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Updates to Brotli compression format, decoder and encoder
This commit contains a batch of changes that were made to the Brotli compression algorithm in the last month. Most important changes: * Fixes to the spec. * Change of code length code order. * Use a 2-level Huffman lookup table in the decoder. * Faster uncompressed meta-block decoding. * Optimized encoding of the Huffman code. * Detection of UTF-8 input encoding. * UTF-8 based literal cost modeling for improved backward reference selection.
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@ -498,11 +498,11 @@ Abstract
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Symbol Code
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------ ----
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0 00
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1 1010
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2 100
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3 11
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4 01
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5 1011
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1 1110
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2 110
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3 01
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4 10
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5 1111
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We can now define the format of the complex Huffman code as
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follows:
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@ -513,7 +513,7 @@ Abstract
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Code lengths for symbols in the code length alphabet given
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just above, in the order: 1, 2, 3, 4, 0, 17, 5, 6, 16, 7,
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just above, in the order: 1, 2, 3, 4, 0, 5, 17, 6, 16, 7,
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8, 9, 10, 11, 12, 13, 14, 15
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The code lengths of code length symbols are between 0 and
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@ -572,7 +572,7 @@ Abstract
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6: last distance - 2
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7: last distance + 2
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8: last distance - 3
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9: last disatnce + 3
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9: last distance + 3
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10: second last distance - 1
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11: second last distance + 1
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12: second last distance - 2
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@ -647,7 +647,7 @@ Abstract
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---- ---- ------ ---- ---- ------- ---- ---- -------
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0 0 0 8 2 10-13 16 6 130-193
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1 0 1 9 2 14-17 17 7 194-321
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2 0 2 10 3 18-25 18 8 322-527
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2 0 2 10 3 18-25 18 8 322-577
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3 0 3 11 3 26-33 19 9 578-1089
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4 0 4 12 4 34-49 20 10 1090-2113
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5 0 5 13 4 50-65 21 12 2114-6209
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@ -681,7 +681,7 @@ Abstract
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| | |
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+---------+---------+---------+
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0-7 | 128-191 | 192-255 | 383-447 |
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0-7 | 128-191 | 192-255 | 384-447 |
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+---------+---------+---------+
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@ -689,7 +689,7 @@ Abstract
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+---------+---------+---------+
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16-23 | 448-551 | 576-639 | 640-703 |
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16-23 | 448-511 | 576-639 | 640-703 |
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+---------+---------+---------+
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@ -1008,9 +1008,10 @@ Abstract
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1 bit: ISEMPTY, set to 1 if the meta-block is empty, this
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field is only present if ISLAST bit is set, since
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only the last meta-block can be empty
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2 bits: MNIBBLES, (# of nibbles to represent the length) - 4
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2 bits: MNIBBLES - 4, where MNIBBLES is # of nibbles to represent
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the length
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(MNIBBLES + 4) x 4 bits: MLEN - 1, where MLEN is the length
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MNIBBLES x 4 bits: MLEN - 1, where MLEN is the length
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of the meta-block in the input data in bytes
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1 bit: ISUNCOMPRESSED, if set to 1, any bits of input up to
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@ -33,7 +33,7 @@ int BrotliInitBitReader(BrotliBitReader* const br, BrotliInput input) {
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br->val_ = 0;
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br->pos_ = 0;
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br->bit_pos_ = 0;
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br->bits_left_ = 64;
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br->bit_end_pos_ = 0;
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br->eos_ = 0;
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if (!BrotliReadMoreInput(br)) {
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return 0;
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@ -42,7 +42,7 @@ int BrotliInitBitReader(BrotliBitReader* const br, BrotliInput input) {
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br->val_ |= ((uint64_t)br->buf_[br->pos_]) << (8 * i);
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++br->pos_;
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}
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return (br->bits_left_ > 64);
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return (br->bit_end_pos_ > 0);
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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@ -31,7 +31,7 @@ extern "C" {
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#define BROTLI_IBUF_SIZE (2 * BROTLI_READ_SIZE + 32)
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#define BROTLI_IBUF_MASK (2 * BROTLI_READ_SIZE - 1)
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#define UNALIGNED_COPY64(dst, src) *(uint64_t*)(dst) = *(const uint64_t*)(src)
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#define UNALIGNED_COPY64(dst, src) memcpy(dst, src, 8)
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static const uint32_t kBitMask[BROTLI_MAX_NUM_BIT_READ] = {
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0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767,
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@ -42,13 +42,13 @@ typedef struct {
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/* Input byte buffer, consist of a ringbuffer and a "slack" region where */
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/* bytes from the start of the ringbuffer are copied. */
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uint8_t buf_[BROTLI_IBUF_SIZE];
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uint8_t* buf_ptr_; /* next input will write here */
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BrotliInput input_; /* input callback */
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uint64_t val_; /* pre-fetched bits */
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uint32_t pos_; /* byte position in stream */
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uint32_t bit_pos_; /* current bit-reading position in val_ */
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uint32_t bits_left_; /* how many valid bits left */
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int eos_; /* input stream is finished */
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uint8_t* buf_ptr_; /* next input will write here */
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BrotliInput input_; /* input callback */
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uint64_t val_; /* pre-fetched bits */
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uint32_t pos_; /* byte position in stream */
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uint32_t bit_pos_; /* current bit-reading position in val_ */
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uint32_t bit_end_pos_; /* bit-reading end position from LSB of val_ */
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int eos_; /* input stream is finished */
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} BrotliBitReader;
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int BrotliInitBitReader(BrotliBitReader* const br, BrotliInput input);
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@ -65,7 +65,7 @@ static BROTLI_INLINE void BrotliSetBitPos(BrotliBitReader* const br,
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#ifdef BROTLI_DECODE_DEBUG
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uint32_t n_bits = val - br->bit_pos_;
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const uint32_t bval = (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
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printf("[BrotliReadBits] %010ld %2d val: %6x\n",
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printf("[BrotliReadBits] %010d %2d val: %6x\n",
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(br->pos_ << 3) + br->bit_pos_ - 64, n_bits, bval);
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#endif
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br->bit_pos_ = val;
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@ -78,7 +78,7 @@ static BROTLI_INLINE void ShiftBytes(BrotliBitReader* const br) {
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br->val_ |= ((uint64_t)br->buf_[br->pos_ & BROTLI_IBUF_MASK]) << 56;
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++br->pos_;
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br->bit_pos_ -= 8;
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br->bits_left_ -= 8;
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br->bit_end_pos_ -= 8;
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}
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}
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@ -95,10 +95,10 @@ static BROTLI_INLINE void ShiftBytes(BrotliBitReader* const br) {
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every 32 bytes of input is read.
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*/
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static BROTLI_INLINE int BrotliReadMoreInput(BrotliBitReader* const br) {
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if (br->bits_left_ > 320) {
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if (br->bit_end_pos_ > 256) {
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return 1;
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} else if (br->eos_) {
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return br->bit_pos_ <= br->bits_left_;
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return br->bit_pos_ <= br->bit_end_pos_;
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} else {
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uint8_t* dst = br->buf_ptr_;
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int bytes_read = BrotliRead(br->input_, dst, BROTLI_READ_SIZE);
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@ -131,7 +131,7 @@ static BROTLI_INLINE int BrotliReadMoreInput(BrotliBitReader* const br) {
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} else {
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br->buf_ptr_ = br->buf_;
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}
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br->bits_left_ += ((uint32_t)bytes_read << 3);
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br->bit_end_pos_ += ((uint32_t)bytes_read << 3);
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return 1;
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}
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}
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@ -147,7 +147,7 @@ static BROTLI_INLINE void BrotliFillBitWindow(BrotliBitReader* const br) {
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br->buf_ + (br->pos_ & BROTLI_IBUF_MASK)) << 24;
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br->pos_ += 5;
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br->bit_pos_ -= 40;
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br->bits_left_ -= 40;
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br->bit_end_pos_ -= 40;
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#else
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ShiftBytes(br);
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#endif
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@ -155,14 +155,13 @@ static BROTLI_INLINE void BrotliFillBitWindow(BrotliBitReader* const br) {
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}
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/* Reads the specified number of bits from Read Buffer. */
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/* Requires that n_bits is positive. */
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static BROTLI_INLINE uint32_t BrotliReadBits(
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BrotliBitReader* const br, int n_bits) {
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uint32_t val;
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BrotliFillBitWindow(br);
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val = (uint32_t)(br->val_ >> br->bit_pos_) & kBitMask[n_bits];
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#ifdef BROTLI_DECODE_DEBUG
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printf("[BrotliReadBits] %010ld %2d val: %6x\n",
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printf("[BrotliReadBits] %010d %2d val: %6x\n",
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(br->pos_ << 3) + br->bit_pos_ - 64, n_bits, val);
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#endif
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br->bit_pos_ += (uint32_t)n_bits;
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dec/decode.c
538
dec/decode.c
@ -46,9 +46,14 @@ static const int kNumBlockLengthCodes = 26;
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static const int kLiteralContextBits = 6;
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static const int kDistanceContextBits = 2;
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#define HUFFMAN_TABLE_BITS 8
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#define HUFFMAN_TABLE_MASK 0xff
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/* This is a rough estimate, not an exact bound. */
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#define HUFFMAN_MAX_TABLE_SIZE 2048
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#define CODE_LENGTH_CODES 18
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static const uint8_t kCodeLengthCodeOrder[CODE_LENGTH_CODES] = {
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1, 2, 3, 4, 0, 17, 5, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15,
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1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15,
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};
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#define NUM_DISTANCE_SHORT_CODES 16
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@ -104,36 +109,19 @@ static void DecodeMetaBlockLength(BrotliBitReader* br,
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}
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/* Decodes the next Huffman code from bit-stream. */
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static BROTLI_INLINE int ReadSymbol(const HuffmanTree* tree,
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static BROTLI_INLINE int ReadSymbol(const HuffmanCode* table,
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BrotliBitReader* br) {
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uint32_t bits;
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uint32_t bitpos;
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int lut_ix;
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uint8_t lut_bits;
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const HuffmanTreeNode* node = tree->root_;
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int nbits;
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BrotliFillBitWindow(br);
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bits = BrotliPrefetchBits(br);
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bitpos = br->bit_pos_;
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/* Check if we find the bit combination from the Huffman lookup table. */
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lut_ix = bits & (HUFF_LUT - 1);
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lut_bits = tree->lut_bits_[lut_ix];
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if (lut_bits <= HUFF_LUT_BITS) {
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BrotliSetBitPos(br, bitpos + lut_bits);
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return tree->lut_symbol_[lut_ix];
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table += (int)(br->val_ >> br->bit_pos_) & HUFFMAN_TABLE_MASK;
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nbits = table->bits - HUFFMAN_TABLE_BITS;
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if (nbits > 0) {
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br->bit_pos_ += HUFFMAN_TABLE_BITS;
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table += table->value;
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table += (int)(br->val_ >> br->bit_pos_) & ((1 << nbits) - 1);
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}
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node += tree->lut_jump_[lut_ix];
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bitpos += HUFF_LUT_BITS;
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bits >>= HUFF_LUT_BITS;
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/* Decode the value from a binary tree. */
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assert(node != NULL);
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do {
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node = HuffmanTreeNextNode(node, bits & 1);
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bits >>= 1;
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++bitpos;
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} while (HuffmanTreeNodeIsNotLeaf(node));
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BrotliSetBitPos(br, bitpos);
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return node->symbol_;
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br->bit_pos_ += table->bits;
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return table->value;
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}
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static void PrintUcharVector(const uint8_t* v, int len) {
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@ -145,47 +133,34 @@ static int ReadHuffmanCodeLengths(
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const uint8_t* code_length_code_lengths,
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int num_symbols, uint8_t* code_lengths,
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BrotliBitReader* br) {
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int ok = 0;
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int symbol;
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int symbol = 0;
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uint8_t prev_code_len = kDefaultCodeLength;
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int repeat = 0;
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uint8_t repeat_length = 0;
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uint8_t repeat_code_len = 0;
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int space = 32768;
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HuffmanTree tree;
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HuffmanCode table[32];
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if (!BrotliHuffmanTreeBuildImplicit(&tree, code_length_code_lengths,
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CODE_LENGTH_CODES)) {
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if (!BrotliBuildHuffmanTable(table, 5,
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code_length_code_lengths,
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CODE_LENGTH_CODES)) {
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printf("[ReadHuffmanCodeLengths] Building code length tree failed: ");
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PrintUcharVector(code_length_code_lengths, CODE_LENGTH_CODES);
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return 0;
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}
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if (!BrotliReadMoreInput(br)) {
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printf("[ReadHuffmanCodeLengths] Unexpected end of input.\n");
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return 0;
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}
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symbol = 0;
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while (symbol + repeat < num_symbols && space > 0) {
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while (symbol < num_symbols && space > 0) {
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const HuffmanCode* p = table;
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uint8_t code_len;
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if (!BrotliReadMoreInput(br)) {
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printf("[ReadHuffmanCodeLengths] Unexpected end of input.\n");
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goto End;
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}
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code_len = (uint8_t)ReadSymbol(&tree, br);
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BROTLI_LOG_UINT(symbol);
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BROTLI_LOG_UINT(repeat);
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BROTLI_LOG_UINT(repeat_length);
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BROTLI_LOG_UINT(code_len);
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if ((code_len < kCodeLengthRepeatCode) ||
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(code_len == kCodeLengthRepeatCode && repeat_length == 0) ||
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(code_len > kCodeLengthRepeatCode && repeat_length > 0)) {
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while (repeat > 0) {
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code_lengths[symbol++] = repeat_length;
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--repeat;
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}
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return 0;
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}
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BrotliFillBitWindow(br);
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p += (br->val_ >> br->bit_pos_) & 31;
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br->bit_pos_ += p->bits;
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code_len = (uint8_t)p->value;
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if (code_len < kCodeLengthRepeatCode) {
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repeat = 0;
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code_lengths[symbol++] = code_len;
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if (code_len != 0) {
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prev_code_len = code_len;
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@ -193,47 +168,46 @@ static int ReadHuffmanCodeLengths(
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}
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} else {
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const int extra_bits = code_len - 14;
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int i = repeat;
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int old_repeat;
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int repeat_delta;
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uint8_t new_len = 0;
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if (code_len == kCodeLengthRepeatCode) {
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new_len = prev_code_len;
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}
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if (repeat_code_len != new_len) {
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repeat = 0;
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repeat_code_len = new_len;
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}
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old_repeat = repeat;
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if (repeat > 0) {
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repeat -= 2;
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repeat <<= extra_bits;
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}
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repeat += (int)BrotliReadBits(br, extra_bits) + 3;
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if (repeat + symbol > num_symbols) {
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goto End;
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repeat_delta = repeat - old_repeat;
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if (symbol + repeat_delta > num_symbols) {
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return 0;
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}
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if (code_len == kCodeLengthRepeatCode) {
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repeat_length = prev_code_len;
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for (; i < repeat; ++i) {
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space -= 32768 >> repeat_length;
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}
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} else {
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repeat_length = 0;
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memset(&code_lengths[symbol], repeat_code_len, (size_t)repeat_delta);
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symbol += repeat_delta;
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if (repeat_code_len != 0) {
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space -= repeat_delta << (15 - repeat_code_len);
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}
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}
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}
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if (space != 0) {
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printf("[ReadHuffmanCodeLengths] space = %d\n", space);
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goto End;
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return 0;
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}
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if (symbol + repeat > num_symbols) {
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printf("[ReadHuffmanCodeLengths] symbol + repeat > num_symbols "
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"(%d + %d vs %d)\n", symbol, repeat, num_symbols);
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goto End;
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}
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while (repeat-- > 0) code_lengths[symbol++] = repeat_length;
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while (symbol < num_symbols) code_lengths[symbol++] = 0;
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ok = 1;
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End:
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BrotliHuffmanTreeRelease(&tree);
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return ok;
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memset(&code_lengths[symbol], 0, (size_t)(num_symbols - symbol));
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return 1;
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}
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static int ReadHuffmanCode(int alphabet_size,
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HuffmanTree* tree,
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HuffmanCode* table,
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BrotliBitReader* br) {
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int ok = 1;
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int table_size = 0;
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int simple_code_or_skip;
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uint8_t* code_lengths = NULL;
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@ -290,109 +264,49 @@ static int ReadHuffmanCode(int alphabet_size,
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int i;
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uint8_t code_length_code_lengths[CODE_LENGTH_CODES] = { 0 };
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int space = 32;
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for (i = simple_code_or_skip;
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i < CODE_LENGTH_CODES && space > 0; ++i) {
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int code_len_idx = kCodeLengthCodeOrder[i];
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uint8_t v = (uint8_t)BrotliReadBits(br, 2);
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if (v == 1) {
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v = (uint8_t)BrotliReadBits(br, 1);
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if (v == 0) {
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v = 2;
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} else {
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v = (uint8_t)BrotliReadBits(br, 1);
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if (v == 0) {
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v = 1;
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} else {
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v = 5;
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}
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}
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} else if (v == 2) {
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v = 4;
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}
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/* Static Huffman code for the code length code lengths */
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static const HuffmanCode huff[16] = {
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{2, 0}, {2, 4}, {2, 3}, {3, 2}, {2, 0}, {2, 4}, {2, 3}, {4, 1},
|
||||
{2, 0}, {2, 4}, {2, 3}, {3, 2}, {2, 0}, {2, 4}, {2, 3}, {4, 5},
|
||||
};
|
||||
for (i = simple_code_or_skip; i < CODE_LENGTH_CODES && space > 0; ++i) {
|
||||
const int code_len_idx = kCodeLengthCodeOrder[i];
|
||||
const HuffmanCode* p = huff;
|
||||
uint8_t v;
|
||||
BrotliFillBitWindow(br);
|
||||
p += (br->val_ >> br->bit_pos_) & 15;
|
||||
br->bit_pos_ += p->bits;
|
||||
v = (uint8_t)p->value;
|
||||
code_length_code_lengths[code_len_idx] = v;
|
||||
BROTLI_LOG_ARRAY_INDEX(code_length_code_lengths, code_len_idx);
|
||||
if (v != 0) {
|
||||
space -= (32 >> v);
|
||||
}
|
||||
}
|
||||
ok = ReadHuffmanCodeLengths(code_length_code_lengths, alphabet_size,
|
||||
code_lengths, br);
|
||||
ok = ReadHuffmanCodeLengths(code_length_code_lengths,
|
||||
alphabet_size, code_lengths, br);
|
||||
}
|
||||
if (ok) {
|
||||
ok = BrotliHuffmanTreeBuildImplicit(tree, code_lengths, alphabet_size);
|
||||
if (!ok) {
|
||||
printf("[ReadHuffmanCode] HuffmanTreeBuildImplicit failed: ");
|
||||
table_size = BrotliBuildHuffmanTable(table, HUFFMAN_TABLE_BITS,
|
||||
code_lengths, alphabet_size);
|
||||
if (table_size == 0) {
|
||||
printf("[ReadHuffmanCode] BuildHuffmanTable failed: ");
|
||||
PrintUcharVector(code_lengths, alphabet_size);
|
||||
}
|
||||
}
|
||||
free(code_lengths);
|
||||
return ok;
|
||||
return table_size;
|
||||
}
|
||||
|
||||
static int ReadCopyDistance(const HuffmanTree* tree,
|
||||
int num_direct_codes,
|
||||
int postfix_bits,
|
||||
int postfix_mask,
|
||||
BrotliBitReader* br) {
|
||||
static BROTLI_INLINE int ReadBlockLength(const HuffmanCode* table,
|
||||
BrotliBitReader* br) {
|
||||
int code;
|
||||
int nbits;
|
||||
int postfix;
|
||||
int offset;
|
||||
code = ReadSymbol(tree, br);
|
||||
if (code < num_direct_codes) {
|
||||
return code;
|
||||
}
|
||||
code -= num_direct_codes;
|
||||
postfix = code & postfix_mask;
|
||||
code >>= postfix_bits;
|
||||
nbits = (code >> 1) + 1;
|
||||
offset = ((2 + (code & 1)) << nbits) - 4;
|
||||
return (num_direct_codes +
|
||||
((offset + (int)BrotliReadBits(br, nbits)) << postfix_bits) +
|
||||
postfix);
|
||||
}
|
||||
|
||||
static int ReadBlockLength(const HuffmanTree* tree, BrotliBitReader* br) {
|
||||
int code;
|
||||
int nbits;
|
||||
code = ReadSymbol(tree, br);
|
||||
code = ReadSymbol(table, br);
|
||||
nbits = kBlockLengthPrefixCode[code].nbits;
|
||||
return kBlockLengthPrefixCode[code].offset + (int)BrotliReadBits(br, nbits);
|
||||
}
|
||||
|
||||
static void ReadInsertAndCopy(const HuffmanTree* tree,
|
||||
int* insert_len,
|
||||
int* copy_len,
|
||||
int* copy_dist,
|
||||
BrotliBitReader* br) {
|
||||
int code;
|
||||
int range_idx;
|
||||
int insert_code;
|
||||
int insert_extra_bits;
|
||||
int copy_code;
|
||||
int copy_extra_bits;
|
||||
code = ReadSymbol(tree, br);
|
||||
range_idx = code >> 6;
|
||||
if (range_idx >= 2) {
|
||||
range_idx -= 2;
|
||||
*copy_dist = -1;
|
||||
} else {
|
||||
*copy_dist = 0;
|
||||
}
|
||||
insert_code = kInsertRangeLut[range_idx] + ((code >> 3) & 7);
|
||||
copy_code = kCopyRangeLut[range_idx] + (code & 7);
|
||||
*insert_len = kInsertLengthPrefixCode[insert_code].offset;
|
||||
insert_extra_bits = kInsertLengthPrefixCode[insert_code].nbits;
|
||||
if (insert_extra_bits > 0) {
|
||||
*insert_len += (int)BrotliReadBits(br, insert_extra_bits);
|
||||
}
|
||||
*copy_len = kCopyLengthPrefixCode[copy_code].offset;
|
||||
copy_extra_bits = kCopyLengthPrefixCode[copy_code].nbits;
|
||||
if (copy_extra_bits > 0) {
|
||||
*copy_len += (int)BrotliReadBits(br, copy_extra_bits);
|
||||
}
|
||||
}
|
||||
|
||||
static int TranslateShortCodes(int code, int* ringbuffer, int index) {
|
||||
int val;
|
||||
if (code < NUM_DISTANCE_SHORT_CODES) {
|
||||
@ -429,24 +343,22 @@ static void InverseMoveToFrontTransform(uint8_t* v, int v_len) {
|
||||
typedef struct {
|
||||
int alphabet_size;
|
||||
int num_htrees;
|
||||
HuffmanTree* htrees;
|
||||
HuffmanCode* codes;
|
||||
HuffmanCode** htrees;
|
||||
} HuffmanTreeGroup;
|
||||
|
||||
static void HuffmanTreeGroupInit(HuffmanTreeGroup* group, int alphabet_size,
|
||||
int ntrees) {
|
||||
int i;
|
||||
group->alphabet_size = alphabet_size;
|
||||
group->num_htrees = ntrees;
|
||||
group->htrees = (HuffmanTree*)malloc(sizeof(HuffmanTree) * (size_t)ntrees);
|
||||
for (i = 0; i < ntrees; ++i) {
|
||||
group->htrees[i].root_ = NULL;
|
||||
}
|
||||
group->codes = (HuffmanCode*)malloc(
|
||||
sizeof(HuffmanCode) * (size_t)(ntrees * HUFFMAN_MAX_TABLE_SIZE));
|
||||
group->htrees = (HuffmanCode**)malloc(sizeof(HuffmanCode*) * (size_t)ntrees);
|
||||
}
|
||||
|
||||
static void HuffmanTreeGroupRelease(HuffmanTreeGroup* group) {
|
||||
int i;
|
||||
for (i = 0; i < group->num_htrees; ++i) {
|
||||
BrotliHuffmanTreeRelease(&group->htrees[i]);
|
||||
if (group->codes) {
|
||||
free(group->codes);
|
||||
}
|
||||
if (group->htrees) {
|
||||
free(group->htrees);
|
||||
@ -456,8 +368,13 @@ static void HuffmanTreeGroupRelease(HuffmanTreeGroup* group) {
|
||||
static int HuffmanTreeGroupDecode(HuffmanTreeGroup* group,
|
||||
BrotliBitReader* br) {
|
||||
int i;
|
||||
int table_size;
|
||||
HuffmanCode* next = group->codes;
|
||||
for (i = 0; i < group->num_htrees; ++i) {
|
||||
if (!ReadHuffmanCode(group->alphabet_size, &group->htrees[i], br)) {
|
||||
group->htrees[i] = next;
|
||||
table_size = ReadHuffmanCode(group->alphabet_size, next, br);
|
||||
next += table_size;
|
||||
if (table_size == 0) {
|
||||
return 0;
|
||||
}
|
||||
}
|
||||
@ -469,6 +386,10 @@ static int DecodeContextMap(int context_map_size,
|
||||
uint8_t** context_map,
|
||||
BrotliBitReader* br) {
|
||||
int ok = 1;
|
||||
int use_rle_for_zeros;
|
||||
int max_run_length_prefix = 0;
|
||||
HuffmanCode* table;
|
||||
int i;
|
||||
if (!BrotliReadMoreInput(br)) {
|
||||
printf("[DecodeContextMap] Unexpected end of input.\n");
|
||||
return 0;
|
||||
@ -487,55 +408,54 @@ static int DecodeContextMap(int context_map_size,
|
||||
return 1;
|
||||
}
|
||||
|
||||
{
|
||||
HuffmanTree tree_index_htree;
|
||||
int use_rle_for_zeros = (int)BrotliReadBits(br, 1);
|
||||
int max_run_length_prefix = 0;
|
||||
int i;
|
||||
if (use_rle_for_zeros) {
|
||||
max_run_length_prefix = (int)BrotliReadBits(br, 4) + 1;
|
||||
use_rle_for_zeros = (int)BrotliReadBits(br, 1);
|
||||
if (use_rle_for_zeros) {
|
||||
max_run_length_prefix = (int)BrotliReadBits(br, 4) + 1;
|
||||
}
|
||||
table = (HuffmanCode*)malloc(HUFFMAN_MAX_TABLE_SIZE * sizeof(*table));
|
||||
if (table == NULL) {
|
||||
return 0;
|
||||
}
|
||||
if (!ReadHuffmanCode(*num_htrees + max_run_length_prefix, table, br)) {
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
for (i = 0; i < context_map_size;) {
|
||||
int code;
|
||||
if (!BrotliReadMoreInput(br)) {
|
||||
printf("[DecodeContextMap] Unexpected end of input.\n");
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
if (!ReadHuffmanCode(*num_htrees + max_run_length_prefix,
|
||||
&tree_index_htree, br)) {
|
||||
return 0;
|
||||
}
|
||||
for (i = 0; i < context_map_size;) {
|
||||
int code;
|
||||
if (!BrotliReadMoreInput(br)) {
|
||||
printf("[DecodeContextMap] Unexpected end of input.\n");
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
code = ReadSymbol(&tree_index_htree, br);
|
||||
if (code == 0) {
|
||||
code = ReadSymbol(table, br);
|
||||
if (code == 0) {
|
||||
(*context_map)[i] = 0;
|
||||
++i;
|
||||
} else if (code <= max_run_length_prefix) {
|
||||
int reps = 1 + (1 << code) + (int)BrotliReadBits(br, code);
|
||||
while (--reps) {
|
||||
if (i >= context_map_size) {
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
(*context_map)[i] = 0;
|
||||
++i;
|
||||
} else if (code <= max_run_length_prefix) {
|
||||
int reps = 1 + (1 << code) + (int)BrotliReadBits(br, code);
|
||||
while (--reps) {
|
||||
if (i >= context_map_size) {
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
(*context_map)[i] = 0;
|
||||
++i;
|
||||
}
|
||||
} else {
|
||||
(*context_map)[i] = (uint8_t)(code - max_run_length_prefix);
|
||||
++i;
|
||||
}
|
||||
} else {
|
||||
(*context_map)[i] = (uint8_t)(code - max_run_length_prefix);
|
||||
++i;
|
||||
}
|
||||
End:
|
||||
BrotliHuffmanTreeRelease(&tree_index_htree);
|
||||
}
|
||||
if (BrotliReadBits(br, 1)) {
|
||||
InverseMoveToFrontTransform(*context_map, context_map_size);
|
||||
}
|
||||
End:
|
||||
free(table);
|
||||
return ok;
|
||||
}
|
||||
|
||||
static BROTLI_INLINE void DecodeBlockType(const int max_block_type,
|
||||
const HuffmanTree* trees,
|
||||
const HuffmanCode* trees,
|
||||
int tree_type,
|
||||
int* block_types,
|
||||
int* ringbuffers,
|
||||
@ -543,7 +463,7 @@ static BROTLI_INLINE void DecodeBlockType(const int max_block_type,
|
||||
BrotliBitReader* br) {
|
||||
int* ringbuffer = ringbuffers + tree_type * 2;
|
||||
int* index = indexes + tree_type;
|
||||
int type_code = ReadSymbol(trees + tree_type, br);
|
||||
int type_code = ReadSymbol(&trees[tree_type * HUFFMAN_MAX_TABLE_SIZE], br);
|
||||
int block_type;
|
||||
if (type_code == 0) {
|
||||
block_type = ringbuffer[*index & 1];
|
||||
@ -608,6 +528,92 @@ static BROTLI_INLINE void IncrementalCopyFastPath(
|
||||
}
|
||||
}
|
||||
|
||||
int CopyUncompressedBlockToOutput(BrotliOutput output, int len, int pos,
|
||||
uint8_t* ringbuffer, int ringbuffer_mask,
|
||||
BrotliBitReader* br) {
|
||||
const int rb_size = ringbuffer_mask + 1;
|
||||
uint8_t* ringbuffer_end = ringbuffer + rb_size;
|
||||
int rb_pos = pos & ringbuffer_mask;
|
||||
int br_pos = br->pos_ & BROTLI_IBUF_MASK;
|
||||
int nbytes;
|
||||
|
||||
/* For short lengths copy byte-by-byte */
|
||||
if (len < 8 || br->bit_pos_ + (uint32_t)(len << 3) < br->bit_end_pos_) {
|
||||
while (len-- > 0) {
|
||||
if (!BrotliReadMoreInput(br)) {
|
||||
return 0;
|
||||
}
|
||||
ringbuffer[rb_pos++]= (uint8_t)BrotliReadBits(br, 8);
|
||||
if (rb_pos == rb_size) {
|
||||
if (BrotliWrite(output, ringbuffer, (size_t)rb_size) < rb_size) {
|
||||
return 0;
|
||||
}
|
||||
rb_pos = 0;
|
||||
}
|
||||
}
|
||||
return 1;
|
||||
}
|
||||
|
||||
if (br->bit_end_pos_ < 64) {
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Copy remaining 0-8 bytes from br->val_ to ringbuffer. */
|
||||
while (br->bit_pos_ < 64) {
|
||||
ringbuffer[rb_pos] = (uint8_t)(br->val_ >> br->bit_pos_);
|
||||
br->bit_pos_ += 8;
|
||||
++rb_pos;
|
||||
--len;
|
||||
}
|
||||
|
||||
/* Copy remaining bytes from br->buf_ to ringbuffer. */
|
||||
nbytes = (int)(br->bit_end_pos_ - br->bit_pos_) >> 3;
|
||||
if (br_pos + nbytes > BROTLI_IBUF_MASK) {
|
||||
int tail = BROTLI_IBUF_MASK + 1 - br_pos;
|
||||
memcpy(&ringbuffer[rb_pos], &br->buf_[br_pos], (size_t)tail);
|
||||
nbytes -= tail;
|
||||
rb_pos += tail;
|
||||
len -= tail;
|
||||
br_pos = 0;
|
||||
}
|
||||
memcpy(&ringbuffer[rb_pos], &br->buf_[br_pos], (size_t)nbytes);
|
||||
rb_pos += nbytes;
|
||||
len -= nbytes;
|
||||
|
||||
/* If we wrote past the logical end of the ringbuffer, copy the tail of the
|
||||
ringbuffer to its beginning and flush the ringbuffer to the output. */
|
||||
if (rb_pos >= rb_size) {
|
||||
if (BrotliWrite(output, ringbuffer, (size_t)rb_size) < rb_size) {
|
||||
return 0;
|
||||
}
|
||||
rb_pos -= rb_size;
|
||||
memcpy(ringbuffer, ringbuffer_end, (size_t)rb_pos);
|
||||
}
|
||||
|
||||
/* If we have more to copy than the remaining size of the ringbuffer, then we
|
||||
first fill the ringbuffer from the input and then flush the ringbuffer to
|
||||
the output */
|
||||
while (rb_pos + len >= rb_size) {
|
||||
nbytes = rb_size - rb_pos;
|
||||
if (BrotliRead(br->input_, &ringbuffer[rb_pos], (size_t)nbytes) < nbytes ||
|
||||
BrotliWrite(output, ringbuffer, (size_t)rb_size) < nbytes) {
|
||||
return 0;
|
||||
}
|
||||
len -= nbytes;
|
||||
rb_pos = 0;
|
||||
}
|
||||
|
||||
/* Copy straight from the input onto the ringbuffer. The ringbuffer will be
|
||||
flushed to the output at a later time. */
|
||||
if (BrotliRead(br->input_, &ringbuffer[rb_pos], (size_t)len) < len) {
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Restore the state of the bit reader. */
|
||||
BrotliInitBitReader(br, br->input_);
|
||||
return 1;
|
||||
}
|
||||
|
||||
int BrotliDecompressedSize(size_t encoded_size,
|
||||
const uint8_t* encoded_buffer,
|
||||
size_t* decoded_size) {
|
||||
@ -662,11 +668,15 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
uint8_t prev_byte1 = 0;
|
||||
uint8_t prev_byte2 = 0;
|
||||
HuffmanTreeGroup hgroup[3];
|
||||
HuffmanCode* block_type_trees = NULL;
|
||||
HuffmanCode* block_len_trees = NULL;
|
||||
BrotliBitReader br;
|
||||
|
||||
/* 16 bytes would be enough, but we add some more slack for transforms */
|
||||
/* to work at the end of the ringbuffer. */
|
||||
static const int kRingBufferWriteAheadSlack = 128;
|
||||
/* We need the slack region for the following reasons:
|
||||
- always doing two 8-byte copies for fast backward copying
|
||||
- transforms
|
||||
- flushing the input ringbuffer when decoding uncompressed blocks */
|
||||
static const int kRingBufferWriteAheadSlack = 128 + BROTLI_READ_SIZE;
|
||||
|
||||
static const int kMaxDictionaryWordLength = 0;
|
||||
|
||||
@ -688,6 +698,16 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
}
|
||||
ringbuffer_end = ringbuffer + ringbuffer_size;
|
||||
|
||||
if (ok) {
|
||||
block_type_trees = (HuffmanCode*)malloc(
|
||||
3 * HUFFMAN_MAX_TABLE_SIZE * sizeof(HuffmanCode));
|
||||
block_len_trees = (HuffmanCode*)malloc(
|
||||
3 * HUFFMAN_MAX_TABLE_SIZE * sizeof(HuffmanCode));
|
||||
if (block_type_trees == NULL || block_len_trees == NULL) {
|
||||
ok = 0;
|
||||
}
|
||||
}
|
||||
|
||||
while (!input_end && ok) {
|
||||
int meta_block_remaining_len = 0;
|
||||
int is_uncompressed;
|
||||
@ -696,8 +716,6 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
int num_block_types[3] = { 1, 1, 1 };
|
||||
int block_type_rb[6] = { 0, 1, 0, 1, 0, 1 };
|
||||
int block_type_rb_index[3] = { 0 };
|
||||
HuffmanTree block_type_trees[3];
|
||||
HuffmanTree block_len_trees[3];
|
||||
int distance_postfix_bits;
|
||||
int num_direct_distance_codes;
|
||||
int distance_postfix_mask;
|
||||
@ -716,12 +734,11 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
int context_lookup_offset1 = 0;
|
||||
int context_lookup_offset2 = 0;
|
||||
uint8_t context_mode;
|
||||
HuffmanCode* htree_command;
|
||||
|
||||
for (i = 0; i < 3; ++i) {
|
||||
hgroup[i].num_htrees = 0;
|
||||
hgroup[i].codes = NULL;
|
||||
hgroup[i].htrees = NULL;
|
||||
block_type_trees[i].root_ = NULL;
|
||||
block_len_trees[i].root_ = NULL;
|
||||
}
|
||||
|
||||
if (!BrotliReadMoreInput(&br)) {
|
||||
@ -738,31 +755,25 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
}
|
||||
if (is_uncompressed) {
|
||||
BrotliSetBitPos(&br, (br.bit_pos_ + 7) & (uint32_t)(~7UL));
|
||||
while (meta_block_remaining_len) {
|
||||
ringbuffer[pos & ringbuffer_mask] = (uint8_t)BrotliReadBits(&br, 8);
|
||||
if ((pos & ringbuffer_mask) == ringbuffer_mask) {
|
||||
if (BrotliWrite(output, ringbuffer, (size_t)ringbuffer_size) < 0) {
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
}
|
||||
++pos;
|
||||
--meta_block_remaining_len;
|
||||
}
|
||||
ok = CopyUncompressedBlockToOutput(output, meta_block_remaining_len, pos,
|
||||
ringbuffer, ringbuffer_mask, &br);
|
||||
pos += meta_block_remaining_len;
|
||||
goto End;
|
||||
}
|
||||
for (i = 0; i < 3; ++i) {
|
||||
block_type_trees[i].root_ = NULL;
|
||||
block_len_trees[i].root_ = NULL;
|
||||
num_block_types[i] = DecodeVarLenUint8(&br) + 1;
|
||||
if (num_block_types[i] >= 2) {
|
||||
if (!ReadHuffmanCode(
|
||||
num_block_types[i] + 2, &block_type_trees[i], &br) ||
|
||||
!ReadHuffmanCode(kNumBlockLengthCodes, &block_len_trees[i], &br)) {
|
||||
if (!ReadHuffmanCode(num_block_types[i] + 2,
|
||||
&block_type_trees[i * HUFFMAN_MAX_TABLE_SIZE],
|
||||
&br) ||
|
||||
!ReadHuffmanCode(kNumBlockLengthCodes,
|
||||
&block_len_trees[i * HUFFMAN_MAX_TABLE_SIZE],
|
||||
&br)) {
|
||||
ok = 0;
|
||||
goto End;
|
||||
}
|
||||
block_length[i] = ReadBlockLength(&block_len_trees[i], &br);
|
||||
block_length[i] = ReadBlockLength(
|
||||
&block_len_trees[i * HUFFMAN_MAX_TABLE_SIZE], &br);
|
||||
block_type_rb_index[i] = 1;
|
||||
}
|
||||
}
|
||||
@ -822,8 +833,13 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
context_mode = context_modes[block_type[0]];
|
||||
context_lookup_offset1 = kContextLookupOffsets[context_mode];
|
||||
context_lookup_offset2 = kContextLookupOffsets[context_mode + 1];
|
||||
htree_command = hgroup[1].htrees[0];
|
||||
|
||||
while (meta_block_remaining_len > 0) {
|
||||
int cmd_code;
|
||||
int range_idx;
|
||||
int insert_code;
|
||||
int copy_code;
|
||||
int insert_length;
|
||||
int copy_length;
|
||||
int distance_code;
|
||||
@ -841,11 +857,25 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
DecodeBlockType(num_block_types[1],
|
||||
block_type_trees, 1, block_type, block_type_rb,
|
||||
block_type_rb_index, &br);
|
||||
block_length[1] = ReadBlockLength(&block_len_trees[1], &br);
|
||||
block_length[1] = ReadBlockLength(
|
||||
&block_len_trees[HUFFMAN_MAX_TABLE_SIZE], &br);
|
||||
htree_command = hgroup[1].htrees[block_type[1]];
|
||||
}
|
||||
--block_length[1];
|
||||
ReadInsertAndCopy(&hgroup[1].htrees[block_type[1]],
|
||||
&insert_length, ©_length, &distance_code, &br);
|
||||
cmd_code = ReadSymbol(htree_command, &br);
|
||||
range_idx = cmd_code >> 6;
|
||||
if (range_idx >= 2) {
|
||||
range_idx -= 2;
|
||||
distance_code = -1;
|
||||
} else {
|
||||
distance_code = 0;
|
||||
}
|
||||
insert_code = kInsertRangeLut[range_idx] + ((cmd_code >> 3) & 7);
|
||||
copy_code = kCopyRangeLut[range_idx] + (cmd_code & 7);
|
||||
insert_length = kInsertLengthPrefixCode[insert_code].offset +
|
||||
(int)BrotliReadBits(&br, kInsertLengthPrefixCode[insert_code].nbits);
|
||||
copy_length = kCopyLengthPrefixCode[copy_code].offset +
|
||||
(int)BrotliReadBits(&br, kCopyLengthPrefixCode[copy_code].nbits);
|
||||
BROTLI_LOG_UINT(insert_length);
|
||||
BROTLI_LOG_UINT(copy_length);
|
||||
BROTLI_LOG_UINT(distance_code);
|
||||
@ -859,7 +889,7 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
DecodeBlockType(num_block_types[0],
|
||||
block_type_trees, 0, block_type, block_type_rb,
|
||||
block_type_rb_index, &br);
|
||||
block_length[0] = ReadBlockLength(&block_len_trees[0], &br);
|
||||
block_length[0] = ReadBlockLength(block_len_trees, &br);
|
||||
context_offset = block_type[0] << kLiteralContextBits;
|
||||
context_map_slice = context_map + context_offset;
|
||||
context_mode = context_modes[block_type[0]];
|
||||
@ -872,7 +902,7 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
literal_htree_index = context_map_slice[context];
|
||||
--block_length[0];
|
||||
prev_byte2 = prev_byte1;
|
||||
prev_byte1 = (uint8_t)ReadSymbol(&hgroup[0].htrees[literal_htree_index],
|
||||
prev_byte1 = (uint8_t)ReadSymbol(hgroup[0].htrees[literal_htree_index],
|
||||
&br);
|
||||
ringbuffer[pos & ringbuffer_mask] = prev_byte1;
|
||||
BROTLI_LOG_UINT(literal_htree_index);
|
||||
@ -899,7 +929,8 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
DecodeBlockType(num_block_types[2],
|
||||
block_type_trees, 2, block_type, block_type_rb,
|
||||
block_type_rb_index, &br);
|
||||
block_length[2] = ReadBlockLength(&block_len_trees[2], &br);
|
||||
block_length[2] = ReadBlockLength(
|
||||
&block_len_trees[2 * HUFFMAN_MAX_TABLE_SIZE], &br);
|
||||
dist_htree_index = (uint8_t)block_type[2];
|
||||
dist_context_offset = block_type[2] << kDistanceContextBits;
|
||||
dist_context_map_slice = dist_context_map + dist_context_offset;
|
||||
@ -907,11 +938,20 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
--block_length[2];
|
||||
context = (uint8_t)(copy_length > 4 ? 3 : copy_length - 2);
|
||||
dist_htree_index = dist_context_map_slice[context];
|
||||
distance_code = ReadCopyDistance(&hgroup[2].htrees[dist_htree_index],
|
||||
num_direct_distance_codes,
|
||||
distance_postfix_bits,
|
||||
distance_postfix_mask,
|
||||
&br);
|
||||
distance_code = ReadSymbol(hgroup[2].htrees[dist_htree_index], &br);
|
||||
if (distance_code >= num_direct_distance_codes) {
|
||||
int nbits;
|
||||
int postfix;
|
||||
int offset;
|
||||
distance_code -= num_direct_distance_codes;
|
||||
postfix = distance_code & distance_postfix_mask;
|
||||
distance_code >>= distance_postfix_bits;
|
||||
nbits = (distance_code >> 1) + 1;
|
||||
offset = ((2 + (distance_code & 1)) << nbits) - 4;
|
||||
distance_code = num_direct_distance_codes +
|
||||
((offset + (int)BrotliReadBits(&br, nbits)) <<
|
||||
distance_postfix_bits) + postfix;
|
||||
}
|
||||
}
|
||||
|
||||
/* Convert the distance code to the actual distance by possibly looking */
|
||||
@ -1004,8 +1044,6 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
}
|
||||
for (i = 0; i < 3; ++i) {
|
||||
HuffmanTreeGroupRelease(&hgroup[i]);
|
||||
BrotliHuffmanTreeRelease(&block_type_trees[i]);
|
||||
BrotliHuffmanTreeRelease(&block_len_trees[i]);
|
||||
}
|
||||
}
|
||||
|
||||
@ -1015,6 +1053,12 @@ int BrotliDecompress(BrotliInput input, BrotliOutput output) {
|
||||
}
|
||||
free(ringbuffer);
|
||||
}
|
||||
if (block_type_trees != 0) {
|
||||
free(block_type_trees);
|
||||
}
|
||||
if (block_len_trees != 0) {
|
||||
free(block_len_trees);
|
||||
}
|
||||
return ok;
|
||||
}
|
||||
|
||||
|
@ -26,6 +26,8 @@ extern "C" {
|
||||
#endif
|
||||
|
||||
/* Sets *decoded_size to the decompressed size of the given encoded stream. */
|
||||
/* This function only works if the encoded buffer has a single meta block, */
|
||||
/* and this meta block must have the "is last" bit set. */
|
||||
/* Returns 1 on success, 0 on failure. */
|
||||
int BrotliDecompressedSize(size_t encoded_size,
|
||||
const uint8_t* encoded_buffer,
|
||||
|
309
dec/huffman.c
309
dec/huffman.c
@ -12,11 +12,12 @@
|
||||
See the License for the specific language governing permissions and
|
||||
limitations under the License.
|
||||
|
||||
Utilities for building and looking up Huffman trees.
|
||||
Utilities for building Huffman decoding tables.
|
||||
*/
|
||||
|
||||
#include <assert.h>
|
||||
#include <stdlib.h>
|
||||
#include <stdio.h>
|
||||
#include <string.h>
|
||||
#include "./huffman.h"
|
||||
#include "./safe_malloc.h"
|
||||
@ -25,231 +26,137 @@
|
||||
extern "C" {
|
||||
#endif
|
||||
|
||||
#define NON_EXISTENT_SYMBOL (-1)
|
||||
#define MAX_ALLOWED_CODE_LENGTH 15
|
||||
#define MAX_LENGTH 15
|
||||
|
||||
static void TreeNodeInit(HuffmanTreeNode* const node) {
|
||||
node->children_ = -1; /* means: 'unassigned so far' */
|
||||
}
|
||||
|
||||
static int NodeIsEmpty(const HuffmanTreeNode* const node) {
|
||||
return (node->children_ < 0);
|
||||
}
|
||||
|
||||
static int IsFull(const HuffmanTree* const tree) {
|
||||
return (tree->num_nodes_ == tree->max_nodes_);
|
||||
}
|
||||
|
||||
static void AssignChildren(HuffmanTree* const tree,
|
||||
HuffmanTreeNode* const node) {
|
||||
HuffmanTreeNode* const children = tree->root_ + tree->num_nodes_;
|
||||
node->children_ = (int)(children - node);
|
||||
assert(children - node == (int)(children - node));
|
||||
tree->num_nodes_ += 2;
|
||||
TreeNodeInit(children + 0);
|
||||
TreeNodeInit(children + 1);
|
||||
}
|
||||
|
||||
static int TreeInit(HuffmanTree* const tree, int num_leaves) {
|
||||
assert(tree != NULL);
|
||||
tree->root_ = NULL;
|
||||
if (num_leaves == 0) return 0;
|
||||
/* We allocate maximum possible nodes in the tree at once. */
|
||||
/* Note that a Huffman tree is a full binary tree; and in a full binary */
|
||||
/* tree with L leaves, the total number of nodes N = 2 * L - 1. */
|
||||
tree->max_nodes_ = 2 * num_leaves - 1;
|
||||
assert(tree->max_nodes_ < (1 << 16)); /* limit for the lut_jump_ table */
|
||||
tree->root_ = (HuffmanTreeNode*)BrotliSafeMalloc((uint64_t)tree->max_nodes_,
|
||||
sizeof(*tree->root_));
|
||||
if (tree->root_ == NULL) return 0;
|
||||
TreeNodeInit(tree->root_); /* Initialize root. */
|
||||
tree->num_nodes_ = 1;
|
||||
memset(tree->lut_bits_, 255, sizeof(tree->lut_bits_));
|
||||
memset(tree->lut_jump_, 0, sizeof(tree->lut_jump_));
|
||||
return 1;
|
||||
}
|
||||
|
||||
void BrotliHuffmanTreeRelease(HuffmanTree* const tree) {
|
||||
if (tree != NULL) {
|
||||
if (tree->root_ != NULL) {
|
||||
free(tree->root_);
|
||||
}
|
||||
tree->root_ = NULL;
|
||||
tree->max_nodes_ = 0;
|
||||
tree->num_nodes_ = 0;
|
||||
/* Returns reverse(reverse(key, len) + 1, len), where reverse(key, len) is the
|
||||
bit-wise reversal of the len least significant bits of key. */
|
||||
static BROTLI_INLINE int GetNextKey(int key, int len) {
|
||||
int step = 1 << (len - 1);
|
||||
while (key & step) {
|
||||
step >>= 1;
|
||||
}
|
||||
return (key & (step - 1)) + step;
|
||||
}
|
||||
|
||||
/* Utility: converts Huffman code lengths to corresponding Huffman codes. */
|
||||
/* 'huff_codes' should be pre-allocated. */
|
||||
/* Returns false in case of error (memory allocation, invalid codes). */
|
||||
static int HuffmanCodeLengthsToCodes(const uint8_t* const code_lengths,
|
||||
int code_lengths_size,
|
||||
int* const huff_codes) {
|
||||
int symbol;
|
||||
int code_len;
|
||||
int code_length_hist[MAX_ALLOWED_CODE_LENGTH + 1] = { 0 };
|
||||
int curr_code;
|
||||
int next_codes[MAX_ALLOWED_CODE_LENGTH + 1] = { 0 };
|
||||
int max_code_length = 0;
|
||||
/* Stores code in table[0], table[step], table[2*step], ..., table[end] */
|
||||
/* Assumes that end is an integer multiple of step */
|
||||
static BROTLI_INLINE void ReplicateValue(HuffmanCode* table,
|
||||
int step, int end,
|
||||
HuffmanCode code) {
|
||||
do {
|
||||
end -= step;
|
||||
table[end] = code;
|
||||
} while (end > 0);
|
||||
}
|
||||
|
||||
assert(code_lengths != NULL);
|
||||
assert(code_lengths_size > 0);
|
||||
assert(huff_codes != NULL);
|
||||
|
||||
/* Calculate max code length. */
|
||||
for (symbol = 0; symbol < code_lengths_size; ++symbol) {
|
||||
if (code_lengths[symbol] > max_code_length) {
|
||||
max_code_length = code_lengths[symbol];
|
||||
}
|
||||
/* Returns the table width of the next 2nd level table. count is the histogram
|
||||
of bit lengths for the remaining symbols, len is the code length of the next
|
||||
processed symbol */
|
||||
static BROTLI_INLINE int NextTableBitSize(const int* const count,
|
||||
int len, int root_bits) {
|
||||
int left = 1 << (len - root_bits);
|
||||
while (len < MAX_LENGTH) {
|
||||
left -= count[len];
|
||||
if (left <= 0) break;
|
||||
++len;
|
||||
left <<= 1;
|
||||
}
|
||||
if (max_code_length > MAX_ALLOWED_CODE_LENGTH) return 0;
|
||||
return len - root_bits;
|
||||
}
|
||||
|
||||
/* Calculate code length histogram. */
|
||||
for (symbol = 0; symbol < code_lengths_size; ++symbol) {
|
||||
++code_length_hist[code_lengths[symbol]];
|
||||
}
|
||||
code_length_hist[0] = 0;
|
||||
int BrotliBuildHuffmanTable(HuffmanCode* root_table,
|
||||
int root_bits,
|
||||
const uint8_t* const code_lengths,
|
||||
int code_lengths_size) {
|
||||
HuffmanCode code; /* current table entry */
|
||||
HuffmanCode* table; /* next available space in table */
|
||||
int len; /* current code length */
|
||||
int symbol; /* symbol index in original or sorted table */
|
||||
int key; /* reversed prefix code */
|
||||
int step; /* step size to replicate values in current table */
|
||||
int low; /* low bits for current root entry */
|
||||
int mask; /* mask for low bits */
|
||||
int table_bits; /* key length of current table */
|
||||
int table_size; /* size of current table */
|
||||
int total_size; /* sum of root table size and 2nd level table sizes */
|
||||
int* sorted; /* symbols sorted by code length */
|
||||
int count[MAX_LENGTH + 1] = { 0 }; /* number of codes of each length */
|
||||
int offset[MAX_LENGTH + 1]; /* offsets in sorted table for each length */
|
||||
|
||||
/* Calculate the initial values of 'next_codes' for each code length. */
|
||||
/* next_codes[code_len] denotes the code to be assigned to the next symbol */
|
||||
/* of code length 'code_len'. */
|
||||
curr_code = 0;
|
||||
next_codes[0] = -1; /* Unused, as code length = 0 implies */
|
||||
/* code doesn't exist. */
|
||||
for (code_len = 1; code_len <= max_code_length; ++code_len) {
|
||||
curr_code = (curr_code + code_length_hist[code_len - 1]) << 1;
|
||||
next_codes[code_len] = curr_code;
|
||||
sorted = (int*)malloc((size_t)code_lengths_size * sizeof(*sorted));
|
||||
if (sorted == NULL) {
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* Get symbols. */
|
||||
for (symbol = 0; symbol < code_lengths_size; ++symbol) {
|
||||
if (code_lengths[symbol] > 0) {
|
||||
huff_codes[symbol] = next_codes[code_lengths[symbol]]++;
|
||||
} else {
|
||||
huff_codes[symbol] = NON_EXISTENT_SYMBOL;
|
||||
}
|
||||
/* build histogram of code lengths */
|
||||
for (symbol = 0; symbol < code_lengths_size; symbol++) {
|
||||
count[code_lengths[symbol]]++;
|
||||
}
|
||||
return 1;
|
||||
}
|
||||
|
||||
static const uint8_t kReverse7[128] = {
|
||||
0, 64, 32, 96, 16, 80, 48, 112, 8, 72, 40, 104, 24, 88, 56, 120,
|
||||
4, 68, 36, 100, 20, 84, 52, 116, 12, 76, 44, 108, 28, 92, 60, 124,
|
||||
2, 66, 34, 98, 18, 82, 50, 114, 10, 74, 42, 106, 26, 90, 58, 122,
|
||||
6, 70, 38, 102, 22, 86, 54, 118, 14, 78, 46, 110, 30, 94, 62, 126,
|
||||
1, 65, 33, 97, 17, 81, 49, 113, 9, 73, 41, 105, 25, 89, 57, 121,
|
||||
5, 69, 37, 101, 21, 85, 53, 117, 13, 77, 45, 109, 29, 93, 61, 125,
|
||||
3, 67, 35, 99, 19, 83, 51, 115, 11, 75, 43, 107, 27, 91, 59, 123,
|
||||
7, 71, 39, 103, 23, 87, 55, 119, 15, 79, 47, 111, 31, 95, 63, 127
|
||||
};
|
||||
|
||||
static int ReverseBitsShort(int bits, int num_bits) {
|
||||
return kReverse7[bits] >> (7 - num_bits);
|
||||
}
|
||||
|
||||
static int TreeAddSymbol(HuffmanTree* const tree,
|
||||
int symbol, int code, int code_length) {
|
||||
int step = HUFF_LUT_BITS;
|
||||
int base_code;
|
||||
HuffmanTreeNode* node = tree->root_;
|
||||
const HuffmanTreeNode* const max_node = tree->root_ + tree->max_nodes_;
|
||||
assert(symbol == (int16_t)symbol);
|
||||
if (code_length <= HUFF_LUT_BITS) {
|
||||
int i = 1 << (HUFF_LUT_BITS - code_length);
|
||||
base_code = ReverseBitsShort(code, code_length);
|
||||
do {
|
||||
int idx;
|
||||
--i;
|
||||
idx = base_code | (i << code_length);
|
||||
tree->lut_symbol_[idx] = (int16_t)symbol;
|
||||
tree->lut_bits_[idx] = (uint8_t)code_length;
|
||||
} while (i > 0);
|
||||
} else {
|
||||
base_code = ReverseBitsShort((code >> (code_length - HUFF_LUT_BITS)),
|
||||
HUFF_LUT_BITS);
|
||||
/* generate offsets into sorted symbol table by code length */
|
||||
offset[1] = 0;
|
||||
for (len = 1; len < MAX_LENGTH; len++) {
|
||||
offset[len + 1] = offset[len] + count[len];
|
||||
}
|
||||
while (code_length-- > 0) {
|
||||
if (node >= max_node) {
|
||||
return 0;
|
||||
}
|
||||
if (NodeIsEmpty(node)) {
|
||||
if (IsFull(tree)) return 0; /* error: too many symbols. */
|
||||
AssignChildren(tree, node);
|
||||
} else if (!HuffmanTreeNodeIsNotLeaf(node)) {
|
||||
return 0; /* leaf is already occupied. */
|
||||
}
|
||||
node += node->children_ + ((code >> code_length) & 1);
|
||||
if (--step == 0) {
|
||||
tree->lut_jump_[base_code] = (int16_t)(node - tree->root_);
|
||||
}
|
||||
}
|
||||
if (NodeIsEmpty(node)) {
|
||||
node->children_ = 0; /* turn newly created node into a leaf. */
|
||||
} else if (HuffmanTreeNodeIsNotLeaf(node)) {
|
||||
return 0; /* trying to assign a symbol to already used code. */
|
||||
}
|
||||
node->symbol_ = symbol; /* Add symbol in this node. */
|
||||
return 1;
|
||||
}
|
||||
|
||||
int BrotliHuffmanTreeBuildImplicit(HuffmanTree* const tree,
|
||||
const uint8_t* const code_lengths,
|
||||
int code_lengths_size) {
|
||||
int symbol;
|
||||
int num_symbols = 0;
|
||||
int root_symbol = 0;
|
||||
|
||||
assert(tree != NULL);
|
||||
assert(code_lengths != NULL);
|
||||
|
||||
/* Find out number of symbols and the root symbol. */
|
||||
for (symbol = 0; symbol < code_lengths_size; ++symbol) {
|
||||
if (code_lengths[symbol] > 0) {
|
||||
/* Note: code length = 0 indicates non-existent symbol. */
|
||||
++num_symbols;
|
||||
root_symbol = symbol;
|
||||
/* sort symbols by length, by symbol order within each length */
|
||||
for (symbol = 0; symbol < code_lengths_size; symbol++) {
|
||||
if (code_lengths[symbol] != 0) {
|
||||
sorted[offset[code_lengths[symbol]]++] = symbol;
|
||||
}
|
||||
}
|
||||
|
||||
/* Initialize the tree. Will fail for num_symbols = 0 */
|
||||
if (!TreeInit(tree, num_symbols)) return 0;
|
||||
table = root_table;
|
||||
table_bits = root_bits;
|
||||
table_size = 1 << table_bits;
|
||||
total_size = table_size;
|
||||
|
||||
/* Build tree. */
|
||||
if (num_symbols == 1) { /* Trivial case. */
|
||||
const int max_symbol = code_lengths_size;
|
||||
if (root_symbol < 0 || root_symbol >= max_symbol) {
|
||||
BrotliHuffmanTreeRelease(tree);
|
||||
return 0;
|
||||
/* special case code with only one value */
|
||||
if (offset[MAX_LENGTH] == 1) {
|
||||
code.bits = 0;
|
||||
code.value = (uint16_t)sorted[0];
|
||||
for (key = 0; key < total_size; ++key) {
|
||||
table[key] = code;
|
||||
}
|
||||
return TreeAddSymbol(tree, root_symbol, 0, 0);
|
||||
} else { /* Normal case. */
|
||||
int ok = 0;
|
||||
free(sorted);
|
||||
return total_size;
|
||||
}
|
||||
|
||||
/* Get Huffman codes from the code lengths. */
|
||||
int* const codes =
|
||||
(int*)BrotliSafeMalloc((uint64_t)code_lengths_size, sizeof(*codes));
|
||||
if (codes == NULL) goto End;
|
||||
|
||||
if (!HuffmanCodeLengthsToCodes(code_lengths, code_lengths_size, codes)) {
|
||||
goto End;
|
||||
/* fill in root table */
|
||||
key = 0;
|
||||
symbol = 0;
|
||||
for (len = 1, step = 2; len <= root_bits; ++len, step <<= 1) {
|
||||
for (; count[len] > 0; --count[len]) {
|
||||
code.bits = (uint8_t)(len);
|
||||
code.value = (uint16_t)sorted[symbol++];
|
||||
ReplicateValue(&table[key], step, table_size, code);
|
||||
key = GetNextKey(key, len);
|
||||
}
|
||||
}
|
||||
|
||||
/* Add symbols one-by-one. */
|
||||
for (symbol = 0; symbol < code_lengths_size; ++symbol) {
|
||||
if (code_lengths[symbol] > 0) {
|
||||
if (!TreeAddSymbol(tree, symbol, codes[symbol], code_lengths[symbol])) {
|
||||
goto End;
|
||||
}
|
||||
/* fill in 2nd level tables and add pointers to root table */
|
||||
mask = total_size - 1;
|
||||
low = -1;
|
||||
for (len = root_bits + 1, step = 2; len <= MAX_LENGTH; ++len, step <<= 1) {
|
||||
for (; count[len] > 0; --count[len]) {
|
||||
if ((key & mask) != low) {
|
||||
table += table_size;
|
||||
table_bits = NextTableBitSize(count, len, root_bits);
|
||||
table_size = 1 << table_bits;
|
||||
total_size += table_size;
|
||||
low = key & mask;
|
||||
root_table[low].bits = (uint8_t)(table_bits + root_bits);
|
||||
root_table[low].value = (uint16_t)((table - root_table) - low);
|
||||
}
|
||||
code.bits = (uint8_t)(len - root_bits);
|
||||
code.value = (uint16_t)sorted[symbol++];
|
||||
ReplicateValue(&table[key >> root_bits], step, table_size, code);
|
||||
key = GetNextKey(key, len);
|
||||
}
|
||||
ok = 1;
|
||||
End:
|
||||
free(codes);
|
||||
ok = ok && IsFull(tree);
|
||||
if (!ok) BrotliHuffmanTreeRelease(tree);
|
||||
return ok;
|
||||
}
|
||||
|
||||
free(sorted);
|
||||
return total_size;
|
||||
}
|
||||
|
||||
#if defined(__cplusplus) || defined(c_plusplus)
|
||||
|
@ -12,7 +12,7 @@
|
||||
See the License for the specific language governing permissions and
|
||||
limitations under the License.
|
||||
|
||||
Utilities for building and looking up Huffman trees.
|
||||
Utilities for building Huffman decoding tables.
|
||||
*/
|
||||
|
||||
#ifndef BROTLI_DEC_HUFFMAN_H_
|
||||
@ -25,48 +25,17 @@
|
||||
extern "C" {
|
||||
#endif
|
||||
|
||||
/* A node of a Huffman tree. */
|
||||
typedef struct {
|
||||
int symbol_;
|
||||
int children_; /* delta offset to both children (contiguous) or 0 if leaf. */
|
||||
} HuffmanTreeNode;
|
||||
uint8_t bits; /* number of bits used for this symbol */
|
||||
uint16_t value; /* symbol value or table offset */
|
||||
} HuffmanCode;
|
||||
|
||||
/* Huffman Tree. */
|
||||
#define HUFF_LUT_BITS 7
|
||||
#define HUFF_LUT (1U << HUFF_LUT_BITS)
|
||||
typedef struct HuffmanTree HuffmanTree;
|
||||
struct HuffmanTree {
|
||||
/* Fast lookup for short bit lengths. */
|
||||
uint8_t lut_bits_[HUFF_LUT];
|
||||
int16_t lut_symbol_[HUFF_LUT];
|
||||
int16_t lut_jump_[HUFF_LUT];
|
||||
/* Complete tree for lookups. */
|
||||
HuffmanTreeNode* root_; /* all the nodes, starting at root. */
|
||||
int max_nodes_; /* max number of nodes */
|
||||
int num_nodes_; /* number of currently occupied nodes */
|
||||
};
|
||||
|
||||
/* Returns true if the given node is not a leaf of the Huffman tree. */
|
||||
static BROTLI_INLINE int HuffmanTreeNodeIsNotLeaf(
|
||||
const HuffmanTreeNode* const node) {
|
||||
return node->children_;
|
||||
}
|
||||
|
||||
/* Go down one level. Most critical function. 'right_child' must be 0 or 1. */
|
||||
static BROTLI_INLINE const HuffmanTreeNode* HuffmanTreeNextNode(
|
||||
const HuffmanTreeNode* node, int right_child) {
|
||||
return node + node->children_ + right_child;
|
||||
}
|
||||
|
||||
/* Releases the nodes of the Huffman tree. */
|
||||
/* Note: It does NOT free 'tree' itself. */
|
||||
void BrotliHuffmanTreeRelease(HuffmanTree* const tree);
|
||||
|
||||
/* Builds Huffman tree assuming code lengths are implicitly in symbol order. */
|
||||
/* Builds Huffman lookup table assuming code lengths are in symbol order. */
|
||||
/* Returns false in case of error (invalid tree or memory error). */
|
||||
int BrotliHuffmanTreeBuildImplicit(HuffmanTree* const tree,
|
||||
const uint8_t* const code_lengths,
|
||||
int code_lengths_size);
|
||||
int BrotliBuildHuffmanTable(HuffmanCode* root_table,
|
||||
int root_bits,
|
||||
const uint8_t* const code_lengths,
|
||||
int code_lengths_size);
|
||||
|
||||
#if defined(__cplusplus) || defined(c_plusplus)
|
||||
} /* extern "C" */
|
||||
|
@ -45,66 +45,97 @@ void CreateBackwardReferences(size_t num_bytes,
|
||||
average_cost /= num_bytes;
|
||||
hasher->set_average_cost(average_cost);
|
||||
|
||||
// M1 match is for considering for two repeated copies, if moving
|
||||
// one literal form the previous copy to the current one allows the
|
||||
// current copy to be more efficient (because the way static dictionary
|
||||
// codes words). M1 matching improves text compression density by ~0.15 %.
|
||||
bool match_found_M1 = false;
|
||||
size_t best_len_M1 = 0;
|
||||
size_t best_len_code_M1 = 0;
|
||||
size_t best_dist_M1 = 0;
|
||||
double best_score_M1 = 0;
|
||||
while (i + 2 < i_end) {
|
||||
size_t best_len = 0;
|
||||
size_t best_len_code = 0;
|
||||
size_t best_dist = 0;
|
||||
double best_score = 0;
|
||||
size_t max_distance = std::min(i + i_diff, max_backward_limit);
|
||||
bool in_dictionary;
|
||||
hasher->set_insert_length(insert_length);
|
||||
bool match_found = hasher->FindLongestMatch(
|
||||
ringbuffer, literal_cost, ringbuffer_mask,
|
||||
i + i_diff, i_end - i, max_distance,
|
||||
&best_len, &best_len_code, &best_dist, &best_score);
|
||||
&best_len, &best_len_code, &best_dist, &best_score, &in_dictionary);
|
||||
bool best_in_dictionary = in_dictionary;
|
||||
if (match_found) {
|
||||
// Found a match. Let's look for something even better ahead.
|
||||
int delayed_backward_references_in_row = 0;
|
||||
while (i + 4 < i_end &&
|
||||
delayed_backward_references_in_row < 4) {
|
||||
size_t best_len_2 = 0;
|
||||
size_t best_len_code_2 = 0;
|
||||
size_t best_dist_2 = 0;
|
||||
double best_score_2 = 0;
|
||||
max_distance = std::min(i + i_diff + 1, max_backward_limit);
|
||||
if (match_found_M1 && best_score_M1 > best_score) {
|
||||
// Two copies after each other. Take the last literal from the
|
||||
// last copy, and use it as the first of this one.
|
||||
(commands->rbegin())->copy_length_ -= 1;
|
||||
(commands->rbegin())->copy_length_code_ -= 1;
|
||||
hasher->Store(ringbuffer + i, i + i_diff);
|
||||
match_found = hasher->FindLongestMatch(
|
||||
ringbuffer, literal_cost, ringbuffer_mask,
|
||||
i + i_diff + 1, i_end - i - 1, max_distance,
|
||||
&best_len_2, &best_len_code_2, &best_dist_2, &best_score_2);
|
||||
double cost_diff_lazy = 0;
|
||||
if (best_len >= 4) {
|
||||
cost_diff_lazy +=
|
||||
literal_cost[(i + 4) & ringbuffer_mask] - average_cost;
|
||||
}
|
||||
{
|
||||
const int tail_length = best_len_2 - best_len + 1;
|
||||
for (int k = 0; k < tail_length; ++k) {
|
||||
cost_diff_lazy -=
|
||||
literal_cost[(i + best_len + k) & ringbuffer_mask] -
|
||||
average_cost;
|
||||
--i;
|
||||
best_len = best_len_M1;
|
||||
best_len_code = best_len_code_M1;
|
||||
best_dist = best_dist_M1;
|
||||
best_score = best_score_M1;
|
||||
// in_dictionary doesn't need to be correct, but it is the only
|
||||
// reason why M1 matching should be beneficial here. Setting it here
|
||||
// will only disable further M1 matching against this copy.
|
||||
best_in_dictionary = true;
|
||||
in_dictionary = true;
|
||||
} else {
|
||||
// Found a match. Let's look for something even better ahead.
|
||||
int delayed_backward_references_in_row = 0;
|
||||
while (i + 4 < i_end &&
|
||||
delayed_backward_references_in_row < 4) {
|
||||
size_t best_len_2 = 0;
|
||||
size_t best_len_code_2 = 0;
|
||||
size_t best_dist_2 = 0;
|
||||
double best_score_2 = 0;
|
||||
max_distance = std::min(i + i_diff + 1, max_backward_limit);
|
||||
hasher->Store(ringbuffer + i, i + i_diff);
|
||||
match_found = hasher->FindLongestMatch(
|
||||
ringbuffer, literal_cost, ringbuffer_mask,
|
||||
i + i_diff + 1, i_end - i - 1, max_distance,
|
||||
&best_len_2, &best_len_code_2, &best_dist_2, &best_score_2,
|
||||
&in_dictionary);
|
||||
double cost_diff_lazy = 0;
|
||||
if (best_len >= 4) {
|
||||
cost_diff_lazy +=
|
||||
literal_cost[(i + 4) & ringbuffer_mask] - average_cost;
|
||||
}
|
||||
}
|
||||
// If we are not inserting any symbols, inserting one is more
|
||||
// expensive than if we were inserting symbols anyways.
|
||||
if (insert_length < 1) {
|
||||
cost_diff_lazy += 0.97;
|
||||
}
|
||||
// Add bias to slightly avoid lazy matching.
|
||||
cost_diff_lazy += 2.0 + delayed_backward_references_in_row * 0.2;
|
||||
cost_diff_lazy += 0.04 * literal_cost[i & ringbuffer_mask];
|
||||
{
|
||||
const int tail_length = best_len_2 - best_len + 1;
|
||||
for (int k = 0; k < tail_length; ++k) {
|
||||
cost_diff_lazy -=
|
||||
literal_cost[(i + best_len + k) & ringbuffer_mask] -
|
||||
average_cost;
|
||||
}
|
||||
}
|
||||
// If we are not inserting any symbols, inserting one is more
|
||||
// expensive than if we were inserting symbols anyways.
|
||||
if (insert_length < 1) {
|
||||
cost_diff_lazy += 0.97;
|
||||
}
|
||||
// Add bias to slightly avoid lazy matching.
|
||||
cost_diff_lazy += 2.0 + delayed_backward_references_in_row * 0.2;
|
||||
cost_diff_lazy += 0.04 * literal_cost[i & ringbuffer_mask];
|
||||
|
||||
if (match_found && best_score_2 >= best_score + cost_diff_lazy) {
|
||||
// Ok, let's just write one byte for now and start a match from the
|
||||
// next byte.
|
||||
++insert_length;
|
||||
++delayed_backward_references_in_row;
|
||||
best_len = best_len_2;
|
||||
best_len_code = best_len_code_2;
|
||||
best_dist = best_dist_2;
|
||||
best_score = best_score_2;
|
||||
i++;
|
||||
} else {
|
||||
break;
|
||||
if (match_found && best_score_2 >= best_score + cost_diff_lazy) {
|
||||
// Ok, let's just write one byte for now and start a match from the
|
||||
// next byte.
|
||||
++insert_length;
|
||||
++delayed_backward_references_in_row;
|
||||
best_len = best_len_2;
|
||||
best_len_code = best_len_code_2;
|
||||
best_dist = best_dist_2;
|
||||
best_score = best_score_2;
|
||||
best_in_dictionary = in_dictionary;
|
||||
i++;
|
||||
} else {
|
||||
break;
|
||||
}
|
||||
}
|
||||
}
|
||||
Command cmd;
|
||||
@ -117,13 +148,40 @@ void CreateBackwardReferences(size_t num_bytes,
|
||||
|
||||
insert_length = 0;
|
||||
++i;
|
||||
for (int j = 1; j < best_len; ++j) {
|
||||
// Copy all copied literals to the hasher, except the last one.
|
||||
// We cannot store the last one yet, otherwise we couldn't find
|
||||
// the possible M1 match.
|
||||
for (int j = 1; j < best_len - 1; ++j) {
|
||||
if (i + 2 < i_end) {
|
||||
hasher->Store(ringbuffer + i, i + i_diff);
|
||||
}
|
||||
++i;
|
||||
}
|
||||
// Prepare M1 match.
|
||||
if (best_len >= 4 && i + 20 < i_end && !best_in_dictionary) {
|
||||
max_distance = std::min(i + i_diff, max_backward_limit);
|
||||
match_found_M1 = hasher->FindLongestMatch(
|
||||
ringbuffer, literal_cost, ringbuffer_mask,
|
||||
i + i_diff, i_end - i, max_distance,
|
||||
&best_len_M1, &best_len_code_M1, &best_dist_M1, &best_score_M1,
|
||||
&in_dictionary);
|
||||
} else {
|
||||
match_found_M1 = false;
|
||||
in_dictionary = false;
|
||||
}
|
||||
// This byte is just moved from the previous copy to the current,
|
||||
// that is no gain.
|
||||
best_score_M1 -= literal_cost[i & ringbuffer_mask];
|
||||
// Adjust for losing the opportunity for lazy matching.
|
||||
best_score_M1 -= 3.75;
|
||||
|
||||
// Store the last one of the match.
|
||||
if (i + 2 < i_end) {
|
||||
hasher->Store(ringbuffer + i, i + i_diff);
|
||||
}
|
||||
++i;
|
||||
} else {
|
||||
match_found_M1 = false;
|
||||
++insert_length;
|
||||
hasher->Store(ringbuffer + i, i + i_diff);
|
||||
++i;
|
||||
|
@ -93,7 +93,7 @@ static inline int HuffmanBitCost(const uint8_t* depth, int length) {
|
||||
cost[17] += 3;
|
||||
|
||||
int tree_size = 0;
|
||||
int bits = 6 + 3 * max_depth; // huffman tree of huffman tree cost
|
||||
int bits = 6 + 2 * max_depth; // huffman tree of huffman tree cost
|
||||
for (int i = 0; i < kCodeLengthCodes; ++i) {
|
||||
bits += histogram[i] * cost[i]; // huffman tree bit cost
|
||||
tree_size += histogram[i];
|
||||
|
@ -31,16 +31,16 @@
|
||||
|
||||
namespace brotli {
|
||||
|
||||
static const int kMaxLiteralHistograms = 48;
|
||||
static const int kMaxLiteralHistograms = 100;
|
||||
static const int kMaxCommandHistograms = 50;
|
||||
static const double kLiteralBlockSwitchCost = 26;
|
||||
static const double kCommandBlockSwitchCost = 13.5;
|
||||
static const double kDistanceBlockSwitchCost = 14.6;
|
||||
static const int kLiteralStrideLength = 70;
|
||||
static const int kCommandStrideLength = 40;
|
||||
static const int kSymbolsPerLiteralHistogram = 550;
|
||||
static const int kSymbolsPerLiteralHistogram = 544;
|
||||
static const int kSymbolsPerCommandHistogram = 530;
|
||||
static const int kSymbolsPerDistanceHistogram = 550;
|
||||
static const int kSymbolsPerDistanceHistogram = 544;
|
||||
static const int kMinLengthForBlockSplitting = 128;
|
||||
static const int kIterMulForRefining = 2;
|
||||
static const int kMinItersForRefining = 100;
|
||||
|
189
enc/encode.cc
189
enc/encode.cc
@ -77,6 +77,68 @@ void EncodeVarLenUint8(int n, int* storage_ix, uint8_t* storage) {
|
||||
}
|
||||
}
|
||||
|
||||
int ParseAsUTF8(int* symbol, const uint8_t* input, int size) {
|
||||
// ASCII
|
||||
if ((input[0] & 0x80) == 0) {
|
||||
*symbol = input[0];
|
||||
if (*symbol > 0) {
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
// 2-byte UTF8
|
||||
if (size > 1 &&
|
||||
(input[0] & 0xe0) == 0xc0 &&
|
||||
(input[1] & 0xc0) == 0x80) {
|
||||
*symbol = (((input[0] & 0x1f) << 6) |
|
||||
(input[1] & 0x3f));
|
||||
if (*symbol > 0x7f) {
|
||||
return 2;
|
||||
}
|
||||
}
|
||||
// 3-byte UFT8
|
||||
if (size > 2 &&
|
||||
(input[0] & 0xf0) == 0xe0 &&
|
||||
(input[1] & 0xc0) == 0x80 &&
|
||||
(input[2] & 0xc0) == 0x80) {
|
||||
*symbol = (((input[0] & 0x0f) << 12) |
|
||||
((input[1] & 0x3f) << 6) |
|
||||
(input[2] & 0x3f));
|
||||
if (*symbol > 0x7ff) {
|
||||
return 3;
|
||||
}
|
||||
}
|
||||
// 4-byte UFT8
|
||||
if (size > 3 &&
|
||||
(input[0] & 0xf8) == 0xf0 &&
|
||||
(input[1] & 0xc0) == 0x80 &&
|
||||
(input[2] & 0xc0) == 0x80 &&
|
||||
(input[3] & 0xc0) == 0x80) {
|
||||
*symbol = (((input[0] & 0x07) << 18) |
|
||||
((input[1] & 0x3f) << 12) |
|
||||
((input[2] & 0x3f) << 6) |
|
||||
(input[3] & 0x3f));
|
||||
if (*symbol > 0xffff && *symbol <= 0x10ffff) {
|
||||
return 4;
|
||||
}
|
||||
}
|
||||
// Not UTF8, emit a special symbol above the UTF8-code space
|
||||
*symbol = 0x110000 | input[0];
|
||||
return 1;
|
||||
}
|
||||
|
||||
// Returns true if at least min_fraction of the data is UTF8-encoded.
|
||||
bool IsMostlyUTF8(const uint8_t* data, size_t length, double min_fraction) {
|
||||
size_t size_utf8 = 0;
|
||||
size_t pos = 0;
|
||||
while (pos < length) {
|
||||
int symbol;
|
||||
int bytes_read = ParseAsUTF8(&symbol, data + pos, length - pos);
|
||||
pos += bytes_read;
|
||||
if (symbol < 0x110000) size_utf8 += bytes_read;
|
||||
}
|
||||
return size_utf8 > min_fraction * length;
|
||||
}
|
||||
|
||||
void EncodeMetaBlockLength(size_t meta_block_size,
|
||||
bool is_last,
|
||||
bool is_uncompressed,
|
||||
@ -118,7 +180,7 @@ void StoreHuffmanTreeOfHuffmanTreeToBitMask(
|
||||
const uint8_t* code_length_bitdepth,
|
||||
int* storage_ix, uint8_t* storage) {
|
||||
static const uint8_t kStorageOrder[kCodeLengthCodes] = {
|
||||
1, 2, 3, 4, 0, 17, 5, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15,
|
||||
1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15,
|
||||
};
|
||||
// Throw away trailing zeros:
|
||||
int codes_to_store = kCodeLengthCodes;
|
||||
@ -147,7 +209,7 @@ void StoreHuffmanTreeOfHuffmanTreeToBitMask(
|
||||
WriteBits(2, skip_some, storage_ix, storage);
|
||||
for (int i = skip_some; i < codes_to_store; ++i) {
|
||||
uint8_t len[] = { 2, 4, 3, 2, 2, 4 };
|
||||
uint8_t bits[] = { 0, 5, 1, 3, 2, 13 };
|
||||
uint8_t bits[] = { 0, 7, 3, 2, 1, 15 };
|
||||
int v = code_length_bitdepth[kStorageOrder[i]];
|
||||
WriteBits(len[v], bits[v], storage_ix, storage);
|
||||
}
|
||||
@ -175,54 +237,49 @@ void StoreHuffmanTreeToBitMask(
|
||||
}
|
||||
|
||||
template<int kSize>
|
||||
void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size,
|
||||
int* storage_ix, uint8_t* storage) {
|
||||
void StoreHuffmanCodeSimple(
|
||||
const EntropyCode<kSize>& code, int alphabet_size,
|
||||
int max_bits,
|
||||
int* storage_ix, uint8_t* storage) {
|
||||
const uint8_t *depth = &code.depth_[0];
|
||||
int max_bits_counter = alphabet_size - 1;
|
||||
int max_bits = 0;
|
||||
while (max_bits_counter) {
|
||||
max_bits_counter >>= 1;
|
||||
++max_bits;
|
||||
int symbols[4];
|
||||
// Quadratic sort.
|
||||
int k, j;
|
||||
for (k = 0; k < code.count_; ++k) {
|
||||
symbols[k] = code.symbols_[k];
|
||||
}
|
||||
if (code.count_ == 0) { // emit minimal tree for empty cases
|
||||
// bits: small tree marker: 1, count-1: 0, max_bits-sized encoding for 0
|
||||
WriteBits(4 + max_bits, 0x1, storage_ix, storage);
|
||||
return;
|
||||
}
|
||||
if (code.count_ <= 4) {
|
||||
int symbols[4];
|
||||
// Quadratic sort.
|
||||
int k, j;
|
||||
for (k = 0; k < code.count_; ++k) {
|
||||
symbols[k] = code.symbols_[k];
|
||||
}
|
||||
for (k = 0; k < code.count_; ++k) {
|
||||
for (j = k + 1; j < code.count_; ++j) {
|
||||
if (depth[symbols[j]] < depth[symbols[k]]) {
|
||||
int t = symbols[k];
|
||||
symbols[k] = symbols[j];
|
||||
symbols[j] = t;
|
||||
}
|
||||
for (k = 0; k < code.count_; ++k) {
|
||||
for (j = k + 1; j < code.count_; ++j) {
|
||||
if (depth[symbols[j]] < depth[symbols[k]]) {
|
||||
int t = symbols[k];
|
||||
symbols[k] = symbols[j];
|
||||
symbols[j] = t;
|
||||
}
|
||||
}
|
||||
// Small tree marker to encode 1-4 symbols.
|
||||
WriteBits(2, 1, storage_ix, storage);
|
||||
WriteBits(2, code.count_ - 1, storage_ix, storage);
|
||||
for (int i = 0; i < code.count_; ++i) {
|
||||
WriteBits(max_bits, symbols[i], storage_ix, storage);
|
||||
}
|
||||
if (code.count_ == 4) {
|
||||
if (depth[symbols[0]] == 2 &&
|
||||
depth[symbols[1]] == 2 &&
|
||||
depth[symbols[2]] == 2 &&
|
||||
depth[symbols[3]] == 2) {
|
||||
WriteBits(1, 0, storage_ix, storage);
|
||||
} else {
|
||||
WriteBits(1, 1, storage_ix, storage);
|
||||
}
|
||||
}
|
||||
return;
|
||||
}
|
||||
// Small tree marker to encode 1-4 symbols.
|
||||
WriteBits(2, 1, storage_ix, storage);
|
||||
WriteBits(2, code.count_ - 1, storage_ix, storage);
|
||||
for (int i = 0; i < code.count_; ++i) {
|
||||
WriteBits(max_bits, symbols[i], storage_ix, storage);
|
||||
}
|
||||
if (code.count_ == 4) {
|
||||
if (depth[symbols[0]] == 2 &&
|
||||
depth[symbols[1]] == 2 &&
|
||||
depth[symbols[2]] == 2 &&
|
||||
depth[symbols[3]] == 2) {
|
||||
WriteBits(1, 0, storage_ix, storage);
|
||||
} else {
|
||||
WriteBits(1, 1, storage_ix, storage);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
template<int kSize>
|
||||
void StoreHuffmanCodeComplex(
|
||||
const EntropyCode<kSize>& code, int alphabet_size,
|
||||
int* storage_ix, uint8_t* storage) {
|
||||
const uint8_t *depth = &code.depth_[0];
|
||||
uint8_t huffman_tree[kSize];
|
||||
uint8_t huffman_tree_extra_bits[kSize];
|
||||
int huffman_tree_size = 0;
|
||||
@ -246,6 +303,31 @@ void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size,
|
||||
storage_ix, storage);
|
||||
}
|
||||
|
||||
|
||||
template<int kSize>
|
||||
void StoreHuffmanCode(const EntropyCode<kSize>& code, int alphabet_size,
|
||||
int* storage_ix, uint8_t* storage) {
|
||||
int max_bits_counter = alphabet_size - 1;
|
||||
int max_bits = 0;
|
||||
while (max_bits_counter) {
|
||||
max_bits_counter >>= 1;
|
||||
++max_bits;
|
||||
}
|
||||
if (code.count_ == 0) {
|
||||
// Emit a minimal tree for empty cases.
|
||||
// bits: small tree marker: 1, count-1: 0, max_bits-sized encoding for 0
|
||||
WriteBits(4 + max_bits, 0x1, storage_ix, storage);
|
||||
} else if (code.count_ <= 4) {
|
||||
StoreHuffmanCodeSimple(
|
||||
code, alphabet_size, max_bits,
|
||||
storage_ix, storage);
|
||||
} else {
|
||||
StoreHuffmanCodeComplex(
|
||||
code, alphabet_size,
|
||||
storage_ix, storage);
|
||||
}
|
||||
}
|
||||
|
||||
template<int kSize>
|
||||
void StoreHuffmanCodes(const std::vector<EntropyCode<kSize> >& codes,
|
||||
int alphabet_size,
|
||||
@ -798,12 +880,23 @@ void BrotliCompressor::WriteMetaBlock(const size_t input_size,
|
||||
const bool is_last,
|
||||
size_t* encoded_size,
|
||||
uint8_t* encoded_buffer) {
|
||||
static const double kMinUTF8Ratio = 0.75;
|
||||
bool utf8_mode = false;
|
||||
std::vector<Command> commands;
|
||||
if (input_size > 0) {
|
||||
ringbuffer_.Write(input_buffer, input_size);
|
||||
EstimateBitCostsForLiterals(input_pos_, input_size,
|
||||
kRingBufferMask, ringbuffer_.start(),
|
||||
&literal_cost_[0]);
|
||||
utf8_mode = IsMostlyUTF8(
|
||||
&ringbuffer_.start()[input_pos_ & kRingBufferMask],
|
||||
input_size, kMinUTF8Ratio);
|
||||
if (utf8_mode) {
|
||||
EstimateBitCostsForLiteralsUTF8(input_pos_, input_size,
|
||||
kRingBufferMask, ringbuffer_.start(),
|
||||
&literal_cost_[0]);
|
||||
} else {
|
||||
EstimateBitCostsForLiterals(input_pos_, input_size,
|
||||
kRingBufferMask, ringbuffer_.start(),
|
||||
&literal_cost_[0]);
|
||||
}
|
||||
CreateBackwardReferences(input_size, input_pos_,
|
||||
ringbuffer_.start(),
|
||||
&literal_cost_[0],
|
||||
|
@ -182,6 +182,12 @@ void WriteHuffmanTreeRepetitions(
|
||||
++(*tree_size);
|
||||
--repetitions;
|
||||
}
|
||||
if (repetitions == 7) {
|
||||
tree[*tree_size] = value;
|
||||
extra_bits[*tree_size] = 0;
|
||||
++(*tree_size);
|
||||
--repetitions;
|
||||
}
|
||||
if (repetitions < 3) {
|
||||
for (int i = 0; i < repetitions; ++i) {
|
||||
tree[*tree_size] = value;
|
||||
@ -208,6 +214,12 @@ void WriteHuffmanTreeRepetitionsZeros(
|
||||
uint8_t* tree,
|
||||
uint8_t* extra_bits,
|
||||
int* tree_size) {
|
||||
if (repetitions == 11) {
|
||||
tree[*tree_size] = 0;
|
||||
extra_bits[*tree_size] = 0;
|
||||
++(*tree_size);
|
||||
--repetitions;
|
||||
}
|
||||
if (repetitions < 3) {
|
||||
for (int i = 0; i < repetitions; ++i) {
|
||||
tree[*tree_size] = 0;
|
||||
@ -230,11 +242,6 @@ void WriteHuffmanTreeRepetitionsZeros(
|
||||
}
|
||||
|
||||
|
||||
// Heuristics for selecting the stride ranges to collapse.
|
||||
int ValuesShouldBeCollapsedToStrideAverage(int a, int b) {
|
||||
return abs(a - b) < 4;
|
||||
}
|
||||
|
||||
int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
int stride;
|
||||
int limit;
|
||||
@ -251,6 +258,35 @@ int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
{
|
||||
int nonzeros = 0;
|
||||
int smallest_nonzero = 1 << 30;
|
||||
for (i = 0; i < length; ++i) {
|
||||
if (counts[i] != 0) {
|
||||
++nonzeros;
|
||||
if (smallest_nonzero > counts[i]) {
|
||||
smallest_nonzero = counts[i];
|
||||
}
|
||||
}
|
||||
}
|
||||
if (nonzeros < 5) {
|
||||
// Small histogram will model it well.
|
||||
return 1;
|
||||
}
|
||||
int zeros = length - nonzeros;
|
||||
if (smallest_nonzero < 4) {
|
||||
if (zeros < 6) {
|
||||
for (i = 1; i < length - 1; ++i) {
|
||||
if (counts[i - 1] != 0 && counts[i] == 0 && counts[i + 1] != 0) {
|
||||
counts[i] = 1;
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
if (nonzeros < 28) {
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
// 2) Let's mark all population counts that already can be encoded
|
||||
// with an rle code.
|
||||
good_for_rle = (uint8_t*)calloc(length, 1);
|
||||
@ -282,13 +318,15 @@ int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
}
|
||||
}
|
||||
// 3) Let's replace those population counts that lead to more rle codes.
|
||||
// Math here is in 24.8 fixed point representation.
|
||||
const int streak_limit = 1240;
|
||||
stride = 0;
|
||||
limit = (counts[0] + counts[1] + counts[2]) / 3 + 1;
|
||||
limit = 256 * (counts[0] + counts[1] + counts[2]) / 3 + 420;
|
||||
sum = 0;
|
||||
for (i = 0; i < length + 1; ++i) {
|
||||
if (i == length || good_for_rle[i] ||
|
||||
(i != 0 && good_for_rle[i - 1]) ||
|
||||
!ValuesShouldBeCollapsedToStrideAverage(counts[i], limit)) {
|
||||
abs(256 * counts[i] - limit) >= streak_limit) {
|
||||
if (stride >= 4 || (stride >= 3 && sum == 0)) {
|
||||
int k;
|
||||
// The stride must end, collapse what we have, if we have enough (4).
|
||||
@ -311,9 +349,9 @@ int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
if (i < length - 2) {
|
||||
// All interesting strides have a count of at least 4,
|
||||
// at least when non-zeros.
|
||||
limit = (counts[i] + counts[i + 1] + counts[i + 2]) / 3 + 1;
|
||||
limit = 256 * (counts[i] + counts[i + 1] + counts[i + 2]) / 3 + 420;
|
||||
} else if (i < length) {
|
||||
limit = counts[i];
|
||||
limit = 256 * counts[i];
|
||||
} else {
|
||||
limit = 0;
|
||||
}
|
||||
@ -322,7 +360,10 @@ int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
if (i != length) {
|
||||
sum += counts[i];
|
||||
if (stride >= 4) {
|
||||
limit = (sum + stride / 2) / stride;
|
||||
limit = (256 * sum + stride / 2) / stride;
|
||||
}
|
||||
if (stride == 4) {
|
||||
limit += 120;
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -331,16 +372,70 @@ int OptimizeHuffmanCountsForRle(int length, int* counts) {
|
||||
}
|
||||
|
||||
|
||||
static void DecideOverRleUse(const uint8_t* depth, const int length,
|
||||
bool *use_rle_for_non_zero,
|
||||
bool *use_rle_for_zero) {
|
||||
int total_reps_zero = 0;
|
||||
int total_reps_non_zero = 0;
|
||||
int count_reps_zero = 0;
|
||||
int count_reps_non_zero = 0;
|
||||
int new_length = length;
|
||||
for (int i = 0; i < length; ++i) {
|
||||
if (depth[length - i - 1] == 0) {
|
||||
--new_length;
|
||||
} else {
|
||||
break;
|
||||
}
|
||||
}
|
||||
for (uint32_t i = 0; i < new_length;) {
|
||||
const int value = depth[i];
|
||||
int reps = 1;
|
||||
// Find rle coding for longer codes.
|
||||
// Shorter codes seem not to benefit from rle.
|
||||
for (uint32_t k = i + 1; k < new_length && depth[k] == value; ++k) {
|
||||
++reps;
|
||||
}
|
||||
if (reps >= 3 && value == 0) {
|
||||
total_reps_zero += reps;
|
||||
++count_reps_zero;
|
||||
}
|
||||
if (reps >= 4 && value != 0) {
|
||||
total_reps_non_zero += reps;
|
||||
++count_reps_non_zero;
|
||||
}
|
||||
i += reps;
|
||||
}
|
||||
total_reps_non_zero -= count_reps_non_zero * 2;
|
||||
total_reps_zero -= count_reps_zero * 2;
|
||||
*use_rle_for_non_zero = total_reps_non_zero > 2;
|
||||
*use_rle_for_zero = total_reps_zero > 2;
|
||||
}
|
||||
|
||||
|
||||
void WriteHuffmanTree(const uint8_t* depth, const int length,
|
||||
uint8_t* tree,
|
||||
uint8_t* extra_bits_data,
|
||||
int* huffman_tree_size) {
|
||||
int previous_value = 8;
|
||||
|
||||
// First gather statistics on if it is a good idea to do rle.
|
||||
bool use_rle_for_non_zero;
|
||||
bool use_rle_for_zero;
|
||||
DecideOverRleUse(depth, length, &use_rle_for_non_zero, &use_rle_for_zero);
|
||||
|
||||
// Actual rle coding.
|
||||
for (uint32_t i = 0; i < length;) {
|
||||
const int value = depth[i];
|
||||
int reps = 1;
|
||||
for (uint32_t k = i + 1; k < length && depth[k] == value; ++k) {
|
||||
++reps;
|
||||
if (length > 50) {
|
||||
// Find rle coding for longer codes.
|
||||
// Shorter codes seem not to benefit from rle.
|
||||
if ((value != 0 && use_rle_for_non_zero) ||
|
||||
(value == 0 && use_rle_for_zero)) {
|
||||
for (uint32_t k = i + 1; k < length && depth[k] == value; ++k) {
|
||||
++reps;
|
||||
}
|
||||
}
|
||||
}
|
||||
if (value == 0) {
|
||||
WriteHuffmanTreeRepetitionsZeros(reps, tree, extra_bits_data,
|
||||
|
@ -86,7 +86,7 @@ void BuildEntropyCode(const Histogram<kSize>& histogram,
|
||||
++code->count_;
|
||||
}
|
||||
}
|
||||
if (code->count_ >= 64) {
|
||||
if (alphabet_size >= 50 && code->count_ >= 16) {
|
||||
int counts[kSize];
|
||||
memcpy(counts, &histogram.data_[0], sizeof(counts[0]) * kSize);
|
||||
OptimizeHuffmanCountsForRle(alphabet_size, counts);
|
||||
|
13
enc/hash.h
13
enc/hash.h
@ -150,7 +150,10 @@ class HashLongestMatch {
|
||||
size_t * __restrict best_len_out,
|
||||
size_t * __restrict best_len_code_out,
|
||||
size_t * __restrict best_distance_out,
|
||||
double * __restrict best_score_out) {
|
||||
double * __restrict best_score_out,
|
||||
bool * __restrict in_dictionary) {
|
||||
*in_dictionary = true;
|
||||
*best_len_code_out = 0;
|
||||
const size_t cur_ix_masked = cur_ix & ring_buffer_mask;
|
||||
const double start_cost4 = literal_cost == NULL ? 20 :
|
||||
literal_cost[cur_ix_masked] +
|
||||
@ -166,9 +169,9 @@ class HashLongestMatch {
|
||||
literal_cost[(cur_ix + 1) & ring_buffer_mask] + 1.2;
|
||||
bool match_found = false;
|
||||
// Don't accept a short copy from far away.
|
||||
double best_score = 8.25;
|
||||
double best_score = 8.11;
|
||||
if (insert_length_ < 4) {
|
||||
double cost_diff[4] = { 0.20, 0.09, 0.05, 0.03 };
|
||||
double cost_diff[4] = { 0.10, 0.04, 0.02, 0.01 };
|
||||
best_score += cost_diff[insert_length_];
|
||||
}
|
||||
size_t best_len = *best_len_out;
|
||||
@ -235,6 +238,7 @@ class HashLongestMatch {
|
||||
*best_distance_out = best_ix;
|
||||
*best_score_out = best_score;
|
||||
match_found = true;
|
||||
*in_dictionary = backward > max_backward;
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -257,7 +261,7 @@ class HashLongestMatch {
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continue;
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}
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int len = 2;
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const double score = start_cost2 - 1.70 * Log2Floor(backward);
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const double score = start_cost2 - 2.3 * Log2Floor(backward);
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||||
|
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if (best_score < score) {
|
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best_score = score;
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@ -309,6 +313,7 @@ class HashLongestMatch {
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*best_distance_out = best_ix;
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*best_score_out = best_score;
|
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match_found = true;
|
||||
*in_dictionary = false;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
@ -22,6 +22,104 @@
|
||||
|
||||
namespace brotli {
|
||||
|
||||
static int UTF8Position(int last, int c, int clamp) {
|
||||
if (c < 128) {
|
||||
return 0; // Next one is the 'Byte 1' again.
|
||||
} else if (c >= 192) {
|
||||
return std::min(1, clamp); // Next one is the 'Byte 2' of utf-8 encoding.
|
||||
} else {
|
||||
// Let's decide over the last byte if this ends the sequence.
|
||||
if (last < 0xe0) {
|
||||
return 0; // Completed two or three byte coding.
|
||||
} else {
|
||||
return std::min(2, clamp); // Next one is the 'Byte 3' of utf-8 encoding.
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
static int DecideMultiByteStatsLevel(size_t pos, size_t len, size_t mask,
|
||||
const uint8_t *data) {
|
||||
int counts[3] = { 0 };
|
||||
int max_utf8 = 1; // should be 2, but 1 compresses better.
|
||||
int last_c = 0;
|
||||
int utf8_pos = 0;
|
||||
for (int i = 0; i < len; ++i) {
|
||||
int c = data[(pos + i) & mask];
|
||||
utf8_pos = UTF8Position(last_c, c, 2);
|
||||
++counts[utf8_pos];
|
||||
last_c = c;
|
||||
}
|
||||
if (counts[2] < 500) {
|
||||
max_utf8 = 1;
|
||||
}
|
||||
if (counts[1] + counts[2] < 25) {
|
||||
max_utf8 = 0;
|
||||
}
|
||||
return max_utf8;
|
||||
}
|
||||
|
||||
void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask,
|
||||
const uint8_t *data, float *cost) {
|
||||
|
||||
// max_utf8 is 0 (normal ascii single byte modeling),
|
||||
// 1 (for 2-byte utf-8 modeling), or 2 (for 3-byte utf-8 modeling).
|
||||
const int max_utf8 = DecideMultiByteStatsLevel(pos, len, mask, data);
|
||||
int histogram[3][256] = { { 0 } };
|
||||
int window_half = 495;
|
||||
int in_window = std::min(static_cast<size_t>(window_half), len);
|
||||
int in_window_utf8[3] = { 0 };
|
||||
|
||||
// Bootstrap histograms.
|
||||
int last_c = 0;
|
||||
int utf8_pos = 0;
|
||||
for (int i = 0; i < in_window; ++i) {
|
||||
int c = data[(pos + i) & mask];
|
||||
++histogram[utf8_pos][c];
|
||||
++in_window_utf8[utf8_pos];
|
||||
utf8_pos = UTF8Position(last_c, c, max_utf8);
|
||||
last_c = c;
|
||||
}
|
||||
|
||||
// Compute bit costs with sliding window.
|
||||
for (int i = 0; i < len; ++i) {
|
||||
if (i - window_half >= 0) {
|
||||
// Remove a byte in the past.
|
||||
int c = (i - window_half - 1) < 0 ?
|
||||
0 : data[(pos + i - window_half - 1) & mask];
|
||||
int last_c = (i - window_half - 2) < 0 ?
|
||||
0 : data[(pos + i - window_half - 2) & mask];
|
||||
int utf8_pos2 = UTF8Position(last_c, c, max_utf8);
|
||||
--histogram[utf8_pos2][data[(pos + i - window_half) & mask]];
|
||||
--in_window_utf8[utf8_pos2];
|
||||
}
|
||||
if (i + window_half < len) {
|
||||
// Add a byte in the future.
|
||||
int c = (i + window_half - 1) < 0 ?
|
||||
0 : data[(pos + i + window_half - 1) & mask];
|
||||
int last_c = (i + window_half - 2) < 0 ?
|
||||
0 : data[(pos + i + window_half - 2) & mask];
|
||||
int utf8_pos2 = UTF8Position(last_c, c, max_utf8);
|
||||
++histogram[utf8_pos2][data[(pos + i + window_half) & mask]];
|
||||
++in_window_utf8[utf8_pos2];
|
||||
}
|
||||
int c = i < 1 ? 0 : data[(pos + i - 1) & mask];
|
||||
int last_c = i < 2 ? 0 : data[(pos + i - 2) & mask];
|
||||
int utf8_pos = UTF8Position(last_c, c, max_utf8);
|
||||
int masked_pos = (pos + i) & mask;
|
||||
int histo = histogram[utf8_pos][data[masked_pos]];
|
||||
if (histo == 0) {
|
||||
histo = 1;
|
||||
}
|
||||
cost[masked_pos] = log2(static_cast<double>(in_window_utf8[utf8_pos])
|
||||
/ histo);
|
||||
cost[masked_pos] += 0.02905;
|
||||
if (cost[masked_pos] < 1.0) {
|
||||
cost[masked_pos] *= 0.5;
|
||||
cost[masked_pos] += 0.5;
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask,
|
||||
const uint8_t *data, float *cost) {
|
||||
int histogram[256] = { 0 };
|
||||
@ -59,4 +157,5 @@ void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask,
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
} // namespace brotli
|
||||
|
@ -26,7 +26,12 @@ namespace brotli {
|
||||
// ringbuffer (data, mask) will take entropy coded and writes these estimates
|
||||
// to the ringbuffer (cost, mask).
|
||||
void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask,
|
||||
const uint8_t *data, float *cost);
|
||||
const uint8_t *data,
|
||||
float *cost);
|
||||
|
||||
void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask,
|
||||
const uint8_t *data,
|
||||
float *cost);
|
||||
|
||||
} // namespace brotli
|
||||
|
||||
|
Loading…
Reference in New Issue
Block a user