mirror of
https://github.com/google/brotli.git
synced 2024-11-29 22:51:05 +00:00
667f70adcb
* Cluster at most 64 histograms at a time in the first
round of clustering.
* Use a faster histogram cost estimation function.
* Don't compute the log2(total) multiple times in the
block splitter.
885 lines
30 KiB
C++
885 lines
30 KiB
C++
// Copyright 2014 Google Inc. All Rights Reserved.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
//
|
|
// Brotli bit stream functions to support the low level format. There are no
|
|
// compression algorithms here, just the right ordering of bits to match the
|
|
// specs.
|
|
|
|
#include "./brotli_bit_stream.h"
|
|
|
|
#include <algorithm>
|
|
#include <limits>
|
|
#include <vector>
|
|
|
|
#include "./bit_cost.h"
|
|
#include "./context.h"
|
|
#include "./entropy_encode.h"
|
|
#include "./fast_log.h"
|
|
#include "./prefix.h"
|
|
#include "./write_bits.h"
|
|
|
|
namespace brotli {
|
|
|
|
// returns false if fail
|
|
// nibblesbits represents the 2 bits to encode MNIBBLES (0-3)
|
|
bool EncodeMlen(size_t length, int* bits, int* numbits, int* nibblesbits) {
|
|
length--; // MLEN - 1 is encoded
|
|
int lg = length == 0 ? 1 : Log2Floor(length) + 1;
|
|
if (lg > 24) return false;
|
|
int mnibbles = (lg < 16 ? 16 : (lg + 3)) / 4;
|
|
*nibblesbits = mnibbles - 4;
|
|
*numbits = mnibbles * 4;
|
|
*bits = length;
|
|
return true;
|
|
}
|
|
|
|
void StoreVarLenUint8(int n, int* storage_ix, uint8_t* storage) {
|
|
if (n == 0) {
|
|
WriteBits(1, 0, storage_ix, storage);
|
|
} else {
|
|
WriteBits(1, 1, storage_ix, storage);
|
|
int nbits = Log2Floor(n);
|
|
WriteBits(3, nbits, storage_ix, storage);
|
|
WriteBits(nbits, n - (1 << nbits), storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
bool StoreCompressedMetaBlockHeader(bool final_block,
|
|
size_t length,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
// Write ISLAST bit.
|
|
WriteBits(1, final_block, storage_ix, storage);
|
|
// Write ISEMPTY bit.
|
|
if (final_block) {
|
|
WriteBits(1, length == 0, storage_ix, storage);
|
|
if (length == 0) {
|
|
return true;
|
|
}
|
|
}
|
|
|
|
if (length == 0) {
|
|
// Only the last meta-block can be empty.
|
|
return false;
|
|
}
|
|
|
|
int lenbits;
|
|
int nlenbits;
|
|
int nibblesbits;
|
|
if (!EncodeMlen(length, &lenbits, &nlenbits, &nibblesbits)) {
|
|
return false;
|
|
}
|
|
|
|
WriteBits(2, nibblesbits, storage_ix, storage);
|
|
WriteBits(nlenbits, lenbits, storage_ix, storage);
|
|
|
|
if (!final_block) {
|
|
// Write ISUNCOMPRESSED bit.
|
|
WriteBits(1, 0, storage_ix, storage);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool StoreUncompressedMetaBlockHeader(size_t length,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
// Write ISLAST bit. Uncompressed block cannot be the last one, so set to 0.
|
|
WriteBits(1, 0, storage_ix, storage);
|
|
int lenbits;
|
|
int nlenbits;
|
|
int nibblesbits;
|
|
if (!EncodeMlen(length, &lenbits, &nlenbits, &nibblesbits)) {
|
|
return false;
|
|
}
|
|
WriteBits(2, nibblesbits, storage_ix, storage);
|
|
WriteBits(nlenbits, lenbits, storage_ix, storage);
|
|
// Write ISUNCOMPRESSED bit.
|
|
WriteBits(1, 1, storage_ix, storage);
|
|
return true;
|
|
}
|
|
|
|
void StoreHuffmanTreeOfHuffmanTreeToBitMask(
|
|
const int num_codes,
|
|
const uint8_t *code_length_bitdepth,
|
|
int *storage_ix,
|
|
uint8_t *storage) {
|
|
static const uint8_t kStorageOrder[kCodeLengthCodes] = {
|
|
1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15
|
|
};
|
|
// The bit lengths of the Huffman code over the code length alphabet
|
|
// are compressed with the following static Huffman code:
|
|
// Symbol Code
|
|
// ------ ----
|
|
// 0 00
|
|
// 1 1110
|
|
// 2 110
|
|
// 3 01
|
|
// 4 10
|
|
// 5 1111
|
|
static const uint8_t kHuffmanBitLengthHuffmanCodeSymbols[6] = {
|
|
0, 7, 3, 2, 1, 15
|
|
};
|
|
static const uint8_t kHuffmanBitLengthHuffmanCodeBitLengths[6] = {
|
|
2, 4, 3, 2, 2, 4
|
|
};
|
|
|
|
// Throw away trailing zeros:
|
|
int codes_to_store = kCodeLengthCodes;
|
|
if (num_codes > 1) {
|
|
for (; codes_to_store > 0; --codes_to_store) {
|
|
if (code_length_bitdepth[kStorageOrder[codes_to_store - 1]] != 0) {
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
int skip_some = 0; // skips none.
|
|
if (code_length_bitdepth[kStorageOrder[0]] == 0 &&
|
|
code_length_bitdepth[kStorageOrder[1]] == 0) {
|
|
skip_some = 2; // skips two.
|
|
if (code_length_bitdepth[kStorageOrder[2]] == 0) {
|
|
skip_some = 3; // skips three.
|
|
}
|
|
}
|
|
WriteBits(2, skip_some, storage_ix, storage);
|
|
for (int i = skip_some; i < codes_to_store; ++i) {
|
|
uint8_t l = code_length_bitdepth[kStorageOrder[i]];
|
|
WriteBits(kHuffmanBitLengthHuffmanCodeBitLengths[l],
|
|
kHuffmanBitLengthHuffmanCodeSymbols[l], storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
void StoreHuffmanTreeToBitMask(
|
|
const std::vector<uint8_t> &huffman_tree,
|
|
const std::vector<uint8_t> &huffman_tree_extra_bits,
|
|
const uint8_t *code_length_bitdepth,
|
|
const std::vector<uint16_t> &code_length_bitdepth_symbols,
|
|
int * __restrict storage_ix,
|
|
uint8_t * __restrict storage) {
|
|
for (int i = 0; i < huffman_tree.size(); ++i) {
|
|
int ix = huffman_tree[i];
|
|
WriteBits(code_length_bitdepth[ix], code_length_bitdepth_symbols[ix],
|
|
storage_ix, storage);
|
|
// Extra bits
|
|
switch (ix) {
|
|
case 16:
|
|
WriteBits(2, huffman_tree_extra_bits[i], storage_ix, storage);
|
|
break;
|
|
case 17:
|
|
WriteBits(3, huffman_tree_extra_bits[i], storage_ix, storage);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
void StoreSimpleHuffmanTree(const uint8_t* depths,
|
|
int symbols[4],
|
|
int num_symbols,
|
|
int max_bits,
|
|
int *storage_ix, uint8_t *storage) {
|
|
// value of 1 indicates a simple Huffman code
|
|
WriteBits(2, 1, storage_ix, storage);
|
|
WriteBits(2, num_symbols - 1, storage_ix, storage); // NSYM - 1
|
|
|
|
// Sort
|
|
for (int i = 0; i < num_symbols; i++) {
|
|
for (int j = i + 1; j < num_symbols; j++) {
|
|
if (depths[symbols[j]] < depths[symbols[i]]) {
|
|
std::swap(symbols[j], symbols[i]);
|
|
}
|
|
}
|
|
}
|
|
|
|
if (num_symbols == 2) {
|
|
WriteBits(max_bits, symbols[0], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[1], storage_ix, storage);
|
|
} else if (num_symbols == 3) {
|
|
WriteBits(max_bits, symbols[0], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[1], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[2], storage_ix, storage);
|
|
} else {
|
|
WriteBits(max_bits, symbols[0], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[1], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[2], storage_ix, storage);
|
|
WriteBits(max_bits, symbols[3], storage_ix, storage);
|
|
// tree-select
|
|
WriteBits(1, depths[symbols[0]] == 1 ? 1 : 0, storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
// num = alphabet size
|
|
// depths = symbol depths
|
|
void StoreHuffmanTree(const uint8_t* depths, size_t num,
|
|
int *storage_ix, uint8_t *storage) {
|
|
// Write the Huffman tree into the brotli-representation.
|
|
std::vector<uint8_t> huffman_tree;
|
|
std::vector<uint8_t> huffman_tree_extra_bits;
|
|
// TODO: Consider allocating these from stack.
|
|
huffman_tree.reserve(256);
|
|
huffman_tree_extra_bits.reserve(256);
|
|
WriteHuffmanTree(depths, num, &huffman_tree, &huffman_tree_extra_bits);
|
|
|
|
// Calculate the statistics of the Huffman tree in brotli-representation.
|
|
int huffman_tree_histogram[kCodeLengthCodes] = { 0 };
|
|
for (int i = 0; i < huffman_tree.size(); ++i) {
|
|
++huffman_tree_histogram[huffman_tree[i]];
|
|
}
|
|
|
|
int num_codes = 0;
|
|
int code = 0;
|
|
for (int i = 0; i < kCodeLengthCodes; ++i) {
|
|
if (huffman_tree_histogram[i]) {
|
|
if (num_codes == 0) {
|
|
code = i;
|
|
num_codes = 1;
|
|
} else if (num_codes == 1) {
|
|
num_codes = 2;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Calculate another Huffman tree to use for compressing both the
|
|
// earlier Huffman tree with.
|
|
// TODO: Consider allocating these from stack.
|
|
uint8_t code_length_bitdepth[kCodeLengthCodes] = { 0 };
|
|
std::vector<uint16_t> code_length_bitdepth_symbols(kCodeLengthCodes);
|
|
CreateHuffmanTree(&huffman_tree_histogram[0], kCodeLengthCodes,
|
|
5, &code_length_bitdepth[0]);
|
|
ConvertBitDepthsToSymbols(code_length_bitdepth, kCodeLengthCodes,
|
|
code_length_bitdepth_symbols.data());
|
|
|
|
// 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,
|
|
huffman_tree_extra_bits,
|
|
&code_length_bitdepth[0],
|
|
code_length_bitdepth_symbols,
|
|
storage_ix, storage);
|
|
}
|
|
|
|
void BuildAndStoreHuffmanTree(const int *histogram,
|
|
const int length,
|
|
uint8_t* depth,
|
|
uint16_t* bits,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
int count = 0;
|
|
int s4[4] = { 0 };
|
|
for (size_t i = 0; i < length; i++) {
|
|
if (histogram[i]) {
|
|
if (count < 4) {
|
|
s4[count] = i;
|
|
} else if (count > 4) {
|
|
break;
|
|
}
|
|
count++;
|
|
}
|
|
}
|
|
|
|
int max_bits_counter = length - 1;
|
|
int max_bits = 0;
|
|
while (max_bits_counter) {
|
|
max_bits_counter >>= 1;
|
|
++max_bits;
|
|
}
|
|
|
|
if (count <= 1) {
|
|
WriteBits(4, 1, storage_ix, storage);
|
|
WriteBits(max_bits, s4[0], storage_ix, storage);
|
|
return;
|
|
}
|
|
|
|
CreateHuffmanTree(histogram, length, 15, depth);
|
|
ConvertBitDepthsToSymbols(depth, length, bits);
|
|
|
|
if (count <= 4) {
|
|
StoreSimpleHuffmanTree(depth, s4, count, max_bits, storage_ix, storage);
|
|
} else {
|
|
StoreHuffmanTree(depth, length, storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
int IndexOf(const std::vector<int>& v, int value) {
|
|
for (int i = 0; i < v.size(); ++i) {
|
|
if (v[i] == value) return i;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
void MoveToFront(std::vector<int>* v, int index) {
|
|
int value = (*v)[index];
|
|
for (int i = index; i > 0; --i) {
|
|
(*v)[i] = (*v)[i - 1];
|
|
}
|
|
(*v)[0] = value;
|
|
}
|
|
|
|
std::vector<int> MoveToFrontTransform(const std::vector<int>& v) {
|
|
if (v.empty()) return v;
|
|
std::vector<int> mtf(*std::max_element(v.begin(), v.end()) + 1);
|
|
for (int i = 0; i < mtf.size(); ++i) mtf[i] = i;
|
|
std::vector<int> result(v.size());
|
|
for (int i = 0; i < v.size(); ++i) {
|
|
int index = IndexOf(mtf, v[i]);
|
|
result[i] = index;
|
|
MoveToFront(&mtf, index);
|
|
}
|
|
return result;
|
|
}
|
|
|
|
// Finds runs of zeros in v_in and replaces them with a prefix code of the run
|
|
// length plus extra bits in *v_out and *extra_bits. Non-zero values in v_in 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.
|
|
void RunLengthCodeZeros(const std::vector<int>& v_in,
|
|
int* max_run_length_prefix,
|
|
std::vector<int>* v_out,
|
|
std::vector<int>* extra_bits) {
|
|
int max_reps = 0;
|
|
for (int i = 0; i < v_in.size();) {
|
|
for (; i < v_in.size() && v_in[i] != 0; ++i) ;
|
|
int reps = 0;
|
|
for (; i < v_in.size() && v_in[i] == 0; ++i) {
|
|
++reps;
|
|
}
|
|
max_reps = std::max(reps, max_reps);
|
|
}
|
|
int max_prefix = max_reps > 0 ? Log2Floor(max_reps) : 0;
|
|
*max_run_length_prefix = std::min(max_prefix, *max_run_length_prefix);
|
|
for (int i = 0; i < v_in.size();) {
|
|
if (v_in[i] != 0) {
|
|
v_out->push_back(v_in[i] + *max_run_length_prefix);
|
|
extra_bits->push_back(0);
|
|
++i;
|
|
} else {
|
|
int reps = 1;
|
|
for (uint32_t k = i + 1; k < v_in.size() && v_in[k] == 0; ++k) {
|
|
++reps;
|
|
}
|
|
i += reps;
|
|
while (reps) {
|
|
if (reps < (2 << *max_run_length_prefix)) {
|
|
int run_length_prefix = Log2Floor(reps);
|
|
v_out->push_back(run_length_prefix);
|
|
extra_bits->push_back(reps - (1 << run_length_prefix));
|
|
break;
|
|
} else {
|
|
v_out->push_back(*max_run_length_prefix);
|
|
extra_bits->push_back((1 << *max_run_length_prefix) - 1);
|
|
reps -= (2 << *max_run_length_prefix) - 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void EncodeContextMap(const std::vector<int>& context_map,
|
|
int num_clusters,
|
|
int* storage_ix, uint8_t* storage) {
|
|
StoreVarLenUint8(num_clusters - 1, storage_ix, storage);
|
|
|
|
if (num_clusters == 1) {
|
|
return;
|
|
}
|
|
|
|
std::vector<int> transformed_symbols = MoveToFrontTransform(context_map);
|
|
std::vector<int> rle_symbols;
|
|
std::vector<int> extra_bits;
|
|
int max_run_length_prefix = 6;
|
|
RunLengthCodeZeros(transformed_symbols, &max_run_length_prefix,
|
|
&rle_symbols, &extra_bits);
|
|
HistogramContextMap symbol_histogram;
|
|
for (int i = 0; i < rle_symbols.size(); ++i) {
|
|
symbol_histogram.Add(rle_symbols[i]);
|
|
}
|
|
bool use_rle = max_run_length_prefix > 0;
|
|
WriteBits(1, use_rle, storage_ix, storage);
|
|
if (use_rle) {
|
|
WriteBits(4, max_run_length_prefix - 1, storage_ix, storage);
|
|
}
|
|
EntropyCodeContextMap symbol_code;
|
|
memset(symbol_code.depth_, 0, sizeof(symbol_code.depth_));
|
|
memset(symbol_code.bits_, 0, sizeof(symbol_code.bits_));
|
|
BuildAndStoreHuffmanTree(symbol_histogram.data_,
|
|
num_clusters + max_run_length_prefix,
|
|
symbol_code.depth_, symbol_code.bits_,
|
|
storage_ix, storage);
|
|
for (int i = 0; i < rle_symbols.size(); ++i) {
|
|
WriteBits(symbol_code.depth_[rle_symbols[i]],
|
|
symbol_code.bits_[rle_symbols[i]],
|
|
storage_ix, storage);
|
|
if (rle_symbols[i] > 0 && rle_symbols[i] <= max_run_length_prefix) {
|
|
WriteBits(rle_symbols[i], extra_bits[i], storage_ix, storage);
|
|
}
|
|
}
|
|
WriteBits(1, 1, storage_ix, storage); // use move-to-front
|
|
}
|
|
|
|
void StoreBlockSwitch(const BlockSplitCode& code,
|
|
const int block_ix,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
if (block_ix > 0) {
|
|
int typecode = code.type_code[block_ix];
|
|
WriteBits(code.type_depths[typecode], code.type_bits[typecode],
|
|
storage_ix, storage);
|
|
}
|
|
int lencode = code.length_prefix[block_ix];
|
|
WriteBits(code.length_depths[lencode], code.length_bits[lencode],
|
|
storage_ix, storage);
|
|
WriteBits(code.length_nextra[block_ix], code.length_extra[block_ix],
|
|
storage_ix, storage);
|
|
}
|
|
|
|
void BuildAndStoreBlockSplitCode(const std::vector<int>& types,
|
|
const std::vector<int>& lengths,
|
|
const int num_types,
|
|
BlockSplitCode* code,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
const int num_blocks = types.size();
|
|
std::vector<int> type_histo(num_types + 2);
|
|
std::vector<int> length_histo(26);
|
|
int last_type = 1;
|
|
int second_last_type = 0;
|
|
code->type_code.resize(num_blocks);
|
|
code->length_prefix.resize(num_blocks);
|
|
code->length_nextra.resize(num_blocks);
|
|
code->length_extra.resize(num_blocks);
|
|
code->type_depths.resize(num_types + 2);
|
|
code->type_bits.resize(num_types + 2);
|
|
code->length_depths.resize(26);
|
|
code->length_bits.resize(26);
|
|
for (int i = 0; i < num_blocks; ++i) {
|
|
int type = types[i];
|
|
int type_code = (type == last_type + 1 ? 1 :
|
|
type == second_last_type ? 0 :
|
|
type + 2);
|
|
second_last_type = last_type;
|
|
last_type = type;
|
|
code->type_code[i] = type_code;
|
|
if (i > 0) ++type_histo[type_code];
|
|
GetBlockLengthPrefixCode(lengths[i],
|
|
&code->length_prefix[i],
|
|
&code->length_nextra[i],
|
|
&code->length_extra[i]);
|
|
++length_histo[code->length_prefix[i]];
|
|
}
|
|
StoreVarLenUint8(num_types - 1, storage_ix, storage);
|
|
if (num_types > 1) {
|
|
BuildAndStoreHuffmanTree(&type_histo[0], num_types + 2,
|
|
&code->type_depths[0], &code->type_bits[0],
|
|
storage_ix, storage);
|
|
BuildAndStoreHuffmanTree(&length_histo[0], 26,
|
|
&code->length_depths[0], &code->length_bits[0],
|
|
storage_ix, storage);
|
|
StoreBlockSwitch(*code, 0, storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
void StoreTrivialContextMap(int num_types,
|
|
int context_bits,
|
|
int* storage_ix,
|
|
uint8_t* storage) {
|
|
StoreVarLenUint8(num_types - 1, storage_ix, storage);
|
|
if (num_types > 1) {
|
|
int repeat_code = context_bits - 1;
|
|
int repeat_bits = (1 << repeat_code) - 1;
|
|
int alphabet_size = num_types + repeat_code;
|
|
std::vector<int> histogram(alphabet_size);
|
|
std::vector<uint8_t> depths(alphabet_size);
|
|
std::vector<uint16_t> bits(alphabet_size);
|
|
// Write RLEMAX.
|
|
WriteBits(1, 1, storage_ix, storage);
|
|
WriteBits(4, repeat_code - 1, storage_ix, storage);
|
|
histogram[repeat_code] = num_types;
|
|
histogram[0] = 1;
|
|
for (int i = context_bits; i < alphabet_size; ++i) {
|
|
histogram[i] = 1;
|
|
}
|
|
BuildAndStoreHuffmanTree(&histogram[0], alphabet_size,
|
|
&depths[0], &bits[0],
|
|
storage_ix, storage);
|
|
for (int i = 0; i < num_types; ++i) {
|
|
int code = (i == 0 ? 0 : i + context_bits - 1);
|
|
WriteBits(depths[code], bits[code], storage_ix, storage);
|
|
WriteBits(depths[repeat_code], bits[repeat_code], storage_ix, storage);
|
|
WriteBits(repeat_code, repeat_bits, storage_ix, storage);
|
|
}
|
|
// Write IMTF (inverse-move-to-front) bit.
|
|
WriteBits(1, 1, storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
// Manages the encoding of one block category (literal, command or distance).
|
|
class BlockEncoder {
|
|
public:
|
|
BlockEncoder(int alphabet_size,
|
|
int num_block_types,
|
|
const std::vector<int>& block_types,
|
|
const std::vector<int>& block_lengths)
|
|
: alphabet_size_(alphabet_size),
|
|
num_block_types_(num_block_types),
|
|
block_types_(block_types),
|
|
block_lengths_(block_lengths),
|
|
block_ix_(0),
|
|
block_len_(block_lengths.empty() ? 0 : block_lengths[0]),
|
|
entropy_ix_(0) {}
|
|
|
|
// Creates entropy codes of block lengths and block types and stores them
|
|
// to the bit stream.
|
|
void BuildAndStoreBlockSwitchEntropyCodes(int* storage_ix, uint8_t* storage) {
|
|
BuildAndStoreBlockSplitCode(
|
|
block_types_, block_lengths_, num_block_types_,
|
|
&block_split_code_, storage_ix, storage);
|
|
}
|
|
|
|
// Creates entropy codes for all block types and stores them to the bit
|
|
// stream.
|
|
template<int kSize>
|
|
void BuildAndStoreEntropyCodes(
|
|
const std::vector<Histogram<kSize> >& histograms,
|
|
int* storage_ix, uint8_t* storage) {
|
|
depths_.resize(histograms.size() * alphabet_size_);
|
|
bits_.resize(histograms.size() * alphabet_size_);
|
|
for (int i = 0; i < histograms.size(); ++i) {
|
|
int ix = i * alphabet_size_;
|
|
BuildAndStoreHuffmanTree(&histograms[i].data_[0], alphabet_size_,
|
|
&depths_[ix], &bits_[ix],
|
|
storage_ix, storage);
|
|
}
|
|
}
|
|
|
|
// Stores the next symbol with the entropy code of the current block type.
|
|
// Updates the block type and block length at block boundaries.
|
|
void StoreSymbol(int symbol, int* storage_ix, uint8_t* storage) {
|
|
if (block_len_ == 0) {
|
|
++block_ix_;
|
|
block_len_ = block_lengths_[block_ix_];
|
|
entropy_ix_ = block_types_[block_ix_] * alphabet_size_;
|
|
StoreBlockSwitch(block_split_code_, block_ix_, storage_ix, storage);
|
|
}
|
|
--block_len_;
|
|
int ix = entropy_ix_ + symbol;
|
|
WriteBits(depths_[ix], bits_[ix], storage_ix, storage);
|
|
}
|
|
|
|
// Stores the next symbol with the entropy code of the current block type and
|
|
// context value.
|
|
// Updates the block type and block length at block boundaries.
|
|
template<int kContextBits>
|
|
void StoreSymbolWithContext(int symbol, int context,
|
|
const std::vector<int>& context_map,
|
|
int* storage_ix, uint8_t* storage) {
|
|
if (block_len_ == 0) {
|
|
++block_ix_;
|
|
block_len_ = block_lengths_[block_ix_];
|
|
entropy_ix_ = block_types_[block_ix_] << kContextBits;
|
|
StoreBlockSwitch(block_split_code_, block_ix_, storage_ix, storage);
|
|
}
|
|
--block_len_;
|
|
int histo_ix = context_map[entropy_ix_ + context];
|
|
int ix = histo_ix * alphabet_size_ + symbol;
|
|
WriteBits(depths_[ix], bits_[ix], storage_ix, storage);
|
|
}
|
|
|
|
private:
|
|
const int alphabet_size_;
|
|
const int num_block_types_;
|
|
const std::vector<int>& block_types_;
|
|
const std::vector<int>& block_lengths_;
|
|
BlockSplitCode block_split_code_;
|
|
int block_ix_;
|
|
int block_len_;
|
|
int entropy_ix_;
|
|
std::vector<uint8_t> depths_;
|
|
std::vector<uint16_t> bits_;
|
|
};
|
|
|
|
void JumpToByteBoundary(int* storage_ix, uint8_t* storage) {
|
|
*storage_ix = (*storage_ix + 7) & ~7;
|
|
storage[*storage_ix >> 3] = 0;
|
|
}
|
|
|
|
bool StoreMetaBlock(const uint8_t* input,
|
|
size_t start_pos,
|
|
size_t length,
|
|
size_t mask,
|
|
uint8_t prev_byte,
|
|
uint8_t prev_byte2,
|
|
bool is_last,
|
|
int num_direct_distance_codes,
|
|
int distance_postfix_bits,
|
|
int literal_context_mode,
|
|
const brotli::Command *commands,
|
|
size_t n_commands,
|
|
const MetaBlockSplit& mb,
|
|
int *storage_ix,
|
|
uint8_t *storage) {
|
|
if (!StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage)) {
|
|
return false;
|
|
}
|
|
|
|
if (length == 0) {
|
|
// Only the last meta-block can be empty, so jump to next byte.
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
return true;
|
|
}
|
|
|
|
int num_distance_codes =
|
|
kNumDistanceShortCodes + num_direct_distance_codes +
|
|
(48 << distance_postfix_bits);
|
|
|
|
BlockEncoder literal_enc(256,
|
|
mb.literal_split.num_types,
|
|
mb.literal_split.types,
|
|
mb.literal_split.lengths);
|
|
BlockEncoder command_enc(kNumCommandPrefixes,
|
|
mb.command_split.num_types,
|
|
mb.command_split.types,
|
|
mb.command_split.lengths);
|
|
BlockEncoder distance_enc(num_distance_codes,
|
|
mb.distance_split.num_types,
|
|
mb.distance_split.types,
|
|
mb.distance_split.lengths);
|
|
|
|
literal_enc.BuildAndStoreBlockSwitchEntropyCodes(storage_ix, storage);
|
|
command_enc.BuildAndStoreBlockSwitchEntropyCodes(storage_ix, storage);
|
|
distance_enc.BuildAndStoreBlockSwitchEntropyCodes(storage_ix, storage);
|
|
|
|
WriteBits(2, distance_postfix_bits, storage_ix, storage);
|
|
WriteBits(4, num_direct_distance_codes >> distance_postfix_bits,
|
|
storage_ix, storage);
|
|
for (int i = 0; i < mb.literal_split.num_types; ++i) {
|
|
WriteBits(2, literal_context_mode, storage_ix, storage);
|
|
}
|
|
|
|
if (mb.literal_context_map.empty()) {
|
|
StoreTrivialContextMap(mb.literal_histograms.size(), kLiteralContextBits,
|
|
storage_ix, storage);
|
|
} else {
|
|
EncodeContextMap(mb.literal_context_map, mb.literal_histograms.size(),
|
|
storage_ix, storage);
|
|
}
|
|
|
|
if (mb.distance_context_map.empty()) {
|
|
StoreTrivialContextMap(mb.distance_histograms.size(), kDistanceContextBits,
|
|
storage_ix, storage);
|
|
} else {
|
|
EncodeContextMap(mb.distance_context_map, mb.distance_histograms.size(),
|
|
storage_ix, storage);
|
|
}
|
|
|
|
literal_enc.BuildAndStoreEntropyCodes(mb.literal_histograms,
|
|
storage_ix, storage);
|
|
command_enc.BuildAndStoreEntropyCodes(mb.command_histograms,
|
|
storage_ix, storage);
|
|
distance_enc.BuildAndStoreEntropyCodes(mb.distance_histograms,
|
|
storage_ix, storage);
|
|
|
|
size_t pos = start_pos;
|
|
for (int i = 0; i < n_commands; ++i) {
|
|
const Command cmd = commands[i];
|
|
int cmd_code = cmd.cmd_prefix_;
|
|
int lennumextra = cmd.cmd_extra_ >> 48;
|
|
uint64_t lenextra = cmd.cmd_extra_ & 0xffffffffffffULL;
|
|
command_enc.StoreSymbol(cmd_code, storage_ix, storage);
|
|
WriteBits(lennumextra, lenextra, storage_ix, storage);
|
|
if (mb.literal_context_map.empty()) {
|
|
for (int j = 0; j < cmd.insert_len_; j++) {
|
|
literal_enc.StoreSymbol(input[pos & mask], storage_ix, storage);
|
|
++pos;
|
|
}
|
|
} else {
|
|
for (int j = 0; j < cmd.insert_len_; ++j) {
|
|
int context = Context(prev_byte, prev_byte2,
|
|
literal_context_mode);
|
|
int literal = input[pos & mask];
|
|
literal_enc.StoreSymbolWithContext<kLiteralContextBits>(
|
|
literal, context, mb.literal_context_map, storage_ix, storage);
|
|
prev_byte2 = prev_byte;
|
|
prev_byte = literal;
|
|
++pos;
|
|
}
|
|
}
|
|
pos += cmd.copy_len_;
|
|
if (cmd.copy_len_ > 0) {
|
|
prev_byte2 = input[(pos - 2) & mask];
|
|
prev_byte = input[(pos - 1) & mask];
|
|
if (cmd.cmd_prefix_ >= 128) {
|
|
int dist_code = cmd.dist_prefix_;
|
|
int distnumextra = cmd.dist_extra_ >> 24;
|
|
int distextra = cmd.dist_extra_ & 0xffffff;
|
|
if (mb.distance_context_map.empty()) {
|
|
distance_enc.StoreSymbol(dist_code, storage_ix, storage);
|
|
} else {
|
|
int context = cmd.DistanceContext();
|
|
distance_enc.StoreSymbolWithContext<kDistanceContextBits>(
|
|
dist_code, context, mb.distance_context_map, storage_ix, storage);
|
|
}
|
|
brotli::WriteBits(distnumextra, distextra, storage_ix, storage);
|
|
}
|
|
}
|
|
}
|
|
if (is_last) {
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool StoreMetaBlockTrivial(const uint8_t* input,
|
|
size_t start_pos,
|
|
size_t length,
|
|
size_t mask,
|
|
bool is_last,
|
|
const brotli::Command *commands,
|
|
size_t n_commands,
|
|
int *storage_ix,
|
|
uint8_t *storage) {
|
|
if (!StoreCompressedMetaBlockHeader(is_last, length, storage_ix, storage)) {
|
|
return false;
|
|
}
|
|
|
|
if (length == 0) {
|
|
// Only the last meta-block can be empty, so jump to next byte.
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
return true;
|
|
}
|
|
|
|
HistogramLiteral lit_histo;
|
|
HistogramCommand cmd_histo;
|
|
HistogramDistance dist_histo;
|
|
|
|
size_t pos = start_pos;
|
|
for (int i = 0; i < n_commands; ++i) {
|
|
const Command cmd = commands[i];
|
|
cmd_histo.Add(cmd.cmd_prefix_);
|
|
for (int j = 0; j < cmd.insert_len_; ++j) {
|
|
lit_histo.Add(input[pos & mask]);
|
|
++pos;
|
|
}
|
|
pos += cmd.copy_len_;
|
|
if (cmd.copy_len_ > 0 && cmd.cmd_prefix_ >= 128) {
|
|
dist_histo.Add(cmd.dist_prefix_);
|
|
}
|
|
}
|
|
|
|
WriteBits(13, 0, storage_ix, storage);
|
|
|
|
std::vector<uint8_t> lit_depth(256);
|
|
std::vector<uint16_t> lit_bits(256);
|
|
std::vector<uint8_t> cmd_depth(kNumCommandPrefixes);
|
|
std::vector<uint16_t> cmd_bits(kNumCommandPrefixes);
|
|
std::vector<uint8_t> dist_depth(64);
|
|
std::vector<uint16_t> dist_bits(64);
|
|
|
|
BuildAndStoreHuffmanTree(&lit_histo.data_[0], 256,
|
|
&lit_depth[0], &lit_bits[0],
|
|
storage_ix, storage);
|
|
BuildAndStoreHuffmanTree(&cmd_histo.data_[0], kNumCommandPrefixes,
|
|
&cmd_depth[0], &cmd_bits[0],
|
|
storage_ix, storage);
|
|
BuildAndStoreHuffmanTree(&dist_histo.data_[0], 64,
|
|
&dist_depth[0], &dist_bits[0],
|
|
storage_ix, storage);
|
|
|
|
pos = start_pos;
|
|
for (int i = 0; i < n_commands; ++i) {
|
|
const Command cmd = commands[i];
|
|
const int cmd_code = cmd.cmd_prefix_;
|
|
const int lennumextra = cmd.cmd_extra_ >> 48;
|
|
const uint64_t lenextra = cmd.cmd_extra_ & 0xffffffffffffULL;
|
|
WriteBits(cmd_depth[cmd_code], cmd_bits[cmd_code], storage_ix, storage);
|
|
WriteBits(lennumextra, lenextra, storage_ix, storage);
|
|
for (int j = 0; j < cmd.insert_len_; j++) {
|
|
const uint8_t literal = input[pos & mask];
|
|
WriteBits(lit_depth[literal], lit_bits[literal], storage_ix, storage);
|
|
++pos;
|
|
}
|
|
pos += cmd.copy_len_;
|
|
if (cmd.copy_len_ > 0 && cmd.cmd_prefix_ >= 128) {
|
|
const int dist_code = cmd.dist_prefix_;
|
|
const int distnumextra = cmd.dist_extra_ >> 24;
|
|
const int distextra = cmd.dist_extra_ & 0xffffff;
|
|
WriteBits(dist_depth[dist_code], dist_bits[dist_code],
|
|
storage_ix, storage);
|
|
WriteBits(distnumextra, distextra, storage_ix, storage);
|
|
}
|
|
}
|
|
if (is_last) {
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// This is for storing uncompressed blocks (simple raw storage of
|
|
// bytes-as-bytes).
|
|
bool StoreUncompressedMetaBlock(bool final_block,
|
|
const uint8_t * __restrict input,
|
|
size_t position, size_t mask,
|
|
size_t len,
|
|
int * __restrict storage_ix,
|
|
uint8_t * __restrict storage) {
|
|
if (!brotli::StoreUncompressedMetaBlockHeader(len, storage_ix, storage)) {
|
|
return false;
|
|
}
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
|
|
size_t masked_pos = position & mask;
|
|
if (masked_pos + len > mask + 1) {
|
|
size_t len1 = mask + 1 - masked_pos;
|
|
memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len1);
|
|
*storage_ix += len1 << 3;
|
|
len -= len1;
|
|
masked_pos = 0;
|
|
}
|
|
memcpy(&storage[*storage_ix >> 3], &input[masked_pos], len);
|
|
*storage_ix += len << 3;
|
|
|
|
// We need to clear the next 4 bytes to continue to be
|
|
// compatible with WriteBits.
|
|
brotli::WriteBitsPrepareStorage(*storage_ix, storage);
|
|
|
|
// Since the uncomressed block itself may not be the final block, add an empty
|
|
// one after this.
|
|
if (final_block) {
|
|
brotli::WriteBits(1, 1, storage_ix, storage); // islast
|
|
brotli::WriteBits(1, 1, storage_ix, storage); // isempty
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
void StoreSyncMetaBlock(int * __restrict storage_ix,
|
|
uint8_t * __restrict storage) {
|
|
// Empty metadata meta-block bit pattern:
|
|
// 1 bit: is_last (0)
|
|
// 2 bits: num nibbles (3)
|
|
// 1 bit: reserved (0)
|
|
// 2 bits: metadata length bytes (0)
|
|
WriteBits(6, 6, storage_ix, storage);
|
|
JumpToByteBoundary(storage_ix, storage);
|
|
}
|
|
|
|
} // namespace brotli
|