diff options
Diffstat (limited to 'web/server/h2o/libh2o/deps/brotli/enc/compress_fragment.cc')
| -rw-r--r-- | web/server/h2o/libh2o/deps/brotli/enc/compress_fragment.cc | 693 |
1 files changed, 0 insertions, 693 deletions
diff --git a/web/server/h2o/libh2o/deps/brotli/enc/compress_fragment.cc b/web/server/h2o/libh2o/deps/brotli/enc/compress_fragment.cc deleted file mode 100644 index 047d7fe97..000000000 --- a/web/server/h2o/libh2o/deps/brotli/enc/compress_fragment.cc +++ /dev/null @@ -1,693 +0,0 @@ -/* 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" - -#include <algorithm> -#include <cstring> - -#include "./brotli_bit_stream.h" -#include "./entropy_encode.h" -#include "./fast_log.h" -#include "./find_match_length.h" -#include "./port.h" -#include "./write_bits.h" - -namespace brotli { - -// kHashMul32 multiplier has these properties: -// * The multiplier must be odd. Otherwise we may lose the highest bit. -// * No long streaks of 1s or 0s. -// * 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 inline uint32_t Hash(const uint8_t* p, size_t shift) { - const uint64_t h = (BROTLI_UNALIGNED_LOAD64(p) << 24) * kHashMul32; - return static_cast<uint32_t>(h >> shift); -} - -static inline uint32_t HashBytesAtOffset(uint64_t v, int offset, size_t shift) { - assert(offset >= 0); - assert(offset <= 3); - const uint64_t h = ((v >> (8 * offset)) << 24) * kHashMul32; - return static_cast<uint32_t>(h >> shift); -} - -static inline int IsMatch(const uint8_t* p1, const uint8_t* p2) { - return (BROTLI_UNALIGNED_LOAD32(p1) == BROTLI_UNALIGNED_LOAD32(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. -void BuildAndStoreLiteralPrefixCode(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; - if (input_size < (1 << 15)) { - for (size_t i = 0; i < input_size; ++i) { - ++histogram[input[i]]; - } - histogram_total = input_size; - for (size_t 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 * std::min(histogram[i], 11u); - histogram[i] += adjust; - histogram_total += adjust; - } - } else { - static const size_t kSampleRate = 29; - for (size_t i = 0; i < input_size; i += kSampleRate) { - ++histogram[input[i]]; - } - histogram_total = (input_size + kSampleRate - 1) / kSampleRate; - for (size_t 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 * std::min(histogram[i], 11u); - histogram[i] += adjust; - histogram_total += adjust; - } - } - BuildAndStoreHuffmanTreeFast(histogram, histogram_total, - /* max_bits = */ 8, - depths, bits, storage_ix, storage); -} - -// Builds a command and distance prefix code (each 64 symbols) into "depth" and -// "bits" based on "histogram" and stores it into the bit stream. -void BuildAndStoreCommandPrefixCode(const uint32_t histogram[128], - uint8_t depth[128], uint16_t bits[128], - size_t* storage_ix, uint8_t* storage) { - CreateHuffmanTree(histogram, 64, 15, depth); - CreateHuffmanTree(&histogram[64], 64, 14, &depth[64]); - // We have to jump through a few hoopes 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. - uint8_t cmd_depth[64]; - uint16_t cmd_bits[64]; - 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); - ConvertBitDepthsToSymbols(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); - ConvertBitDepthsToSymbols(&depth[64], 64, &bits[64]); - { - // Create the bit length array for the full command alphabet. - uint8_t cmd_depth[704] = { 0 }; - 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 (size_t 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]; - } - StoreHuffmanTree(cmd_depth, 704, storage_ix, storage); - } - StoreHuffmanTree(&depth[64], 64, storage_ix, storage); -} - -// REQUIRES: insertlen < 6210 -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; - WriteBits(depth[code], bits[code], storage_ix, storage); - ++histo[code]; - } else if (insertlen < 130) { - insertlen -= 2; - const uint32_t nbits = Log2FloorNonZero(insertlen) - 1u; - const size_t prefix = insertlen >> nbits; - const size_t inscode = (nbits << 1) + prefix + 42; - WriteBits(depth[inscode], bits[inscode], storage_ix, storage); - WriteBits(nbits, insertlen - (prefix << nbits), storage_ix, storage); - ++histo[inscode]; - } else if (insertlen < 2114) { - insertlen -= 66; - const uint32_t nbits = Log2FloorNonZero(insertlen); - const size_t code = nbits + 50; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(nbits, insertlen - (1 << nbits), storage_ix, storage); - ++histo[code]; - } else { - WriteBits(depth[61], bits[61], storage_ix, storage); - WriteBits(12, insertlen - 2114, storage_ix, storage); - ++histo[21]; - } -} - -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) { - WriteBits(depth[62], bits[62], storage_ix, storage); - WriteBits(14, insertlen - 6210, storage_ix, storage); - ++histo[22]; - } else { - WriteBits(depth[63], bits[63], storage_ix, storage); - WriteBits(24, insertlen - 22594, storage_ix, storage); - ++histo[23]; - } -} - -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) { - WriteBits(depth[copylen + 14], bits[copylen + 14], storage_ix, storage); - ++histo[copylen + 14]; - } else if (copylen < 134) { - copylen -= 6; - const uint32_t nbits = Log2FloorNonZero(copylen) - 1u; - const size_t prefix = copylen >> nbits; - const size_t code = (nbits << 1) + prefix + 20; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(nbits, copylen - (prefix << nbits), storage_ix, storage); - ++histo[code]; - } else if (copylen < 2118) { - copylen -= 70; - const uint32_t nbits = Log2FloorNonZero(copylen); - const size_t code = nbits + 28; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(nbits, copylen - (1 << nbits), storage_ix, storage); - ++histo[code]; - } else { - WriteBits(depth[39], bits[39], storage_ix, storage); - WriteBits(24, copylen - 2118, storage_ix, storage); - ++histo[47]; - } -} - -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) { - WriteBits(depth[copylen - 4], bits[copylen - 4], storage_ix, storage); - ++histo[copylen - 4]; - } else if (copylen < 72) { - copylen -= 8; - const uint32_t nbits = Log2FloorNonZero(copylen) - 1; - const size_t prefix = copylen >> nbits; - const size_t code = (nbits << 1) + prefix + 4; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(nbits, copylen - (prefix << nbits), storage_ix, storage); - ++histo[code]; - } else if (copylen < 136) { - copylen -= 8; - const size_t code = (copylen >> 5) + 30; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(5, copylen & 31, storage_ix, storage); - WriteBits(depth[64], bits[64], storage_ix, storage); - ++histo[code]; - ++histo[64]; - } else if (copylen < 2120) { - copylen -= 72; - const uint32_t nbits = Log2FloorNonZero(copylen); - const size_t code = nbits + 28; - WriteBits(depth[code], bits[code], storage_ix, storage); - WriteBits(nbits, copylen - (1 << nbits), storage_ix, storage); - WriteBits(depth[64], bits[64], storage_ix, storage); - ++histo[code]; - ++histo[64]; - } else { - WriteBits(depth[39], bits[39], storage_ix, storage); - WriteBits(24, copylen - 2120, storage_ix, storage); - WriteBits(depth[64], bits[64], storage_ix, storage); - ++histo[47]; - ++histo[64]; - } -} - -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) { - distance += 3; - const uint32_t nbits = Log2FloorNonZero(distance) - 1u; - const size_t prefix = (distance >> nbits) & 1; - const size_t offset = (2 + prefix) << nbits; - const size_t distcode = 2 * (nbits - 1) + prefix + 80; - WriteBits(depth[distcode], bits[distcode], storage_ix, storage); - WriteBits(nbits, distance - offset, storage_ix, storage); - ++histo[distcode]; -} - -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) { - for (size_t j = 0; j < len; j++) { - const uint8_t lit = input[j]; - WriteBits(depth[lit], bits[lit], storage_ix, storage); - } -} - -// REQUIRES: len <= 1 << 20. -static void StoreMetaBlockHeader( - size_t len, bool is_uncompressed, size_t* storage_ix, uint8_t* storage) { - // ISLAST - WriteBits(1, 0, storage_ix, storage); - if (len <= (1U << 16)) { - // MNIBBLES is 4 - WriteBits(2, 0, storage_ix, storage); - WriteBits(16, len - 1, storage_ix, storage); - } else { - // MNIBBLES is 5 - WriteBits(2, 1, storage_ix, storage); - WriteBits(20, len - 1, storage_ix, storage); - } - // ISUNCOMPRESSED - WriteBits(1, is_uncompressed, storage_ix, storage); -} - -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 = std::min(n_bits, 8 - n_unchanged_bits); - size_t total_bits = n_unchanged_bits + n_changed_bits; - uint32_t mask = (~((1 << total_bits) - 1)) | ((1 << n_unchanged_bits) - 1); - uint32_t unchanged_bits = array[byte_pos] & mask; - uint32_t changed_bits = bits & ((1 << n_changed_bits) - 1); - array[byte_pos] = - static_cast<uint8_t>((changed_bits << n_unchanged_bits) | - unchanged_bits); - n_bits -= n_changed_bits; - bits >>= n_changed_bits; - pos += n_changed_bits; - } -} - -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] &= static_cast<uint8_t>(mask); - *storage_ix = new_storage_ix; -} - -bool ShouldMergeBlock(const uint8_t* data, size_t len, const uint8_t* depths) { - size_t histo[256] = { 0 }; - static const size_t kSampleRate = 43; - for (size_t i = 0; i < len; i += kSampleRate) { - ++histo[data[i]]; - } - const size_t total = (len + kSampleRate - 1) / kSampleRate; - double r = (FastLog2(total) + 0.5) * static_cast<double>(total) + 200; - for (size_t i = 0; i < 256; ++i) { - r -= static_cast<double>(histo[i]) * (depths[i] + FastLog2(histo[i])); - } - return r >= 0.0; -} - -inline bool ShouldUseUncompressedMode(const uint8_t* metablock_start, - const uint8_t* next_emit, - const size_t insertlen, - const uint8_t literal_depths[256]) { - const size_t compressed = static_cast<size_t>(next_emit - metablock_start); - if (compressed * 50 > insertlen) { - return false; - } - static const double kAcceptableLossForUncompressibleSpeedup = 0.02; - static const double kMinEntropy = - 8 * (1.0 - kAcceptableLossForUncompressibleSpeedup); - uint32_t sum = 0; - for (int i = 0; i < 256; ++i) { - const uint32_t n = literal_depths[i]; - sum += n << (15 - n); - } - return sum > static_cast<uint32_t>((1 << 15) * kMinEntropy); -} - -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 = static_cast<size_t>(end - begin); - RewindBitPosition(storage_ix_start, storage_ix, storage); - StoreMetaBlockHeader(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; -} - -void BrotliCompressFragmentFast(const uint8_t* input, size_t input_size, - 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) { - if (input_size == 0) { - assert(is_last); - WriteBits(1, 1, storage_ix, storage); // islast - WriteBits(1, 1, storage_ix, storage); // isempty - *storage_ix = (*storage_ix + 7u) & ~7u; - return; - } - - // "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 uint8_t* metablock_start = input; - size_t block_size = std::min(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; - StoreMetaBlockHeader(block_size, 0, storage_ix, storage); - // No block splits, no contexts. - WriteBits(13, 0, storage_ix, storage); - - uint8_t lit_depth[256] = { 0 }; - uint16_t lit_bits[256] = { 0 }; - BuildAndStoreLiteralPrefixCode(input, block_size, lit_depth, lit_bits, - storage_ix, storage); - - // Store the pre-compressed command and distance prefix codes. - for (size_t i = 0; i + 7 < *cmd_code_numbits; i += 8) { - WriteBits(8, cmd_code[i >> 3], storage_ix, storage); - } - WriteBits(*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. - uint32_t cmd_histo[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, - }; - - // "ip" is the input pointer. - const uint8_t* ip = input; - assert(table_size); - assert(table_size <= (1u << 31)); - assert((table_size & (table_size - 1)) == 0); // table must be power of two - const size_t shift = 64u - Log2FloorNonZero(table_size); - assert(static_cast<size_t>(0xffffffffffffffffU >> shift) == table_size - 1); - const uint8_t* ip_end = input + block_size; - - int last_distance = -1; - const size_t kInputMarginBytes = 16; - const size_t kMinMatchLen = 5; - if (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 = std::min(block_size - kMinMatchLen, - input_size - kInputMarginBytes); - const uint8_t* ip_limit = input + len_limit; - - for (uint32_t next_hash = Hash(++ip, shift); ; ) { - assert(next_emit < ip); - // 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 (ie. 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; - do { - ip = next_ip; - uint32_t hash = next_hash; - assert(hash == Hash(ip, shift)); - uint32_t bytes_between_hash_lookups = skip++ >> 5; - next_ip = ip + bytes_between_hash_lookups; - if (PREDICT_FALSE(next_ip > ip_limit)) { - goto emit_remainder; - } - next_hash = Hash(next_ip, shift); - candidate = ip - last_distance; - if (IsMatch(ip, candidate)) { - if (PREDICT_TRUE(candidate < ip)) { - table[hash] = static_cast<int>(ip - base_ip); - break; - } - } - candidate = base_ip + table[hash]; - assert(candidate >= base_ip); - assert(candidate < ip); - - table[hash] = static_cast<int>(ip - base_ip); - } while (PREDICT_TRUE(!IsMatch(ip, candidate))); - - // 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 macth - // immediately afterwards. Repeat until we find no match for the input - // without emitting some literal bytes. - uint64_t input_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, static_cast<size_t>(ip_end - ip) - 5); - ip += matched; - int distance = static_cast<int>(base - candidate); /* > 0 */ - size_t insert = static_cast<size_t>(base - next_emit); - assert(0 == memcmp(base, candidate, matched)); - if (PREDICT_TRUE(insert < 6210)) { - EmitInsertLen(insert, cmd_depth, cmd_bits, cmd_histo, - storage_ix, storage); - } else if (ShouldUseUncompressedMode(metablock_start, next_emit, insert, - lit_depth)) { - EmitUncompressedMetaBlock(metablock_start, base, mlen_storage_ix - 3, - storage_ix, storage); - input_size -= static_cast<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) { - WriteBits(cmd_depth[64], cmd_bits[64], storage_ix, storage); - ++cmd_histo[64]; - } else { - EmitDistance(static_cast<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 (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. - input_bytes = BROTLI_UNALIGNED_LOAD64(ip - 3); - uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 3); - prev_hash = HashBytesAtOffset(input_bytes, 1, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 2); - prev_hash = HashBytesAtOffset(input_bytes, 2, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 1); - - uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift); - candidate = base_ip + table[cur_hash]; - table[cur_hash] = static_cast<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, static_cast<size_t>(ip_end - ip) - 5); - ip += matched; - last_distance = static_cast<int>(base - candidate); /* > 0 */ - assert(0 == memcmp(base, candidate, matched)); - EmitCopyLen(matched, cmd_depth, cmd_bits, cmd_histo, - storage_ix, storage); - EmitDistance(static_cast<size_t>(last_distance), cmd_depth, cmd_bits, - cmd_histo, storage_ix, storage); - - next_emit = ip; - if (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. - input_bytes = BROTLI_UNALIGNED_LOAD64(ip - 3); - uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 3); - prev_hash = HashBytesAtOffset(input_bytes, 1, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 2); - prev_hash = HashBytesAtOffset(input_bytes, 2, shift); - table[prev_hash] = static_cast<int>(ip - base_ip - 1); - - uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift); - candidate = base_ip + table[cur_hash]; - table[cur_hash] = static_cast<int>(ip - base_ip); - } - - next_hash = Hash(++ip, shift); - } - } - - emit_remainder: - assert(next_emit <= ip_end); - input += block_size; - input_size -= block_size; - block_size = std::min(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)) { - assert(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, static_cast<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 = static_cast<size_t>(ip_end - next_emit); - if (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, - lit_depth)) { - 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 = std::min(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; - StoreMetaBlockHeader(block_size, 0, storage_ix, storage); - // No block splits, no contexts. - WriteBits(13, 0, storage_ix, storage); - memset(lit_depth, 0, sizeof(lit_depth)); - memset(lit_bits, 0, sizeof(lit_bits)); - BuildAndStoreLiteralPrefixCode(input, block_size, lit_depth, lit_bits, - storage_ix, storage); - BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depth, cmd_bits, - storage_ix, storage); - goto emit_commands; - } - - if (is_last) { - WriteBits(1, 1, storage_ix, storage); // islast - WriteBits(1, 1, storage_ix, storage); // isempty - *storage_ix = (*storage_ix + 7u) & ~7u; - } else { - // 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); - } -} - -} // namespace brotli |