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encode.c
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encode.c
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/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
/* Implementation of Brotli compressor. */
#include <brotli/encode.h>
#include <brotli/shared_dictionary.h>
#include <brotli/types.h>
#include <stdlib.h> /* free, malloc */
#include <string.h> /* memcpy, memset */
#include "../common/constants.h"
#include "../common/context.h"
#include "../common/platform.h"
#include "../common/version.h"
#include "backward_references.h"
#include "backward_references_hq.h"
#include "bit_cost.h"
#include "brotli_bit_stream.h"
#include "compress_fragment.h"
#include "compress_fragment_two_pass.h"
#include "dictionary_hash.h"
#include "encoder_dict.h"
#include "entropy_encode.h"
#include "fast_log.h"
#include "hash.h"
#include "histogram.h"
#include "memory.h"
#include "metablock.h"
#include "prefix.h"
#include "state.h"
#include "quality.h"
#include "ringbuffer.h"
#include "utf8_util.h"
#include "write_bits.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
#define COPY_ARRAY(dst, src) memcpy(dst, src, sizeof(src));
static size_t InputBlockSize(BrotliEncoderState* s) {
return (size_t)1 << s->params.lgblock;
}
static uint64_t UnprocessedInputSize(BrotliEncoderState* s) {
return s->input_pos_ - s->last_processed_pos_;
}
static size_t RemainingInputBlockSize(BrotliEncoderState* s) {
const uint64_t delta = UnprocessedInputSize(s);
size_t block_size = InputBlockSize(s);
if (delta >= block_size) return 0;
return block_size - (size_t)delta;
}
BROTLI_BOOL BrotliEncoderSetParameter(
BrotliEncoderState* state, BrotliEncoderParameter p, uint32_t value) {
/* Changing parameters on the fly is not implemented yet. */
if (state->is_initialized_) return BROTLI_FALSE;
/* TODO(eustas): Validate/clamp parameters here. */
switch (p) {
case BROTLI_PARAM_MODE:
state->params.mode = (BrotliEncoderMode)value;
return BROTLI_TRUE;
case BROTLI_PARAM_QUALITY:
state->params.quality = (int)value;
return BROTLI_TRUE;
case BROTLI_PARAM_LGWIN:
state->params.lgwin = (int)value;
return BROTLI_TRUE;
case BROTLI_PARAM_LGBLOCK:
state->params.lgblock = (int)value;
return BROTLI_TRUE;
case BROTLI_PARAM_DISABLE_LITERAL_CONTEXT_MODELING:
if ((value != 0) && (value != 1)) return BROTLI_FALSE;
state->params.disable_literal_context_modeling = TO_BROTLI_BOOL(!!value);
return BROTLI_TRUE;
case BROTLI_PARAM_SIZE_HINT:
state->params.size_hint = value;
return BROTLI_TRUE;
case BROTLI_PARAM_LARGE_WINDOW:
state->params.large_window = TO_BROTLI_BOOL(!!value);
return BROTLI_TRUE;
case BROTLI_PARAM_NPOSTFIX:
state->params.dist.distance_postfix_bits = value;
return BROTLI_TRUE;
case BROTLI_PARAM_NDIRECT:
state->params.dist.num_direct_distance_codes = value;
return BROTLI_TRUE;
case BROTLI_PARAM_STREAM_OFFSET:
if (value > (1u << 30)) return BROTLI_FALSE;
state->params.stream_offset = value;
return BROTLI_TRUE;
default: return BROTLI_FALSE;
}
}
/* Wraps 64-bit input position to 32-bit ring-buffer position preserving
"not-a-first-lap" feature. */
static uint32_t WrapPosition(uint64_t position) {
uint32_t result = (uint32_t)position;
uint64_t gb = position >> 30;
if (gb > 2) {
/* Wrap every 2GiB; The first 3GB are continuous. */
result = (result & ((1u << 30) - 1)) | ((uint32_t)((gb - 1) & 1) + 1) << 30;
}
return result;
}
static uint8_t* GetBrotliStorage(BrotliEncoderState* s, size_t size) {
MemoryManager* m = &s->memory_manager_;
if (s->storage_size_ < size) {
BROTLI_FREE(m, s->storage_);
s->storage_ = BROTLI_ALLOC(m, uint8_t, size);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(s->storage_)) return NULL;
s->storage_size_ = size;
}
return s->storage_;
}
static size_t HashTableSize(size_t max_table_size, size_t input_size) {
size_t htsize = 256;
while (htsize < max_table_size && htsize < input_size) {
htsize <<= 1;
}
return htsize;
}
static int* GetHashTable(BrotliEncoderState* s, int quality,
size_t input_size, size_t* table_size) {
/* Use smaller hash table when input.size() is smaller, since we
fill the table, incurring O(hash table size) overhead for
compression, and if the input is short, we won't need that
many hash table entries anyway. */
MemoryManager* m = &s->memory_manager_;
const size_t max_table_size = MaxHashTableSize(quality);
size_t htsize = HashTableSize(max_table_size, input_size);
int* table;
BROTLI_DCHECK(max_table_size >= 256);
if (quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
/* Only odd shifts are supported by fast-one-pass. */
if ((htsize & 0xAAAAA) == 0) {
htsize <<= 1;
}
}
if (htsize <= sizeof(s->small_table_) / sizeof(s->small_table_[0])) {
table = s->small_table_;
} else {
if (htsize > s->large_table_size_) {
s->large_table_size_ = htsize;
BROTLI_FREE(m, s->large_table_);
s->large_table_ = BROTLI_ALLOC(m, int, htsize);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(s->large_table_)) return 0;
}
table = s->large_table_;
}
*table_size = htsize;
memset(table, 0, htsize * sizeof(*table));
return table;
}
static void EncodeWindowBits(int lgwin, BROTLI_BOOL large_window,
uint16_t* last_bytes, uint8_t* last_bytes_bits) {
if (large_window) {
*last_bytes = (uint16_t)(((lgwin & 0x3F) << 8) | 0x11);
*last_bytes_bits = 14;
} else {
if (lgwin == 16) {
*last_bytes = 0;
*last_bytes_bits = 1;
} else if (lgwin == 17) {
*last_bytes = 1;
*last_bytes_bits = 7;
} else if (lgwin > 17) {
*last_bytes = (uint16_t)(((lgwin - 17) << 1) | 0x01);
*last_bytes_bits = 4;
} else {
*last_bytes = (uint16_t)(((lgwin - 8) << 4) | 0x01);
*last_bytes_bits = 7;
}
}
}
/* TODO(eustas): move to compress_fragment.c? */
/* Initializes the command and distance prefix codes for the first block. */
static void InitCommandPrefixCodes(BrotliOnePassArena* s) {
static const uint8_t kDefaultCommandDepths[128] = {
0, 4, 4, 5, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8,
0, 0, 0, 4, 4, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7,
7, 7, 10, 10, 10, 10, 10, 10, 0, 4, 4, 5, 5, 5, 6, 6,
7, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
6, 6, 6, 6, 6, 6, 5, 5, 5, 5, 5, 5, 4, 4, 4, 4,
4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 7, 7, 7, 8, 10,
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
};
static const uint16_t kDefaultCommandBits[128] = {
0, 0, 8, 9, 3, 35, 7, 71,
39, 103, 23, 47, 175, 111, 239, 31,
0, 0, 0, 4, 12, 2, 10, 6,
13, 29, 11, 43, 27, 59, 87, 55,
15, 79, 319, 831, 191, 703, 447, 959,
0, 14, 1, 25, 5, 21, 19, 51,
119, 159, 95, 223, 479, 991, 63, 575,
127, 639, 383, 895, 255, 767, 511, 1023,
14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
27, 59, 7, 39, 23, 55, 30, 1, 17, 9, 25, 5, 0, 8, 4, 12,
2, 10, 6, 21, 13, 29, 3, 19, 11, 15, 47, 31, 95, 63, 127, 255,
767, 2815, 1791, 3839, 511, 2559, 1535, 3583, 1023, 3071, 2047, 4095,
};
static const uint8_t kDefaultCommandCode[] = {
0xff, 0x77, 0xd5, 0xbf, 0xe7, 0xde, 0xea, 0x9e, 0x51, 0x5d, 0xde, 0xc6,
0x70, 0x57, 0xbc, 0x58, 0x58, 0x58, 0xd8, 0xd8, 0x58, 0xd5, 0xcb, 0x8c,
0xea, 0xe0, 0xc3, 0x87, 0x1f, 0x83, 0xc1, 0x60, 0x1c, 0x67, 0xb2, 0xaa,
0x06, 0x83, 0xc1, 0x60, 0x30, 0x18, 0xcc, 0xa1, 0xce, 0x88, 0x54, 0x94,
0x46, 0xe1, 0xb0, 0xd0, 0x4e, 0xb2, 0xf7, 0x04, 0x00,
};
static const size_t kDefaultCommandCodeNumBits = 448;
COPY_ARRAY(s->cmd_depth, kDefaultCommandDepths);
COPY_ARRAY(s->cmd_bits, kDefaultCommandBits);
/* Initialize the pre-compressed form of the command and distance prefix
codes. */
COPY_ARRAY(s->cmd_code, kDefaultCommandCode);
s->cmd_code_numbits = kDefaultCommandCodeNumBits;
}
/* Decide about the context map based on the ability of the prediction
ability of the previous byte UTF8-prefix on the next byte. The
prediction ability is calculated as Shannon entropy. Here we need
Shannon entropy instead of 'BitsEntropy' since the prefix will be
encoded with the remaining 6 bits of the following byte, and
BitsEntropy will assume that symbol to be stored alone using Huffman
coding. */
static void ChooseContextMap(int quality,
uint32_t* bigram_histo,
size_t* num_literal_contexts,
const uint32_t** literal_context_map) {
static const uint32_t kStaticContextMapContinuation[64] = {
1, 1, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
static const uint32_t kStaticContextMapSimpleUTF8[64] = {
0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
};
uint32_t monogram_histo[3] = { 0 };
uint32_t two_prefix_histo[6] = { 0 };
size_t total;
size_t i;
size_t dummy;
double entropy[4];
for (i = 0; i < 9; ++i) {
monogram_histo[i % 3] += bigram_histo[i];
two_prefix_histo[i % 6] += bigram_histo[i];
}
entropy[1] = ShannonEntropy(monogram_histo, 3, &dummy);
entropy[2] = (ShannonEntropy(two_prefix_histo, 3, &dummy) +
ShannonEntropy(two_prefix_histo + 3, 3, &dummy));
entropy[3] = 0;
for (i = 0; i < 3; ++i) {
entropy[3] += ShannonEntropy(bigram_histo + 3 * i, 3, &dummy);
}
total = monogram_histo[0] + monogram_histo[1] + monogram_histo[2];
BROTLI_DCHECK(total != 0);
entropy[0] = 1.0 / (double)total;
entropy[1] *= entropy[0];
entropy[2] *= entropy[0];
entropy[3] *= entropy[0];
if (quality < MIN_QUALITY_FOR_HQ_CONTEXT_MODELING) {
/* 3 context models is a bit slower, don't use it at lower qualities. */
entropy[3] = entropy[1] * 10;
}
/* If expected savings by symbol are less than 0.2 bits, skip the
context modeling -- in exchange for faster decoding speed. */
if (entropy[1] - entropy[2] < 0.2 &&
entropy[1] - entropy[3] < 0.2) {
*num_literal_contexts = 1;
} else if (entropy[2] - entropy[3] < 0.02) {
*num_literal_contexts = 2;
*literal_context_map = kStaticContextMapSimpleUTF8;
} else {
*num_literal_contexts = 3;
*literal_context_map = kStaticContextMapContinuation;
}
}
/* Decide if we want to use a more complex static context map containing 13
context values, based on the entropy reduction of histograms over the
first 5 bits of literals. */
static BROTLI_BOOL ShouldUseComplexStaticContextMap(const uint8_t* input,
size_t start_pos, size_t length, size_t mask, int quality, size_t size_hint,
size_t* num_literal_contexts, const uint32_t** literal_context_map,
uint32_t* arena) {
static const uint32_t kStaticContextMapComplexUTF8[64] = {
11, 11, 12, 12, /* 0 special */
0, 0, 0, 0, /* 4 lf */
1, 1, 9, 9, /* 8 space */
2, 2, 2, 2, /* !, first after space/lf and after something else. */
1, 1, 1, 1, /* " */
8, 3, 3, 3, /* % */
1, 1, 1, 1, /* ({[ */
2, 2, 2, 2, /* }]) */
8, 4, 4, 4, /* :; */
8, 7, 4, 4, /* . */
8, 0, 0, 0, /* > */
3, 3, 3, 3, /* [0..9] */
5, 5, 10, 5, /* [A-Z] */
5, 5, 10, 5,
6, 6, 6, 6, /* [a-z] */
6, 6, 6, 6,
};
BROTLI_UNUSED(quality);
/* Try the more complex static context map only for long data. */
if (size_hint < (1 << 20)) {
return BROTLI_FALSE;
} else {
const size_t end_pos = start_pos + length;
/* To make entropy calculations faster, we collect histograms
over the 5 most significant bits of literals. One histogram
without context and 13 additional histograms for each context value. */
uint32_t* BROTLI_RESTRICT const combined_histo = arena;
uint32_t* BROTLI_RESTRICT const context_histo = arena + 32;
uint32_t total = 0;
double entropy[3];
size_t dummy;
size_t i;
ContextLut utf8_lut = BROTLI_CONTEXT_LUT(CONTEXT_UTF8);
memset(arena, 0, sizeof(arena[0]) * 32 * 14);
for (; start_pos + 64 <= end_pos; start_pos += 4096) {
const size_t stride_end_pos = start_pos + 64;
uint8_t prev2 = input[start_pos & mask];
uint8_t prev1 = input[(start_pos + 1) & mask];
size_t pos;
/* To make the analysis of the data faster we only examine 64 byte long
strides at every 4kB intervals. */
for (pos = start_pos + 2; pos < stride_end_pos; ++pos) {
const uint8_t literal = input[pos & mask];
const uint8_t context = (uint8_t)kStaticContextMapComplexUTF8[
BROTLI_CONTEXT(prev1, prev2, utf8_lut)];
++total;
++combined_histo[literal >> 3];
++context_histo[(context << 5) + (literal >> 3)];
prev2 = prev1;
prev1 = literal;
}
}
entropy[1] = ShannonEntropy(combined_histo, 32, &dummy);
entropy[2] = 0;
for (i = 0; i < 13; ++i) {
entropy[2] += ShannonEntropy(context_histo + (i << 5), 32, &dummy);
}
entropy[0] = 1.0 / (double)total;
entropy[1] *= entropy[0];
entropy[2] *= entropy[0];
/* The triggering heuristics below were tuned by compressing the individual
files of the silesia corpus. If we skip this kind of context modeling
for not very well compressible input (i.e. entropy using context modeling
is 60% of maximal entropy) or if expected savings by symbol are less
than 0.2 bits, then in every case when it triggers, the final compression
ratio is improved. Note however that this heuristics might be too strict
for some cases and could be tuned further. */
if (entropy[2] > 3.0 || entropy[1] - entropy[2] < 0.2) {
return BROTLI_FALSE;
} else {
*num_literal_contexts = 13;
*literal_context_map = kStaticContextMapComplexUTF8;
return BROTLI_TRUE;
}
}
}
static void DecideOverLiteralContextModeling(const uint8_t* input,
size_t start_pos, size_t length, size_t mask, int quality, size_t size_hint,
size_t* num_literal_contexts, const uint32_t** literal_context_map,
uint32_t* arena) {
if (quality < MIN_QUALITY_FOR_CONTEXT_MODELING || length < 64) {
return;
} else if (ShouldUseComplexStaticContextMap(
input, start_pos, length, mask, quality, size_hint,
num_literal_contexts, literal_context_map, arena)) {
/* Context map was already set, nothing else to do. */
} else {
/* Gather bi-gram data of the UTF8 byte prefixes. To make the analysis of
UTF8 data faster we only examine 64 byte long strides at every 4kB
intervals. */
const size_t end_pos = start_pos + length;
uint32_t* BROTLI_RESTRICT const bigram_prefix_histo = arena;
memset(bigram_prefix_histo, 0, sizeof(arena[0]) * 9);
for (; start_pos + 64 <= end_pos; start_pos += 4096) {
static const int lut[4] = { 0, 0, 1, 2 };
const size_t stride_end_pos = start_pos + 64;
int prev = lut[input[start_pos & mask] >> 6] * 3;
size_t pos;
for (pos = start_pos + 1; pos < stride_end_pos; ++pos) {
const uint8_t literal = input[pos & mask];
++bigram_prefix_histo[prev + lut[literal >> 6]];
prev = lut[literal >> 6] * 3;
}
}
ChooseContextMap(quality, &bigram_prefix_histo[0], num_literal_contexts,
literal_context_map);
}
}
static BROTLI_BOOL ShouldCompress(
const uint8_t* data, const size_t mask, const uint64_t last_flush_pos,
const size_t bytes, const size_t num_literals, const size_t num_commands) {
/* TODO(eustas): find more precise minimal block overhead. */
if (bytes <= 2) return BROTLI_FALSE;
if (num_commands < (bytes >> 8) + 2) {
if ((double)num_literals > 0.99 * (double)bytes) {
uint32_t literal_histo[256] = { 0 };
static const uint32_t kSampleRate = 13;
static const double kMinEntropy = 7.92;
const double bit_cost_threshold =
(double)bytes * kMinEntropy / kSampleRate;
size_t t = (bytes + kSampleRate - 1) / kSampleRate;
uint32_t pos = (uint32_t)last_flush_pos;
size_t i;
for (i = 0; i < t; i++) {
++literal_histo[data[pos & mask]];
pos += kSampleRate;
}
if (BitsEntropy(literal_histo, 256) > bit_cost_threshold) {
return BROTLI_FALSE;
}
}
}
return BROTLI_TRUE;
}
/* Chooses the literal context mode for a metablock */
static ContextType ChooseContextMode(const BrotliEncoderParams* params,
const uint8_t* data, const size_t pos, const size_t mask,
const size_t length) {
/* We only do the computation for the option of something else than
CONTEXT_UTF8 for the highest qualities */
if (params->quality >= MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING &&
!BrotliIsMostlyUTF8(data, pos, mask, length, kMinUTF8Ratio)) {
return CONTEXT_SIGNED;
}
return CONTEXT_UTF8;
}
static void WriteMetaBlockInternal(MemoryManager* m,
const uint8_t* data,
const size_t mask,
const uint64_t last_flush_pos,
const size_t bytes,
const BROTLI_BOOL is_last,
ContextType literal_context_mode,
const BrotliEncoderParams* params,
const uint8_t prev_byte,
const uint8_t prev_byte2,
const size_t num_literals,
const size_t num_commands,
Command* commands,
const int* saved_dist_cache,
int* dist_cache,
size_t* storage_ix,
uint8_t* storage) {
const uint32_t wrapped_last_flush_pos = WrapPosition(last_flush_pos);
uint16_t last_bytes;
uint8_t last_bytes_bits;
ContextLut literal_context_lut = BROTLI_CONTEXT_LUT(literal_context_mode);
BrotliEncoderParams block_params = *params;
if (bytes == 0) {
/* Write the ISLAST and ISEMPTY bits. */
BrotliWriteBits(2, 3, storage_ix, storage);
*storage_ix = (*storage_ix + 7u) & ~7u;
return;
}
if (!ShouldCompress(data, mask, last_flush_pos, bytes,
num_literals, num_commands)) {
/* Restore the distance cache, as its last update by
CreateBackwardReferences is now unused. */
memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
BrotliStoreUncompressedMetaBlock(is_last, data,
wrapped_last_flush_pos, mask, bytes,
storage_ix, storage);
return;
}
BROTLI_DCHECK(*storage_ix <= 14);
last_bytes = (uint16_t)((storage[1] << 8) | storage[0]);
last_bytes_bits = (uint8_t)(*storage_ix);
if (params->quality <= MAX_QUALITY_FOR_STATIC_ENTROPY_CODES) {
BrotliStoreMetaBlockFast(m, data, wrapped_last_flush_pos,
bytes, mask, is_last, params,
commands, num_commands,
storage_ix, storage);
if (BROTLI_IS_OOM(m)) return;
} else if (params->quality < MIN_QUALITY_FOR_BLOCK_SPLIT) {
BrotliStoreMetaBlockTrivial(m, data, wrapped_last_flush_pos,
bytes, mask, is_last, params,
commands, num_commands,
storage_ix, storage);
if (BROTLI_IS_OOM(m)) return;
} else {
MetaBlockSplit mb;
InitMetaBlockSplit(&mb);
if (params->quality < MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING) {
size_t num_literal_contexts = 1;
const uint32_t* literal_context_map = NULL;
if (!params->disable_literal_context_modeling) {
/* TODO(eustas): pull to higher level and reuse. */
uint32_t* arena = BROTLI_ALLOC(m, uint32_t, 14 * 32);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(arena)) return;
DecideOverLiteralContextModeling(
data, wrapped_last_flush_pos, bytes, mask, params->quality,
params->size_hint, &num_literal_contexts,
&literal_context_map, arena);
BROTLI_FREE(m, arena);
}
BrotliBuildMetaBlockGreedy(m, data, wrapped_last_flush_pos, mask,
prev_byte, prev_byte2, literal_context_lut, num_literal_contexts,
literal_context_map, commands, num_commands, &mb);
if (BROTLI_IS_OOM(m)) return;
} else {
BrotliBuildMetaBlock(m, data, wrapped_last_flush_pos, mask, &block_params,
prev_byte, prev_byte2,
commands, num_commands,
literal_context_mode,
&mb);
if (BROTLI_IS_OOM(m)) return;
}
if (params->quality >= MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS) {
/* The number of distance symbols effectively used for distance
histograms. It might be less than distance alphabet size
for "Large Window Brotli" (32-bit). */
BrotliOptimizeHistograms(block_params.dist.alphabet_size_limit, &mb);
}
BrotliStoreMetaBlock(m, data, wrapped_last_flush_pos, bytes, mask,
prev_byte, prev_byte2,
is_last,
&block_params,
literal_context_mode,
commands, num_commands,
&mb,
storage_ix, storage);
if (BROTLI_IS_OOM(m)) return;
DestroyMetaBlockSplit(m, &mb);
}
if (bytes + 4 < (*storage_ix >> 3)) {
/* Restore the distance cache and last byte. */
memcpy(dist_cache, saved_dist_cache, 4 * sizeof(dist_cache[0]));
storage[0] = (uint8_t)last_bytes;
storage[1] = (uint8_t)(last_bytes >> 8);
*storage_ix = last_bytes_bits;
BrotliStoreUncompressedMetaBlock(is_last, data,
wrapped_last_flush_pos, mask,
bytes, storage_ix, storage);
}
}
static void ChooseDistanceParams(BrotliEncoderParams* params) {
uint32_t distance_postfix_bits = 0;
uint32_t num_direct_distance_codes = 0;
if (params->quality >= MIN_QUALITY_FOR_NONZERO_DISTANCE_PARAMS) {
uint32_t ndirect_msb;
if (params->mode == BROTLI_MODE_FONT) {
distance_postfix_bits = 1;
num_direct_distance_codes = 12;
} else {
distance_postfix_bits = params->dist.distance_postfix_bits;
num_direct_distance_codes = params->dist.num_direct_distance_codes;
}
ndirect_msb = (num_direct_distance_codes >> distance_postfix_bits) & 0x0F;
if (distance_postfix_bits > BROTLI_MAX_NPOSTFIX ||
num_direct_distance_codes > BROTLI_MAX_NDIRECT ||
(ndirect_msb << distance_postfix_bits) != num_direct_distance_codes) {
distance_postfix_bits = 0;
num_direct_distance_codes = 0;
}
}
BrotliInitDistanceParams(¶ms->dist, distance_postfix_bits,
num_direct_distance_codes, params->large_window);
}
static BROTLI_BOOL EnsureInitialized(BrotliEncoderState* s) {
MemoryManager* m = &s->memory_manager_;
if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
if (s->is_initialized_) return BROTLI_TRUE;
s->last_bytes_bits_ = 0;
s->last_bytes_ = 0;
s->flint_ = BROTLI_FLINT_DONE;
s->remaining_metadata_bytes_ = BROTLI_UINT32_MAX;
SanitizeParams(&s->params);
s->params.lgblock = ComputeLgBlock(&s->params);
ChooseDistanceParams(&s->params);
if (s->params.stream_offset != 0) {
s->flint_ = BROTLI_FLINT_NEEDS_2_BYTES;
/* Poison the distance cache. -16 +- 3 is still less than zero (invalid). */
s->dist_cache_[0] = -16;
s->dist_cache_[1] = -16;
s->dist_cache_[2] = -16;
s->dist_cache_[3] = -16;
memcpy(s->saved_dist_cache_, s->dist_cache_, sizeof(s->saved_dist_cache_));
}
RingBufferSetup(&s->params, &s->ringbuffer_);
/* Initialize last byte with stream header. */
{
int lgwin = s->params.lgwin;
if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
lgwin = BROTLI_MAX(int, lgwin, 18);
}
if (s->params.stream_offset == 0) {
EncodeWindowBits(lgwin, s->params.large_window,
&s->last_bytes_, &s->last_bytes_bits_);
} else {
/* Bigger values have the same effect, but could cause overflows. */
s->params.stream_offset = BROTLI_MIN(size_t,
s->params.stream_offset, BROTLI_MAX_BACKWARD_LIMIT(lgwin));
}
}
if (s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY) {
s->one_pass_arena_ = BROTLI_ALLOC(m, BrotliOnePassArena, 1);
if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
InitCommandPrefixCodes(s->one_pass_arena_);
} else if (s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
s->two_pass_arena_ = BROTLI_ALLOC(m, BrotliTwoPassArena, 1);
if (BROTLI_IS_OOM(m)) return BROTLI_FALSE;
}
s->is_initialized_ = BROTLI_TRUE;
return BROTLI_TRUE;
}
static void BrotliEncoderInitParams(BrotliEncoderParams* params) {
params->mode = BROTLI_DEFAULT_MODE;
params->large_window = BROTLI_FALSE;
params->quality = BROTLI_DEFAULT_QUALITY;
params->lgwin = BROTLI_DEFAULT_WINDOW;
params->lgblock = 0;
params->stream_offset = 0;
params->size_hint = 0;
params->disable_literal_context_modeling = BROTLI_FALSE;
BrotliInitSharedEncoderDictionary(¶ms->dictionary);
params->dist.distance_postfix_bits = 0;
params->dist.num_direct_distance_codes = 0;
params->dist.alphabet_size_max =
BROTLI_DISTANCE_ALPHABET_SIZE(0, 0, BROTLI_MAX_DISTANCE_BITS);
params->dist.alphabet_size_limit = params->dist.alphabet_size_max;
params->dist.max_distance = BROTLI_MAX_DISTANCE;
}
static void BrotliEncoderCleanupParams(MemoryManager* m,
BrotliEncoderParams* params) {
BrotliCleanupSharedEncoderDictionary(m, ¶ms->dictionary);
}
static void BrotliEncoderInitState(BrotliEncoderState* s) {
BrotliEncoderInitParams(&s->params);
s->input_pos_ = 0;
s->num_commands_ = 0;
s->num_literals_ = 0;
s->last_insert_len_ = 0;
s->last_flush_pos_ = 0;
s->last_processed_pos_ = 0;
s->prev_byte_ = 0;
s->prev_byte2_ = 0;
s->storage_size_ = 0;
s->storage_ = 0;
HasherInit(&s->hasher_);
s->large_table_ = NULL;
s->large_table_size_ = 0;
s->one_pass_arena_ = NULL;
s->two_pass_arena_ = NULL;
s->command_buf_ = NULL;
s->literal_buf_ = NULL;
s->total_in_ = 0;
s->next_out_ = NULL;
s->available_out_ = 0;
s->total_out_ = 0;
s->stream_state_ = BROTLI_STREAM_PROCESSING;
s->is_last_block_emitted_ = BROTLI_FALSE;
s->is_initialized_ = BROTLI_FALSE;
RingBufferInit(&s->ringbuffer_);
s->commands_ = 0;
s->cmd_alloc_size_ = 0;
/* Initialize distance cache. */
s->dist_cache_[0] = 4;
s->dist_cache_[1] = 11;
s->dist_cache_[2] = 15;
s->dist_cache_[3] = 16;
/* Save the state of the distance cache in case we need to restore it for
emitting an uncompressed block. */
memcpy(s->saved_dist_cache_, s->dist_cache_, sizeof(s->saved_dist_cache_));
}
BrotliEncoderState* BrotliEncoderCreateInstance(
brotli_alloc_func alloc_func, brotli_free_func free_func, void* opaque) {
BrotliEncoderState* state = (BrotliEncoderState*)BrotliBootstrapAlloc(
sizeof(BrotliEncoderState), alloc_func, free_func, opaque);
if (state == NULL) {
/* BROTLI_DUMP(); */
return 0;
}
BrotliInitMemoryManager(
&state->memory_manager_, alloc_func, free_func, opaque);
BrotliEncoderInitState(state);
return state;
}
#ifdef BROTLI_REPORTING
/* When BROTLI_REPORTING is defined extra reporting module have to be linked. */
void BrotliEncoderOnFinish(const BrotliEncoderState* s);
#define BROTLI_ENCODER_ON_FINISH(s) BrotliEncoderOnFinish(s);
#else
#if !defined(BROTLI_ENCODER_ON_FINISH)
#define BROTLI_ENCODER_ON_FINISH(s) (void)(s);
#endif
#endif
static void BrotliEncoderCleanupState(BrotliEncoderState* s) {
MemoryManager* m = &s->memory_manager_;
BROTLI_ENCODER_ON_FINISH(s);
if (BROTLI_IS_OOM(m)) {
BrotliWipeOutMemoryManager(m);
return;
}
BROTLI_FREE(m, s->storage_);
BROTLI_FREE(m, s->commands_);
RingBufferFree(m, &s->ringbuffer_);
DestroyHasher(m, &s->hasher_);
BROTLI_FREE(m, s->large_table_);
BROTLI_FREE(m, s->one_pass_arena_);
BROTLI_FREE(m, s->two_pass_arena_);
BROTLI_FREE(m, s->command_buf_);
BROTLI_FREE(m, s->literal_buf_);
BrotliEncoderCleanupParams(m, &s->params);
}
/* Deinitializes and frees BrotliEncoderState instance. */
void BrotliEncoderDestroyInstance(BrotliEncoderState* state) {
if (!state) {
return;
} else {
BrotliEncoderCleanupState(state);
BrotliBootstrapFree(state, &state->memory_manager_);
}
}
/*
Copies the given input data to the internal ring buffer of the compressor.
No processing of the data occurs at this time and this function can be
called multiple times before calling WriteBrotliData() to process the
accumulated input. At most input_block_size() bytes of input data can be
copied to the ring buffer, otherwise the next WriteBrotliData() will fail.
*/
static void CopyInputToRingBuffer(BrotliEncoderState* s,
const size_t input_size,
const uint8_t* input_buffer) {
RingBuffer* ringbuffer_ = &s->ringbuffer_;
MemoryManager* m = &s->memory_manager_;
RingBufferWrite(m, input_buffer, input_size, ringbuffer_);
if (BROTLI_IS_OOM(m)) return;
s->input_pos_ += input_size;
/* TL;DR: If needed, initialize 7 more bytes in the ring buffer to make the
hashing not depend on uninitialized data. This makes compression
deterministic and it prevents uninitialized memory warnings in Valgrind.
Even without erasing, the output would be valid (but nondeterministic).
Background information: The compressor stores short (at most 8 bytes)
substrings of the input already read in a hash table, and detects
repetitions by looking up such substrings in the hash table. If it
can find a substring, it checks whether the substring is really there
in the ring buffer (or it's just a hash collision). Should the hash
table become corrupt, this check makes sure that the output is
still valid, albeit the compression ratio would be bad.
The compressor populates the hash table from the ring buffer as it's
reading new bytes from the input. However, at the last few indexes of
the ring buffer, there are not enough bytes to build full-length
substrings from. Since the hash table always contains full-length
substrings, we erase with dummy zeros here to make sure that those
substrings will contain zeros at the end instead of uninitialized
data.
Please note that erasing is not necessary (because the
memory region is already initialized since he ring buffer
has a `tail' that holds a copy of the beginning,) so we
skip erasing if we have already gone around at least once in
the ring buffer.
Only clear during the first round of ring-buffer writes. On
subsequent rounds data in the ring-buffer would be affected. */
if (ringbuffer_->pos_ <= ringbuffer_->mask_) {
/* This is the first time when the ring buffer is being written.
We clear 7 bytes just after the bytes that have been copied from
the input buffer.
The ring-buffer has a "tail" that holds a copy of the beginning,
but only once the ring buffer has been fully written once, i.e.,
pos <= mask. For the first time, we need to write values
in this tail (where index may be larger than mask), so that
we have exactly defined behavior and don't read uninitialized
memory. Due to performance reasons, hashing reads data using a
LOAD64, which can go 7 bytes beyond the bytes written in the
ring-buffer. */
memset(ringbuffer_->buffer_ + ringbuffer_->pos_, 0, 7);
}
}
/* Marks all input as processed.
Returns true if position wrapping occurs. */
static BROTLI_BOOL UpdateLastProcessedPos(BrotliEncoderState* s) {
uint32_t wrapped_last_processed_pos = WrapPosition(s->last_processed_pos_);
uint32_t wrapped_input_pos = WrapPosition(s->input_pos_);
s->last_processed_pos_ = s->input_pos_;
return TO_BROTLI_BOOL(wrapped_input_pos < wrapped_last_processed_pos);
}
static void ExtendLastCommand(BrotliEncoderState* s, uint32_t* bytes,
uint32_t* wrapped_last_processed_pos) {
Command* last_command = &s->commands_[s->num_commands_ - 1];
const uint8_t* data = s->ringbuffer_.buffer_;
const uint32_t mask = s->ringbuffer_.mask_;
uint64_t max_backward_distance =
(((uint64_t)1) << s->params.lgwin) - BROTLI_WINDOW_GAP;
uint64_t last_copy_len = last_command->copy_len_ & 0x1FFFFFF;
uint64_t last_processed_pos = s->last_processed_pos_ - last_copy_len;
uint64_t max_distance = last_processed_pos < max_backward_distance ?
last_processed_pos : max_backward_distance;
uint64_t cmd_dist = (uint64_t)s->dist_cache_[0];
uint32_t distance_code = CommandRestoreDistanceCode(last_command,
&s->params.dist);
const CompoundDictionary* dict = &s->params.dictionary.compound;
size_t compound_dictionary_size = dict->total_size;
if (distance_code < BROTLI_NUM_DISTANCE_SHORT_CODES ||
distance_code - (BROTLI_NUM_DISTANCE_SHORT_CODES - 1) == cmd_dist) {
if (cmd_dist <= max_distance) {
while (*bytes != 0 && data[*wrapped_last_processed_pos & mask] ==
data[(*wrapped_last_processed_pos - cmd_dist) & mask]) {
last_command->copy_len_++;
(*bytes)--;
(*wrapped_last_processed_pos)++;
}
} else {
if ((cmd_dist - max_distance - 1) < compound_dictionary_size &&
last_copy_len < cmd_dist - max_distance) {
size_t address =
compound_dictionary_size - (size_t)(cmd_dist - max_distance) +
(size_t)last_copy_len;
size_t br_index = 0;
size_t br_offset;
const uint8_t* chunk;
size_t chunk_length;
while (address >= dict->chunk_offsets[br_index + 1]) br_index++;
br_offset = address - dict->chunk_offsets[br_index];
chunk = dict->chunk_source[br_index];
chunk_length =
dict->chunk_offsets[br_index + 1] - dict->chunk_offsets[br_index];
while (*bytes != 0 && data[*wrapped_last_processed_pos & mask] ==
chunk[br_offset]) {
last_command->copy_len_++;
(*bytes)--;
(*wrapped_last_processed_pos)++;
if (++br_offset == chunk_length) {
br_index++;
br_offset = 0;
if (br_index != dict->num_chunks) {
chunk = dict->chunk_source[br_index];
chunk_length = dict->chunk_offsets[br_index + 1] -
dict->chunk_offsets[br_index];
} else {
break;
}
}
}
}
}
/* The copy length is at most the metablock size, and thus expressible. */
GetLengthCode(last_command->insert_len_,
(size_t)((int)(last_command->copy_len_ & 0x1FFFFFF) +
(int)(last_command->copy_len_ >> 25)),
TO_BROTLI_BOOL((last_command->dist_prefix_ & 0x3FF) == 0),
&last_command->cmd_prefix_);
}
}
/*
Processes the accumulated input data and sets |*out_size| to the length of
the new output meta-block, or to zero if no new output meta-block has been
created (in this case the processed input data is buffered internally).
If |*out_size| is positive, |*output| points to the start of the output
data. If |is_last| or |force_flush| is BROTLI_TRUE, an output meta-block is
always created. However, until |is_last| is BROTLI_TRUE encoder may retain up
to 7 bits of the last byte of output. Byte-alignment could be enforced by
emitting an empty meta-data block.
Returns BROTLI_FALSE if the size of the input data is larger than
input_block_size().
*/
static BROTLI_BOOL EncodeData(
BrotliEncoderState* s, const BROTLI_BOOL is_last,
const BROTLI_BOOL force_flush, size_t* out_size, uint8_t** output) {
const uint64_t delta = UnprocessedInputSize(s);
uint32_t bytes = (uint32_t)delta;
uint32_t wrapped_last_processed_pos = WrapPosition(s->last_processed_pos_);
uint8_t* data;
uint32_t mask;
MemoryManager* m = &s->memory_manager_;
ContextType literal_context_mode;
ContextLut literal_context_lut;
BROTLI_BOOL fast_compress =
s->params.quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY;
data = s->ringbuffer_.buffer_;
mask = s->ringbuffer_.mask_;
if (delta == 0) { /* No new input; still might want to flush or finish. */
if (!data) { /* No input has been processed so far. */
if (is_last) { /* Emit complete finalized stream. */
BROTLI_DCHECK(s->last_bytes_bits_ <= 14);
s->last_bytes_ |= (uint16_t)(3u << s->last_bytes_bits_);
s->last_bytes_bits_ = (uint8_t)(s->last_bytes_bits_ + 2u);
s->tiny_buf_.u8[0] = (uint8_t)s->last_bytes_;
s->tiny_buf_.u8[1] = (uint8_t)(s->last_bytes_ >> 8);
*output = s->tiny_buf_.u8;
*out_size = (s->last_bytes_bits_ + 7u) >> 3u;
return BROTLI_TRUE;
} else { /* No data, not last -> no-op. */
*out_size = 0;
return BROTLI_TRUE;
}
} else {
/* Fast compress performs flush every block -> flush is no-op. */
if (!is_last && (!force_flush || fast_compress)) { /* Another no-op. */
*out_size = 0;
return BROTLI_TRUE;
}
}
}
BROTLI_DCHECK(data);
if (s->params.quality > s->params.dictionary.max_quality) return BROTLI_FALSE;
/* Adding more blocks after "last" block is forbidden. */
if (s->is_last_block_emitted_) return BROTLI_FALSE;
if (is_last) s->is_last_block_emitted_ = BROTLI_TRUE;
if (delta > InputBlockSize(s)) {
return BROTLI_FALSE;
}
if (s->params.quality == FAST_TWO_PASS_COMPRESSION_QUALITY &&
!s->command_buf_) {
s->command_buf_ =
BROTLI_ALLOC(m, uint32_t, kCompressFragmentTwoPassBlockSize);
s->literal_buf_ =
BROTLI_ALLOC(m, uint8_t, kCompressFragmentTwoPassBlockSize);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(s->command_buf_) ||
BROTLI_IS_NULL(s->literal_buf_)) {
return BROTLI_FALSE;
}
}