| /* Copyright 2015 Google Inc. All Rights Reserved. |
| |
| Distributed under MIT license. |
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| */ |
| |
| /* Function for fast encoding of an input fragment, independently from the input |
| history. This function uses one-pass processing: when we find a backward |
| match, we immediately emit the corresponding command and literal codes to |
| the bit stream. |
| |
| Adapted from the CompressFragment() function in |
| https://github.com/google/snappy/blob/master/snappy.cc */ |
| |
| #include "./compress_fragment.h" |
| |
| #if !defined(STARBOARD) |
| #include <string.h> /* memcmp, memcpy, memset */ |
| #else |
| #include "starboard/client_porting/poem/string_poem.h" |
| #endif |
| |
| #include "../common/constants.h" |
| #include "../common/platform.h" |
| #include <brotli/types.h> |
| #include "./brotli_bit_stream.h" |
| #include "./entropy_encode.h" |
| #include "./fast_log.h" |
| #include "./find_match_length.h" |
| #include "./memory.h" |
| #include "./write_bits.h" |
| |
| #if defined(__cplusplus) || defined(c_plusplus) |
| extern "C" { |
| #endif |
| |
| #define MAX_DISTANCE (long)BROTLI_MAX_BACKWARD_LIMIT(18) |
| |
| /* kHashMul32 multiplier has these properties: |
| * The multiplier must be odd. Otherwise we may lose the highest bit. |
| * No long streaks of ones or zeros. |
| * There is no effort to ensure that it is a prime, the oddity is enough |
| for this use. |
| * The number has been tuned heuristically against compression benchmarks. */ |
| static const uint32_t kHashMul32 = 0x1e35a7bd; |
| |
| static BROTLI_INLINE uint32_t Hash(const uint8_t* p, size_t shift) { |
| const uint64_t h = (BROTLI_UNALIGNED_LOAD64LE(p) << 24) * kHashMul32; |
| return (uint32_t)(h >> shift); |
| } |
| |
| static BROTLI_INLINE uint32_t HashBytesAtOffset( |
| uint64_t v, int offset, size_t shift) { |
| BROTLI_DCHECK(offset >= 0); |
| BROTLI_DCHECK(offset <= 3); |
| { |
| const uint64_t h = ((v >> (8 * offset)) << 24) * kHashMul32; |
| return (uint32_t)(h >> shift); |
| } |
| } |
| |
| static BROTLI_INLINE BROTLI_BOOL IsMatch(const uint8_t* p1, const uint8_t* p2) { |
| return TO_BROTLI_BOOL( |
| BrotliUnalignedRead32(p1) == BrotliUnalignedRead32(p2) && |
| p1[4] == p2[4]); |
| } |
| |
| /* Builds a literal prefix code into "depths" and "bits" based on the statistics |
| of the "input" string and stores it into the bit stream. |
| Note that the prefix code here is built from the pre-LZ77 input, therefore |
| we can only approximate the statistics of the actual literal stream. |
| Moreover, for long inputs we build a histogram from a sample of the input |
| and thus have to assign a non-zero depth for each literal. |
| Returns estimated compression ratio millibytes/char for encoding given input |
| with generated code. */ |
| static size_t BuildAndStoreLiteralPrefixCode(MemoryManager* m, |
| const uint8_t* input, |
| const size_t input_size, |
| uint8_t depths[256], |
| uint16_t bits[256], |
| size_t* storage_ix, |
| uint8_t* storage) { |
| uint32_t histogram[256] = { 0 }; |
| size_t histogram_total; |
| size_t i; |
| if (input_size < (1 << 15)) { |
| for (i = 0; i < input_size; ++i) { |
| ++histogram[input[i]]; |
| } |
| histogram_total = input_size; |
| for (i = 0; i < 256; ++i) { |
| /* We weigh the first 11 samples with weight 3 to account for the |
| balancing effect of the LZ77 phase on the histogram. */ |
| const uint32_t adjust = 2 * BROTLI_MIN(uint32_t, histogram[i], 11u); |
| histogram[i] += adjust; |
| histogram_total += adjust; |
| } |
| } else { |
| static const size_t kSampleRate = 29; |
| for (i = 0; i < input_size; i += kSampleRate) { |
| ++histogram[input[i]]; |
| } |
| histogram_total = (input_size + kSampleRate - 1) / kSampleRate; |
| for (i = 0; i < 256; ++i) { |
| /* We add 1 to each population count to avoid 0 bit depths (since this is |
| only a sample and we don't know if the symbol appears or not), and we |
| weigh the first 11 samples with weight 3 to account for the balancing |
| effect of the LZ77 phase on the histogram (more frequent symbols are |
| more likely to be in backward references instead as literals). */ |
| const uint32_t adjust = 1 + 2 * BROTLI_MIN(uint32_t, histogram[i], 11u); |
| histogram[i] += adjust; |
| histogram_total += adjust; |
| } |
| } |
| BrotliBuildAndStoreHuffmanTreeFast(m, histogram, histogram_total, |
| /* max_bits = */ 8, |
| depths, bits, storage_ix, storage); |
| if (BROTLI_IS_OOM(m)) return 0; |
| { |
| size_t literal_ratio = 0; |
| for (i = 0; i < 256; ++i) { |
| if (histogram[i]) literal_ratio += histogram[i] * depths[i]; |
| } |
| /* Estimated encoding ratio, millibytes per symbol. */ |
| return (literal_ratio * 125) / histogram_total; |
| } |
| } |
| |
| /* Builds a command and distance prefix code (each 64 symbols) into "depth" and |
| "bits" based on "histogram" and stores it into the bit stream. */ |
| static void BuildAndStoreCommandPrefixCode(const uint32_t histogram[128], |
| uint8_t depth[128], uint16_t bits[128], size_t* storage_ix, |
| uint8_t* storage) { |
| /* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */ |
| HuffmanTree tree[129]; |
| uint8_t cmd_depth[BROTLI_NUM_COMMAND_SYMBOLS] = { 0 }; |
| uint16_t cmd_bits[64]; |
| |
| BrotliCreateHuffmanTree(histogram, 64, 15, tree, depth); |
| BrotliCreateHuffmanTree(&histogram[64], 64, 14, tree, &depth[64]); |
| /* We have to jump through a few hoops here in order to compute |
| the command bits because the symbols are in a different order than in |
| the full alphabet. This looks complicated, but having the symbols |
| in this order in the command bits saves a few branches in the Emit* |
| functions. */ |
| memcpy(cmd_depth, depth, 24); |
| memcpy(cmd_depth + 24, depth + 40, 8); |
| memcpy(cmd_depth + 32, depth + 24, 8); |
| memcpy(cmd_depth + 40, depth + 48, 8); |
| memcpy(cmd_depth + 48, depth + 32, 8); |
| memcpy(cmd_depth + 56, depth + 56, 8); |
| BrotliConvertBitDepthsToSymbols(cmd_depth, 64, cmd_bits); |
| memcpy(bits, cmd_bits, 48); |
| memcpy(bits + 24, cmd_bits + 32, 16); |
| memcpy(bits + 32, cmd_bits + 48, 16); |
| memcpy(bits + 40, cmd_bits + 24, 16); |
| memcpy(bits + 48, cmd_bits + 40, 16); |
| memcpy(bits + 56, cmd_bits + 56, 16); |
| BrotliConvertBitDepthsToSymbols(&depth[64], 64, &bits[64]); |
| { |
| /* Create the bit length array for the full command alphabet. */ |
| size_t i; |
| memset(cmd_depth, 0, 64); /* only 64 first values were used */ |
| memcpy(cmd_depth, depth, 8); |
| memcpy(cmd_depth + 64, depth + 8, 8); |
| memcpy(cmd_depth + 128, depth + 16, 8); |
| memcpy(cmd_depth + 192, depth + 24, 8); |
| memcpy(cmd_depth + 384, depth + 32, 8); |
| for (i = 0; i < 8; ++i) { |
| cmd_depth[128 + 8 * i] = depth[40 + i]; |
| cmd_depth[256 + 8 * i] = depth[48 + i]; |
| cmd_depth[448 + 8 * i] = depth[56 + i]; |
| } |
| BrotliStoreHuffmanTree( |
| cmd_depth, BROTLI_NUM_COMMAND_SYMBOLS, tree, storage_ix, storage); |
| } |
| BrotliStoreHuffmanTree(&depth[64], 64, tree, storage_ix, storage); |
| } |
| |
| /* REQUIRES: insertlen < 6210 */ |
| static BROTLI_INLINE void EmitInsertLen(size_t insertlen, |
| const uint8_t depth[128], |
| const uint16_t bits[128], |
| uint32_t histo[128], |
| size_t* storage_ix, |
| uint8_t* storage) { |
| if (insertlen < 6) { |
| const size_t code = insertlen + 40; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| ++histo[code]; |
| } else if (insertlen < 130) { |
| const size_t tail = insertlen - 2; |
| const uint32_t nbits = Log2FloorNonZero(tail) - 1u; |
| const size_t prefix = tail >> nbits; |
| const size_t inscode = (nbits << 1) + prefix + 42; |
| BrotliWriteBits(depth[inscode], bits[inscode], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage); |
| ++histo[inscode]; |
| } else if (insertlen < 2114) { |
| const size_t tail = insertlen - 66; |
| const uint32_t nbits = Log2FloorNonZero(tail); |
| const size_t code = nbits + 50; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage); |
| ++histo[code]; |
| } else { |
| BrotliWriteBits(depth[61], bits[61], storage_ix, storage); |
| BrotliWriteBits(12, insertlen - 2114, storage_ix, storage); |
| ++histo[21]; |
| } |
| } |
| |
| static BROTLI_INLINE void EmitLongInsertLen(size_t insertlen, |
| const uint8_t depth[128], |
| const uint16_t bits[128], |
| uint32_t histo[128], |
| size_t* storage_ix, |
| uint8_t* storage) { |
| if (insertlen < 22594) { |
| BrotliWriteBits(depth[62], bits[62], storage_ix, storage); |
| BrotliWriteBits(14, insertlen - 6210, storage_ix, storage); |
| ++histo[22]; |
| } else { |
| BrotliWriteBits(depth[63], bits[63], storage_ix, storage); |
| BrotliWriteBits(24, insertlen - 22594, storage_ix, storage); |
| ++histo[23]; |
| } |
| } |
| |
| static BROTLI_INLINE void EmitCopyLen(size_t copylen, |
| const uint8_t depth[128], |
| const uint16_t bits[128], |
| uint32_t histo[128], |
| size_t* storage_ix, |
| uint8_t* storage) { |
| if (copylen < 10) { |
| BrotliWriteBits( |
| depth[copylen + 14], bits[copylen + 14], storage_ix, storage); |
| ++histo[copylen + 14]; |
| } else if (copylen < 134) { |
| const size_t tail = copylen - 6; |
| const uint32_t nbits = Log2FloorNonZero(tail) - 1u; |
| const size_t prefix = tail >> nbits; |
| const size_t code = (nbits << 1) + prefix + 20; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage); |
| ++histo[code]; |
| } else if (copylen < 2118) { |
| const size_t tail = copylen - 70; |
| const uint32_t nbits = Log2FloorNonZero(tail); |
| const size_t code = nbits + 28; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage); |
| ++histo[code]; |
| } else { |
| BrotliWriteBits(depth[39], bits[39], storage_ix, storage); |
| BrotliWriteBits(24, copylen - 2118, storage_ix, storage); |
| ++histo[47]; |
| } |
| } |
| |
| static BROTLI_INLINE void EmitCopyLenLastDistance(size_t copylen, |
| const uint8_t depth[128], |
| const uint16_t bits[128], |
| uint32_t histo[128], |
| size_t* storage_ix, |
| uint8_t* storage) { |
| if (copylen < 12) { |
| BrotliWriteBits(depth[copylen - 4], bits[copylen - 4], storage_ix, storage); |
| ++histo[copylen - 4]; |
| } else if (copylen < 72) { |
| const size_t tail = copylen - 8; |
| const uint32_t nbits = Log2FloorNonZero(tail) - 1; |
| const size_t prefix = tail >> nbits; |
| const size_t code = (nbits << 1) + prefix + 4; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage); |
| ++histo[code]; |
| } else if (copylen < 136) { |
| const size_t tail = copylen - 8; |
| const size_t code = (tail >> 5) + 30; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(5, tail & 31, storage_ix, storage); |
| BrotliWriteBits(depth[64], bits[64], storage_ix, storage); |
| ++histo[code]; |
| ++histo[64]; |
| } else if (copylen < 2120) { |
| const size_t tail = copylen - 72; |
| const uint32_t nbits = Log2FloorNonZero(tail); |
| const size_t code = nbits + 28; |
| BrotliWriteBits(depth[code], bits[code], storage_ix, storage); |
| BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage); |
| BrotliWriteBits(depth[64], bits[64], storage_ix, storage); |
| ++histo[code]; |
| ++histo[64]; |
| } else { |
| BrotliWriteBits(depth[39], bits[39], storage_ix, storage); |
| BrotliWriteBits(24, copylen - 2120, storage_ix, storage); |
| BrotliWriteBits(depth[64], bits[64], storage_ix, storage); |
| ++histo[47]; |
| ++histo[64]; |
| } |
| } |
| |
| static BROTLI_INLINE void EmitDistance(size_t distance, |
| const uint8_t depth[128], |
| const uint16_t bits[128], |
| uint32_t histo[128], |
| size_t* storage_ix, uint8_t* storage) { |
| const size_t d = distance + 3; |
| const uint32_t nbits = Log2FloorNonZero(d) - 1u; |
| const size_t prefix = (d >> nbits) & 1; |
| const size_t offset = (2 + prefix) << nbits; |
| const size_t distcode = 2 * (nbits - 1) + prefix + 80; |
| BrotliWriteBits(depth[distcode], bits[distcode], storage_ix, storage); |
| BrotliWriteBits(nbits, d - offset, storage_ix, storage); |
| ++histo[distcode]; |
| } |
| |
| static BROTLI_INLINE void EmitLiterals(const uint8_t* input, const size_t len, |
| const uint8_t depth[256], |
| const uint16_t bits[256], |
| size_t* storage_ix, uint8_t* storage) { |
| size_t j; |
| for (j = 0; j < len; j++) { |
| const uint8_t lit = input[j]; |
| BrotliWriteBits(depth[lit], bits[lit], storage_ix, storage); |
| } |
| } |
| |
| /* REQUIRES: len <= 1 << 24. */ |
| static void BrotliStoreMetaBlockHeader( |
| size_t len, BROTLI_BOOL is_uncompressed, size_t* storage_ix, |
| uint8_t* storage) { |
| size_t nibbles = 6; |
| /* ISLAST */ |
| BrotliWriteBits(1, 0, storage_ix, storage); |
| if (len <= (1U << 16)) { |
| nibbles = 4; |
| } else if (len <= (1U << 20)) { |
| nibbles = 5; |
| } |
| BrotliWriteBits(2, nibbles - 4, storage_ix, storage); |
| BrotliWriteBits(nibbles * 4, len - 1, storage_ix, storage); |
| /* ISUNCOMPRESSED */ |
| BrotliWriteBits(1, (uint64_t)is_uncompressed, storage_ix, storage); |
| } |
| |
| static void UpdateBits(size_t n_bits, uint32_t bits, size_t pos, |
| uint8_t *array) { |
| while (n_bits > 0) { |
| size_t byte_pos = pos >> 3; |
| size_t n_unchanged_bits = pos & 7; |
| size_t n_changed_bits = BROTLI_MIN(size_t, n_bits, 8 - n_unchanged_bits); |
| size_t total_bits = n_unchanged_bits + n_changed_bits; |
| uint32_t mask = |
| (~((1u << total_bits) - 1u)) | ((1u << n_unchanged_bits) - 1u); |
| uint32_t unchanged_bits = array[byte_pos] & mask; |
| uint32_t changed_bits = bits & ((1u << n_changed_bits) - 1u); |
| array[byte_pos] = |
| (uint8_t)((changed_bits << n_unchanged_bits) | unchanged_bits); |
| n_bits -= n_changed_bits; |
| bits >>= n_changed_bits; |
| pos += n_changed_bits; |
| } |
| } |
| |
| static void RewindBitPosition(const size_t new_storage_ix, |
| size_t* storage_ix, uint8_t* storage) { |
| const size_t bitpos = new_storage_ix & 7; |
| const size_t mask = (1u << bitpos) - 1; |
| storage[new_storage_ix >> 3] &= (uint8_t)mask; |
| *storage_ix = new_storage_ix; |
| } |
| |
| static BROTLI_BOOL ShouldMergeBlock( |
| const uint8_t* data, size_t len, const uint8_t* depths) { |
| size_t histo[256] = { 0 }; |
| static const size_t kSampleRate = 43; |
| size_t i; |
| for (i = 0; i < len; i += kSampleRate) { |
| ++histo[data[i]]; |
| } |
| { |
| const size_t total = (len + kSampleRate - 1) / kSampleRate; |
| double r = (FastLog2(total) + 0.5) * (double)total + 200; |
| for (i = 0; i < 256; ++i) { |
| r -= (double)histo[i] * (depths[i] + FastLog2(histo[i])); |
| } |
| return TO_BROTLI_BOOL(r >= 0.0); |
| } |
| } |
| |
| /* Acceptable loss for uncompressible speedup is 2% */ |
| #define MIN_RATIO 980 |
| |
| static BROTLI_INLINE BROTLI_BOOL ShouldUseUncompressedMode( |
| const uint8_t* metablock_start, const uint8_t* next_emit, |
| const size_t insertlen, const size_t literal_ratio) { |
| const size_t compressed = (size_t)(next_emit - metablock_start); |
| if (compressed * 50 > insertlen) { |
| return BROTLI_FALSE; |
| } else { |
| return TO_BROTLI_BOOL(literal_ratio > MIN_RATIO); |
| } |
| } |
| |
| static void EmitUncompressedMetaBlock(const uint8_t* begin, const uint8_t* end, |
| const size_t storage_ix_start, |
| size_t* storage_ix, uint8_t* storage) { |
| const size_t len = (size_t)(end - begin); |
| RewindBitPosition(storage_ix_start, storage_ix, storage); |
| BrotliStoreMetaBlockHeader(len, 1, storage_ix, storage); |
| *storage_ix = (*storage_ix + 7u) & ~7u; |
| memcpy(&storage[*storage_ix >> 3], begin, len); |
| *storage_ix += len << 3; |
| storage[*storage_ix >> 3] = 0; |
| } |
| |
| static uint32_t kCmdHistoSeed[128] = { |
| 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, |
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, |
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, |
| 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
| 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, |
| 1, 1, 1, 1, 0, 0, 0, 0, |
| }; |
| |
| static BROTLI_INLINE void BrotliCompressFragmentFastImpl( |
| MemoryManager* m, const uint8_t* input, size_t input_size, |
| BROTLI_BOOL is_last, int* table, size_t table_bits, uint8_t cmd_depth[128], |
| uint16_t cmd_bits[128], size_t* cmd_code_numbits, uint8_t* cmd_code, |
| size_t* storage_ix, uint8_t* storage) { |
| uint32_t cmd_histo[128]; |
| const uint8_t* ip_end; |
| |
| /* "next_emit" is a pointer to the first byte that is not covered by a |
| previous copy. Bytes between "next_emit" and the start of the next copy or |
| the end of the input will be emitted as literal bytes. */ |
| const uint8_t* next_emit = input; |
| /* Save the start of the first block for position and distance computations. |
| */ |
| const uint8_t* base_ip = input; |
| |
| static const size_t kFirstBlockSize = 3 << 15; |
| static const size_t kMergeBlockSize = 1 << 16; |
| |
| const size_t kInputMarginBytes = BROTLI_WINDOW_GAP; |
| const size_t kMinMatchLen = 5; |
| |
| const uint8_t* metablock_start = input; |
| size_t block_size = BROTLI_MIN(size_t, input_size, kFirstBlockSize); |
| size_t total_block_size = block_size; |
| /* Save the bit position of the MLEN field of the meta-block header, so that |
| we can update it later if we decide to extend this meta-block. */ |
| size_t mlen_storage_ix = *storage_ix + 3; |
| |
| uint8_t lit_depth[256]; |
| uint16_t lit_bits[256]; |
| |
| size_t literal_ratio; |
| |
| const uint8_t* ip; |
| int last_distance; |
| |
| const size_t shift = 64u - table_bits; |
| |
| BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage); |
| /* No block splits, no contexts. */ |
| BrotliWriteBits(13, 0, storage_ix, storage); |
| |
| literal_ratio = BuildAndStoreLiteralPrefixCode( |
| m, input, block_size, lit_depth, lit_bits, storage_ix, storage); |
| if (BROTLI_IS_OOM(m)) return; |
| |
| { |
| /* Store the pre-compressed command and distance prefix codes. */ |
| size_t i; |
| for (i = 0; i + 7 < *cmd_code_numbits; i += 8) { |
| BrotliWriteBits(8, cmd_code[i >> 3], storage_ix, storage); |
| } |
| } |
| BrotliWriteBits(*cmd_code_numbits & 7, cmd_code[*cmd_code_numbits >> 3], |
| storage_ix, storage); |
| |
| emit_commands: |
| /* Initialize the command and distance histograms. We will gather |
| statistics of command and distance codes during the processing |
| of this block and use it to update the command and distance |
| prefix codes for the next block. */ |
| memcpy(cmd_histo, kCmdHistoSeed, sizeof(kCmdHistoSeed)); |
| |
| /* "ip" is the input pointer. */ |
| ip = input; |
| last_distance = -1; |
| ip_end = input + block_size; |
| |
| if (BROTLI_PREDICT_TRUE(block_size >= kInputMarginBytes)) { |
| /* For the last block, we need to keep a 16 bytes margin so that we can be |
| sure that all distances are at most window size - 16. |
| For all other blocks, we only need to keep a margin of 5 bytes so that |
| we don't go over the block size with a copy. */ |
| const size_t len_limit = BROTLI_MIN(size_t, block_size - kMinMatchLen, |
| input_size - kInputMarginBytes); |
| const uint8_t* ip_limit = input + len_limit; |
| |
| uint32_t next_hash; |
| for (next_hash = Hash(++ip, shift); ; ) { |
| /* Step 1: Scan forward in the input looking for a 5-byte-long match. |
| If we get close to exhausting the input then goto emit_remainder. |
| |
| Heuristic match skipping: If 32 bytes are scanned with no matches |
| found, start looking only at every other byte. If 32 more bytes are |
| scanned, look at every third byte, etc.. When a match is found, |
| immediately go back to looking at every byte. This is a small loss |
| (~5% performance, ~0.1% density) for compressible data due to more |
| bookkeeping, but for non-compressible data (such as JPEG) it's a huge |
| win since the compressor quickly "realizes" the data is incompressible |
| and doesn't bother looking for matches everywhere. |
| |
| The "skip" variable keeps track of how many bytes there are since the |
| last match; dividing it by 32 (i.e. right-shifting by five) gives the |
| number of bytes to move ahead for each iteration. */ |
| uint32_t skip = 32; |
| |
| const uint8_t* next_ip = ip; |
| const uint8_t* candidate; |
| BROTLI_DCHECK(next_emit < ip); |
| trawl: |
| do { |
| uint32_t hash = next_hash; |
| uint32_t bytes_between_hash_lookups = skip++ >> 5; |
| BROTLI_DCHECK(hash == Hash(next_ip, shift)); |
| ip = next_ip; |
| next_ip = ip + bytes_between_hash_lookups; |
| if (BROTLI_PREDICT_FALSE(next_ip > ip_limit)) { |
| goto emit_remainder; |
| } |
| next_hash = Hash(next_ip, shift); |
| candidate = ip - last_distance; |
| if (IsMatch(ip, candidate)) { |
| if (BROTLI_PREDICT_TRUE(candidate < ip)) { |
| table[hash] = (int)(ip - base_ip); |
| break; |
| } |
| } |
| candidate = base_ip + table[hash]; |
| BROTLI_DCHECK(candidate >= base_ip); |
| BROTLI_DCHECK(candidate < ip); |
| |
| table[hash] = (int)(ip - base_ip); |
| } while (BROTLI_PREDICT_TRUE(!IsMatch(ip, candidate))); |
| |
| /* Check copy distance. If candidate is not feasible, continue search. |
| Checking is done outside of hot loop to reduce overhead. */ |
| if (ip - candidate > MAX_DISTANCE) goto trawl; |
| |
| /* Step 2: Emit the found match together with the literal bytes from |
| "next_emit" to the bit stream, and then see if we can find a next match |
| immediately afterwards. Repeat until we find no match for the input |
| without emitting some literal bytes. */ |
| |
| { |
| /* We have a 5-byte match at ip, and we need to emit bytes in |
| [next_emit, ip). */ |
| const uint8_t* base = ip; |
| size_t matched = 5 + FindMatchLengthWithLimit( |
| candidate + 5, ip + 5, (size_t)(ip_end - ip) - 5); |
| int distance = (int)(base - candidate); /* > 0 */ |
| size_t insert = (size_t)(base - next_emit); |
| ip += matched; |
| BROTLI_DCHECK(0 == memcmp(base, candidate, matched)); |
| if (BROTLI_PREDICT_TRUE(insert < 6210)) { |
| EmitInsertLen(insert, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| } else if (ShouldUseUncompressedMode(metablock_start, next_emit, insert, |
| literal_ratio)) { |
| EmitUncompressedMetaBlock(metablock_start, base, mlen_storage_ix - 3, |
| storage_ix, storage); |
| input_size -= (size_t)(base - input); |
| input = base; |
| next_emit = input; |
| goto next_block; |
| } else { |
| EmitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| } |
| EmitLiterals(next_emit, insert, lit_depth, lit_bits, |
| storage_ix, storage); |
| if (distance == last_distance) { |
| BrotliWriteBits(cmd_depth[64], cmd_bits[64], storage_ix, storage); |
| ++cmd_histo[64]; |
| } else { |
| EmitDistance((size_t)distance, cmd_depth, cmd_bits, |
| cmd_histo, storage_ix, storage); |
| last_distance = distance; |
| } |
| EmitCopyLenLastDistance(matched, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| |
| next_emit = ip; |
| if (BROTLI_PREDICT_FALSE(ip >= ip_limit)) { |
| goto emit_remainder; |
| } |
| /* We could immediately start working at ip now, but to improve |
| compression we first update "table" with the hashes of some positions |
| within the last copy. */ |
| { |
| uint64_t input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3); |
| uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift); |
| uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift); |
| table[prev_hash] = (int)(ip - base_ip - 3); |
| prev_hash = HashBytesAtOffset(input_bytes, 1, shift); |
| table[prev_hash] = (int)(ip - base_ip - 2); |
| prev_hash = HashBytesAtOffset(input_bytes, 2, shift); |
| table[prev_hash] = (int)(ip - base_ip - 1); |
| |
| candidate = base_ip + table[cur_hash]; |
| table[cur_hash] = (int)(ip - base_ip); |
| } |
| } |
| |
| while (IsMatch(ip, candidate)) { |
| /* We have a 5-byte match at ip, and no need to emit any literal bytes |
| prior to ip. */ |
| const uint8_t* base = ip; |
| size_t matched = 5 + FindMatchLengthWithLimit( |
| candidate + 5, ip + 5, (size_t)(ip_end - ip) - 5); |
| if (ip - candidate > MAX_DISTANCE) break; |
| ip += matched; |
| last_distance = (int)(base - candidate); /* > 0 */ |
| BROTLI_DCHECK(0 == memcmp(base, candidate, matched)); |
| EmitCopyLen(matched, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| EmitDistance((size_t)last_distance, cmd_depth, cmd_bits, |
| cmd_histo, storage_ix, storage); |
| |
| next_emit = ip; |
| if (BROTLI_PREDICT_FALSE(ip >= ip_limit)) { |
| goto emit_remainder; |
| } |
| /* We could immediately start working at ip now, but to improve |
| compression we first update "table" with the hashes of some positions |
| within the last copy. */ |
| { |
| uint64_t input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3); |
| uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift); |
| uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift); |
| table[prev_hash] = (int)(ip - base_ip - 3); |
| prev_hash = HashBytesAtOffset(input_bytes, 1, shift); |
| table[prev_hash] = (int)(ip - base_ip - 2); |
| prev_hash = HashBytesAtOffset(input_bytes, 2, shift); |
| table[prev_hash] = (int)(ip - base_ip - 1); |
| |
| candidate = base_ip + table[cur_hash]; |
| table[cur_hash] = (int)(ip - base_ip); |
| } |
| } |
| |
| next_hash = Hash(++ip, shift); |
| } |
| } |
| |
| emit_remainder: |
| BROTLI_DCHECK(next_emit <= ip_end); |
| input += block_size; |
| input_size -= block_size; |
| block_size = BROTLI_MIN(size_t, input_size, kMergeBlockSize); |
| |
| /* Decide if we want to continue this meta-block instead of emitting the |
| last insert-only command. */ |
| if (input_size > 0 && |
| total_block_size + block_size <= (1 << 20) && |
| ShouldMergeBlock(input, block_size, lit_depth)) { |
| BROTLI_DCHECK(total_block_size > (1 << 16)); |
| /* Update the size of the current meta-block and continue emitting commands. |
| We can do this because the current size and the new size both have 5 |
| nibbles. */ |
| total_block_size += block_size; |
| UpdateBits(20, (uint32_t)(total_block_size - 1), mlen_storage_ix, storage); |
| goto emit_commands; |
| } |
| |
| /* Emit the remaining bytes as literals. */ |
| if (next_emit < ip_end) { |
| const size_t insert = (size_t)(ip_end - next_emit); |
| if (BROTLI_PREDICT_TRUE(insert < 6210)) { |
| EmitInsertLen(insert, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| EmitLiterals(next_emit, insert, lit_depth, lit_bits, storage_ix, storage); |
| } else if (ShouldUseUncompressedMode(metablock_start, next_emit, insert, |
| literal_ratio)) { |
| EmitUncompressedMetaBlock(metablock_start, ip_end, mlen_storage_ix - 3, |
| storage_ix, storage); |
| } else { |
| EmitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo, |
| storage_ix, storage); |
| EmitLiterals(next_emit, insert, lit_depth, lit_bits, |
| storage_ix, storage); |
| } |
| } |
| next_emit = ip_end; |
| |
| next_block: |
| /* If we have more data, write a new meta-block header and prefix codes and |
| then continue emitting commands. */ |
| if (input_size > 0) { |
| metablock_start = input; |
| block_size = BROTLI_MIN(size_t, input_size, kFirstBlockSize); |
| total_block_size = block_size; |
| /* Save the bit position of the MLEN field of the meta-block header, so that |
| we can update it later if we decide to extend this meta-block. */ |
| mlen_storage_ix = *storage_ix + 3; |
| BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage); |
| /* No block splits, no contexts. */ |
| BrotliWriteBits(13, 0, storage_ix, storage); |
| literal_ratio = BuildAndStoreLiteralPrefixCode( |
| m, input, block_size, lit_depth, lit_bits, storage_ix, storage); |
| if (BROTLI_IS_OOM(m)) return; |
| BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depth, cmd_bits, |
| storage_ix, storage); |
| goto emit_commands; |
| } |
| |
| if (!is_last) { |
| /* If this is not the last block, update the command and distance prefix |
| codes for the next block and store the compressed forms. */ |
| cmd_code[0] = 0; |
| *cmd_code_numbits = 0; |
| BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depth, cmd_bits, |
| cmd_code_numbits, cmd_code); |
| } |
| } |
| |
| #define FOR_TABLE_BITS_(X) X(9) X(11) X(13) X(15) |
| |
| #define BAKE_METHOD_PARAM_(B) \ |
| static BROTLI_NOINLINE void BrotliCompressFragmentFastImpl ## B( \ |
| MemoryManager* m, const uint8_t* input, size_t input_size, \ |
| BROTLI_BOOL is_last, int* table, uint8_t cmd_depth[128], \ |
| uint16_t cmd_bits[128], size_t* cmd_code_numbits, uint8_t* cmd_code, \ |
| size_t* storage_ix, uint8_t* storage) { \ |
| BrotliCompressFragmentFastImpl(m, input, input_size, is_last, table, B, \ |
| cmd_depth, cmd_bits, cmd_code_numbits, cmd_code, storage_ix, storage); \ |
| } |
| FOR_TABLE_BITS_(BAKE_METHOD_PARAM_) |
| #undef BAKE_METHOD_PARAM_ |
| |
| void BrotliCompressFragmentFast( |
| MemoryManager* m, const uint8_t* input, size_t input_size, |
| BROTLI_BOOL is_last, int* table, size_t table_size, uint8_t cmd_depth[128], |
| uint16_t cmd_bits[128], size_t* cmd_code_numbits, uint8_t* cmd_code, |
| size_t* storage_ix, uint8_t* storage) { |
| const size_t initial_storage_ix = *storage_ix; |
| const size_t table_bits = Log2FloorNonZero(table_size); |
| |
| if (input_size == 0) { |
| BROTLI_DCHECK(is_last); |
| BrotliWriteBits(1, 1, storage_ix, storage); /* islast */ |
| BrotliWriteBits(1, 1, storage_ix, storage); /* isempty */ |
| *storage_ix = (*storage_ix + 7u) & ~7u; |
| return; |
| } |
| |
| switch (table_bits) { |
| #define CASE_(B) \ |
| case B: \ |
| BrotliCompressFragmentFastImpl ## B( \ |
| m, input, input_size, is_last, table, cmd_depth, cmd_bits, \ |
| cmd_code_numbits, cmd_code, storage_ix, storage); \ |
| break; |
| FOR_TABLE_BITS_(CASE_) |
| #undef CASE_ |
| default: BROTLI_DCHECK(0); break; |
| } |
| |
| /* If output is larger than single uncompressed block, rewrite it. */ |
| if (*storage_ix - initial_storage_ix > 31 + (input_size << 3)) { |
| EmitUncompressedMetaBlock(input, input + input_size, initial_storage_ix, |
| storage_ix, storage); |
| } |
| |
| if (is_last) { |
| BrotliWriteBits(1, 1, storage_ix, storage); /* islast */ |
| BrotliWriteBits(1, 1, storage_ix, storage); /* isempty */ |
| *storage_ix = (*storage_ix + 7u) & ~7u; |
| } |
| } |
| |
| #undef FOR_TABLE_BITS_ |
| |
| #if defined(__cplusplus) || defined(c_plusplus) |
| } /* extern "C" */ |
| #endif |