diff options
Diffstat (limited to 'modules/brotli/enc/compress_fragment_two_pass.c')
| -rw-r--r-- | modules/brotli/enc/compress_fragment_two_pass.c | 645 |
1 files changed, 645 insertions, 0 deletions
diff --git a/modules/brotli/enc/compress_fragment_two_pass.c b/modules/brotli/enc/compress_fragment_two_pass.c new file mode 100644 index 000000000..f8a560638 --- /dev/null +++ b/modules/brotli/enc/compress_fragment_two_pass.c @@ -0,0 +1,645 @@ +/* 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 two-pass processing: in the first pass we save + the found backward matches and literal bytes into a buffer, and in the + second pass we emit them into the bit stream using prefix codes built based + on the actual command and literal byte histograms. */ + +#include "./compress_fragment_two_pass.h" + +#include <string.h> /* memcmp, memcpy, memset */ + +#include "../common/constants.h" +#include "../common/platform.h" +#include <brotli/types.h> +#include "./bit_cost.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, size_t length) { + const uint64_t h = + (BROTLI_UNALIGNED_LOAD64LE(p) << ((8 - length) * 8)) * kHashMul32; + return (uint32_t)(h >> shift); +} + +static BROTLI_INLINE uint32_t HashBytesAtOffset(uint64_t v, size_t offset, + size_t shift, size_t length) { + BROTLI_DCHECK(offset <= 8 - length); + { + const uint64_t h = ((v >> (8 * offset)) << ((8 - length) * 8)) * kHashMul32; + return (uint32_t)(h >> shift); + } +} + +static BROTLI_INLINE BROTLI_BOOL IsMatch(const uint8_t* p1, const uint8_t* p2, + size_t length) { + if (BrotliUnalignedRead32(p1) == BrotliUnalignedRead32(p2)) { + if (length == 4) return BROTLI_TRUE; + return TO_BROTLI_BOOL(p1[4] == p2[4] && p1[5] == p2[5]); + } + return BROTLI_FALSE; +} + +/* 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, 24); + memcpy(cmd_depth + 24, depth, 8); + memcpy(cmd_depth + 32, depth + 48, 8); + memcpy(cmd_depth + 40, depth + 8, 8); + memcpy(cmd_depth + 48, depth + 56, 8); + memcpy(cmd_depth + 56, depth + 16, 8); + BrotliConvertBitDepthsToSymbols(cmd_depth, 64, cmd_bits); + memcpy(bits, cmd_bits + 24, 16); + memcpy(bits + 8, cmd_bits + 40, 16); + memcpy(bits + 16, cmd_bits + 56, 16); + memcpy(bits + 24, cmd_bits, 48); + memcpy(bits + 48, cmd_bits + 32, 16); + memcpy(bits + 56, cmd_bits + 48, 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 + 24, 8); + memcpy(cmd_depth + 64, depth + 32, 8); + memcpy(cmd_depth + 128, depth + 40, 8); + memcpy(cmd_depth + 192, depth + 48, 8); + memcpy(cmd_depth + 384, depth + 56, 8); + for (i = 0; i < 8; ++i) { + cmd_depth[128 + 8 * i] = depth[i]; + cmd_depth[256 + 8 * i] = depth[8 + i]; + cmd_depth[448 + 8 * i] = depth[16 + i]; + } + BrotliStoreHuffmanTree( + cmd_depth, BROTLI_NUM_COMMAND_SYMBOLS, tree, storage_ix, storage); + } + BrotliStoreHuffmanTree(&depth[64], 64, tree, storage_ix, storage); +} + +static BROTLI_INLINE void EmitInsertLen( + uint32_t insertlen, uint32_t** commands) { + if (insertlen < 6) { + **commands = insertlen; + } else if (insertlen < 130) { + const uint32_t tail = insertlen - 2; + const uint32_t nbits = Log2FloorNonZero(tail) - 1u; + const uint32_t prefix = tail >> nbits; + const uint32_t inscode = (nbits << 1) + prefix + 2; + const uint32_t extra = tail - (prefix << nbits); + **commands = inscode | (extra << 8); + } else if (insertlen < 2114) { + const uint32_t tail = insertlen - 66; + const uint32_t nbits = Log2FloorNonZero(tail); + const uint32_t code = nbits + 10; + const uint32_t extra = tail - (1u << nbits); + **commands = code | (extra << 8); + } else if (insertlen < 6210) { + const uint32_t extra = insertlen - 2114; + **commands = 21 | (extra << 8); + } else if (insertlen < 22594) { + const uint32_t extra = insertlen - 6210; + **commands = 22 | (extra << 8); + } else { + const uint32_t extra = insertlen - 22594; + **commands = 23 | (extra << 8); + } + ++(*commands); +} + +static BROTLI_INLINE void EmitCopyLen(size_t copylen, uint32_t** commands) { + if (copylen < 10) { + **commands = (uint32_t)(copylen + 38); + } else if (copylen < 134) { + const size_t tail = copylen - 6; + const size_t nbits = Log2FloorNonZero(tail) - 1; + const size_t prefix = tail >> nbits; + const size_t code = (nbits << 1) + prefix + 44; + const size_t extra = tail - (prefix << nbits); + **commands = (uint32_t)(code | (extra << 8)); + } else if (copylen < 2118) { + const size_t tail = copylen - 70; + const size_t nbits = Log2FloorNonZero(tail); + const size_t code = nbits + 52; + const size_t extra = tail - ((size_t)1 << nbits); + **commands = (uint32_t)(code | (extra << 8)); + } else { + const size_t extra = copylen - 2118; + **commands = (uint32_t)(63 | (extra << 8)); + } + ++(*commands); +} + +static BROTLI_INLINE void EmitCopyLenLastDistance( + size_t copylen, uint32_t** commands) { + if (copylen < 12) { + **commands = (uint32_t)(copylen + 20); + ++(*commands); + } else if (copylen < 72) { + const size_t tail = copylen - 8; + const size_t nbits = Log2FloorNonZero(tail) - 1; + const size_t prefix = tail >> nbits; + const size_t code = (nbits << 1) + prefix + 28; + const size_t extra = tail - (prefix << nbits); + **commands = (uint32_t)(code | (extra << 8)); + ++(*commands); + } else if (copylen < 136) { + const size_t tail = copylen - 8; + const size_t code = (tail >> 5) + 54; + const size_t extra = tail & 31; + **commands = (uint32_t)(code | (extra << 8)); + ++(*commands); + **commands = 64; + ++(*commands); + } else if (copylen < 2120) { + const size_t tail = copylen - 72; + const size_t nbits = Log2FloorNonZero(tail); + const size_t code = nbits + 52; + const size_t extra = tail - ((size_t)1 << nbits); + **commands = (uint32_t)(code | (extra << 8)); + ++(*commands); + **commands = 64; + ++(*commands); + } else { + const size_t extra = copylen - 2120; + **commands = (uint32_t)(63 | (extra << 8)); + ++(*commands); + **commands = 64; + ++(*commands); + } +} + +static BROTLI_INLINE void EmitDistance(uint32_t distance, uint32_t** commands) { + uint32_t d = distance + 3; + uint32_t nbits = Log2FloorNonZero(d) - 1; + const uint32_t prefix = (d >> nbits) & 1; + const uint32_t offset = (2 + prefix) << nbits; + const uint32_t distcode = 2 * (nbits - 1) + prefix + 80; + uint32_t extra = d - offset; + **commands = distcode | (extra << 8); + ++(*commands); +} + +/* 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 BROTLI_INLINE void CreateCommands(const uint8_t* input, + size_t block_size, size_t input_size, const uint8_t* base_ip, int* table, + size_t table_bits, size_t min_match, + uint8_t** literals, uint32_t** commands) { + /* "ip" is the input pointer. */ + const uint8_t* ip = input; + const size_t shift = 64u - table_bits; + const uint8_t* ip_end = input + block_size; + /* "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; + + int last_distance = -1; + const size_t kInputMarginBytes = BROTLI_WINDOW_GAP; + + 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 - min_match, + input_size - kInputMarginBytes); + const uint8_t* ip_limit = input + len_limit; + + uint32_t next_hash; + for (next_hash = Hash(++ip, shift, min_match); ; ) { + /* Step 1: Scan forward in the input looking for a 6-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; + + BROTLI_DCHECK(next_emit < ip); +trawl: + do { + uint32_t hash = next_hash; + uint32_t bytes_between_hash_lookups = skip++ >> 5; + ip = next_ip; + BROTLI_DCHECK(hash == Hash(ip, shift, min_match)); + next_ip = ip + bytes_between_hash_lookups; + if (BROTLI_PREDICT_FALSE(next_ip > ip_limit)) { + goto emit_remainder; + } + next_hash = Hash(next_ip, shift, min_match); + candidate = ip - last_distance; + if (IsMatch(ip, candidate, min_match)) { + 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, min_match))); + + /* 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", 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 6-byte match at ip, and we need to emit bytes in + [next_emit, ip). */ + const uint8_t* base = ip; + size_t matched = min_match + FindMatchLengthWithLimit( + candidate + min_match, ip + min_match, + (size_t)(ip_end - ip) - min_match); + int distance = (int)(base - candidate); /* > 0 */ + int insert = (int)(base - next_emit); + ip += matched; + BROTLI_DCHECK(0 == memcmp(base, candidate, matched)); + EmitInsertLen((uint32_t)insert, commands); + memcpy(*literals, next_emit, (size_t)insert); + *literals += insert; + if (distance == last_distance) { + **commands = 64; + ++(*commands); + } else { + EmitDistance((uint32_t)distance, commands); + last_distance = distance; + } + EmitCopyLenLastDistance(matched, commands); + + 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; + uint32_t cur_hash; + uint32_t prev_hash; + if (min_match == 4) { + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3); + cur_hash = HashBytesAtOffset(input_bytes, 3, shift, min_match); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 3); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 2); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 1); + } else { + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 5); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 5); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 4); + prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 3); + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 2); + cur_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 2); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 1); + } + + candidate = base_ip + table[cur_hash]; + table[cur_hash] = (int)(ip - base_ip); + } + } + + while (ip - candidate <= MAX_DISTANCE && + IsMatch(ip, candidate, min_match)) { + /* We have a 6-byte match at ip, and no need to emit any + literal bytes prior to ip. */ + const uint8_t* base = ip; + size_t matched = min_match + FindMatchLengthWithLimit( + candidate + min_match, ip + min_match, + (size_t)(ip_end - ip) - min_match); + ip += matched; + last_distance = (int)(base - candidate); /* > 0 */ + BROTLI_DCHECK(0 == memcmp(base, candidate, matched)); + EmitCopyLen(matched, commands); + EmitDistance((uint32_t)last_distance, commands); + + 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; + uint32_t cur_hash; + uint32_t prev_hash; + if (min_match == 4) { + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 3); + cur_hash = HashBytesAtOffset(input_bytes, 3, shift, min_match); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 3); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 2); + prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 1); + } else { + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 5); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 5); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 4); + prev_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 3); + input_bytes = BROTLI_UNALIGNED_LOAD64LE(ip - 2); + cur_hash = HashBytesAtOffset(input_bytes, 2, shift, min_match); + prev_hash = HashBytesAtOffset(input_bytes, 0, shift, min_match); + table[prev_hash] = (int)(ip - base_ip - 2); + prev_hash = HashBytesAtOffset(input_bytes, 1, shift, min_match); + 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, min_match); + } + } + +emit_remainder: + BROTLI_DCHECK(next_emit <= ip_end); + /* Emit the remaining bytes as literals. */ + if (next_emit < ip_end) { + const uint32_t insert = (uint32_t)(ip_end - next_emit); + EmitInsertLen(insert, commands); + memcpy(*literals, next_emit, insert); + *literals += insert; + } +} + +static void StoreCommands(MemoryManager* m, + const uint8_t* literals, const size_t num_literals, + const uint32_t* commands, const size_t num_commands, + size_t* storage_ix, uint8_t* storage) { + static const uint32_t kNumExtraBits[128] = { + 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 7, 8, 9, 10, 12, 14, 24, + 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, + 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 7, 8, 9, 10, 24, + 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, + 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, + 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, + 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, + }; + static const uint32_t kInsertOffset[24] = { + 0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26, 34, 50, 66, 98, 130, 194, 322, 578, + 1090, 2114, 6210, 22594, + }; + + uint8_t lit_depths[256]; + uint16_t lit_bits[256]; + uint32_t lit_histo[256] = { 0 }; + uint8_t cmd_depths[128] = { 0 }; + uint16_t cmd_bits[128] = { 0 }; + uint32_t cmd_histo[128] = { 0 }; + size_t i; + for (i = 0; i < num_literals; ++i) { + ++lit_histo[literals[i]]; + } + BrotliBuildAndStoreHuffmanTreeFast(m, lit_histo, num_literals, + /* max_bits = */ 8, + lit_depths, lit_bits, + storage_ix, storage); + if (BROTLI_IS_OOM(m)) return; + + for (i = 0; i < num_commands; ++i) { + const uint32_t code = commands[i] & 0xFF; + BROTLI_DCHECK(code < 128); + ++cmd_histo[code]; + } + cmd_histo[1] += 1; + cmd_histo[2] += 1; + cmd_histo[64] += 1; + cmd_histo[84] += 1; + BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depths, cmd_bits, + storage_ix, storage); + + for (i = 0; i < num_commands; ++i) { + const uint32_t cmd = commands[i]; + const uint32_t code = cmd & 0xFF; + const uint32_t extra = cmd >> 8; + BROTLI_DCHECK(code < 128); + BrotliWriteBits(cmd_depths[code], cmd_bits[code], storage_ix, storage); + BrotliWriteBits(kNumExtraBits[code], extra, storage_ix, storage); + if (code < 24) { + const uint32_t insert = kInsertOffset[code] + extra; + uint32_t j; + for (j = 0; j < insert; ++j) { + const uint8_t lit = *literals; + BrotliWriteBits(lit_depths[lit], lit_bits[lit], storage_ix, storage); + ++literals; + } + } + } +} + +/* Acceptable loss for uncompressible speedup is 2% */ +#define MIN_RATIO 0.98 +#define SAMPLE_RATE 43 + +static BROTLI_BOOL ShouldCompress( + const uint8_t* input, size_t input_size, size_t num_literals) { + double corpus_size = (double)input_size; + if (num_literals < MIN_RATIO * corpus_size) { + return BROTLI_TRUE; + } else { + uint32_t literal_histo[256] = { 0 }; + const double max_total_bit_cost = corpus_size * 8 * MIN_RATIO / SAMPLE_RATE; + size_t i; + for (i = 0; i < input_size; i += SAMPLE_RATE) { + ++literal_histo[input[i]]; + } + return TO_BROTLI_BOOL(BitsEntropy(literal_histo, 256) < max_total_bit_cost); + } +} + +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 void EmitUncompressedMetaBlock(const uint8_t* input, size_t input_size, + size_t* storage_ix, uint8_t* storage) { + BrotliStoreMetaBlockHeader(input_size, 1, storage_ix, storage); + *storage_ix = (*storage_ix + 7u) & ~7u; + memcpy(&storage[*storage_ix >> 3], input, input_size); + *storage_ix += input_size << 3; + storage[*storage_ix >> 3] = 0; +} + +static BROTLI_INLINE void BrotliCompressFragmentTwoPassImpl( + MemoryManager* m, const uint8_t* input, size_t input_size, + BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf, + int* table, size_t table_bits, size_t min_match, + size_t* storage_ix, uint8_t* storage) { + /* Save the start of the first block for position and distance computations. + */ + const uint8_t* base_ip = input; + BROTLI_UNUSED(is_last); + + while (input_size > 0) { + size_t block_size = + BROTLI_MIN(size_t, input_size, kCompressFragmentTwoPassBlockSize); + uint32_t* commands = command_buf; + uint8_t* literals = literal_buf; + size_t num_literals; + CreateCommands(input, block_size, input_size, base_ip, table, + table_bits, min_match, &literals, &commands); + num_literals = (size_t)(literals - literal_buf); + if (ShouldCompress(input, block_size, num_literals)) { + const size_t num_commands = (size_t)(commands - command_buf); + BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage); + /* No block splits, no contexts. */ + BrotliWriteBits(13, 0, storage_ix, storage); + StoreCommands(m, literal_buf, num_literals, command_buf, num_commands, + storage_ix, storage); + if (BROTLI_IS_OOM(m)) return; + } else { + /* Since we did not find many backward references and the entropy of + the data is close to 8 bits, we can simply emit an uncompressed block. + This makes compression speed of uncompressible data about 3x faster. */ + EmitUncompressedMetaBlock(input, block_size, storage_ix, storage); + } + input += block_size; + input_size -= block_size; + } +} + +#define FOR_TABLE_BITS_(X) \ + X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15) X(16) X(17) + +#define BAKE_METHOD_PARAM_(B) \ +static BROTLI_NOINLINE void BrotliCompressFragmentTwoPassImpl ## B( \ + MemoryManager* m, const uint8_t* input, size_t input_size, \ + BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf, \ + int* table, size_t* storage_ix, uint8_t* storage) { \ + size_t min_match = (B <= 15) ? 4 : 6; \ + BrotliCompressFragmentTwoPassImpl(m, input, input_size, is_last, command_buf,\ + literal_buf, table, B, min_match, storage_ix, storage); \ +} +FOR_TABLE_BITS_(BAKE_METHOD_PARAM_) +#undef BAKE_METHOD_PARAM_ + +void BrotliCompressFragmentTwoPass( + MemoryManager* m, const uint8_t* input, size_t input_size, + BROTLI_BOOL is_last, uint32_t* command_buf, uint8_t* literal_buf, + int* table, size_t table_size, size_t* storage_ix, uint8_t* storage) { + const size_t initial_storage_ix = *storage_ix; + const size_t table_bits = Log2FloorNonZero(table_size); + switch (table_bits) { +#define CASE_(B) \ + case B: \ + BrotliCompressFragmentTwoPassImpl ## B( \ + m, input, input_size, is_last, command_buf, \ + literal_buf, table, 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)) { + RewindBitPosition(initial_storage_ix, storage_ix, storage); + EmitUncompressedMetaBlock(input, input_size, 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 |