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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
*/
/* Block split point selection utilities. */
#include "block_splitter.h"
#include <string.h> /* memcpy, memset */
#include "../common/platform.h"
#include "bit_cost.h"
#include "cluster.h"
#include "command.h"
#include "fast_log.h"
#include "histogram.h"
#include "memory.h"
#include "quality.h"
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#endif
static const size_t kMaxLiteralHistograms = 100;
static const size_t kMaxCommandHistograms = 50;
static const double kLiteralBlockSwitchCost = 28.1;
static const double kCommandBlockSwitchCost = 13.5;
static const double kDistanceBlockSwitchCost = 14.6;
static const size_t kLiteralStrideLength = 70;
static const size_t kCommandStrideLength = 40;
static const size_t kDistanceStrideLength = 40;
static const size_t kSymbolsPerLiteralHistogram = 544;
static const size_t kSymbolsPerCommandHistogram = 530;
static const size_t kSymbolsPerDistanceHistogram = 544;
static const size_t kMinLengthForBlockSplitting = 128;
static const size_t kIterMulForRefining = 2;
static const size_t kMinItersForRefining = 100;
static size_t CountLiterals(const Command* cmds, const size_t num_commands) {
/* Count how many we have. */
size_t total_length = 0;
size_t i;
for (i = 0; i < num_commands; ++i) {
total_length += cmds[i].insert_len_;
}
return total_length;
}
static void CopyLiteralsToByteArray(const Command* cmds,
const size_t num_commands,
const uint8_t* data,
const size_t offset,
const size_t mask,
uint8_t* literals) {
size_t pos = 0;
size_t from_pos = offset & mask;
size_t i;
for (i = 0; i < num_commands; ++i) {
size_t insert_len = cmds[i].insert_len_;
if (from_pos + insert_len > mask) {
size_t head_size = mask + 1 - from_pos;
memcpy(literals + pos, data + from_pos, head_size);
from_pos = 0;
pos += head_size;
insert_len -= head_size;
}
if (insert_len > 0) {
memcpy(literals + pos, data + from_pos, insert_len);
pos += insert_len;
}
from_pos = (from_pos + insert_len + CommandCopyLen(&cmds[i])) & mask;
}
}
static BROTLI_INLINE uint32_t MyRand(uint32_t* seed) {
/* Initial seed should be 7. In this case, loop length is (1 << 29). */
*seed *= 16807U;
return *seed;
}
static BROTLI_INLINE double BitCost(size_t count) {
return count == 0 ? -2.0 : FastLog2(count);
}
#define HISTOGRAMS_PER_BATCH 64
#define CLUSTERS_PER_BATCH 16
#define FN(X) X ## Literal
#define DataType uint8_t
/* NOLINTNEXTLINE(build/include) */
#include "block_splitter_inc.h"
#undef DataType
#undef FN
#define FN(X) X ## Command
#define DataType uint16_t
/* NOLINTNEXTLINE(build/include) */
#include "block_splitter_inc.h"
#undef FN
#define FN(X) X ## Distance
/* NOLINTNEXTLINE(build/include) */
#include "block_splitter_inc.h"
#undef DataType
#undef FN
void BrotliInitBlockSplit(BlockSplit* self) {
self->num_types = 0;
self->num_blocks = 0;
self->types = 0;
self->lengths = 0;
self->types_alloc_size = 0;
self->lengths_alloc_size = 0;
}
void BrotliDestroyBlockSplit(MemoryManager* m, BlockSplit* self) {
BROTLI_FREE(m, self->types);
BROTLI_FREE(m, self->lengths);
}
/* Extracts literals, command distance and prefix codes, then applies
* SplitByteVector to create partitioning. */
void BrotliSplitBlock(MemoryManager* m,
const Command* cmds,
const size_t num_commands,
const uint8_t* data,
const size_t pos,
const size_t mask,
const BrotliEncoderParams* params,
BlockSplit* literal_split,
BlockSplit* insert_and_copy_split,
BlockSplit* dist_split) {
{
size_t literals_count = CountLiterals(cmds, num_commands);
uint8_t* literals = BROTLI_ALLOC(m, uint8_t, literals_count);
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(literals)) return;
/* Create a continuous array of literals. */
CopyLiteralsToByteArray(cmds, num_commands, data, pos, mask, literals);
/* Create the block split on the array of literals.
* Literal histograms can have alphabet size up to 256.
* Though, to accomodate context modeling, less than half of maximum size
* is allowed. */
SplitByteVectorLiteral(
m, literals, literals_count,
kSymbolsPerLiteralHistogram, kMaxLiteralHistograms,
kLiteralStrideLength, kLiteralBlockSwitchCost, params,
literal_split);
if (BROTLI_IS_OOM(m)) return;
BROTLI_FREE(m, literals);
/* NB: this might be a good place for injecting extra splitting without
* increasing encoder complexity; however, output parition would be less
* optimal than one produced with forced splitting inside
* SplitByteVector (FindBlocks / ClusterBlocks). */
}
{
/* Compute prefix codes for commands. */
uint16_t* insert_and_copy_codes = BROTLI_ALLOC(m, uint16_t, num_commands);
size_t i;
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(insert_and_copy_codes)) return;
for (i = 0; i < num_commands; ++i) {
insert_and_copy_codes[i] = cmds[i].cmd_prefix_;
}
/* Create the block split on the array of command prefixes. */
SplitByteVectorCommand(
m, insert_and_copy_codes, num_commands,
kSymbolsPerCommandHistogram, kMaxCommandHistograms,
kCommandStrideLength, kCommandBlockSwitchCost, params,
insert_and_copy_split);
if (BROTLI_IS_OOM(m)) return;
/* TODO(eustas): reuse for distances? */
BROTLI_FREE(m, insert_and_copy_codes);
}
{
/* Create a continuous array of distance prefixes. */
uint16_t* distance_prefixes = BROTLI_ALLOC(m, uint16_t, num_commands);
size_t j = 0;
size_t i;
if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(distance_prefixes)) return;
for (i = 0; i < num_commands; ++i) {
const Command* cmd = &cmds[i];
if (CommandCopyLen(cmd) && cmd->cmd_prefix_ >= 128) {
distance_prefixes[j++] = cmd->dist_prefix_ & 0x3FF;
}
}
/* Create the block split on the array of distance prefixes. */
SplitByteVectorDistance(
m, distance_prefixes, j,
kSymbolsPerDistanceHistogram, kMaxCommandHistograms,
kDistanceStrideLength, kDistanceBlockSwitchCost, params,
dist_split);
if (BROTLI_IS_OOM(m)) return;
BROTLI_FREE(m, distance_prefixes);
}
}
#if defined(BROTLI_TEST)
size_t CountLiteralsForTest(const Command*, const size_t);
size_t CountLiteralsForTest(const Command* cmds, const size_t num_commands) {
return CountLiterals(cmds, num_commands);
}
void CopyLiteralsToByteArrayForTest(const Command*,
const size_t, const uint8_t*, const size_t, const size_t, uint8_t*);
void CopyLiteralsToByteArrayForTest(const Command* cmds,
const size_t num_commands, const uint8_t* data, const size_t offset,
const size_t mask, uint8_t* literals) {
CopyLiteralsToByteArray(cmds, num_commands, data, offset, mask, literals);
}
#endif
#if defined(__cplusplus) || defined(c_plusplus)
} /* extern "C" */
#endif
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