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brotli/brotli_bit_stream.go

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package brotli
import (
"math"
"sort"
)
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<<insnumextra | insextraval
writeBits(uint(insnumextra+getCopyExtra(copycode)), bits, storage_ix, storage)
}
/* Data structure that stores almost everything that is needed to encode each
block switch command. */
type blockSplitCode struct {
type_code_calculator blockTypeCodeCalculator
type_depths [maxBlockTypeSymbols]byte
type_bits [maxBlockTypeSymbols]uint16
length_depths [numBlockLenSymbols]byte
length_bits [numBlockLenSymbols]uint16
}
/* Stores a number between 0 and 255. */
func storeVarLenUint8(n uint, storage_ix *uint, storage []byte) {
if n == 0 {
writeBits(1, 0, storage_ix, storage)
} else {
var nbits uint = uint(log2FloorNonZero(n))
writeBits(1, 1, storage_ix, storage)
writeBits(3, uint64(nbits), storage_ix, storage)
writeBits(nbits, uint64(n)-(uint64(uint(1))<<nbits), storage_ix, storage)
}
}
/* Stores the compressed meta-block header.
REQUIRES: length > 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 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
sort.Sort(sortHuffmanTree(tree[:n]))
/* 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<<max_prefix {
var run_length_prefix uint32 = log2FloorNonZero(uint(reps))
var extra_bits uint32 = reps - (1 << run_length_prefix)
v[*out_size] = run_length_prefix + (extra_bits << 9)
(*out_size)++
break
} else {
var extra_bits uint32 = (1 << max_prefix) - 1
v[*out_size] = max_prefix + (extra_bits << 9)
reps -= (2 << max_prefix) - 1
(*out_size)++
}
}
}
}
}
const symbolBits = 9
var encodeContextMap_kSymbolMask uint32 = (1 << symbolBits) - 1
func encodeContextMap(context_map []uint32, context_map_size uint, num_clusters uint, tree []huffmanTree, storage_ix *uint, storage []byte) {
var i uint
var rle_symbols []uint32
var max_run_length_prefix uint32 = 6
var num_rle_symbols uint = 0
var histogram [maxContextMapSymbols]uint32
var depths [maxContextMapSymbols]byte
var bits [maxContextMapSymbols]uint16
storeVarLenUint8(num_clusters-1, storage_ix, storage)
if num_clusters == 1 {
return
}
rle_symbols = make([]uint32, context_map_size)
moveToFrontTransform(context_map, context_map_size, rle_symbols)
runLengthCodeZeros(context_map_size, rle_symbols, &num_rle_symbols, &max_run_length_prefix)
histogram = [maxContextMapSymbols]uint32{}
for i = 0; i < num_rle_symbols; i++ {
histogram[rle_symbols[i]&encodeContextMap_kSymbolMask]++
}
{
var use_rle bool = (max_run_length_prefix > 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 = &params.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)
}
}
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