (s->meta_block_remaining_len == 0) {
s->state = BROTLI_STATE_METABLOCK_DONE;
break;
@ -1000,6 +1022,17 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
if (result != BROTLI_RESULT_SUCCESS) break;
s->state = BROTLI_STATE_METABLOCK_DONE;
break;
case BROTLI_STATE_METADATA:
for (; s->meta_block_remaining_len > 0; --s->meta_block_remaining_len) {
if (!BrotliReadMoreInput(&s->br)) {
result = BROTLI_RESULT_PARTIAL;
break;
}
/* Read one byte and ignore it. */
BrotliReadBits(&s->br, 8);
}
s->state = BROTLI_STATE_METABLOCK_DONE;
break;
case BROTLI_STATE_HUFFMAN_CODE_0:
if (i >= 3) {
BROTLI_LOG_UINT(s->num_block_types[0]);

2
dec/state.h
View File

@ -39,6 +39,7 @@ typedef enum {
BROTLI_STATE_BLOCK_DISTANCE = 15,
BROTLI_STATE_BLOCK_POST = 16,
BROTLI_STATE_UNCOMPRESSED = 17,
BROTLI_STATE_METADATA = 18,
BROTLI_STATE_METABLOCK_DONE = 20,
BROTLI_STATE_HUFFMAN_CODE_0 = 30,
BROTLI_STATE_HUFFMAN_CODE_1 = 31,
@ -91,6 +92,7 @@ typedef struct {
int trivial_literal_context;
int meta_block_remaining_len;
int is_metadata;
int is_uncompressed;
int block_length[3];
int block_type[3];