package brotli import "math" const maxHuffmanTreeSize = (2*numCommandSymbols + 1) /* The maximum size of Huffman dictionary for distances assuming that NPOSTFIX = 0 and NDIRECT = 0. */ const maxSimpleDistanceAlphabetSize = 140 /* Represents the range of values belonging to a prefix code: [offset, offset + 2^nbits) */ type prefixCodeRange struct { offset uint32 nbits uint32 } var kBlockLengthPrefixCode = [numBlockLenSymbols]prefixCodeRange{ prefixCodeRange{1, 2}, prefixCodeRange{5, 2}, prefixCodeRange{9, 2}, prefixCodeRange{13, 2}, prefixCodeRange{17, 3}, prefixCodeRange{25, 3}, prefixCodeRange{33, 3}, prefixCodeRange{41, 3}, prefixCodeRange{49, 4}, prefixCodeRange{65, 4}, prefixCodeRange{81, 4}, prefixCodeRange{97, 4}, prefixCodeRange{113, 5}, prefixCodeRange{145, 5}, prefixCodeRange{177, 5}, prefixCodeRange{209, 5}, prefixCodeRange{241, 6}, prefixCodeRange{305, 6}, prefixCodeRange{369, 7}, prefixCodeRange{497, 8}, prefixCodeRange{753, 9}, prefixCodeRange{1265, 10}, prefixCodeRange{2289, 11}, prefixCodeRange{4337, 12}, prefixCodeRange{8433, 13}, prefixCodeRange{16625, 24}, } func blockLengthPrefixCode(len uint32) uint32 { var code uint32 if len >= 177 { if len >= 753 { code = 20 } else { code = 14 } } else if len >= 41 { code = 7 } else { code = 0 } for code < (numBlockLenSymbols-1) && len >= kBlockLengthPrefixCode[code+1].offset { code++ } return code } func getBlockLengthPrefixCode(len uint32, code *uint, n_extra *uint32, extra *uint32) { *code = uint(blockLengthPrefixCode(uint32(len))) *n_extra = kBlockLengthPrefixCode[*code].nbits *extra = len - kBlockLengthPrefixCode[*code].offset } type blockTypeCodeCalculator struct { last_type uint second_last_type uint } func initBlockTypeCodeCalculator(self *blockTypeCodeCalculator) { self.last_type = 1 self.second_last_type = 0 } func nextBlockTypeCode(calculator *blockTypeCodeCalculator, type_ byte) uint { var type_code uint if uint(type_) == calculator.last_type+1 { type_code = 1 } else if uint(type_) == calculator.second_last_type { type_code = 0 } else { type_code = uint(type_) + 2 } calculator.second_last_type = calculator.last_type calculator.last_type = uint(type_) return type_code } /* |nibblesbits| represents the 2 bits to encode MNIBBLES (0-3) REQUIRES: length > 0 REQUIRES: length <= (1 << 24) */ func encodeMlen(length uint, bits *uint64, numbits *uint, nibblesbits *uint64) { var lg uint if length == 1 { lg = 1 } else { lg = uint(log2FloorNonZero(uint(uint32(length-1)))) + 1 } var tmp uint if lg < 16 { tmp = 16 } else { tmp = (lg + 3) } var mnibbles uint = tmp / 4 assert(length > 0) assert(length <= 1<<24) assert(lg <= 24) *nibblesbits = uint64(mnibbles) - 4 *numbits = mnibbles * 4 *bits = uint64(length) - 1 } func storeCommandExtra(cmd *command, storage_ix *uint, storage []byte) { var copylen_code uint32 = commandCopyLenCode(cmd) var inscode uint16 = getInsertLengthCode(uint(cmd.insert_len_)) var copycode uint16 = getCopyLengthCode(uint(copylen_code)) var insnumextra uint32 = getInsertExtra(inscode) var insextraval uint64 = uint64(cmd.insert_len_) - uint64(getInsertBase(inscode)) var copyextraval uint64 = uint64(copylen_code) - uint64(getCopyBase(copycode)) var bits uint64 = copyextraval< 0 REQUIRES: length <= (1 << 24) */ func storeCompressedMetaBlockHeader(is_final_block bool, length uint, storage_ix *uint, storage []byte) { var lenbits uint64 var nlenbits uint var nibblesbits uint64 var is_final uint64 if is_final_block { is_final = 1 } else { is_final = 0 } /* Write ISLAST bit. */ writeBits(1, is_final, storage_ix, storage) /* Write ISEMPTY bit. */ if is_final_block { writeBits(1, 0, storage_ix, storage) } encodeMlen(length, &lenbits, &nlenbits, &nibblesbits) writeBits(2, nibblesbits, storage_ix, storage) writeBits(nlenbits, lenbits, storage_ix, storage) if !is_final_block { /* Write ISUNCOMPRESSED bit. */ writeBits(1, 0, storage_ix, storage) } } /* Stores the uncompressed meta-block header. REQUIRES: length > 0 REQUIRES: length <= (1 << 24) */ func storeUncompressedMetaBlockHeader(length uint, storage_ix *uint, storage []byte) { var lenbits uint64 var nlenbits uint var nibblesbits uint64 /* Write ISLAST bit. Uncompressed block cannot be the last one, so set to 0. */ writeBits(1, 0, storage_ix, storage) 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) } var storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder = [codeLengthCodes]byte{1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15} var storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeSymbols = [6]byte{0, 7, 3, 2, 1, 15} var storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeBitLengths = [6]byte{2, 4, 3, 2, 2, 4} func storeHuffmanTreeOfHuffmanTreeToBitMask(num_codes int, code_length_bitdepth []byte, storage_ix *uint, storage []byte) { var skip_some uint = 0 var codes_to_store uint = codeLengthCodes /* 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 */ /* Throw away trailing zeros: */ if num_codes > 1 { for ; codes_to_store > 0; codes_to_store-- { if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[codes_to_store-1]] != 0 { break } } } if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[0]] == 0 && code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[1]] == 0 { skip_some = 2 /* skips two. */ if code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[2]] == 0 { skip_some = 3 /* skips three. */ } } writeBits(2, uint64(skip_some), storage_ix, storage) { var i uint for i = skip_some; i < codes_to_store; i++ { var l uint = uint(code_length_bitdepth[storeHuffmanTreeOfHuffmanTreeToBitMask_kStorageOrder[i]]) writeBits(uint(storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeBitLengths[l]), uint64(storeHuffmanTreeOfHuffmanTreeToBitMask_kHuffmanBitLengthHuffmanCodeSymbols[l]), storage_ix, storage) } } } func storeHuffmanTreeToBitMask(huffman_tree_size uint, huffman_tree []byte, huffman_tree_extra_bits []byte, code_length_bitdepth []byte, code_length_bitdepth_symbols []uint16, storage_ix *uint, storage []byte) { var i uint for i = 0; i < huffman_tree_size; i++ { var ix uint = uint(huffman_tree[i]) writeBits(uint(code_length_bitdepth[ix]), uint64(code_length_bitdepth_symbols[ix]), storage_ix, storage) /* Extra bits */ switch ix { case repeatPreviousCodeLength: writeBits(2, uint64(huffman_tree_extra_bits[i]), storage_ix, storage) case repeatZeroCodeLength: writeBits(3, uint64(huffman_tree_extra_bits[i]), storage_ix, storage) } } } func storeSimpleHuffmanTree(depths []byte, symbols []uint, num_symbols uint, max_bits uint, storage_ix *uint, storage []byte) { /* value of 1 indicates a simple Huffman code */ writeBits(2, 1, storage_ix, storage) writeBits(2, uint64(num_symbols)-1, storage_ix, storage) /* NSYM - 1 */ { /* Sort */ var i uint for i = 0; i < num_symbols; i++ { var j uint for j = i + 1; j < num_symbols; j++ { if depths[symbols[j]] < depths[symbols[i]] { var tmp uint = symbols[j] symbols[j] = symbols[i] symbols[i] = tmp } } } } if num_symbols == 2 { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) } else if num_symbols == 3 { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) writeBits(max_bits, uint64(symbols[2]), storage_ix, storage) } else { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) writeBits(max_bits, uint64(symbols[2]), storage_ix, storage) writeBits(max_bits, uint64(symbols[3]), storage_ix, storage) /* tree-select */ var tmp int if depths[symbols[0]] == 1 { tmp = 1 } else { tmp = 0 } writeBits(1, uint64(tmp), storage_ix, storage) } } /* num = alphabet size depths = symbol depths */ func storeHuffmanTree(depths []byte, num uint, tree []huffmanTree, storage_ix *uint, storage []byte) { var huffman_tree [numCommandSymbols]byte var huffman_tree_extra_bits [numCommandSymbols]byte var huffman_tree_size uint = 0 var code_length_bitdepth = [codeLengthCodes]byte{0} var code_length_bitdepth_symbols [codeLengthCodes]uint16 var huffman_tree_histogram = [codeLengthCodes]uint32{0} var i uint var num_codes int = 0 /* Write the Huffman tree into the brotli-representation. The command alphabet is the largest, so this allocation will fit all alphabets. */ var code uint = 0 assert(num <= numCommandSymbols) writeHuffmanTree(depths, num, &huffman_tree_size, huffman_tree[:], huffman_tree_extra_bits[:]) /* Calculate the statistics of the Huffman tree in brotli-representation. */ for i = 0; i < huffman_tree_size; i++ { huffman_tree_histogram[huffman_tree[i]]++ } for i = 0; i < codeLengthCodes; i++ { if huffman_tree_histogram[i] != 0 { 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. */ createHuffmanTree(huffman_tree_histogram[:], codeLengthCodes, 5, tree, code_length_bitdepth[:]) convertBitDepthsToSymbols(code_length_bitdepth[:], codeLengthCodes, code_length_bitdepth_symbols[:]) /* 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[:], code_length_bitdepth_symbols[:], storage_ix, storage) } /* Builds a Huffman tree from histogram[0:length] into depth[0:length] and bits[0:length] and stores the encoded tree to the bit stream. */ func buildAndStoreHuffmanTree(histogram []uint32, histogram_length uint, alphabet_size uint, tree []huffmanTree, depth []byte, bits []uint16, storage_ix *uint, storage []byte) { var count uint = 0 var s4 = [4]uint{0} var i uint var max_bits uint = 0 for i = 0; i < histogram_length; i++ { if histogram[i] != 0 { if count < 4 { s4[count] = i } else if count > 4 { break } count++ } } { var max_bits_counter uint = alphabet_size - 1 for max_bits_counter != 0 { max_bits_counter >>= 1 max_bits++ } } if count <= 1 { writeBits(4, 1, storage_ix, storage) writeBits(max_bits, uint64(s4[0]), storage_ix, storage) depth[s4[0]] = 0 bits[s4[0]] = 0 return } for i := 0; i < int(histogram_length); i++ { depth[i] = 0 } createHuffmanTree(histogram, histogram_length, 15, tree, depth) convertBitDepthsToSymbols(depth, histogram_length, bits) if count <= 4 { storeSimpleHuffmanTree(depth, s4[:], count, max_bits, storage_ix, storage) } else { storeHuffmanTree(depth, histogram_length, tree, storage_ix, storage) } } func sortHuffmanTree1(v0 huffmanTree, v1 huffmanTree) bool { return v0.total_count_ < v1.total_count_ } func buildAndStoreHuffmanTreeFast(histogram []uint32, histogram_total uint, max_bits uint, depth []byte, bits []uint16, storage_ix *uint, storage []byte) { var count uint = 0 var symbols = [4]uint{0} var length uint = 0 var total uint = histogram_total for total != 0 { if histogram[length] != 0 { if count < 4 { symbols[count] = length } count++ total -= uint(histogram[length]) } length++ } if count <= 1 { writeBits(4, 1, storage_ix, storage) writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) depth[symbols[0]] = 0 bits[symbols[0]] = 0 return } for i := 0; i < int(length); i++ { depth[i] = 0 } { var max_tree_size uint = 2*length + 1 var tree []huffmanTree = make([]huffmanTree, max_tree_size) var count_limit uint32 for count_limit = 1; ; count_limit *= 2 { var node int = 0 var l uint for l = length; l != 0; { l-- if histogram[l] != 0 { if histogram[l] >= count_limit { initHuffmanTree(&tree[node:][0], histogram[l], -1, int16(l)) } else { initHuffmanTree(&tree[node:][0], count_limit, -1, int16(l)) } node++ } } { var n int = node /* Points to the next leaf node. */ /* Points to the next non-leaf node. */ var sentinel huffmanTree var i int = 0 var j int = n + 1 var k int sortHuffmanTreeItems(tree, uint(n), huffmanTreeComparator(sortHuffmanTree1)) /* 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. */ initHuffmanTree(&sentinel, math.MaxUint32, -1, -1) tree[node] = sentinel node++ tree[node] = sentinel node++ for k = n - 1; k > 0; k-- { var left int var right int 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. */ tree[node-1].total_count_ = tree[left].total_count_ + tree[right].total_count_ tree[node-1].index_left_ = int16(left) tree[node-1].index_right_or_value_ = int16(right) /* Add back the last sentinel node. */ tree[node] = sentinel node++ } if setDepth(2*n-1, tree, depth, 14) { /* We need to pack the Huffman tree in 14 bits. If this was not successful, add fake entities to the lowest values and retry. */ break } } } tree = nil } convertBitDepthsToSymbols(depth, length, bits) if count <= 4 { var i uint /* value of 1 indicates a simple Huffman code */ writeBits(2, 1, storage_ix, storage) writeBits(2, uint64(count)-1, storage_ix, storage) /* NSYM - 1 */ /* Sort */ for i = 0; i < count; i++ { var j uint for j = i + 1; j < count; j++ { if depth[symbols[j]] < depth[symbols[i]] { var tmp uint = symbols[j] symbols[j] = symbols[i] symbols[i] = tmp } } } if count == 2 { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) } else if count == 3 { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) writeBits(max_bits, uint64(symbols[2]), storage_ix, storage) } else { writeBits(max_bits, uint64(symbols[0]), storage_ix, storage) writeBits(max_bits, uint64(symbols[1]), storage_ix, storage) writeBits(max_bits, uint64(symbols[2]), storage_ix, storage) writeBits(max_bits, uint64(symbols[3]), storage_ix, storage) /* tree-select */ var tmp int if depth[symbols[0]] == 1 { tmp = 1 } else { tmp = 0 } writeBits(1, uint64(tmp), storage_ix, storage) } } else { var previous_value byte = 8 var i uint /* Complex Huffman Tree */ storeStaticCodeLengthCode(storage_ix, storage) /* Actual RLE coding. */ for i = 0; i < length; { var value byte = depth[i] var reps uint = 1 var k uint for k = i + 1; k < length && depth[k] == value; k++ { reps++ } i += reps if value == 0 { writeBits(uint(kZeroRepsDepth[reps]), kZeroRepsBits[reps], storage_ix, storage) } else { if previous_value != value { writeBits(uint(kCodeLengthDepth[value]), uint64(kCodeLengthBits[value]), storage_ix, storage) reps-- } if reps < 3 { for reps != 0 { reps-- writeBits(uint(kCodeLengthDepth[value]), uint64(kCodeLengthBits[value]), storage_ix, storage) } } else { reps -= 3 writeBits(uint(kNonZeroRepsDepth[reps]), kNonZeroRepsBits[reps], storage_ix, storage) } previous_value = value } } } } func indexOf(v []byte, v_size uint, value byte) uint { var i uint = 0 for ; i < v_size; i++ { if v[i] == value { return i } } return i } func moveToFront(v []byte, index uint) { var value byte = v[index] var i uint for i = index; i != 0; i-- { v[i] = v[i-1] } v[0] = value } func moveToFrontTransform(v_in []uint32, v_size uint, v_out []uint32) { var i uint var mtf [256]byte var max_value uint32 if v_size == 0 { return } max_value = v_in[0] for i = 1; i < v_size; i++ { if v_in[i] > max_value { max_value = v_in[i] } } assert(max_value < 256) for i = 0; uint32(i) <= max_value; i++ { mtf[i] = byte(i) } { var mtf_size uint = uint(max_value + 1) for i = 0; i < v_size; i++ { var index uint = indexOf(mtf[:], mtf_size, byte(v_in[i])) assert(index < mtf_size) v_out[i] = uint32(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. */ func runLengthCodeZeros(in_size uint, v []uint32, out_size *uint, max_run_length_prefix *uint32) { var max_reps uint32 = 0 var i uint var max_prefix uint32 for i = 0; i < in_size; { var reps uint32 = 0 for ; i < in_size && v[i] != 0; i++ { } for ; i < in_size && v[i] == 0; i++ { reps++ } max_reps = brotli_max_uint32_t(reps, max_reps) } if max_reps > 0 { max_prefix = log2FloorNonZero(uint(max_reps)) } else { max_prefix = 0 } max_prefix = brotli_min_uint32_t(max_prefix, *max_run_length_prefix) *max_run_length_prefix = max_prefix *out_size = 0 for 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 { var reps uint32 = 1 var k uint for k = i + 1; k < in_size && v[k] == 0; k++ { reps++ } i += uint(reps) for reps != 0 { if reps < 2< 0) writeSingleBit(use_rle, storage_ix, storage) if use_rle { writeBits(4, uint64(max_run_length_prefix)-1, storage_ix, storage) } } buildAndStoreHuffmanTree(histogram[:], uint(uint32(num_clusters)+max_run_length_prefix), uint(uint32(num_clusters)+max_run_length_prefix), tree, depths[:], bits[:], storage_ix, storage) for i = 0; i < num_rle_symbols; i++ { var rle_symbol uint32 = rle_symbols[i] & encodeContextMap_kSymbolMask var extra_bits_val uint32 = rle_symbols[i] >> symbolBits writeBits(uint(depths[rle_symbol]), uint64(bits[rle_symbol]), storage_ix, storage) if rle_symbol > 0 && rle_symbol <= max_run_length_prefix { writeBits(uint(rle_symbol), uint64(extra_bits_val), storage_ix, storage) } } writeBits(1, 1, storage_ix, storage) /* use move-to-front */ rle_symbols = nil } /* Stores the block switch command with index block_ix to the bit stream. */ func storeBlockSwitch(code *blockSplitCode, block_len uint32, block_type byte, is_first_block bool, storage_ix *uint, storage []byte) { var typecode uint = nextBlockTypeCode(&code.type_code_calculator, block_type) var lencode uint var len_nextra uint32 var len_extra uint32 if !is_first_block { writeBits(uint(code.type_depths[typecode]), uint64(code.type_bits[typecode]), storage_ix, storage) } getBlockLengthPrefixCode(block_len, &lencode, &len_nextra, &len_extra) writeBits(uint(code.length_depths[lencode]), uint64(code.length_bits[lencode]), storage_ix, storage) writeBits(uint(len_nextra), uint64(len_extra), storage_ix, storage) } /* Builds a BlockSplitCode data structure from the block split given by the vector of block types and block lengths and stores it to the bit stream. */ func buildAndStoreBlockSplitCode(types []byte, lengths []uint32, num_blocks uint, num_types uint, tree []huffmanTree, code *blockSplitCode, storage_ix *uint, storage []byte) { var type_histo [maxBlockTypeSymbols]uint32 var length_histo [numBlockLenSymbols]uint32 var i uint var type_code_calculator blockTypeCodeCalculator for i := 0; i < int(num_types+2); i++ { type_histo[i] = 0 } length_histo = [numBlockLenSymbols]uint32{} initBlockTypeCodeCalculator(&type_code_calculator) for i = 0; i < num_blocks; i++ { var type_code uint = nextBlockTypeCode(&type_code_calculator, types[i]) if i != 0 { type_histo[type_code]++ } length_histo[blockLengthPrefixCode(lengths[i])]++ } storeVarLenUint8(num_types-1, storage_ix, storage) if num_types > 1 { /* TODO: else? could StoreBlockSwitch occur? */ buildAndStoreHuffmanTree(type_histo[0:], num_types+2, num_types+2, tree, code.type_depths[0:], code.type_bits[0:], storage_ix, storage) buildAndStoreHuffmanTree(length_histo[0:], numBlockLenSymbols, numBlockLenSymbols, tree, code.length_depths[0:], code.length_bits[0:], storage_ix, storage) storeBlockSwitch(code, lengths[0], types[0], true, storage_ix, storage) } } /* Stores a context map where the histogram type is always the block type. */ func storeTrivialContextMap(num_types uint, context_bits uint, tree []huffmanTree, storage_ix *uint, storage []byte) { storeVarLenUint8(num_types-1, storage_ix, storage) if num_types > 1 { var repeat_code uint = context_bits - 1 var repeat_bits uint = (1 << repeat_code) - 1 var alphabet_size uint = num_types + repeat_code var histogram [maxContextMapSymbols]uint32 var depths [maxContextMapSymbols]byte var bits [maxContextMapSymbols]uint16 var i uint for i := 0; i < int(alphabet_size); i++ { histogram[i] = 0 } /* Write RLEMAX. */ writeBits(1, 1, storage_ix, storage) writeBits(4, uint64(repeat_code)-1, storage_ix, storage) histogram[repeat_code] = uint32(num_types) histogram[0] = 1 for i = context_bits; i < alphabet_size; i++ { histogram[i] = 1 } buildAndStoreHuffmanTree(histogram[:], alphabet_size, alphabet_size, tree, depths[:], bits[:], storage_ix, storage) for i = 0; i < num_types; i++ { var tmp uint if i == 0 { tmp = 0 } else { tmp = i + context_bits - 1 } var code uint = tmp writeBits(uint(depths[code]), uint64(bits[code]), storage_ix, storage) writeBits(uint(depths[repeat_code]), uint64(bits[repeat_code]), storage_ix, storage) writeBits(repeat_code, uint64(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). */ type blockEncoder struct { histogram_length_ uint num_block_types_ uint block_types_ []byte block_lengths_ []uint32 num_blocks_ uint block_split_code_ blockSplitCode block_ix_ uint block_len_ uint entropy_ix_ uint depths_ []byte bits_ []uint16 } func initBlockEncoder(self *blockEncoder, histogram_length uint, num_block_types uint, block_types []byte, block_lengths []uint32, num_blocks uint) { self.histogram_length_ = histogram_length self.num_block_types_ = num_block_types self.block_types_ = block_types self.block_lengths_ = block_lengths self.num_blocks_ = num_blocks initBlockTypeCodeCalculator(&self.block_split_code_.type_code_calculator) self.block_ix_ = 0 if num_blocks == 0 { self.block_len_ = 0 } else { self.block_len_ = uint(block_lengths[0]) } self.entropy_ix_ = 0 self.depths_ = nil self.bits_ = nil } func cleanupBlockEncoder(self *blockEncoder) { self.depths_ = nil self.bits_ = nil } /* Creates entropy codes of block lengths and block types and stores them to the bit stream. */ func buildAndStoreBlockSwitchEntropyCodes(self *blockEncoder, tree []huffmanTree, storage_ix *uint, storage []byte) { buildAndStoreBlockSplitCode(self.block_types_, self.block_lengths_, self.num_blocks_, self.num_block_types_, tree, &self.block_split_code_, 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. */ func storeSymbol(self *blockEncoder, symbol uint, storage_ix *uint, storage []byte) { if self.block_len_ == 0 { self.block_ix_++ var block_ix uint = self.block_ix_ var block_len uint32 = self.block_lengths_[block_ix] var block_type byte = self.block_types_[block_ix] self.block_len_ = uint(block_len) self.entropy_ix_ = uint(block_type) * self.histogram_length_ storeBlockSwitch(&self.block_split_code_, block_len, block_type, false, storage_ix, storage) } self.block_len_-- { var ix uint = self.entropy_ix_ + symbol writeBits(uint(self.depths_[ix]), uint64(self.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. */ func storeSymbolWithContext(self *blockEncoder, symbol uint, context uint, context_map []uint32, storage_ix *uint, storage []byte, context_bits uint) { if self.block_len_ == 0 { self.block_ix_++ var block_ix uint = self.block_ix_ var block_len uint32 = self.block_lengths_[block_ix] var block_type byte = self.block_types_[block_ix] self.block_len_ = uint(block_len) self.entropy_ix_ = uint(block_type) << context_bits storeBlockSwitch(&self.block_split_code_, block_len, block_type, false, storage_ix, storage) } self.block_len_-- { var histo_ix uint = uint(context_map[self.entropy_ix_+context]) var ix uint = histo_ix*self.histogram_length_ + symbol writeBits(uint(self.depths_[ix]), uint64(self.bits_[ix]), storage_ix, storage) } } func buildAndStoreEntropyCodesLiteral(self *blockEncoder, histograms []histogramLiteral, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) { var table_size uint = histograms_size * self.histogram_length_ self.depths_ = make([]byte, table_size) self.bits_ = make([]uint16, table_size) { var i uint for i = 0; i < histograms_size; i++ { var ix uint = i * self.histogram_length_ buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage) } } } func buildAndStoreEntropyCodesCommand(self *blockEncoder, histograms []histogramCommand, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) { var table_size uint = histograms_size * self.histogram_length_ self.depths_ = make([]byte, table_size) self.bits_ = make([]uint16, table_size) { var i uint for i = 0; i < histograms_size; i++ { var ix uint = i * self.histogram_length_ buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage) } } } func buildAndStoreEntropyCodesDistance(self *blockEncoder, histograms []histogramDistance, histograms_size uint, alphabet_size uint, tree []huffmanTree, storage_ix *uint, storage []byte) { var table_size uint = histograms_size * self.histogram_length_ self.depths_ = make([]byte, table_size) self.bits_ = make([]uint16, table_size) { var i uint for i = 0; i < histograms_size; i++ { var ix uint = i * self.histogram_length_ buildAndStoreHuffmanTree(histograms[i].data_[0:], self.histogram_length_, alphabet_size, tree, self.depths_[ix:], self.bits_[ix:], storage_ix, storage) } } } func jumpToByteBoundary(storage_ix *uint, storage []byte) { *storage_ix = (*storage_ix + 7) &^ 7 storage[*storage_ix>>3] = 0 } func storeMetaBlock(input []byte, start_pos uint, length uint, mask uint, prev_byte byte, prev_byte2 byte, is_last bool, params *encoderParams, literal_context_mode int, commands []command, n_commands uint, mb *metaBlockSplit, storage_ix *uint, storage []byte) { var pos uint = start_pos var i uint var num_distance_symbols uint32 = params.dist.alphabet_size var num_effective_distance_symbols uint32 = num_distance_symbols var tree []huffmanTree var literal_context_lut contextLUT = getContextLUT(literal_context_mode) var literal_enc blockEncoder var command_enc blockEncoder var distance_enc blockEncoder var dist *distanceParams = ¶ms.dist if params.large_window && num_effective_distance_symbols > numHistogramDistanceSymbols { num_effective_distance_symbols = numHistogramDistanceSymbols } storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage) tree = make([]huffmanTree, maxHuffmanTreeSize) initBlockEncoder(&literal_enc, numLiteralSymbols, mb.literal_split.num_types, mb.literal_split.types, mb.literal_split.lengths, mb.literal_split.num_blocks) initBlockEncoder(&command_enc, numCommandSymbols, mb.command_split.num_types, mb.command_split.types, mb.command_split.lengths, mb.command_split.num_blocks) initBlockEncoder(&distance_enc, uint(num_effective_distance_symbols), mb.distance_split.num_types, mb.distance_split.types, mb.distance_split.lengths, mb.distance_split.num_blocks) buildAndStoreBlockSwitchEntropyCodes(&literal_enc, tree, storage_ix, storage) buildAndStoreBlockSwitchEntropyCodes(&command_enc, tree, storage_ix, storage) buildAndStoreBlockSwitchEntropyCodes(&distance_enc, tree, storage_ix, storage) writeBits(2, uint64(dist.distance_postfix_bits), storage_ix, storage) writeBits(4, uint64(dist.num_direct_distance_codes)>>dist.distance_postfix_bits, storage_ix, storage) for i = 0; i < mb.literal_split.num_types; i++ { writeBits(2, uint64(literal_context_mode), storage_ix, storage) } if mb.literal_context_map_size == 0 { storeTrivialContextMap(mb.literal_histograms_size, literalContextBits, tree, storage_ix, storage) } else { encodeContextMap(mb.literal_context_map, mb.literal_context_map_size, mb.literal_histograms_size, tree, storage_ix, storage) } if mb.distance_context_map_size == 0 { storeTrivialContextMap(mb.distance_histograms_size, distanceContextBits, tree, storage_ix, storage) } else { encodeContextMap(mb.distance_context_map, mb.distance_context_map_size, mb.distance_histograms_size, tree, storage_ix, storage) } buildAndStoreEntropyCodesLiteral(&literal_enc, mb.literal_histograms, mb.literal_histograms_size, numLiteralSymbols, tree, storage_ix, storage) buildAndStoreEntropyCodesCommand(&command_enc, mb.command_histograms, mb.command_histograms_size, numCommandSymbols, tree, storage_ix, storage) buildAndStoreEntropyCodesDistance(&distance_enc, mb.distance_histograms, mb.distance_histograms_size, uint(num_distance_symbols), tree, storage_ix, storage) tree = nil for i = 0; i < n_commands; i++ { var cmd command = commands[i] var cmd_code uint = uint(cmd.cmd_prefix_) storeSymbol(&command_enc, cmd_code, storage_ix, storage) storeCommandExtra(&cmd, storage_ix, storage) if mb.literal_context_map_size == 0 { var j uint for j = uint(cmd.insert_len_); j != 0; j-- { storeSymbol(&literal_enc, uint(input[pos&mask]), storage_ix, storage) pos++ } } else { var j uint for j = uint(cmd.insert_len_); j != 0; j-- { var context uint = uint(getContext(prev_byte, prev_byte2, literal_context_lut)) var literal byte = input[pos&mask] storeSymbolWithContext(&literal_enc, uint(literal), context, mb.literal_context_map, storage_ix, storage, literalContextBits) prev_byte2 = prev_byte prev_byte = literal pos++ } } pos += uint(commandCopyLen(&cmd)) if commandCopyLen(&cmd) != 0 { prev_byte2 = input[(pos-2)&mask] prev_byte = input[(pos-1)&mask] if cmd.cmd_prefix_ >= 128 { var dist_code uint = uint(cmd.dist_prefix_) & 0x3FF var distnumextra uint32 = uint32(cmd.dist_prefix_) >> 10 var distextra uint64 = uint64(cmd.dist_extra_) if mb.distance_context_map_size == 0 { storeSymbol(&distance_enc, dist_code, storage_ix, storage) } else { var context uint = uint(commandDistanceContext(&cmd)) storeSymbolWithContext(&distance_enc, dist_code, context, mb.distance_context_map, storage_ix, storage, distanceContextBits) } writeBits(uint(distnumextra), distextra, storage_ix, storage) } } } cleanupBlockEncoder(&distance_enc) cleanupBlockEncoder(&command_enc) cleanupBlockEncoder(&literal_enc) if is_last { jumpToByteBoundary(storage_ix, storage) } } func buildHistograms(input []byte, start_pos uint, mask uint, commands []command, n_commands uint, lit_histo *histogramLiteral, cmd_histo *histogramCommand, dist_histo *histogramDistance) { var pos uint = start_pos var i uint for i = 0; i < n_commands; i++ { var cmd command = commands[i] var j uint histogramAddCommand(cmd_histo, uint(cmd.cmd_prefix_)) for j = uint(cmd.insert_len_); j != 0; j-- { histogramAddLiteral(lit_histo, uint(input[pos&mask])) pos++ } pos += uint(commandCopyLen(&cmd)) if commandCopyLen(&cmd) != 0 && cmd.cmd_prefix_ >= 128 { histogramAddDistance(dist_histo, uint(cmd.dist_prefix_)&0x3FF) } } } func storeDataWithHuffmanCodes(input []byte, start_pos uint, mask uint, commands []command, n_commands uint, lit_depth []byte, lit_bits []uint16, cmd_depth []byte, cmd_bits []uint16, dist_depth []byte, dist_bits []uint16, storage_ix *uint, storage []byte) { var pos uint = start_pos var i uint for i = 0; i < n_commands; i++ { var cmd command = commands[i] var cmd_code uint = uint(cmd.cmd_prefix_) var j uint writeBits(uint(cmd_depth[cmd_code]), uint64(cmd_bits[cmd_code]), storage_ix, storage) storeCommandExtra(&cmd, storage_ix, storage) for j = uint(cmd.insert_len_); j != 0; j-- { var literal byte = input[pos&mask] writeBits(uint(lit_depth[literal]), uint64(lit_bits[literal]), storage_ix, storage) pos++ } pos += uint(commandCopyLen(&cmd)) if commandCopyLen(&cmd) != 0 && cmd.cmd_prefix_ >= 128 { var dist_code uint = uint(cmd.dist_prefix_) & 0x3FF var distnumextra uint32 = uint32(cmd.dist_prefix_) >> 10 var distextra uint32 = cmd.dist_extra_ writeBits(uint(dist_depth[dist_code]), uint64(dist_bits[dist_code]), storage_ix, storage) writeBits(uint(distnumextra), uint64(distextra), storage_ix, storage) } } } func storeMetaBlockTrivial(input []byte, start_pos uint, length uint, mask uint, is_last bool, params *encoderParams, commands []command, n_commands uint, storage_ix *uint, storage []byte) { var lit_histo histogramLiteral var cmd_histo histogramCommand var dist_histo histogramDistance var lit_depth [numLiteralSymbols]byte var lit_bits [numLiteralSymbols]uint16 var cmd_depth [numCommandSymbols]byte var cmd_bits [numCommandSymbols]uint16 var dist_depth [maxSimpleDistanceAlphabetSize]byte var dist_bits [maxSimpleDistanceAlphabetSize]uint16 var tree []huffmanTree var num_distance_symbols uint32 = params.dist.alphabet_size storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage) histogramClearLiteral(&lit_histo) histogramClearCommand(&cmd_histo) histogramClearDistance(&dist_histo) buildHistograms(input, start_pos, mask, commands, n_commands, &lit_histo, &cmd_histo, &dist_histo) writeBits(13, 0, storage_ix, storage) tree = make([]huffmanTree, maxHuffmanTreeSize) buildAndStoreHuffmanTree(lit_histo.data_[:], numLiteralSymbols, numLiteralSymbols, tree, lit_depth[:], lit_bits[:], storage_ix, storage) buildAndStoreHuffmanTree(cmd_histo.data_[:], numCommandSymbols, numCommandSymbols, tree, cmd_depth[:], cmd_bits[:], storage_ix, storage) buildAndStoreHuffmanTree(dist_histo.data_[:], maxSimpleDistanceAlphabetSize, uint(num_distance_symbols), tree, dist_depth[:], dist_bits[:], storage_ix, storage) tree = nil storeDataWithHuffmanCodes(input, start_pos, mask, commands, n_commands, lit_depth[:], lit_bits[:], cmd_depth[:], cmd_bits[:], dist_depth[:], dist_bits[:], storage_ix, storage) if is_last { jumpToByteBoundary(storage_ix, storage) } } func storeMetaBlockFast(input []byte, start_pos uint, length uint, mask uint, is_last bool, params *encoderParams, commands []command, n_commands uint, storage_ix *uint, storage []byte) { var num_distance_symbols uint32 = params.dist.alphabet_size var distance_alphabet_bits uint32 = log2FloorNonZero(uint(num_distance_symbols-1)) + 1 storeCompressedMetaBlockHeader(is_last, length, storage_ix, storage) writeBits(13, 0, storage_ix, storage) if n_commands <= 128 { var histogram = [numLiteralSymbols]uint32{0} var pos uint = start_pos var num_literals uint = 0 var i uint var lit_depth [numLiteralSymbols]byte var lit_bits [numLiteralSymbols]uint16 for i = 0; i < n_commands; i++ { var cmd command = commands[i] var j uint for j = uint(cmd.insert_len_); j != 0; j-- { histogram[input[pos&mask]]++ pos++ } num_literals += uint(cmd.insert_len_) pos += uint(commandCopyLen(&cmd)) } 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[:], lit_bits[:], kStaticCommandCodeDepth[:], kStaticCommandCodeBits[:], kStaticDistanceCodeDepth[:], kStaticDistanceCodeBits[:], storage_ix, storage) } else { var lit_histo histogramLiteral var cmd_histo histogramCommand var dist_histo histogramDistance var lit_depth [numLiteralSymbols]byte var lit_bits [numLiteralSymbols]uint16 var cmd_depth [numCommandSymbols]byte var cmd_bits [numCommandSymbols]uint16 var dist_depth [maxSimpleDistanceAlphabetSize]byte var dist_bits [maxSimpleDistanceAlphabetSize]uint16 histogramClearLiteral(&lit_histo) histogramClearCommand(&cmd_histo) histogramClearDistance(&dist_histo) buildHistograms(input, start_pos, mask, commands, n_commands, &lit_histo, &cmd_histo, &dist_histo) buildAndStoreHuffmanTreeFast(lit_histo.data_[:], lit_histo.total_count_, /* max_bits = */ 8, lit_depth[:], lit_bits[:], storage_ix, storage) buildAndStoreHuffmanTreeFast(cmd_histo.data_[:], cmd_histo.total_count_, /* max_bits = */ 10, cmd_depth[:], cmd_bits[:], storage_ix, storage) buildAndStoreHuffmanTreeFast(dist_histo.data_[:], dist_histo.total_count_, /* max_bits = */ uint(distance_alphabet_bits), dist_depth[:], dist_bits[:], storage_ix, storage) storeDataWithHuffmanCodes(input, start_pos, mask, commands, n_commands, lit_depth[:], lit_bits[:], cmd_depth[:], cmd_bits[:], dist_depth[:], dist_bits[:], storage_ix, storage) } if is_last { jumpToByteBoundary(storage_ix, storage) } } /* This is for storing uncompressed blocks (simple raw storage of bytes-as-bytes). */ func storeUncompressedMetaBlock(is_final_block bool, input []byte, position uint, mask uint, len uint, storage_ix *uint, storage []byte) { var masked_pos uint = position & mask storeUncompressedMetaBlockHeader(uint(len), storage_ix, storage) jumpToByteBoundary(storage_ix, storage) if masked_pos+len > mask+1 { var len1 uint = mask + 1 - masked_pos copy(storage[*storage_ix>>3:], input[masked_pos:][:len1]) *storage_ix += len1 << 3 len -= len1 masked_pos = 0 } copy(storage[*storage_ix>>3:], input[masked_pos:][:len]) *storage_ix += uint(len << 3) /* We need to clear the next 4 bytes to continue to be compatible with BrotliWriteBits. */ writeBitsPrepareStorage(*storage_ix, storage) /* Since the uncompressed block itself may not be the final block, add an empty one after this. */ if is_final_block { writeBits(1, 1, storage_ix, storage) /* islast */ writeBits(1, 1, storage_ix, storage) /* isempty */ jumpToByteBoundary(storage_ix, storage) } }