| /* Copyright 2014 Google Inc. All Rights Reserved. |
| |
| Distributed under MIT license. |
| See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
| */ |
| |
| // Brotli bit stream functions to support the low level format. There are no |
| // compression algorithms here, just the right ordering of bits to match the |
| // specs. |
| |
| #include "./brotli_bit_stream.h" |
| |
| #include <algorithm> |
| #include <cstdlib> /* free, malloc */ |
| #include <cstring> |
| #include <limits> |
| #include <vector> |
| |
| #include "./bit_cost.h" |
| #include "./context.h" |
| #include "./entropy_encode.h" |
| #include "./entropy_encode_static.h" |
| #include "./fast_log.h" |
| #include "./prefix.h" |
| #include "./write_bits.h" |
| |
| namespace brotli { |
| |
| namespace { |
| |
| static const size_t kMaxHuffmanTreeSize = 2 * kNumCommandPrefixes + 1; |
| // Context map alphabet has 256 context id symbols plus max 16 rle symbols. |
| static const size_t kContextMapAlphabetSize = 256 + 16; |
| // Block type alphabet has 256 block id symbols plus 2 special symbols. |
| static const size_t kBlockTypeAlphabetSize = 256 + 2; |
| |
| // nibblesbits represents the 2 bits to encode MNIBBLES (0-3) |
| // REQUIRES: length > 0 |
| // REQUIRES: length <= (1 << 24) |
| void EncodeMlen(size_t length, uint64_t* bits, |
| size_t* numbits, uint64_t* nibblesbits) { |
| assert(length > 0); |
| assert(length <= (1 << 24)); |
| length--; // MLEN - 1 is encoded |
| size_t lg = length == 0 ? 1 : Log2FloorNonZero( |
| static_cast<uint32_t>(length)) + 1; |
| assert(lg <= 24); |
| size_t mnibbles = (lg < 16 ? 16 : (lg + 3)) / 4; |
| *nibblesbits = mnibbles - 4; |
| *numbits = mnibbles * 4; |
| *bits = length; |
| } |
| |
| static inline void StoreCommandExtra( |
| const Command& cmd, size_t* storage_ix, uint8_t* storage) { |
| uint32_t copylen_code = cmd.copy_len_code(); |
| uint16_t inscode = GetInsertLengthCode(cmd.insert_len_); |
| uint16_t copycode = GetCopyLengthCode(copylen_code); |
| uint32_t insnumextra = GetInsertExtra(inscode); |
| uint64_t insextraval = cmd.insert_len_ - GetInsertBase(inscode); |
| uint64_t copyextraval = copylen_code - GetCopyBase(copycode); |
| uint64_t bits = (copyextraval << insnumextra) | insextraval; |
| WriteBits(insnumextra + GetCopyExtra(copycode), bits, storage_ix, storage); |
| } |
| |
| } // namespace |
| |
| void StoreVarLenUint8(size_t n, size_t* storage_ix, uint8_t* storage) { |
| if (n == 0) { |
| WriteBits(1, 0, storage_ix, storage); |
| } else { |
| WriteBits(1, 1, storage_ix, storage); |
| size_t nbits = Log2FloorNonZero(n); |
| WriteBits(3, nbits, storage_ix, storage); |
| WriteBits(nbits, n - (1 << nbits), storage_ix, storage); |
| } |
| } |
| |
| void StoreCompressedMetaBlockHeader(bool final_block, |
| size_t length, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| // Write ISLAST bit. |
| WriteBits(1, final_block, storage_ix, storage); |
| // Write ISEMPTY bit. |
| if (final_block) { |
| WriteBits(1, 0, storage_ix, storage); |
| } |
| |
| uint64_t lenbits; |
| size_t nlenbits; |
| uint64_t nibblesbits; |
| EncodeMlen(length, &lenbits, &nlenbits, &nibblesbits); |
| WriteBits(2, nibblesbits, storage_ix, storage); |
| WriteBits(nlenbits, lenbits, storage_ix, storage); |
| |
| if (!final_block) { |
| // Write ISUNCOMPRESSED bit. |
| WriteBits(1, 0, storage_ix, storage); |
| } |
| } |
| |
| void StoreUncompressedMetaBlockHeader(size_t length, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| // Write ISLAST bit. Uncompressed block cannot be the last one, so set to 0. |
| WriteBits(1, 0, storage_ix, storage); |
| uint64_t lenbits; |
| size_t nlenbits; |
| uint64_t nibblesbits; |
| EncodeMlen(length, &lenbits, &nlenbits, &nibblesbits); |
| WriteBits(2, nibblesbits, storage_ix, storage); |
| WriteBits(nlenbits, lenbits, storage_ix, storage); |
| // Write ISUNCOMPRESSED bit. |
| WriteBits(1, 1, storage_ix, storage); |
| } |
| |
| void StoreHuffmanTreeOfHuffmanTreeToBitMask( |
| const int num_codes, |
| const uint8_t *code_length_bitdepth, |
| size_t *storage_ix, |
| uint8_t *storage) { |
| static const uint8_t kStorageOrder[kCodeLengthCodes] = { |
| 1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15 |
| }; |
| // The bit lengths of the Huffman code over the code length alphabet |
| // are compressed with the following static Huffman code: |
| // Symbol Code |
| // ------ ---- |
| // 0 00 |
| // 1 1110 |
| // 2 110 |
| // 3 01 |
| // 4 10 |
| // 5 1111 |
| static const uint8_t kHuffmanBitLengthHuffmanCodeSymbols[6] = { |
| 0, 7, 3, 2, 1, 15 |
| }; |
| static const uint8_t kHuffmanBitLengthHuffmanCodeBitLengths[6] = { |
| 2, 4, 3, 2, 2, 4 |
| }; |
| |
| // Throw away trailing zeros: |
| size_t codes_to_store = kCodeLengthCodes; |
| if (num_codes > 1) { |
| for (; codes_to_store > 0; --codes_to_store) { |
| if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) { |
| break; |
| } |
| } |
| } |
| size_t skip_some = 0; // skips none. |
| if (code_length_bitdepth[kStorageOrder[0]] == 0 && |
| code_length_bitdepth[kStorageOrder[1]] == 0) { |
| skip_some = 2; // skips two. |
| if (code_length_bitdepth[kStorageOrder[2]] == 0) { |
| skip_some = 3; // skips three. |
| } |
| } |
| WriteBits(2, skip_some, storage_ix, storage); |
| for (size_t i = skip_some; i < codes_to_store; ++i) { |
| size_t l = code_length_bitdepth[kStorageOrder[i]]; |
| WriteBits(kHuffmanBitLengthHuffmanCodeBitLengths[l], |
| kHuffmanBitLengthHuffmanCodeSymbols[l], storage_ix, storage); |
| } |
| } |
| |
| static void StoreHuffmanTreeToBitMask( |
| const size_t huffman_tree_size, |
| const uint8_t* huffman_tree, |
| const uint8_t* huffman_tree_extra_bits, |
| const uint8_t* code_length_bitdepth, |
| const uint16_t* code_length_bitdepth_symbols, |
| size_t * __restrict storage_ix, |
| uint8_t * __restrict storage) { |
| for (size_t i = 0; i < huffman_tree_size; ++i) { |
| size_t ix = huffman_tree[i]; |
| WriteBits(code_length_bitdepth[ix], code_length_bitdepth_symbols[ix], |
| storage_ix, storage); |
| // Extra bits |
| switch (ix) { |
| case 16: |
| WriteBits(2, huffman_tree_extra_bits[i], storage_ix, storage); |
| break; |
| case 17: |
| WriteBits(3, huffman_tree_extra_bits[i], storage_ix, storage); |
| break; |
| } |
| } |
| } |
| |
| static void StoreSimpleHuffmanTree(const uint8_t* depths, |
| size_t symbols[4], |
| size_t num_symbols, |
| size_t max_bits, |
| size_t *storage_ix, uint8_t *storage) { |
| // value of 1 indicates a simple Huffman code |
| WriteBits(2, 1, storage_ix, storage); |
| WriteBits(2, num_symbols - 1, storage_ix, storage); // NSYM - 1 |
| |
| // Sort |
| for (size_t i = 0; i < num_symbols; i++) { |
| for (size_t j = i + 1; j < num_symbols; j++) { |
| if (depths[symbols[j]] < depths[symbols[i]]) { |
| std::swap(symbols[j], symbols[i]); |
| } |
| } |
| } |
| |
| if (num_symbols == 2) { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| } else if (num_symbols == 3) { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| WriteBits(max_bits, symbols[2], storage_ix, storage); |
| } else { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| WriteBits(max_bits, symbols[2], storage_ix, storage); |
| WriteBits(max_bits, symbols[3], storage_ix, storage); |
| // tree-select |
| WriteBits(1, depths[symbols[0]] == 1 ? 1 : 0, storage_ix, storage); |
| } |
| } |
| |
| // num = alphabet size |
| // depths = symbol depths |
| void StoreHuffmanTree(const uint8_t* depths, size_t num, |
| HuffmanTree* tree, |
| size_t *storage_ix, uint8_t *storage) { |
| // Write the Huffman tree into the brotli-representation. |
| // The command alphabet is the largest, so this allocation will fit all |
| // alphabets. |
| assert(num <= kNumCommandPrefixes); |
| uint8_t huffman_tree[kNumCommandPrefixes]; |
| uint8_t huffman_tree_extra_bits[kNumCommandPrefixes]; |
| size_t huffman_tree_size = 0; |
| WriteHuffmanTree(depths, num, &huffman_tree_size, huffman_tree, |
| huffman_tree_extra_bits); |
| |
| // Calculate the statistics of the Huffman tree in brotli-representation. |
| uint32_t huffman_tree_histogram[kCodeLengthCodes] = { 0 }; |
| for (size_t i = 0; i < huffman_tree_size; ++i) { |
| ++huffman_tree_histogram[huffman_tree[i]]; |
| } |
| |
| int num_codes = 0; |
| int code = 0; |
| for (int i = 0; i < kCodeLengthCodes; ++i) { |
| if (huffman_tree_histogram[i]) { |
| if (num_codes == 0) { |
| code = i; |
| num_codes = 1; |
| } else if (num_codes == 1) { |
| num_codes = 2; |
| break; |
| } |
| } |
| } |
| |
| // Calculate another Huffman tree to use for compressing both the |
| // earlier Huffman tree with. |
| uint8_t code_length_bitdepth[kCodeLengthCodes] = { 0 }; |
| uint16_t code_length_bitdepth_symbols[kCodeLengthCodes] = { 0 }; |
| CreateHuffmanTree(&huffman_tree_histogram[0], kCodeLengthCodes, |
| 5, tree, &code_length_bitdepth[0]); |
| ConvertBitDepthsToSymbols(code_length_bitdepth, kCodeLengthCodes, |
| &code_length_bitdepth_symbols[0]); |
| |
| // Now, we have all the data, let's start storing it |
| StoreHuffmanTreeOfHuffmanTreeToBitMask(num_codes, code_length_bitdepth, |
| storage_ix, storage); |
| |
| if (num_codes == 1) { |
| code_length_bitdepth[code] = 0; |
| } |
| |
| // Store the real huffman tree now. |
| StoreHuffmanTreeToBitMask(huffman_tree_size, |
| huffman_tree, |
| huffman_tree_extra_bits, |
| &code_length_bitdepth[0], |
| code_length_bitdepth_symbols, |
| storage_ix, storage); |
| } |
| |
| void BuildAndStoreHuffmanTree(const uint32_t *histogram, |
| const size_t length, |
| HuffmanTree* tree, |
| uint8_t* depth, |
| uint16_t* bits, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| size_t count = 0; |
| size_t s4[4] = { 0 }; |
| for (size_t i = 0; i < length; i++) { |
| if (histogram[i]) { |
| if (count < 4) { |
| s4[count] = i; |
| } else if (count > 4) { |
| break; |
| } |
| count++; |
| } |
| } |
| |
| size_t max_bits_counter = length - 1; |
| size_t max_bits = 0; |
| while (max_bits_counter) { |
| max_bits_counter >>= 1; |
| ++max_bits; |
| } |
| |
| if (count <= 1) { |
| WriteBits(4, 1, storage_ix, storage); |
| WriteBits(max_bits, s4[0], storage_ix, storage); |
| return; |
| } |
| |
| CreateHuffmanTree(histogram, length, 15, tree, depth); |
| ConvertBitDepthsToSymbols(depth, length, bits); |
| |
| if (count <= 4) { |
| StoreSimpleHuffmanTree(depth, s4, count, max_bits, storage_ix, storage); |
| } else { |
| StoreHuffmanTree(depth, length, tree, storage_ix, storage); |
| } |
| } |
| |
| static inline bool SortHuffmanTree(const HuffmanTree& v0, |
| const HuffmanTree& v1) { |
| return v0.total_count_ < v1.total_count_; |
| } |
| |
| void BuildAndStoreHuffmanTreeFast(const uint32_t *histogram, |
| const size_t histogram_total, |
| const size_t max_bits, |
| uint8_t* depth, |
| uint16_t* bits, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| size_t count = 0; |
| size_t symbols[4] = { 0 }; |
| size_t length = 0; |
| size_t total = histogram_total; |
| while (total != 0) { |
| if (histogram[length]) { |
| if (count < 4) { |
| symbols[count] = length; |
| } |
| ++count; |
| total -= histogram[length]; |
| } |
| ++length; |
| } |
| |
| if (count <= 1) { |
| WriteBits(4, 1, storage_ix, storage); |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| return; |
| } |
| |
| const size_t max_tree_size = 2 * length + 1; |
| HuffmanTree* const tree = |
| static_cast<HuffmanTree*>(malloc(max_tree_size * sizeof(HuffmanTree))); |
| for (uint32_t count_limit = 1; ; count_limit *= 2) { |
| HuffmanTree* node = tree; |
| for (size_t i = length; i != 0;) { |
| --i; |
| if (histogram[i]) { |
| if (PREDICT_TRUE(histogram[i] >= count_limit)) { |
| *node = HuffmanTree(histogram[i], -1, static_cast<int16_t>(i)); |
| } else { |
| *node = HuffmanTree(count_limit, -1, static_cast<int16_t>(i)); |
| } |
| ++node; |
| } |
| } |
| const int n = static_cast<int>(node - tree); |
| std::sort(tree, node, SortHuffmanTree); |
| // The nodes are: |
| // [0, n): the sorted leaf nodes that we start with. |
| // [n]: we add a sentinel here. |
| // [n + 1, 2n): new parent nodes are added here, starting from |
| // (n+1). These are naturally in ascending order. |
| // [2n]: we add a sentinel at the end as well. |
| // There will be (2n+1) elements at the end. |
| const HuffmanTree sentinel(std::numeric_limits<int>::max(), -1, -1); |
| *node++ = sentinel; |
| *node++ = sentinel; |
| |
| int i = 0; // Points to the next leaf node. |
| int j = n + 1; // Points to the next non-leaf node. |
| for (int k = n - 1; k > 0; --k) { |
| int left, right; |
| if (tree[i].total_count_ <= tree[j].total_count_) { |
| left = i; |
| ++i; |
| } else { |
| left = j; |
| ++j; |
| } |
| if (tree[i].total_count_ <= tree[j].total_count_) { |
| right = i; |
| ++i; |
| } else { |
| right = j; |
| ++j; |
| } |
| // The sentinel node becomes the parent node. |
| node[-1].total_count_ = |
| tree[left].total_count_ + tree[right].total_count_; |
| node[-1].index_left_ = static_cast<int16_t>(left); |
| node[-1].index_right_or_value_ = static_cast<int16_t>(right); |
| // Add back the last sentinel node. |
| *node++ = sentinel; |
| } |
| SetDepth(tree[2 * n - 1], &tree[0], depth, 0); |
| // We need to pack the Huffman tree in 14 bits. |
| // If this was not successful, add fake entities to the lowest values |
| // and retry. |
| if (PREDICT_TRUE(*std::max_element(&depth[0], &depth[length]) <= 14)) { |
| break; |
| } |
| } |
| free(tree); |
| ConvertBitDepthsToSymbols(depth, length, bits); |
| if (count <= 4) { |
| // value of 1 indicates a simple Huffman code |
| WriteBits(2, 1, storage_ix, storage); |
| WriteBits(2, count - 1, storage_ix, storage); // NSYM - 1 |
| |
| // Sort |
| for (size_t i = 0; i < count; i++) { |
| for (size_t j = i + 1; j < count; j++) { |
| if (depth[symbols[j]] < depth[symbols[i]]) { |
| std::swap(symbols[j], symbols[i]); |
| } |
| } |
| } |
| |
| if (count == 2) { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| } else if (count == 3) { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| WriteBits(max_bits, symbols[2], storage_ix, storage); |
| } else { |
| WriteBits(max_bits, symbols[0], storage_ix, storage); |
| WriteBits(max_bits, symbols[1], storage_ix, storage); |
| WriteBits(max_bits, symbols[2], storage_ix, storage); |
| WriteBits(max_bits, symbols[3], storage_ix, storage); |
| // tree-select |
| WriteBits(1, depth[symbols[0]] == 1 ? 1 : 0, storage_ix, storage); |
| } |
| } else { |
| // Complex Huffman Tree |
| StoreStaticCodeLengthCode(storage_ix, storage); |
| |
| // Actual rle coding. |
| uint8_t previous_value = 8; |
| for (size_t i = 0; i < length;) { |
| const uint8_t value = depth[i]; |
| size_t reps = 1; |
| for (size_t k = i + 1; k < length && depth[k] == value; ++k) { |
| ++reps; |
| } |
| i += reps; |
| if (value == 0) { |
| WriteBits(kZeroRepsDepth[reps], kZeroRepsBits[reps], |
| storage_ix, storage); |
| } else { |
| if (previous_value != value) { |
| WriteBits(kCodeLengthDepth[value], kCodeLengthBits[value], |
| storage_ix, storage); |
| --reps; |
| } |
| if (reps < 3) { |
| while (reps != 0) { |
| reps--; |
| WriteBits(kCodeLengthDepth[value], kCodeLengthBits[value], |
| storage_ix, storage); |
| } |
| } else { |
| reps -= 3; |
| WriteBits(kNonZeroRepsDepth[reps], kNonZeroRepsBits[reps], |
| storage_ix, storage); |
| } |
| previous_value = value; |
| } |
| } |
| } |
| } |
| |
| static size_t IndexOf(const uint8_t* v, size_t v_size, uint8_t value) { |
| size_t i = 0; |
| for (; i < v_size; ++i) { |
| if (v[i] == value) return i; |
| } |
| return i; |
| } |
| |
| static void MoveToFront(uint8_t* v, size_t index) { |
| uint8_t value = v[index]; |
| for (size_t i = index; i != 0; --i) { |
| v[i] = v[i - 1]; |
| } |
| v[0] = value; |
| } |
| |
| static void MoveToFrontTransform(const uint32_t* __restrict v_in, |
| const size_t v_size, |
| uint32_t* v_out) { |
| if (v_size == 0) { |
| return; |
| } |
| uint32_t max_value = *std::max_element(v_in, v_in + v_size); |
| assert(max_value < 256u); |
| uint8_t mtf[256]; |
| size_t mtf_size = max_value + 1; |
| for (uint32_t i = 0; i <= max_value; ++i) { |
| mtf[i] = static_cast<uint8_t>(i); |
| } |
| for (size_t i = 0; i < v_size; ++i) { |
| size_t index = IndexOf(mtf, mtf_size, static_cast<uint8_t>(v_in[i])); |
| assert(index < mtf_size); |
| v_out[i] = static_cast<uint32_t>(index); |
| MoveToFront(mtf, index); |
| } |
| } |
| |
| // Finds runs of zeros in v[0..in_size) and replaces them with a prefix code of |
| // the run length plus extra bits (lower 9 bits is the prefix code and the rest |
| // are the extra bits). Non-zero values in v[] are shifted by |
| // *max_length_prefix. Will not create prefix codes bigger than the initial |
| // value of *max_run_length_prefix. The prefix code of run length L is simply |
| // Log2Floor(L) and the number of extra bits is the same as the prefix code. |
| static void RunLengthCodeZeros(const size_t in_size, |
| uint32_t* __restrict v, |
| size_t* __restrict out_size, |
| uint32_t* __restrict max_run_length_prefix) { |
| uint32_t max_reps = 0; |
| for (size_t i = 0; i < in_size;) { |
| for (; i < in_size && v[i] != 0; ++i) ; |
| uint32_t reps = 0; |
| for (; i < in_size && v[i] == 0; ++i) { |
| ++reps; |
| } |
| max_reps = std::max(reps, max_reps); |
| } |
| uint32_t max_prefix = max_reps > 0 ? Log2FloorNonZero(max_reps) : 0; |
| max_prefix = std::min(max_prefix, *max_run_length_prefix); |
| *max_run_length_prefix = max_prefix; |
| *out_size = 0; |
| for (size_t i = 0; i < in_size;) { |
| assert(*out_size <= i); |
| if (v[i] != 0) { |
| v[*out_size] = v[i] + *max_run_length_prefix; |
| ++i; |
| ++(*out_size); |
| } else { |
| uint32_t reps = 1; |
| for (size_t k = i + 1; k < in_size && v[k] == 0; ++k) { |
| ++reps; |
| } |
| i += reps; |
| while (reps != 0) { |
| if (reps < (2u << max_prefix)) { |
| uint32_t run_length_prefix = Log2FloorNonZero(reps); |
| const uint32_t extra_bits = reps - (1u << run_length_prefix); |
| v[*out_size] = run_length_prefix + (extra_bits << 9); |
| ++(*out_size); |
| break; |
| } else { |
| const uint32_t extra_bits = (1u << max_prefix) - 1u; |
| v[*out_size] = max_prefix + (extra_bits << 9); |
| reps -= (2u << max_prefix) - 1u; |
| ++(*out_size); |
| } |
| } |
| } |
| } |
| } |
| |
| void EncodeContextMap(const std::vector<uint32_t>& context_map, |
| size_t num_clusters, |
| HuffmanTree* tree, |
| size_t* storage_ix, uint8_t* storage) { |
| StoreVarLenUint8(num_clusters - 1, storage_ix, storage); |
| |
| if (num_clusters == 1) { |
| return; |
| } |
| |
| uint32_t* rle_symbols = new uint32_t[context_map.size()]; |
| MoveToFrontTransform(&context_map[0], context_map.size(), rle_symbols); |
| uint32_t max_run_length_prefix = 6; |
| size_t num_rle_symbols = 0; |
| RunLengthCodeZeros(context_map.size(), rle_symbols, |
| &num_rle_symbols, &max_run_length_prefix); |
| uint32_t histogram[kContextMapAlphabetSize]; |
| memset(histogram, 0, sizeof(histogram)); |
| static const int kSymbolBits = 9; |
| static const uint32_t kSymbolMask = (1u << kSymbolBits) - 1u; |
| for (size_t i = 0; i < num_rle_symbols; ++i) { |
| ++histogram[rle_symbols[i] & kSymbolMask]; |
| } |
| bool use_rle = max_run_length_prefix > 0; |
| WriteBits(1, use_rle, storage_ix, storage); |
| if (use_rle) { |
| WriteBits(4, max_run_length_prefix - 1, storage_ix, storage); |
| } |
| uint8_t depths[kContextMapAlphabetSize]; |
| uint16_t bits[kContextMapAlphabetSize]; |
| memset(depths, 0, sizeof(depths)); |
| memset(bits, 0, sizeof(bits)); |
| BuildAndStoreHuffmanTree(histogram, num_clusters + max_run_length_prefix, |
| tree, depths, bits, storage_ix, storage); |
| for (size_t i = 0; i < num_rle_symbols; ++i) { |
| const uint32_t rle_symbol = rle_symbols[i] & kSymbolMask; |
| const uint32_t extra_bits_val = rle_symbols[i] >> kSymbolBits; |
| WriteBits(depths[rle_symbol], bits[rle_symbol], storage_ix, storage); |
| if (rle_symbol > 0 && rle_symbol <= max_run_length_prefix) { |
| WriteBits(rle_symbol, extra_bits_val, storage_ix, storage); |
| } |
| } |
| WriteBits(1, 1, storage_ix, storage); // use move-to-front |
| delete[] rle_symbols; |
| } |
| |
| void StoreBlockSwitch(const BlockSplitCode& code, |
| const size_t block_ix, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| if (block_ix > 0) { |
| size_t typecode = code.type_code[block_ix]; |
| WriteBits(code.type_depths[typecode], code.type_bits[typecode], |
| storage_ix, storage); |
| } |
| size_t lencode = code.length_prefix[block_ix]; |
| WriteBits(code.length_depths[lencode], code.length_bits[lencode], |
| storage_ix, storage); |
| WriteBits(code.length_nextra[block_ix], code.length_extra[block_ix], |
| storage_ix, storage); |
| } |
| |
| static void BuildAndStoreBlockSplitCode(const std::vector<uint8_t>& types, |
| const std::vector<uint32_t>& lengths, |
| const size_t num_types, |
| HuffmanTree* tree, |
| BlockSplitCode* code, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| const size_t num_blocks = types.size(); |
| uint32_t type_histo[kBlockTypeAlphabetSize]; |
| uint32_t length_histo[kNumBlockLenPrefixes]; |
| memset(type_histo, 0, (num_types + 2) * sizeof(type_histo[0])); |
| memset(length_histo, 0, sizeof(length_histo)); |
| size_t last_type = 1; |
| size_t second_last_type = 0; |
| code->type_code.resize(num_blocks); |
| code->length_prefix.resize(num_blocks); |
| code->length_nextra.resize(num_blocks); |
| code->length_extra.resize(num_blocks); |
| code->type_depths.resize(num_types + 2); |
| code->type_bits.resize(num_types + 2); |
| memset(code->length_depths, 0, sizeof(code->length_depths)); |
| memset(code->length_bits, 0, sizeof(code->length_bits)); |
| for (size_t i = 0; i < num_blocks; ++i) { |
| size_t type = types[i]; |
| size_t type_code = (type == last_type + 1 ? 1 : |
| type == second_last_type ? 0 : |
| type + 2); |
| second_last_type = last_type; |
| last_type = type; |
| code->type_code[i] = static_cast<uint32_t>(type_code); |
| if (i != 0) ++type_histo[type_code]; |
| GetBlockLengthPrefixCode(lengths[i], |
| &code->length_prefix[i], |
| &code->length_nextra[i], |
| &code->length_extra[i]); |
| ++length_histo[code->length_prefix[i]]; |
| } |
| StoreVarLenUint8(num_types - 1, storage_ix, storage); |
| if (num_types > 1) { |
| BuildAndStoreHuffmanTree(&type_histo[0], num_types + 2, tree, |
| &code->type_depths[0], &code->type_bits[0], |
| storage_ix, storage); |
| BuildAndStoreHuffmanTree(&length_histo[0], kNumBlockLenPrefixes, tree, |
| &code->length_depths[0], &code->length_bits[0], |
| storage_ix, storage); |
| StoreBlockSwitch(*code, 0, storage_ix, storage); |
| } |
| } |
| |
| void StoreTrivialContextMap(size_t num_types, |
| size_t context_bits, |
| HuffmanTree* tree, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| StoreVarLenUint8(num_types - 1, storage_ix, storage); |
| if (num_types > 1) { |
| size_t repeat_code = context_bits - 1u; |
| size_t repeat_bits = (1u << repeat_code) - 1u; |
| size_t alphabet_size = num_types + repeat_code; |
| uint32_t histogram[kContextMapAlphabetSize]; |
| uint8_t depths[kContextMapAlphabetSize]; |
| uint16_t bits[kContextMapAlphabetSize]; |
| memset(histogram, 0, alphabet_size * sizeof(histogram[0])); |
| memset(depths, 0, alphabet_size * sizeof(depths[0])); |
| memset(bits, 0, alphabet_size * sizeof(bits[0])); |
| // Write RLEMAX. |
| WriteBits(1, 1, storage_ix, storage); |
| WriteBits(4, repeat_code - 1, storage_ix, storage); |
| histogram[repeat_code] = static_cast<uint32_t>(num_types); |
| histogram[0] = 1; |
| for (size_t i = context_bits; i < alphabet_size; ++i) { |
| histogram[i] = 1; |
| } |
| BuildAndStoreHuffmanTree(&histogram[0], alphabet_size, tree, |
| &depths[0], &bits[0], |
| storage_ix, storage); |
| for (size_t i = 0; i < num_types; ++i) { |
| size_t code = (i == 0 ? 0 : i + context_bits - 1); |
| WriteBits(depths[code], bits[code], storage_ix, storage); |
| WriteBits(depths[repeat_code], bits[repeat_code], storage_ix, storage); |
| WriteBits(repeat_code, repeat_bits, storage_ix, storage); |
| } |
| // Write IMTF (inverse-move-to-front) bit. |
| WriteBits(1, 1, storage_ix, storage); |
| } |
| } |
| |
| // Manages the encoding of one block category (literal, command or distance). |
| class BlockEncoder { |
| public: |
| BlockEncoder(size_t alphabet_size, |
| size_t num_block_types, |
| const std::vector<uint8_t>& block_types, |
| const std::vector<uint32_t>& block_lengths) |
| : alphabet_size_(alphabet_size), |
| num_block_types_(num_block_types), |
| block_types_(block_types), |
| block_lengths_(block_lengths), |
| block_ix_(0), |
| block_len_(block_lengths.empty() ? 0 : block_lengths[0]), |
| entropy_ix_(0) {} |
| |
| // Creates entropy codes of block lengths and block types and stores them |
| // to the bit stream. |
| void BuildAndStoreBlockSwitchEntropyCodes(HuffmanTree* tree, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| BuildAndStoreBlockSplitCode( |
| block_types_, block_lengths_, num_block_types_, |
| tree, &block_split_code_, storage_ix, storage); |
| } |
| |
| // Creates entropy codes for all block types and stores them to the bit |
| // stream. |
| template<int kSize> |
| void BuildAndStoreEntropyCodes( |
| const std::vector<Histogram<kSize> >& histograms, |
| HuffmanTree* tree, |
| size_t* storage_ix, uint8_t* storage) { |
| depths_.resize(histograms.size() * alphabet_size_); |
| bits_.resize(histograms.size() * alphabet_size_); |
| for (size_t i = 0; i < histograms.size(); ++i) { |
| size_t ix = i * alphabet_size_; |
| BuildAndStoreHuffmanTree(&histograms[i].data_[0], alphabet_size_, |
| tree, |
| &depths_[ix], &bits_[ix], |
| storage_ix, storage); |
| } |
| } |
| |
| // Stores the next symbol with the entropy code of the current block type. |
| // Updates the block type and block length at block boundaries. |
| void StoreSymbol(size_t symbol, size_t* storage_ix, uint8_t* storage) { |
| if (block_len_ == 0) { |
| ++block_ix_; |
| block_len_ = block_lengths_[block_ix_]; |
| entropy_ix_ = block_types_[block_ix_] * alphabet_size_; |
| StoreBlockSwitch(block_split_code_, block_ix_, storage_ix, storage); |
| } |
| --block_len_; |
| size_t ix = entropy_ix_ + symbol; |
| WriteBits(depths_[ix], bits_[ix], storage_ix, storage); |
| } |
| |
| // Stores the next symbol with the entropy code of the current block type and |
| // context value. |
| // Updates the block type and block length at block boundaries. |
| template<int kContextBits> |
| void StoreSymbolWithContext(size_t symbol, size_t context, |
| const std::vector<uint32_t>& context_map, |
| size_t* storage_ix, uint8_t* storage) { |
| if (block_len_ == 0) { |
| ++block_ix_; |
| block_len_ = block_lengths_[block_ix_]; |
| size_t block_type = block_types_[block_ix_]; |
| entropy_ix_ = block_type << kContextBits; |
| StoreBlockSwitch(block_split_code_, block_ix_, storage_ix, storage); |
| } |
| --block_len_; |
| size_t histo_ix = context_map[entropy_ix_ + context]; |
| size_t ix = histo_ix * alphabet_size_ + symbol; |
| WriteBits(depths_[ix], bits_[ix], storage_ix, storage); |
| } |
| |
| private: |
| const size_t alphabet_size_; |
| const size_t num_block_types_; |
| const std::vector<uint8_t>& block_types_; |
| const std::vector<uint32_t>& block_lengths_; |
| BlockSplitCode block_split_code_; |
| size_t block_ix_; |
| size_t block_len_; |
| size_t entropy_ix_; |
| std::vector<uint8_t> depths_; |
| std::vector<uint16_t> bits_; |
| }; |
| |
| static void JumpToByteBoundary(size_t* storage_ix, uint8_t* storage) { |
| *storage_ix = (*storage_ix + 7u) & ~7u; |
| storage[*storage_ix >> 3] = 0; |
| } |
| |
| void StoreMetaBlock(const uint8_t* input, |
| size_t start_pos, |
| size_t length, |
| size_t mask, |
| uint8_t prev_byte, |
| uint8_t prev_byte2, |
| bool is_last, |
| uint32_t num_direct_distance_codes, |
| uint32_t distance_postfix_bits, |
| ContextType literal_context_mode, |
| const brotli::Command *commands, |
| size_t n_commands, |
| const MetaBlockSplit& mb, |
| size_t *storage_ix, |
| uint8_t *storage) { |
| StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage); |
| |
| size_t num_distance_codes = |
| kNumDistanceShortCodes + num_direct_distance_codes + |
| (48u << distance_postfix_bits); |
| |
| HuffmanTree* tree = static_cast<HuffmanTree*>( |
| malloc(kMaxHuffmanTreeSize * sizeof(HuffmanTree))); |
| BlockEncoder literal_enc(256, |
| mb.literal_split.num_types, |
| mb.literal_split.types, |
| mb.literal_split.lengths); |
| BlockEncoder command_enc(kNumCommandPrefixes, |
| mb.command_split.num_types, |
| mb.command_split.types, |
| mb.command_split.lengths); |
| BlockEncoder distance_enc(num_distance_codes, |
| mb.distance_split.num_types, |
| mb.distance_split.types, |
| mb.distance_split.lengths); |
| |
| literal_enc.BuildAndStoreBlockSwitchEntropyCodes(tree, storage_ix, storage); |
| command_enc.BuildAndStoreBlockSwitchEntropyCodes(tree, storage_ix, storage); |
| distance_enc.BuildAndStoreBlockSwitchEntropyCodes(tree, storage_ix, storage); |
| |
| WriteBits(2, distance_postfix_bits, storage_ix, storage); |
| WriteBits(4, num_direct_distance_codes >> distance_postfix_bits, |
| storage_ix, storage); |
| for (size_t i = 0; i < mb.literal_split.num_types; ++i) { |
| WriteBits(2, literal_context_mode, storage_ix, storage); |
| } |
| |
| size_t num_literal_histograms = mb.literal_histograms.size(); |
| if (mb.literal_context_map.empty()) { |
| StoreTrivialContextMap(num_literal_histograms, kLiteralContextBits, tree, |
| storage_ix, storage); |
| } else { |
| EncodeContextMap(mb.literal_context_map, num_literal_histograms, tree, |
| storage_ix, storage); |
| } |
| |
| size_t num_dist_histograms = mb.distance_histograms.size(); |
| if (mb.distance_context_map.empty()) { |
| StoreTrivialContextMap(num_dist_histograms, kDistanceContextBits, tree, |
| storage_ix, storage); |
| } else { |
| EncodeContextMap(mb.distance_context_map, num_dist_histograms, tree, |
| storage_ix, storage); |
| } |
| |
| literal_enc.BuildAndStoreEntropyCodes(mb.literal_histograms, tree, |
| storage_ix, storage); |
| command_enc.BuildAndStoreEntropyCodes(mb.command_histograms, tree, |
| storage_ix, storage); |
| distance_enc.BuildAndStoreEntropyCodes(mb.distance_histograms, tree, |
| storage_ix, storage); |
| free(tree); |
| |
| size_t pos = start_pos; |
| for (size_t i = 0; i < n_commands; ++i) { |
| const Command cmd = commands[i]; |
| size_t cmd_code = cmd.cmd_prefix_; |
| command_enc.StoreSymbol(cmd_code, storage_ix, storage); |
| StoreCommandExtra(cmd, storage_ix, storage); |
| if (mb.literal_context_map.empty()) { |
| for (size_t j = cmd.insert_len_; j != 0; --j) { |
| literal_enc.StoreSymbol(input[pos & mask], storage_ix, storage); |
| ++pos; |
| } |
| } else { |
| for (size_t j = cmd.insert_len_; j != 0; --j) { |
| size_t context = Context(prev_byte, prev_byte2, literal_context_mode); |
| uint8_t literal = input[pos & mask]; |
| literal_enc.StoreSymbolWithContext<kLiteralContextBits>( |
| literal, context, mb.literal_context_map, storage_ix, storage); |
| prev_byte2 = prev_byte; |
| prev_byte = literal; |
| ++pos; |
| } |
| } |
| pos += cmd.copy_len(); |
| if (cmd.copy_len()) { |
| prev_byte2 = input[(pos - 2) & mask]; |
| prev_byte = input[(pos - 1) & mask]; |
| if (cmd.cmd_prefix_ >= 128) { |
| size_t dist_code = cmd.dist_prefix_; |
| uint32_t distnumextra = cmd.dist_extra_ >> 24; |
| uint64_t distextra = cmd.dist_extra_ & 0xffffff; |
| if (mb.distance_context_map.empty()) { |
| distance_enc.StoreSymbol(dist_code, storage_ix, storage); |
| } else { |
| size_t context = cmd.DistanceContext(); |
| distance_enc.StoreSymbolWithContext<kDistanceContextBits>( |
| dist_code, context, mb.distance_context_map, storage_ix, storage); |
| } |
| brotli::WriteBits(distnumextra, distextra, storage_ix, storage); |
| } |
| } |
| } |
| if (is_last) { |
| JumpToByteBoundary(storage_ix, storage); |
| } |
| } |
| |
| static void BuildHistograms(const uint8_t* input, |
| size_t start_pos, |
| size_t mask, |
| const brotli::Command *commands, |
| size_t n_commands, |
| HistogramLiteral* lit_histo, |
| HistogramCommand* cmd_histo, |
| HistogramDistance* dist_histo) { |
| size_t pos = start_pos; |
| for (size_t i = 0; i < n_commands; ++i) { |
| const Command cmd = commands[i]; |
| cmd_histo->Add(cmd.cmd_prefix_); |
| for (size_t j = cmd.insert_len_; j != 0; --j) { |
| lit_histo->Add(input[pos & mask]); |
| ++pos; |
| } |
| pos += cmd.copy_len(); |
| if (cmd.copy_len() && cmd.cmd_prefix_ >= 128) { |
| dist_histo->Add(cmd.dist_prefix_); |
| } |
| } |
| } |
| |
| static void StoreDataWithHuffmanCodes(const uint8_t* input, |
| size_t start_pos, |
| size_t mask, |
| const brotli::Command *commands, |
| size_t n_commands, |
| const uint8_t* lit_depth, |
| const uint16_t* lit_bits, |
| const uint8_t* cmd_depth, |
| const uint16_t* cmd_bits, |
| const uint8_t* dist_depth, |
| const uint16_t* dist_bits, |
| size_t* storage_ix, |
| uint8_t* storage) { |
| size_t pos = start_pos; |
| for (size_t i = 0; i < n_commands; ++i) { |
| const Command cmd = commands[i]; |
| const size_t cmd_code = cmd.cmd_prefix_; |
| WriteBits(cmd_depth[cmd_code], cmd_bits[cmd_code], storage_ix, storage); |
| StoreCommandExtra(cmd, storage_ix, storage); |
| for (size_t j = cmd.insert_len_; j != 0; --j) { |
| const uint8_t literal = input[pos & mask]; |
| WriteBits(lit_depth[literal], lit_bits[literal], storage_ix, storage); |
| ++pos; |
| } |
| pos += cmd.copy_len(); |
| if (cmd.copy_len() && cmd.cmd_prefix_ >= 128) { |
| const size_t dist_code = cmd.dist_prefix_; |
| const uint32_t distnumextra = cmd.dist_extra_ >> 24; |
| const uint32_t distextra = cmd.dist_extra_ & 0xffffff; |
| WriteBits(dist_depth[dist_code], dist_bits[dist_code], |
| storage_ix, storage); |
| WriteBits(distnumextra, distextra, storage_ix, storage); |
| } |
| } |
| } |
| |
| void StoreMetaBlockTrivial(const uint8_t* input, |
| size_t start_pos, |
| size_t length, |
| size_t mask, |
| bool is_last, |
| const brotli::Command *commands, |
| size_t n_commands, |
| size_t *storage_ix, |
| uint8_t *storage) { |
| StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage); |
| |
| HistogramLiteral lit_histo; |
| HistogramCommand cmd_histo; |
| HistogramDistance dist_histo; |
| |
| BuildHistograms(input, start_pos, mask, commands, n_commands, |
| &lit_histo, &cmd_histo, &dist_histo); |
| |
| WriteBits(13, 0, storage_ix, storage); |
| |
| std::vector<uint8_t> lit_depth(256); |
| std::vector<uint16_t> lit_bits(256); |
| std::vector<uint8_t> cmd_depth(kNumCommandPrefixes); |
| std::vector<uint16_t> cmd_bits(kNumCommandPrefixes); |
| std::vector<uint8_t> dist_depth(64); |
| std::vector<uint16_t> dist_bits(64); |
| |
| HuffmanTree* tree = static_cast<HuffmanTree*>( |
| malloc(kMaxHuffmanTreeSize * sizeof(HuffmanTree))); |
| BuildAndStoreHuffmanTree(&lit_histo.data_[0], 256, tree, |
| &lit_depth[0], &lit_bits[0], |
| storage_ix, storage); |
| BuildAndStoreHuffmanTree(&cmd_histo.data_[0], kNumCommandPrefixes, tree, |
| &cmd_depth[0], &cmd_bits[0], |
| storage_ix, storage); |
| BuildAndStoreHuffmanTree(&dist_histo.data_[0], 64, tree, |
| &dist_depth[0], &dist_bits[0], |
| storage_ix, storage); |
| free(tree); |
| StoreDataWithHuffmanCodes(input, start_pos, mask, commands, |
| n_commands, &lit_depth[0], &lit_bits[0], |
| &cmd_depth[0], &cmd_bits[0], |
| &dist_depth[0], &dist_bits[0], |
| storage_ix, storage); |
| if (is_last) { |
| JumpToByteBoundary(storage_ix, storage); |
| } |
| } |
| |
| void StoreMetaBlockFast(const uint8_t* input, |
| size_t start_pos, |
| size_t length, |
| size_t mask, |
| bool is_last, |
| const brotli::Command *commands, |
| size_t n_commands, |
| size_t *storage_ix, |
| uint8_t *storage) { |
| StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage); |
| |
| WriteBits(13, 0, storage_ix, storage); |
| |
| if (n_commands <= 128) { |
| uint32_t histogram[256] = { 0 }; |
| size_t pos = start_pos; |
| size_t num_literals = 0; |
| for (size_t i = 0; i < n_commands; ++i) { |
| const Command cmd = commands[i]; |
| for (size_t j = cmd.insert_len_; j != 0; --j) { |
| ++histogram[input[pos & mask]]; |
| ++pos; |
| } |
| num_literals += cmd.insert_len_; |
| pos += cmd.copy_len(); |
| } |
| uint8_t lit_depth[256] = { 0 }; |
| uint16_t lit_bits[256] = { 0 }; |
| BuildAndStoreHuffmanTreeFast(histogram, num_literals, |
| /* max_bits = */ 8, |
| lit_depth, lit_bits, |
| storage_ix, storage); |
| StoreStaticCommandHuffmanTree(storage_ix, storage); |
| StoreStaticDistanceHuffmanTree(storage_ix, storage); |
| StoreDataWithHuffmanCodes(input, start_pos, mask, commands, |
| n_commands, &lit_depth[0], &lit_bits[0], |
| kStaticCommandCodeDepth, |
| kStaticCommandCodeBits, |
| kStaticDistanceCodeDepth, |
| kStaticDistanceCodeBits, |
| storage_ix, storage); |
| } else { |
| HistogramLiteral lit_histo; |
| HistogramCommand cmd_histo; |
| HistogramDistance dist_histo; |
| BuildHistograms(input, start_pos, mask, commands, n_commands, |
| &lit_histo, &cmd_histo, &dist_histo); |
| std::vector<uint8_t> lit_depth(256); |
| std::vector<uint16_t> lit_bits(256); |
| std::vector<uint8_t> cmd_depth(kNumCommandPrefixes); |
| std::vector<uint16_t> cmd_bits(kNumCommandPrefixes); |
| std::vector<uint8_t> dist_depth(64); |
| std::vector<uint16_t> dist_bits(64); |
| BuildAndStoreHuffmanTreeFast(&lit_histo.data_[0], lit_histo.total_count_, |
| /* max_bits = */ 8, |
| &lit_depth[0], &lit_bits[0], |
| storage_ix, storage); |
| BuildAndStoreHuffmanTreeFast(&cmd_histo.data_[0], cmd_histo.total_count_, |
| /* max_bits = */ 10, |
| &cmd_depth[0], &cmd_bits[0], |
| storage_ix, storage); |
| BuildAndStoreHuffmanTreeFast(&dist_histo.data_[0], dist_histo.total_count_, |
| /* max_bits = */ 6, |
| &dist_depth[0], &dist_bits[0], |
| storage_ix, storage); |
| StoreDataWithHuffmanCodes(input, start_pos, mask, commands, |
| n_commands, &lit_depth[0], &lit_bits[0], |
| &cmd_depth[0], &cmd_bits[0], |
| &dist_depth[0], &dist_bits[0], |
| storage_ix, storage); |
| } |
| |
| if (is_last) { |
| JumpToByteBoundary(storage_ix, storage); |
| } |
| } |
| |
| // This is for storing uncompressed blocks (simple raw storage of |
| // bytes-as-bytes). |
| void StoreUncompressedMetaBlock(bool final_block, |
| const uint8_t * __restrict input, |
| size_t position, size_t mask, |
| size_t len, |
| size_t * __restrict storage_ix, |
| uint8_t * __restrict storage) { |
| StoreUncompressedMetaBlockHeader(len, storage_ix, storage); |
| JumpToByteBoundary(storage_ix, storage); |
| |
| size_t masked_pos = position & mask; |
| if (masked_pos + len > mask + 1) { |
| size_t len1 = mask + 1 - masked_pos; |
| memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len1); |
| *storage_ix += len1 << 3; |
| len -= len1; |
| masked_pos = 0; |
| } |
| memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len); |
| *storage_ix += len << 3; |
| |
| // We need to clear the next 4 bytes to continue to be |
| // compatible with WriteBits. |
| brotli::WriteBitsPrepareStorage(*storage_ix, storage); |
| |
| // Since the uncompressed block itself may not be the final block, add an |
| // empty one after this. |
| if (final_block) { |
| brotli::WriteBits(1, 1, storage_ix, storage); // islast |
| brotli::WriteBits(1, 1, storage_ix, storage); // isempty |
| JumpToByteBoundary(storage_ix, storage); |
| } |
| } |
| |
| void StoreSyncMetaBlock(size_t * __restrict storage_ix, |
| uint8_t * __restrict storage) { |
| // Empty metadata meta-block bit pattern: |
| // 1 bit: is_last (0) |
| // 2 bits: num nibbles (3) |
| // 1 bit: reserved (0) |
| // 2 bits: metadata length bytes (0) |
| WriteBits(6, 6, storage_ix, storage); |
| JumpToByteBoundary(storage_ix, storage); |
| } |
| |
| } // namespace brotli |
