--- /dev/null
+/* Copyright 2015 Google Inc. All Rights Reserved.\r
+\r
+ Distributed under MIT license.\r
+ See file LICENSE for detail or copy at https://opensource.org/licenses/MIT\r
+*/\r
+\r
+/* Function for fast encoding of an input fragment, independently from the input\r
+ history. This function uses one-pass processing: when we find a backward\r
+ match, we immediately emit the corresponding command and literal codes to\r
+ the bit stream.\r
+\r
+ Adapted from the CompressFragment() function in\r
+ https://github.com/google/snappy/blob/master/snappy.cc */\r
+\r
+#include "./compress_fragment.h"\r
+\r
+#include <string.h> /* memcmp, memcpy, memset */\r
+\r
+#include "../common/types.h"\r
+#include "./brotli_bit_stream.h"\r
+#include "./entropy_encode.h"\r
+#include "./fast_log.h"\r
+#include "./find_match_length.h"\r
+#include "./memory.h"\r
+#include "./port.h"\r
+#include "./write_bits.h"\r
+\r
+\r
+#if defined(__cplusplus) || defined(c_plusplus)\r
+extern "C" {\r
+#endif\r
+\r
+/* kHashMul32 multiplier has these properties:\r
+ * The multiplier must be odd. Otherwise we may lose the highest bit.\r
+ * No long streaks of 1s or 0s.\r
+ * There is no effort to ensure that it is a prime, the oddity is enough\r
+ for this use.\r
+ * The number has been tuned heuristically against compression benchmarks. */\r
+static const uint32_t kHashMul32 = 0x1e35a7bd;\r
+\r
+static BROTLI_INLINE uint32_t Hash(const uint8_t* p, size_t shift) {\r
+ const uint64_t h = (BROTLI_UNALIGNED_LOAD64(p) << 24) * kHashMul32;\r
+ return (uint32_t)(h >> shift);\r
+}\r
+\r
+static BROTLI_INLINE uint32_t HashBytesAtOffset(\r
+ uint64_t v, int offset, size_t shift) {\r
+ assert(offset >= 0);\r
+ assert(offset <= 3);\r
+ {\r
+ const uint64_t h = ((v >> (8 * offset)) << 24) * kHashMul32;\r
+ return (uint32_t)(h >> shift);\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE BROTLI_BOOL IsMatch(const uint8_t* p1, const uint8_t* p2) {\r
+ return TO_BROTLI_BOOL(\r
+ BROTLI_UNALIGNED_LOAD32(p1) == BROTLI_UNALIGNED_LOAD32(p2) &&\r
+ p1[4] == p2[4]);\r
+}\r
+\r
+/* Builds a literal prefix code into "depths" and "bits" based on the statistics\r
+ of the "input" string and stores it into the bit stream.\r
+ Note that the prefix code here is built from the pre-LZ77 input, therefore\r
+ we can only approximate the statistics of the actual literal stream.\r
+ Moreover, for long inputs we build a histogram from a sample of the input\r
+ and thus have to assign a non-zero depth for each literal.\r
+ Returns estimated compression ratio millibytes/char for encoding given input\r
+ with generated code. */\r
+static size_t BuildAndStoreLiteralPrefixCode(MemoryManager* m,\r
+ const uint8_t* input,\r
+ const size_t input_size,\r
+ uint8_t depths[256],\r
+ uint16_t bits[256],\r
+ size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ uint32_t histogram[256] = { 0 };\r
+ size_t histogram_total;\r
+ size_t i;\r
+ if (input_size < (1 << 15)) {\r
+ for (i = 0; i < input_size; ++i) {\r
+ ++histogram[input[i]];\r
+ }\r
+ histogram_total = input_size;\r
+ for (i = 0; i < 256; ++i) {\r
+ /* We weigh the first 11 samples with weight 3 to account for the\r
+ balancing effect of the LZ77 phase on the histogram. */\r
+ const uint32_t adjust = 2 * BROTLI_MIN(uint32_t, histogram[i], 11u);\r
+ histogram[i] += adjust;\r
+ histogram_total += adjust;\r
+ }\r
+ } else {\r
+ static const size_t kSampleRate = 29;\r
+ for (i = 0; i < input_size; i += kSampleRate) {\r
+ ++histogram[input[i]];\r
+ }\r
+ histogram_total = (input_size + kSampleRate - 1) / kSampleRate;\r
+ for (i = 0; i < 256; ++i) {\r
+ /* We add 1 to each population count to avoid 0 bit depths (since this is\r
+ only a sample and we don't know if the symbol appears or not), and we\r
+ weigh the first 11 samples with weight 3 to account for the balancing\r
+ effect of the LZ77 phase on the histogram (more frequent symbols are\r
+ more likely to be in backward references instead as literals). */\r
+ const uint32_t adjust = 1 + 2 * BROTLI_MIN(uint32_t, histogram[i], 11u);\r
+ histogram[i] += adjust;\r
+ histogram_total += adjust;\r
+ }\r
+ }\r
+ BrotliBuildAndStoreHuffmanTreeFast(m, histogram, histogram_total,\r
+ /* max_bits = */ 8,\r
+ depths, bits, storage_ix, storage);\r
+ if (BROTLI_IS_OOM(m)) return 0;\r
+ {\r
+ size_t literal_ratio = 0;\r
+ for (i = 0; i < 256; ++i) {\r
+ if (histogram[i]) literal_ratio += histogram[i] * depths[i];\r
+ }\r
+ /* Estimated encoding ratio, millibytes per symbol. */\r
+ return (literal_ratio * 125) / histogram_total;\r
+ }\r
+}\r
+\r
+/* Builds a command and distance prefix code (each 64 symbols) into "depth" and\r
+ "bits" based on "histogram" and stores it into the bit stream. */\r
+static void BuildAndStoreCommandPrefixCode(const uint32_t histogram[128],\r
+ uint8_t depth[128], uint16_t bits[128], size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ /* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */\r
+ HuffmanTree tree[129];\r
+ uint8_t cmd_depth[BROTLI_NUM_COMMAND_SYMBOLS] = { 0 };\r
+ uint16_t cmd_bits[64];\r
+\r
+ BrotliCreateHuffmanTree(histogram, 64, 15, tree, depth);\r
+ BrotliCreateHuffmanTree(&histogram[64], 64, 14, tree, &depth[64]);\r
+ /* We have to jump through a few hoopes here in order to compute\r
+ the command bits because the symbols are in a different order than in\r
+ the full alphabet. This looks complicated, but having the symbols\r
+ in this order in the command bits saves a few branches in the Emit*\r
+ functions. */\r
+ memcpy(cmd_depth, depth, 24);\r
+ memcpy(cmd_depth + 24, depth + 40, 8);\r
+ memcpy(cmd_depth + 32, depth + 24, 8);\r
+ memcpy(cmd_depth + 40, depth + 48, 8);\r
+ memcpy(cmd_depth + 48, depth + 32, 8);\r
+ memcpy(cmd_depth + 56, depth + 56, 8);\r
+ BrotliConvertBitDepthsToSymbols(cmd_depth, 64, cmd_bits);\r
+ memcpy(bits, cmd_bits, 48);\r
+ memcpy(bits + 24, cmd_bits + 32, 16);\r
+ memcpy(bits + 32, cmd_bits + 48, 16);\r
+ memcpy(bits + 40, cmd_bits + 24, 16);\r
+ memcpy(bits + 48, cmd_bits + 40, 16);\r
+ memcpy(bits + 56, cmd_bits + 56, 16);\r
+ BrotliConvertBitDepthsToSymbols(&depth[64], 64, &bits[64]);\r
+ {\r
+ /* Create the bit length array for the full command alphabet. */\r
+ size_t i;\r
+ memset(cmd_depth, 0, 64); /* only 64 first values were used */\r
+ memcpy(cmd_depth, depth, 8);\r
+ memcpy(cmd_depth + 64, depth + 8, 8);\r
+ memcpy(cmd_depth + 128, depth + 16, 8);\r
+ memcpy(cmd_depth + 192, depth + 24, 8);\r
+ memcpy(cmd_depth + 384, depth + 32, 8);\r
+ for (i = 0; i < 8; ++i) {\r
+ cmd_depth[128 + 8 * i] = depth[40 + i];\r
+ cmd_depth[256 + 8 * i] = depth[48 + i];\r
+ cmd_depth[448 + 8 * i] = depth[56 + i];\r
+ }\r
+ BrotliStoreHuffmanTree(\r
+ cmd_depth, BROTLI_NUM_COMMAND_SYMBOLS, tree, storage_ix, storage);\r
+ }\r
+ BrotliStoreHuffmanTree(&depth[64], 64, tree, storage_ix, storage);\r
+}\r
+\r
+/* REQUIRES: insertlen < 6210 */\r
+static BROTLI_INLINE void EmitInsertLen(size_t insertlen,\r
+ const uint8_t depth[128],\r
+ const uint16_t bits[128],\r
+ uint32_t histo[128],\r
+ size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ if (insertlen < 6) {\r
+ const size_t code = insertlen + 40;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ ++histo[code];\r
+ } else if (insertlen < 130) {\r
+ const size_t tail = insertlen - 2;\r
+ const uint32_t nbits = Log2FloorNonZero(tail) - 1u;\r
+ const size_t prefix = tail >> nbits;\r
+ const size_t inscode = (nbits << 1) + prefix + 42;\r
+ BrotliWriteBits(depth[inscode], bits[inscode], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage);\r
+ ++histo[inscode];\r
+ } else if (insertlen < 2114) {\r
+ const size_t tail = insertlen - 66;\r
+ const uint32_t nbits = Log2FloorNonZero(tail);\r
+ const size_t code = nbits + 50;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage);\r
+ ++histo[code];\r
+ } else {\r
+ BrotliWriteBits(depth[61], bits[61], storage_ix, storage);\r
+ BrotliWriteBits(12, insertlen - 2114, storage_ix, storage);\r
+ ++histo[21];\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void EmitLongInsertLen(size_t insertlen,\r
+ const uint8_t depth[128],\r
+ const uint16_t bits[128],\r
+ uint32_t histo[128],\r
+ size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ if (insertlen < 22594) {\r
+ BrotliWriteBits(depth[62], bits[62], storage_ix, storage);\r
+ BrotliWriteBits(14, insertlen - 6210, storage_ix, storage);\r
+ ++histo[22];\r
+ } else {\r
+ BrotliWriteBits(depth[63], bits[63], storage_ix, storage);\r
+ BrotliWriteBits(24, insertlen - 22594, storage_ix, storage);\r
+ ++histo[23];\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void EmitCopyLen(size_t copylen,\r
+ const uint8_t depth[128],\r
+ const uint16_t bits[128],\r
+ uint32_t histo[128],\r
+ size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ if (copylen < 10) {\r
+ BrotliWriteBits(\r
+ depth[copylen + 14], bits[copylen + 14], storage_ix, storage);\r
+ ++histo[copylen + 14];\r
+ } else if (copylen < 134) {\r
+ const size_t tail = copylen - 6;\r
+ const uint32_t nbits = Log2FloorNonZero(tail) - 1u;\r
+ const size_t prefix = tail >> nbits;\r
+ const size_t code = (nbits << 1) + prefix + 20;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage);\r
+ ++histo[code];\r
+ } else if (copylen < 2118) {\r
+ const size_t tail = copylen - 70;\r
+ const uint32_t nbits = Log2FloorNonZero(tail);\r
+ const size_t code = nbits + 28;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage);\r
+ ++histo[code];\r
+ } else {\r
+ BrotliWriteBits(depth[39], bits[39], storage_ix, storage);\r
+ BrotliWriteBits(24, copylen - 2118, storage_ix, storage);\r
+ ++histo[47];\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void EmitCopyLenLastDistance(size_t copylen,\r
+ const uint8_t depth[128],\r
+ const uint16_t bits[128],\r
+ uint32_t histo[128],\r
+ size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ if (copylen < 12) {\r
+ BrotliWriteBits(depth[copylen - 4], bits[copylen - 4], storage_ix, storage);\r
+ ++histo[copylen - 4];\r
+ } else if (copylen < 72) {\r
+ const size_t tail = copylen - 8;\r
+ const uint32_t nbits = Log2FloorNonZero(tail) - 1;\r
+ const size_t prefix = tail >> nbits;\r
+ const size_t code = (nbits << 1) + prefix + 4;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - (prefix << nbits), storage_ix, storage);\r
+ ++histo[code];\r
+ } else if (copylen < 136) {\r
+ const size_t tail = copylen - 8;\r
+ const size_t code = (tail >> 5) + 30;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(5, tail & 31, storage_ix, storage);\r
+ BrotliWriteBits(depth[64], bits[64], storage_ix, storage);\r
+ ++histo[code];\r
+ ++histo[64];\r
+ } else if (copylen < 2120) {\r
+ const size_t tail = copylen - 72;\r
+ const uint32_t nbits = Log2FloorNonZero(tail);\r
+ const size_t code = nbits + 28;\r
+ BrotliWriteBits(depth[code], bits[code], storage_ix, storage);\r
+ BrotliWriteBits(nbits, tail - ((size_t)1 << nbits), storage_ix, storage);\r
+ BrotliWriteBits(depth[64], bits[64], storage_ix, storage);\r
+ ++histo[code];\r
+ ++histo[64];\r
+ } else {\r
+ BrotliWriteBits(depth[39], bits[39], storage_ix, storage);\r
+ BrotliWriteBits(24, copylen - 2120, storage_ix, storage);\r
+ BrotliWriteBits(depth[64], bits[64], storage_ix, storage);\r
+ ++histo[47];\r
+ ++histo[64];\r
+ }\r
+}\r
+\r
+static BROTLI_INLINE void EmitDistance(size_t distance,\r
+ const uint8_t depth[128],\r
+ const uint16_t bits[128],\r
+ uint32_t histo[128],\r
+ size_t* storage_ix, uint8_t* storage) {\r
+ const size_t d = distance + 3;\r
+ const uint32_t nbits = Log2FloorNonZero(d) - 1u;\r
+ const size_t prefix = (d >> nbits) & 1;\r
+ const size_t offset = (2 + prefix) << nbits;\r
+ const size_t distcode = 2 * (nbits - 1) + prefix + 80;\r
+ BrotliWriteBits(depth[distcode], bits[distcode], storage_ix, storage);\r
+ BrotliWriteBits(nbits, d - offset, storage_ix, storage);\r
+ ++histo[distcode];\r
+}\r
+\r
+static BROTLI_INLINE void EmitLiterals(const uint8_t* input, const size_t len,\r
+ const uint8_t depth[256],\r
+ const uint16_t bits[256],\r
+ size_t* storage_ix, uint8_t* storage) {\r
+ size_t j;\r
+ for (j = 0; j < len; j++) {\r
+ const uint8_t lit = input[j];\r
+ BrotliWriteBits(depth[lit], bits[lit], storage_ix, storage);\r
+ }\r
+}\r
+\r
+/* REQUIRES: len <= 1 << 20. */\r
+static void BrotliStoreMetaBlockHeader(\r
+ size_t len, BROTLI_BOOL is_uncompressed, size_t* storage_ix,\r
+ uint8_t* storage) {\r
+ /* ISLAST */\r
+ BrotliWriteBits(1, 0, storage_ix, storage);\r
+ if (len <= (1U << 16)) {\r
+ /* MNIBBLES is 4 */\r
+ BrotliWriteBits(2, 0, storage_ix, storage);\r
+ BrotliWriteBits(16, len - 1, storage_ix, storage);\r
+ } else {\r
+ /* MNIBBLES is 5 */\r
+ BrotliWriteBits(2, 1, storage_ix, storage);\r
+ BrotliWriteBits(20, len - 1, storage_ix, storage);\r
+ }\r
+ /* ISUNCOMPRESSED */\r
+ BrotliWriteBits(1, (uint64_t)is_uncompressed, storage_ix, storage);\r
+}\r
+\r
+static void UpdateBits(size_t n_bits, uint32_t bits, size_t pos,\r
+ uint8_t *array) {\r
+ while (n_bits > 0) {\r
+ size_t byte_pos = pos >> 3;\r
+ size_t n_unchanged_bits = pos & 7;\r
+ size_t n_changed_bits = BROTLI_MIN(size_t, n_bits, 8 - n_unchanged_bits);\r
+ size_t total_bits = n_unchanged_bits + n_changed_bits;\r
+ uint32_t mask =\r
+ (~((1u << total_bits) - 1u)) | ((1u << n_unchanged_bits) - 1u);\r
+ uint32_t unchanged_bits = array[byte_pos] & mask;\r
+ uint32_t changed_bits = bits & ((1u << n_changed_bits) - 1u);\r
+ array[byte_pos] =\r
+ (uint8_t)((changed_bits << n_unchanged_bits) | unchanged_bits);\r
+ n_bits -= n_changed_bits;\r
+ bits >>= n_changed_bits;\r
+ pos += n_changed_bits;\r
+ }\r
+}\r
+\r
+static void RewindBitPosition(const size_t new_storage_ix,\r
+ size_t* storage_ix, uint8_t* storage) {\r
+ const size_t bitpos = new_storage_ix & 7;\r
+ const size_t mask = (1u << bitpos) - 1;\r
+ storage[new_storage_ix >> 3] &= (uint8_t)mask;\r
+ *storage_ix = new_storage_ix;\r
+}\r
+\r
+static BROTLI_BOOL ShouldMergeBlock(\r
+ const uint8_t* data, size_t len, const uint8_t* depths) {\r
+ size_t histo[256] = { 0 };\r
+ static const size_t kSampleRate = 43;\r
+ size_t i;\r
+ for (i = 0; i < len; i += kSampleRate) {\r
+ ++histo[data[i]];\r
+ }\r
+ {\r
+ const size_t total = (len + kSampleRate - 1) / kSampleRate;\r
+ double r = (FastLog2(total) + 0.5) * (double)total + 200;\r
+ for (i = 0; i < 256; ++i) {\r
+ r -= (double)histo[i] * (depths[i] + FastLog2(histo[i]));\r
+ }\r
+ return TO_BROTLI_BOOL(r >= 0.0);\r
+ }\r
+}\r
+\r
+/* Acceptable loss for uncompressible speedup is 2% */\r
+#define MIN_RATIO 980\r
+\r
+static BROTLI_INLINE BROTLI_BOOL ShouldUseUncompressedMode(\r
+ const uint8_t* metablock_start, const uint8_t* next_emit,\r
+ const size_t insertlen, const size_t literal_ratio) {\r
+ const size_t compressed = (size_t)(next_emit - metablock_start);\r
+ if (compressed * 50 > insertlen) {\r
+ return BROTLI_FALSE;\r
+ } else {\r
+ return TO_BROTLI_BOOL(literal_ratio > MIN_RATIO);\r
+ }\r
+}\r
+\r
+static void EmitUncompressedMetaBlock(const uint8_t* begin, const uint8_t* end,\r
+ const size_t storage_ix_start,\r
+ size_t* storage_ix, uint8_t* storage) {\r
+ const size_t len = (size_t)(end - begin);\r
+ RewindBitPosition(storage_ix_start, storage_ix, storage);\r
+ BrotliStoreMetaBlockHeader(len, 1, storage_ix, storage);\r
+ *storage_ix = (*storage_ix + 7u) & ~7u;\r
+ memcpy(&storage[*storage_ix >> 3], begin, len);\r
+ *storage_ix += len << 3;\r
+ storage[*storage_ix >> 3] = 0;\r
+}\r
+\r
+static uint32_t kCmdHistoSeed[128] = {\r
+ 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1,\r
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1,\r
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0,\r
+ 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,\r
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,\r
+ 1, 1, 1, 1, 0, 0, 0, 0,\r
+};\r
+\r
+void BrotliCompressFragmentFast(MemoryManager* m,\r
+ const uint8_t* input, size_t input_size,\r
+ BROTLI_BOOL is_last,\r
+ int* table, size_t table_size,\r
+ uint8_t cmd_depth[128], uint16_t cmd_bits[128],\r
+ size_t* cmd_code_numbits, uint8_t* cmd_code,\r
+ size_t* storage_ix, uint8_t* storage) {\r
+ uint32_t cmd_histo[128];\r
+ const uint8_t* ip_end;\r
+\r
+ /* "next_emit" is a pointer to the first byte that is not covered by a\r
+ previous copy. Bytes between "next_emit" and the start of the next copy or\r
+ the end of the input will be emitted as literal bytes. */\r
+ const uint8_t* next_emit = input;\r
+ /* Save the start of the first block for position and distance computations.\r
+ */\r
+ const uint8_t* base_ip = input;\r
+\r
+ static const size_t kFirstBlockSize = 3 << 15;\r
+ static const size_t kMergeBlockSize = 1 << 16;\r
+\r
+ const size_t kInputMarginBytes = 16;\r
+ const size_t kMinMatchLen = 5;\r
+\r
+ const uint8_t* metablock_start = input;\r
+ size_t block_size = BROTLI_MIN(size_t, input_size, kFirstBlockSize);\r
+ size_t total_block_size = block_size;\r
+ /* Save the bit position of the MLEN field of the meta-block header, so that\r
+ we can update it later if we decide to extend this meta-block. */\r
+ size_t mlen_storage_ix = *storage_ix + 3;\r
+\r
+ uint8_t lit_depth[256];\r
+ uint16_t lit_bits[256];\r
+\r
+ size_t literal_ratio;\r
+\r
+ const uint8_t* ip;\r
+ int last_distance;\r
+\r
+ const size_t shift = 64u - Log2FloorNonZero(table_size);\r
+ assert(table_size);\r
+ assert(table_size <= (1u << 31));\r
+ /* table must be power of two */\r
+ assert((table_size & (table_size - 1)) == 0);\r
+ assert(table_size - 1 ==\r
+ (size_t)(MAKE_UINT64_T(0xFFFFFFFF, 0xFFFFFF) >> shift));\r
+\r
+ if (input_size == 0) {\r
+ assert(is_last);\r
+ BrotliWriteBits(1, 1, storage_ix, storage); /* islast */\r
+ BrotliWriteBits(1, 1, storage_ix, storage); /* isempty */\r
+ *storage_ix = (*storage_ix + 7u) & ~7u;\r
+ return;\r
+ }\r
+\r
+ BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage);\r
+ /* No block splits, no contexts. */\r
+ BrotliWriteBits(13, 0, storage_ix, storage);\r
+\r
+ literal_ratio = BuildAndStoreLiteralPrefixCode(\r
+ m, input, block_size, lit_depth, lit_bits, storage_ix, storage);\r
+ if (BROTLI_IS_OOM(m)) return;\r
+\r
+ {\r
+ /* Store the pre-compressed command and distance prefix codes. */\r
+ size_t i;\r
+ for (i = 0; i + 7 < *cmd_code_numbits; i += 8) {\r
+ BrotliWriteBits(8, cmd_code[i >> 3], storage_ix, storage);\r
+ }\r
+ }\r
+ BrotliWriteBits(*cmd_code_numbits & 7, cmd_code[*cmd_code_numbits >> 3],\r
+ storage_ix, storage);\r
+\r
+ emit_commands:\r
+ /* Initialize the command and distance histograms. We will gather\r
+ statistics of command and distance codes during the processing\r
+ of this block and use it to update the command and distance\r
+ prefix codes for the next block. */\r
+ memcpy(cmd_histo, kCmdHistoSeed, sizeof(kCmdHistoSeed));\r
+\r
+ /* "ip" is the input pointer. */\r
+ ip = input;\r
+ last_distance = -1;\r
+ ip_end = input + block_size;\r
+\r
+ if (PREDICT_TRUE(block_size >= kInputMarginBytes)) {\r
+ /* For the last block, we need to keep a 16 bytes margin so that we can be\r
+ sure that all distances are at most window size - 16.\r
+ For all other blocks, we only need to keep a margin of 5 bytes so that\r
+ we don't go over the block size with a copy. */\r
+ const size_t len_limit = BROTLI_MIN(size_t, block_size - kMinMatchLen,\r
+ input_size - kInputMarginBytes);\r
+ const uint8_t* ip_limit = input + len_limit;\r
+\r
+ uint32_t next_hash;\r
+ for (next_hash = Hash(++ip, shift); ; ) {\r
+ /* Step 1: Scan forward in the input looking for a 5-byte-long match.\r
+ If we get close to exhausting the input then goto emit_remainder.\r
+\r
+ Heuristic match skipping: If 32 bytes are scanned with no matches\r
+ found, start looking only at every other byte. If 32 more bytes are\r
+ scanned, look at every third byte, etc.. When a match is found,\r
+ immediately go back to looking at every byte. This is a small loss\r
+ (~5% performance, ~0.1% density) for compressible data due to more\r
+ bookkeeping, but for non-compressible data (such as JPEG) it's a huge\r
+ win since the compressor quickly "realizes" the data is incompressible\r
+ and doesn't bother looking for matches everywhere.\r
+\r
+ The "skip" variable keeps track of how many bytes there are since the\r
+ last match; dividing it by 32 (ie. right-shifting by five) gives the\r
+ number of bytes to move ahead for each iteration. */\r
+ uint32_t skip = 32;\r
+\r
+ const uint8_t* next_ip = ip;\r
+ const uint8_t* candidate;\r
+ assert(next_emit < ip);\r
+\r
+ do {\r
+ uint32_t hash = next_hash;\r
+ uint32_t bytes_between_hash_lookups = skip++ >> 5;\r
+ assert(hash == Hash(next_ip, shift));\r
+ ip = next_ip;\r
+ next_ip = ip + bytes_between_hash_lookups;\r
+ if (PREDICT_FALSE(next_ip > ip_limit)) {\r
+ goto emit_remainder;\r
+ }\r
+ next_hash = Hash(next_ip, shift);\r
+ candidate = ip - last_distance;\r
+ if (IsMatch(ip, candidate)) {\r
+ if (PREDICT_TRUE(candidate < ip)) {\r
+ table[hash] = (int)(ip - base_ip);\r
+ break;\r
+ }\r
+ }\r
+ candidate = base_ip + table[hash];\r
+ assert(candidate >= base_ip);\r
+ assert(candidate < ip);\r
+\r
+ table[hash] = (int)(ip - base_ip);\r
+ } while (PREDICT_TRUE(!IsMatch(ip, candidate)));\r
+\r
+ /* Step 2: Emit the found match together with the literal bytes from\r
+ "next_emit" to the bit stream, and then see if we can find a next macth\r
+ immediately afterwards. Repeat until we find no match for the input\r
+ without emitting some literal bytes. */\r
+\r
+ {\r
+ /* We have a 5-byte match at ip, and we need to emit bytes in\r
+ [next_emit, ip). */\r
+ const uint8_t* base = ip;\r
+ size_t matched = 5 + FindMatchLengthWithLimit(\r
+ candidate + 5, ip + 5, (size_t)(ip_end - ip) - 5);\r
+ int distance = (int)(base - candidate); /* > 0 */\r
+ size_t insert = (size_t)(base - next_emit);\r
+ ip += matched;\r
+ assert(0 == memcmp(base, candidate, matched));\r
+ if (PREDICT_TRUE(insert < 6210)) {\r
+ EmitInsertLen(insert, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+ } else if (ShouldUseUncompressedMode(metablock_start, next_emit, insert,\r
+ literal_ratio)) {\r
+ EmitUncompressedMetaBlock(metablock_start, base, mlen_storage_ix - 3,\r
+ storage_ix, storage);\r
+ input_size -= (size_t)(base - input);\r
+ input = base;\r
+ next_emit = input;\r
+ goto next_block;\r
+ } else {\r
+ EmitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+ }\r
+ EmitLiterals(next_emit, insert, lit_depth, lit_bits,\r
+ storage_ix, storage);\r
+ if (distance == last_distance) {\r
+ BrotliWriteBits(cmd_depth[64], cmd_bits[64], storage_ix, storage);\r
+ ++cmd_histo[64];\r
+ } else {\r
+ EmitDistance((size_t)distance, cmd_depth, cmd_bits,\r
+ cmd_histo, storage_ix, storage);\r
+ last_distance = distance;\r
+ }\r
+ EmitCopyLenLastDistance(matched, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+\r
+ next_emit = ip;\r
+ if (PREDICT_FALSE(ip >= ip_limit)) {\r
+ goto emit_remainder;\r
+ }\r
+ /* We could immediately start working at ip now, but to improve\r
+ compression we first update "table" with the hashes of some positions\r
+ within the last copy. */\r
+ {\r
+ uint64_t input_bytes = BROTLI_UNALIGNED_LOAD64(ip - 3);\r
+ uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift);\r
+ uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 3);\r
+ prev_hash = HashBytesAtOffset(input_bytes, 1, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 2);\r
+ prev_hash = HashBytesAtOffset(input_bytes, 2, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 1);\r
+\r
+ candidate = base_ip + table[cur_hash];\r
+ table[cur_hash] = (int)(ip - base_ip);\r
+ }\r
+ }\r
+\r
+ while (IsMatch(ip, candidate)) {\r
+ /* We have a 5-byte match at ip, and no need to emit any literal bytes\r
+ prior to ip. */\r
+ const uint8_t* base = ip;\r
+ size_t matched = 5 + FindMatchLengthWithLimit(\r
+ candidate + 5, ip + 5, (size_t)(ip_end - ip) - 5);\r
+ ip += matched;\r
+ last_distance = (int)(base - candidate); /* > 0 */\r
+ assert(0 == memcmp(base, candidate, matched));\r
+ EmitCopyLen(matched, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+ EmitDistance((size_t)last_distance, cmd_depth, cmd_bits,\r
+ cmd_histo, storage_ix, storage);\r
+\r
+ next_emit = ip;\r
+ if (PREDICT_FALSE(ip >= ip_limit)) {\r
+ goto emit_remainder;\r
+ }\r
+ /* We could immediately start working at ip now, but to improve\r
+ compression we first update "table" with the hashes of some positions\r
+ within the last copy. */\r
+ {\r
+ uint64_t input_bytes = BROTLI_UNALIGNED_LOAD64(ip - 3);\r
+ uint32_t prev_hash = HashBytesAtOffset(input_bytes, 0, shift);\r
+ uint32_t cur_hash = HashBytesAtOffset(input_bytes, 3, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 3);\r
+ prev_hash = HashBytesAtOffset(input_bytes, 1, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 2);\r
+ prev_hash = HashBytesAtOffset(input_bytes, 2, shift);\r
+ table[prev_hash] = (int)(ip - base_ip - 1);\r
+\r
+ candidate = base_ip + table[cur_hash];\r
+ table[cur_hash] = (int)(ip - base_ip);\r
+ }\r
+ }\r
+\r
+ next_hash = Hash(++ip, shift);\r
+ }\r
+ }\r
+\r
+ emit_remainder:\r
+ assert(next_emit <= ip_end);\r
+ input += block_size;\r
+ input_size -= block_size;\r
+ block_size = BROTLI_MIN(size_t, input_size, kMergeBlockSize);\r
+\r
+ /* Decide if we want to continue this meta-block instead of emitting the\r
+ last insert-only command. */\r
+ if (input_size > 0 &&\r
+ total_block_size + block_size <= (1 << 20) &&\r
+ ShouldMergeBlock(input, block_size, lit_depth)) {\r
+ assert(total_block_size > (1 << 16));\r
+ /* Update the size of the current meta-block and continue emitting commands.\r
+ We can do this because the current size and the new size both have 5\r
+ nibbles. */\r
+ total_block_size += block_size;\r
+ UpdateBits(20, (uint32_t)(total_block_size - 1), mlen_storage_ix, storage);\r
+ goto emit_commands;\r
+ }\r
+\r
+ /* Emit the remaining bytes as literals. */\r
+ if (next_emit < ip_end) {\r
+ const size_t insert = (size_t)(ip_end - next_emit);\r
+ if (PREDICT_TRUE(insert < 6210)) {\r
+ EmitInsertLen(insert, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+ EmitLiterals(next_emit, insert, lit_depth, lit_bits, storage_ix, storage);\r
+ } else if (ShouldUseUncompressedMode(metablock_start, next_emit, insert,\r
+ literal_ratio)) {\r
+ EmitUncompressedMetaBlock(metablock_start, ip_end, mlen_storage_ix - 3,\r
+ storage_ix, storage);\r
+ } else {\r
+ EmitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo,\r
+ storage_ix, storage);\r
+ EmitLiterals(next_emit, insert, lit_depth, lit_bits,\r
+ storage_ix, storage);\r
+ }\r
+ }\r
+ next_emit = ip_end;\r
+\r
+next_block:\r
+ /* If we have more data, write a new meta-block header and prefix codes and\r
+ then continue emitting commands. */\r
+ if (input_size > 0) {\r
+ metablock_start = input;\r
+ block_size = BROTLI_MIN(size_t, input_size, kFirstBlockSize);\r
+ total_block_size = block_size;\r
+ /* Save the bit position of the MLEN field of the meta-block header, so that\r
+ we can update it later if we decide to extend this meta-block. */\r
+ mlen_storage_ix = *storage_ix + 3;\r
+ BrotliStoreMetaBlockHeader(block_size, 0, storage_ix, storage);\r
+ /* No block splits, no contexts. */\r
+ BrotliWriteBits(13, 0, storage_ix, storage);\r
+ literal_ratio = BuildAndStoreLiteralPrefixCode(\r
+ m, input, block_size, lit_depth, lit_bits, storage_ix, storage);\r
+ if (BROTLI_IS_OOM(m)) return;\r
+ BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depth, cmd_bits,\r
+ storage_ix, storage);\r
+ goto emit_commands;\r
+ }\r
+\r
+ if (is_last) {\r
+ BrotliWriteBits(1, 1, storage_ix, storage); /* islast */\r
+ BrotliWriteBits(1, 1, storage_ix, storage); /* isempty */\r
+ *storage_ix = (*storage_ix + 7u) & ~7u;\r
+ } else {\r
+ /* If this is not the last block, update the command and distance prefix\r
+ codes for the next block and store the compressed forms. */\r
+ cmd_code[0] = 0;\r
+ *cmd_code_numbits = 0;\r
+ BuildAndStoreCommandPrefixCode(cmd_histo, cmd_depth, cmd_bits,\r
+ cmd_code_numbits, cmd_code);\r
+ }\r
+}\r
+\r
+#if defined(__cplusplus) || defined(c_plusplus)\r
+} /* extern "C" */\r
+#endif\r
projects / mirror_edk2.git / blobdiff