forked from Shiloh/githaven
841 lines
26 KiB
Go
841 lines
26 KiB
Go
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package brotli
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import "encoding/binary"
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/* Copyright 2015 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Function for fast encoding of an input fragment, independently from the input
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history. This function uses one-pass processing: when we find a backward
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match, we immediately emit the corresponding command and literal codes to
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the bit stream.
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Adapted from the CompressFragment() function in
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https://github.com/google/snappy/blob/master/snappy.cc */
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const maxDistance_compress_fragment = 262128
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func hash5(p []byte, shift uint) uint32 {
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var h uint64 = (binary.LittleEndian.Uint64(p) << 24) * uint64(kHashMul32)
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return uint32(h >> shift)
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}
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func hashBytesAtOffset5(v uint64, offset int, shift uint) uint32 {
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assert(offset >= 0)
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assert(offset <= 3)
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{
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var h uint64 = ((v >> uint(8*offset)) << 24) * uint64(kHashMul32)
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return uint32(h >> shift)
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}
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}
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func isMatch5(p1 []byte, p2 []byte) bool {
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var i int
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for i = 0; i < 5; i++ {
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if p1[i] != p2[i] {
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return false
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}
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}
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return true
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}
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/* Builds a literal prefix code into "depths" and "bits" based on the statistics
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of the "input" string and stores it into the bit stream.
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Note that the prefix code here is built from the pre-LZ77 input, therefore
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we can only approximate the statistics of the actual literal stream.
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Moreover, for long inputs we build a histogram from a sample of the input
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and thus have to assign a non-zero depth for each literal.
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Returns estimated compression ratio millibytes/char for encoding given input
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with generated code. */
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func buildAndStoreLiteralPrefixCode(input []byte, input_size uint, depths []byte, bits []uint16, storage_ix *uint, storage []byte) uint {
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var histogram = [256]uint32{0}
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var histogram_total uint
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var i uint
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if input_size < 1<<15 {
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for i = 0; i < input_size; i++ {
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histogram[input[i]]++
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}
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histogram_total = input_size
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for i = 0; i < 256; i++ {
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/* We weigh the first 11 samples with weight 3 to account for the
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balancing effect of the LZ77 phase on the histogram. */
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var adjust uint32 = 2 * brotli_min_uint32_t(histogram[i], 11)
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histogram[i] += adjust
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histogram_total += uint(adjust)
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}
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} else {
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const kSampleRate uint = 29
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for i = 0; i < input_size; i += kSampleRate {
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histogram[input[i]]++
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}
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histogram_total = (input_size + kSampleRate - 1) / kSampleRate
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for i = 0; i < 256; i++ {
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/* We add 1 to each population count to avoid 0 bit depths (since this is
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only a sample and we don't know if the symbol appears or not), and we
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weigh the first 11 samples with weight 3 to account for the balancing
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effect of the LZ77 phase on the histogram (more frequent symbols are
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more likely to be in backward references instead as literals). */
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var adjust uint32 = 1 + 2*brotli_min_uint32_t(histogram[i], 11)
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histogram[i] += adjust
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histogram_total += uint(adjust)
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}
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}
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buildAndStoreHuffmanTreeFast(histogram[:], histogram_total, /* max_bits = */
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8, depths, bits, storage_ix, storage)
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{
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var literal_ratio uint = 0
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for i = 0; i < 256; i++ {
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if histogram[i] != 0 {
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literal_ratio += uint(histogram[i] * uint32(depths[i]))
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}
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}
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/* Estimated encoding ratio, millibytes per symbol. */
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return (literal_ratio * 125) / histogram_total
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}
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}
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/* Builds a command and distance prefix code (each 64 symbols) into "depth" and
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"bits" based on "histogram" and stores it into the bit stream. */
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func buildAndStoreCommandPrefixCode1(histogram []uint32, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
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var tree [129]huffmanTree
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var cmd_depth = [numCommandSymbols]byte{0}
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/* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */
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var cmd_bits [64]uint16
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createHuffmanTree(histogram, 64, 15, tree[:], depth)
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createHuffmanTree(histogram[64:], 64, 14, tree[:], depth[64:])
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/* We have to jump through a few hoops here in order to compute
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the command bits because the symbols are in a different order than in
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the full alphabet. This looks complicated, but having the symbols
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in this order in the command bits saves a few branches in the Emit*
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functions. */
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copy(cmd_depth[:], depth[:24])
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copy(cmd_depth[24:][:], depth[40:][:8])
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copy(cmd_depth[32:][:], depth[24:][:8])
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copy(cmd_depth[40:][:], depth[48:][:8])
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copy(cmd_depth[48:][:], depth[32:][:8])
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copy(cmd_depth[56:][:], depth[56:][:8])
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convertBitDepthsToSymbols(cmd_depth[:], 64, cmd_bits[:])
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copy(bits, cmd_bits[:24])
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copy(bits[24:], cmd_bits[32:][:8])
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copy(bits[32:], cmd_bits[48:][:8])
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copy(bits[40:], cmd_bits[24:][:8])
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copy(bits[48:], cmd_bits[40:][:8])
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copy(bits[56:], cmd_bits[56:][:8])
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convertBitDepthsToSymbols(depth[64:], 64, bits[64:])
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{
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/* Create the bit length array for the full command alphabet. */
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var i uint
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for i := 0; i < int(64); i++ {
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cmd_depth[i] = 0
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} /* only 64 first values were used */
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copy(cmd_depth[:], depth[:8])
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copy(cmd_depth[64:][:], depth[8:][:8])
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copy(cmd_depth[128:][:], depth[16:][:8])
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copy(cmd_depth[192:][:], depth[24:][:8])
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copy(cmd_depth[384:][:], depth[32:][:8])
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for i = 0; i < 8; i++ {
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cmd_depth[128+8*i] = depth[40+i]
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cmd_depth[256+8*i] = depth[48+i]
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cmd_depth[448+8*i] = depth[56+i]
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}
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storeHuffmanTree(cmd_depth[:], numCommandSymbols, tree[:], storage_ix, storage)
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}
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storeHuffmanTree(depth[64:], 64, tree[:], storage_ix, storage)
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}
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/* REQUIRES: insertlen < 6210 */
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func emitInsertLen1(insertlen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
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if insertlen < 6 {
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var code uint = insertlen + 40
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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histo[code]++
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} else if insertlen < 130 {
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var tail uint = insertlen - 2
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var nbits uint32 = log2FloorNonZero(tail) - 1
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var prefix uint = tail >> nbits
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var inscode uint = uint((nbits << 1) + uint32(prefix) + 42)
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writeBits(uint(depth[inscode]), uint64(bits[inscode]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
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histo[inscode]++
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} else if insertlen < 2114 {
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var tail uint = insertlen - 66
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var nbits uint32 = log2FloorNonZero(tail)
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var code uint = uint(nbits + 50)
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
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histo[code]++
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} else {
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writeBits(uint(depth[61]), uint64(bits[61]), storage_ix, storage)
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writeBits(12, uint64(insertlen)-2114, storage_ix, storage)
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histo[61]++
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}
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}
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func emitLongInsertLen(insertlen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
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if insertlen < 22594 {
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writeBits(uint(depth[62]), uint64(bits[62]), storage_ix, storage)
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writeBits(14, uint64(insertlen)-6210, storage_ix, storage)
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histo[62]++
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} else {
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writeBits(uint(depth[63]), uint64(bits[63]), storage_ix, storage)
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writeBits(24, uint64(insertlen)-22594, storage_ix, storage)
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histo[63]++
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}
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}
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func emitCopyLen1(copylen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
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if copylen < 10 {
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writeBits(uint(depth[copylen+14]), uint64(bits[copylen+14]), storage_ix, storage)
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histo[copylen+14]++
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} else if copylen < 134 {
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var tail uint = copylen - 6
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var nbits uint32 = log2FloorNonZero(tail) - 1
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var prefix uint = tail >> nbits
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var code uint = uint((nbits << 1) + uint32(prefix) + 20)
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
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histo[code]++
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} else if copylen < 2118 {
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var tail uint = copylen - 70
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var nbits uint32 = log2FloorNonZero(tail)
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var code uint = uint(nbits + 28)
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
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histo[code]++
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} else {
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writeBits(uint(depth[39]), uint64(bits[39]), storage_ix, storage)
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writeBits(24, uint64(copylen)-2118, storage_ix, storage)
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histo[39]++
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}
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}
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func emitCopyLenLastDistance1(copylen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
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if copylen < 12 {
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writeBits(uint(depth[copylen-4]), uint64(bits[copylen-4]), storage_ix, storage)
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histo[copylen-4]++
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} else if copylen < 72 {
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var tail uint = copylen - 8
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var nbits uint32 = log2FloorNonZero(tail) - 1
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var prefix uint = tail >> nbits
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var code uint = uint((nbits << 1) + uint32(prefix) + 4)
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
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histo[code]++
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} else if copylen < 136 {
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var tail uint = copylen - 8
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var code uint = (tail >> 5) + 30
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(5, uint64(tail)&31, storage_ix, storage)
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writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
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histo[code]++
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histo[64]++
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} else if copylen < 2120 {
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var tail uint = copylen - 72
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var nbits uint32 = log2FloorNonZero(tail)
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var code uint = uint(nbits + 28)
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writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
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writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
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writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
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histo[code]++
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histo[64]++
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} else {
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writeBits(uint(depth[39]), uint64(bits[39]), storage_ix, storage)
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writeBits(24, uint64(copylen)-2120, storage_ix, storage)
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writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
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histo[39]++
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histo[64]++
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}
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}
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func emitDistance1(distance uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
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var d uint = distance + 3
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var nbits uint32 = log2FloorNonZero(d) - 1
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var prefix uint = (d >> nbits) & 1
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var offset uint = (2 + prefix) << nbits
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var distcode uint = uint(2*(nbits-1) + uint32(prefix) + 80)
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writeBits(uint(depth[distcode]), uint64(bits[distcode]), storage_ix, storage)
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writeBits(uint(nbits), uint64(d)-uint64(offset), storage_ix, storage)
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histo[distcode]++
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}
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func emitLiterals(input []byte, len uint, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
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var j uint
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for j = 0; j < len; j++ {
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var lit byte = input[j]
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writeBits(uint(depth[lit]), uint64(bits[lit]), storage_ix, storage)
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}
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}
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/* REQUIRES: len <= 1 << 24. */
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func storeMetaBlockHeader1(len uint, is_uncompressed bool, storage_ix *uint, storage []byte) {
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var nibbles uint = 6
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/* ISLAST */
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writeBits(1, 0, storage_ix, storage)
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if len <= 1<<16 {
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nibbles = 4
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} else if len <= 1<<20 {
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nibbles = 5
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}
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writeBits(2, uint64(nibbles)-4, storage_ix, storage)
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writeBits(nibbles*4, uint64(len)-1, storage_ix, storage)
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/* ISUNCOMPRESSED */
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writeSingleBit(is_uncompressed, storage_ix, storage)
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}
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func updateBits(n_bits uint, bits uint32, pos uint, array []byte) {
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for n_bits > 0 {
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var byte_pos uint = pos >> 3
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var n_unchanged_bits uint = pos & 7
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var n_changed_bits uint = brotli_min_size_t(n_bits, 8-n_unchanged_bits)
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var total_bits uint = n_unchanged_bits + n_changed_bits
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var mask uint32 = (^((1 << total_bits) - 1)) | ((1 << n_unchanged_bits) - 1)
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var unchanged_bits uint32 = uint32(array[byte_pos]) & mask
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var changed_bits uint32 = bits & ((1 << n_changed_bits) - 1)
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array[byte_pos] = byte(changed_bits<<n_unchanged_bits | unchanged_bits)
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n_bits -= n_changed_bits
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bits >>= n_changed_bits
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pos += n_changed_bits
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}
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}
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func rewindBitPosition1(new_storage_ix uint, storage_ix *uint, storage []byte) {
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var bitpos uint = new_storage_ix & 7
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var mask uint = (1 << bitpos) - 1
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storage[new_storage_ix>>3] &= byte(mask)
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*storage_ix = new_storage_ix
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}
|
||
|
|
|
||
|
|
var shouldMergeBlock_kSampleRate uint = 43
|
||
|
|
|
||
|
|
func shouldMergeBlock(data []byte, len uint, depths []byte) bool {
|
||
|
|
var histo = [256]uint{0}
|
||
|
|
var i uint
|
||
|
|
for i = 0; i < len; i += shouldMergeBlock_kSampleRate {
|
||
|
|
histo[data[i]]++
|
||
|
|
}
|
||
|
|
{
|
||
|
|
var total uint = (len + shouldMergeBlock_kSampleRate - 1) / shouldMergeBlock_kSampleRate
|
||
|
|
var r float64 = (fastLog2(total)+0.5)*float64(total) + 200
|
||
|
|
for i = 0; i < 256; i++ {
|
||
|
|
r -= float64(histo[i]) * (float64(depths[i]) + fastLog2(histo[i]))
|
||
|
|
}
|
||
|
|
|
||
|
|
return r >= 0.0
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func shouldUseUncompressedMode(metablock_start []byte, next_emit []byte, insertlen uint, literal_ratio uint) bool {
|
||
|
|
var compressed uint = uint(-cap(next_emit) + cap(metablock_start))
|
||
|
|
if compressed*50 > insertlen {
|
||
|
|
return false
|
||
|
|
} else {
|
||
|
|
return literal_ratio > 980
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func emitUncompressedMetaBlock1(begin []byte, end []byte, storage_ix_start uint, storage_ix *uint, storage []byte) {
|
||
|
|
var len uint = uint(-cap(end) + cap(begin))
|
||
|
|
rewindBitPosition1(storage_ix_start, storage_ix, storage)
|
||
|
|
storeMetaBlockHeader1(uint(len), true, storage_ix, storage)
|
||
|
|
*storage_ix = (*storage_ix + 7) &^ 7
|
||
|
|
copy(storage[*storage_ix>>3:], begin[:len])
|
||
|
|
*storage_ix += uint(len << 3)
|
||
|
|
storage[*storage_ix>>3] = 0
|
||
|
|
}
|
||
|
|
|
||
|
|
var kCmdHistoSeed = [128]uint32{
|
||
|
|
0,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
0,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
1,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
0,
|
||
|
|
}
|
||
|
|
|
||
|
|
var compressFragmentFastImpl_kFirstBlockSize uint = 3 << 15
|
||
|
|
var compressFragmentFastImpl_kMergeBlockSize uint = 1 << 16
|
||
|
|
|
||
|
|
func compressFragmentFastImpl(in []byte, input_size uint, is_last bool, table []int, table_bits uint, cmd_depth []byte, cmd_bits []uint16, cmd_code_numbits *uint, cmd_code []byte, storage_ix *uint, storage []byte) {
|
||
|
|
var cmd_histo [128]uint32
|
||
|
|
var ip_end int
|
||
|
|
var next_emit int = 0
|
||
|
|
var base_ip int = 0
|
||
|
|
var input int = 0
|
||
|
|
const kInputMarginBytes uint = windowGap
|
||
|
|
const kMinMatchLen uint = 5
|
||
|
|
var metablock_start int = input
|
||
|
|
var block_size uint = brotli_min_size_t(input_size, compressFragmentFastImpl_kFirstBlockSize)
|
||
|
|
var total_block_size uint = block_size
|
||
|
|
var mlen_storage_ix uint = *storage_ix + 3
|
||
|
|
var lit_depth [256]byte
|
||
|
|
var lit_bits [256]uint16
|
||
|
|
var literal_ratio uint
|
||
|
|
var ip int
|
||
|
|
var last_distance int
|
||
|
|
var shift uint = 64 - table_bits
|
||
|
|
|
||
|
|
/* "next_emit" is a pointer to the first byte that is not covered by a
|
||
|
|
previous copy. Bytes between "next_emit" and the start of the next copy or
|
||
|
|
the end of the input will be emitted as literal bytes. */
|
||
|
|
|
||
|
|
/* Save the start of the first block for position and distance computations.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* Save the bit position of the MLEN field of the meta-block header, so that
|
||
|
|
we can update it later if we decide to extend this meta-block. */
|
||
|
|
storeMetaBlockHeader1(block_size, false, storage_ix, storage)
|
||
|
|
|
||
|
|
/* No block splits, no contexts. */
|
||
|
|
writeBits(13, 0, storage_ix, storage)
|
||
|
|
|
||
|
|
literal_ratio = buildAndStoreLiteralPrefixCode(in[input:], block_size, lit_depth[:], lit_bits[:], storage_ix, storage)
|
||
|
|
{
|
||
|
|
/* Store the pre-compressed command and distance prefix codes. */
|
||
|
|
var i uint
|
||
|
|
for i = 0; i+7 < *cmd_code_numbits; i += 8 {
|
||
|
|
writeBits(8, uint64(cmd_code[i>>3]), storage_ix, storage)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
writeBits(*cmd_code_numbits&7, uint64(cmd_code[*cmd_code_numbits>>3]), storage_ix, storage)
|
||
|
|
|
||
|
|
/* Initialize the command and distance histograms. We will gather
|
||
|
|
statistics of command and distance codes during the processing
|
||
|
|
of this block and use it to update the command and distance
|
||
|
|
prefix codes for the next block. */
|
||
|
|
emit_commands:
|
||
|
|
copy(cmd_histo[:], kCmdHistoSeed[:])
|
||
|
|
|
||
|
|
/* "ip" is the input pointer. */
|
||
|
|
ip = input
|
||
|
|
|
||
|
|
last_distance = -1
|
||
|
|
ip_end = int(uint(input) + block_size)
|
||
|
|
|
||
|
|
if block_size >= kInputMarginBytes {
|
||
|
|
var len_limit uint = brotli_min_size_t(block_size-kMinMatchLen, input_size-kInputMarginBytes)
|
||
|
|
var ip_limit int = int(uint(input) + len_limit)
|
||
|
|
/* For the last block, we need to keep a 16 bytes margin so that we can be
|
||
|
|
sure that all distances are at most window size - 16.
|
||
|
|
For all other blocks, we only need to keep a margin of 5 bytes so that
|
||
|
|
we don't go over the block size with a copy. */
|
||
|
|
|
||
|
|
var next_hash uint32
|
||
|
|
ip++
|
||
|
|
for next_hash = hash5(in[ip:], shift); ; {
|
||
|
|
var skip uint32 = 32
|
||
|
|
var next_ip int = ip
|
||
|
|
/* Step 1: Scan forward in the input looking for a 5-byte-long match.
|
||
|
|
If we get close to exhausting the input then goto emit_remainder.
|
||
|
|
|
||
|
|
Heuristic match skipping: If 32 bytes are scanned with no matches
|
||
|
|
found, start looking only at every other byte. If 32 more bytes are
|
||
|
|
scanned, look at every third byte, etc.. When a match is found,
|
||
|
|
immediately go back to looking at every byte. This is a small loss
|
||
|
|
(~5% performance, ~0.1% density) for compressible data due to more
|
||
|
|
bookkeeping, but for non-compressible data (such as JPEG) it's a huge
|
||
|
|
win since the compressor quickly "realizes" the data is incompressible
|
||
|
|
and doesn't bother looking for matches everywhere.
|
||
|
|
|
||
|
|
The "skip" variable keeps track of how many bytes there are since the
|
||
|
|
last match; dividing it by 32 (i.e. right-shifting by five) gives the
|
||
|
|
number of bytes to move ahead for each iteration. */
|
||
|
|
|
||
|
|
var candidate int
|
||
|
|
assert(next_emit < ip)
|
||
|
|
|
||
|
|
trawl:
|
||
|
|
for {
|
||
|
|
var hash uint32 = next_hash
|
||
|
|
var bytes_between_hash_lookups uint32 = skip >> 5
|
||
|
|
skip++
|
||
|
|
assert(hash == hash5(in[next_ip:], shift))
|
||
|
|
ip = next_ip
|
||
|
|
next_ip = int(uint32(ip) + bytes_between_hash_lookups)
|
||
|
|
if next_ip > ip_limit {
|
||
|
|
goto emit_remainder
|
||
|
|
}
|
||
|
|
|
||
|
|
next_hash = hash5(in[next_ip:], shift)
|
||
|
|
candidate = ip - last_distance
|
||
|
|
if isMatch5(in[ip:], in[candidate:]) {
|
||
|
|
if candidate < ip {
|
||
|
|
table[hash] = int(ip - base_ip)
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
candidate = base_ip + table[hash]
|
||
|
|
assert(candidate >= base_ip)
|
||
|
|
assert(candidate < ip)
|
||
|
|
|
||
|
|
table[hash] = int(ip - base_ip)
|
||
|
|
if !(!isMatch5(in[ip:], in[candidate:])) {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Check copy distance. If candidate is not feasible, continue search.
|
||
|
|
Checking is done outside of hot loop to reduce overhead. */
|
||
|
|
if ip-candidate > maxDistance_compress_fragment {
|
||
|
|
goto trawl
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Step 2: Emit the found match together with the literal bytes from
|
||
|
|
"next_emit" to the bit stream, and then see if we can find a next match
|
||
|
|
immediately afterwards. Repeat until we find no match for the input
|
||
|
|
without emitting some literal bytes. */
|
||
|
|
{
|
||
|
|
var base int = ip
|
||
|
|
/* > 0 */
|
||
|
|
var matched uint = 5 + findMatchLengthWithLimit(in[candidate+5:], in[ip+5:], uint(ip_end-ip)-5)
|
||
|
|
var distance int = int(base - candidate)
|
||
|
|
/* We have a 5-byte match at ip, and we need to emit bytes in
|
||
|
|
[next_emit, ip). */
|
||
|
|
|
||
|
|
var insert uint = uint(base - next_emit)
|
||
|
|
ip += int(matched)
|
||
|
|
if insert < 6210 {
|
||
|
|
emitInsertLen1(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
} else if shouldUseUncompressedMode(in[metablock_start:], in[next_emit:], insert, literal_ratio) {
|
||
|
|
emitUncompressedMetaBlock1(in[metablock_start:], in[base:], mlen_storage_ix-3, storage_ix, storage)
|
||
|
|
input_size -= uint(base - input)
|
||
|
|
input = base
|
||
|
|
next_emit = input
|
||
|
|
goto next_block
|
||
|
|
} else {
|
||
|
|
emitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
}
|
||
|
|
|
||
|
|
emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
|
||
|
|
if distance == last_distance {
|
||
|
|
writeBits(uint(cmd_depth[64]), uint64(cmd_bits[64]), storage_ix, storage)
|
||
|
|
cmd_histo[64]++
|
||
|
|
} else {
|
||
|
|
emitDistance1(uint(distance), cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
last_distance = distance
|
||
|
|
}
|
||
|
|
|
||
|
|
emitCopyLenLastDistance1(matched, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
|
||
|
|
next_emit = ip
|
||
|
|
if ip >= ip_limit {
|
||
|
|
goto emit_remainder
|
||
|
|
}
|
||
|
|
|
||
|
|
/* We could immediately start working at ip now, but to improve
|
||
|
|
compression we first update "table" with the hashes of some positions
|
||
|
|
within the last copy. */
|
||
|
|
{
|
||
|
|
var input_bytes uint64 = binary.LittleEndian.Uint64(in[ip-3:])
|
||
|
|
var prev_hash uint32 = hashBytesAtOffset5(input_bytes, 0, shift)
|
||
|
|
var cur_hash uint32 = hashBytesAtOffset5(input_bytes, 3, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 3)
|
||
|
|
prev_hash = hashBytesAtOffset5(input_bytes, 1, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 2)
|
||
|
|
prev_hash = hashBytesAtOffset5(input_bytes, 2, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 1)
|
||
|
|
|
||
|
|
candidate = base_ip + table[cur_hash]
|
||
|
|
table[cur_hash] = int(ip - base_ip)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
for isMatch5(in[ip:], in[candidate:]) {
|
||
|
|
var base int = ip
|
||
|
|
/* We have a 5-byte match at ip, and no need to emit any literal bytes
|
||
|
|
prior to ip. */
|
||
|
|
|
||
|
|
var matched uint = 5 + findMatchLengthWithLimit(in[candidate+5:], in[ip+5:], uint(ip_end-ip)-5)
|
||
|
|
if ip-candidate > maxDistance_compress_fragment {
|
||
|
|
break
|
||
|
|
}
|
||
|
|
ip += int(matched)
|
||
|
|
last_distance = int(base - candidate) /* > 0 */
|
||
|
|
emitCopyLen1(matched, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
emitDistance1(uint(last_distance), cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
|
||
|
|
next_emit = ip
|
||
|
|
if ip >= ip_limit {
|
||
|
|
goto emit_remainder
|
||
|
|
}
|
||
|
|
|
||
|
|
/* We could immediately start working at ip now, but to improve
|
||
|
|
compression we first update "table" with the hashes of some positions
|
||
|
|
within the last copy. */
|
||
|
|
{
|
||
|
|
var input_bytes uint64 = binary.LittleEndian.Uint64(in[ip-3:])
|
||
|
|
var prev_hash uint32 = hashBytesAtOffset5(input_bytes, 0, shift)
|
||
|
|
var cur_hash uint32 = hashBytesAtOffset5(input_bytes, 3, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 3)
|
||
|
|
prev_hash = hashBytesAtOffset5(input_bytes, 1, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 2)
|
||
|
|
prev_hash = hashBytesAtOffset5(input_bytes, 2, shift)
|
||
|
|
table[prev_hash] = int(ip - base_ip - 1)
|
||
|
|
|
||
|
|
candidate = base_ip + table[cur_hash]
|
||
|
|
table[cur_hash] = int(ip - base_ip)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
ip++
|
||
|
|
next_hash = hash5(in[ip:], shift)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
emit_remainder:
|
||
|
|
assert(next_emit <= ip_end)
|
||
|
|
input += int(block_size)
|
||
|
|
input_size -= block_size
|
||
|
|
block_size = brotli_min_size_t(input_size, compressFragmentFastImpl_kMergeBlockSize)
|
||
|
|
|
||
|
|
/* Decide if we want to continue this meta-block instead of emitting the
|
||
|
|
last insert-only command. */
|
||
|
|
if input_size > 0 && total_block_size+block_size <= 1<<20 && shouldMergeBlock(in[input:], block_size, lit_depth[:]) {
|
||
|
|
assert(total_block_size > 1<<16)
|
||
|
|
|
||
|
|
/* Update the size of the current meta-block and continue emitting commands.
|
||
|
|
We can do this because the current size and the new size both have 5
|
||
|
|
nibbles. */
|
||
|
|
total_block_size += block_size
|
||
|
|
|
||
|
|
updateBits(20, uint32(total_block_size-1), mlen_storage_ix, storage)
|
||
|
|
goto emit_commands
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Emit the remaining bytes as literals. */
|
||
|
|
if next_emit < ip_end {
|
||
|
|
var insert uint = uint(ip_end - next_emit)
|
||
|
|
if insert < 6210 {
|
||
|
|
emitInsertLen1(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
|
||
|
|
} else if shouldUseUncompressedMode(in[metablock_start:], in[next_emit:], insert, literal_ratio) {
|
||
|
|
emitUncompressedMetaBlock1(in[metablock_start:], in[ip_end:], mlen_storage_ix-3, storage_ix, storage)
|
||
|
|
} else {
|
||
|
|
emitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
|
||
|
|
emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
next_emit = ip_end
|
||
|
|
|
||
|
|
/* If we have more data, write a new meta-block header and prefix codes and
|
||
|
|
then continue emitting commands. */
|
||
|
|
next_block:
|
||
|
|
if input_size > 0 {
|
||
|
|
metablock_start = input
|
||
|
|
block_size = brotli_min_size_t(input_size, compressFragmentFastImpl_kFirstBlockSize)
|
||
|
|
total_block_size = block_size
|
||
|
|
|
||
|
|
/* Save the bit position of the MLEN field of the meta-block header, so that
|
||
|
|
we can update it later if we decide to extend this meta-block. */
|
||
|
|
mlen_storage_ix = *storage_ix + 3
|
||
|
|
|
||
|
|
storeMetaBlockHeader1(block_size, false, storage_ix, storage)
|
||
|
|
|
||
|
|
/* No block splits, no contexts. */
|
||
|
|
writeBits(13, 0, storage_ix, storage)
|
||
|
|
|
||
|
|
literal_ratio = buildAndStoreLiteralPrefixCode(in[input:], block_size, lit_depth[:], lit_bits[:], storage_ix, storage)
|
||
|
|
buildAndStoreCommandPrefixCode1(cmd_histo[:], cmd_depth, cmd_bits, storage_ix, storage)
|
||
|
|
goto emit_commands
|
||
|
|
}
|
||
|
|
|
||
|
|
if !is_last {
|
||
|
|
/* If this is not the last block, update the command and distance prefix
|
||
|
|
codes for the next block and store the compressed forms. */
|
||
|
|
cmd_code[0] = 0
|
||
|
|
|
||
|
|
*cmd_code_numbits = 0
|
||
|
|
buildAndStoreCommandPrefixCode1(cmd_histo[:], cmd_depth, cmd_bits, cmd_code_numbits, cmd_code)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Compresses "input" string to the "*storage" buffer as one or more complete
|
||
|
|
meta-blocks, and updates the "*storage_ix" bit position.
|
||
|
|
|
||
|
|
If "is_last" is 1, emits an additional empty last meta-block.
|
||
|
|
|
||
|
|
"cmd_depth" and "cmd_bits" contain the command and distance prefix codes
|
||
|
|
(see comment in encode.h) used for the encoding of this input fragment.
|
||
|
|
If "is_last" is 0, they are updated to reflect the statistics
|
||
|
|
of this input fragment, to be used for the encoding of the next fragment.
|
||
|
|
|
||
|
|
"*cmd_code_numbits" is the number of bits of the compressed representation
|
||
|
|
of the command and distance prefix codes, and "cmd_code" is an array of
|
||
|
|
at least "(*cmd_code_numbits + 7) >> 3" size that contains the compressed
|
||
|
|
command and distance prefix codes. If "is_last" is 0, these are also
|
||
|
|
updated to represent the updated "cmd_depth" and "cmd_bits".
|
||
|
|
|
||
|
|
REQUIRES: "input_size" is greater than zero, or "is_last" is 1.
|
||
|
|
REQUIRES: "input_size" is less or equal to maximal metablock size (1 << 24).
|
||
|
|
REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
|
||
|
|
REQUIRES: "table_size" is an odd (9, 11, 13, 15) power of two
|
||
|
|
OUTPUT: maximal copy distance <= |input_size|
|
||
|
|
OUTPUT: maximal copy distance <= BROTLI_MAX_BACKWARD_LIMIT(18) */
|
||
|
|
func compressFragmentFast(input []byte, input_size uint, is_last bool, table []int, table_size uint, cmd_depth []byte, cmd_bits []uint16, cmd_code_numbits *uint, cmd_code []byte, storage_ix *uint, storage []byte) {
|
||
|
|
var initial_storage_ix uint = *storage_ix
|
||
|
|
var table_bits uint = uint(log2FloorNonZero(table_size))
|
||
|
|
|
||
|
|
if input_size == 0 {
|
||
|
|
assert(is_last)
|
||
|
|
writeBits(1, 1, storage_ix, storage) /* islast */
|
||
|
|
writeBits(1, 1, storage_ix, storage) /* isempty */
|
||
|
|
*storage_ix = (*storage_ix + 7) &^ 7
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
compressFragmentFastImpl(input, input_size, is_last, table, table_bits, cmd_depth, cmd_bits, cmd_code_numbits, cmd_code, storage_ix, storage)
|
||
|
|
|
||
|
|
/* If output is larger than single uncompressed block, rewrite it. */
|
||
|
|
if *storage_ix-initial_storage_ix > 31+(input_size<<3) {
|
||
|
|
emitUncompressedMetaBlock1(input, input[input_size:], initial_storage_ix, storage_ix, storage)
|
||
|
|
}
|
||
|
|
|
||
|
|
if is_last {
|
||
|
|
writeBits(1, 1, storage_ix, storage) /* islast */
|
||
|
|
writeBits(1, 1, storage_ix, storage) /* isempty */
|
||
|
|
*storage_ix = (*storage_ix + 7) &^ 7
|
||
|
|
}
|
||
|
|
}
|