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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 parallel Brotli compressor.
#include "./encode_parallel.h"
#include <algorithm>
#include <limits>
#include "./backward_references.h"
#include "./bit_cost.h"
#include "./block_splitter.h"
#include "./brotli_bit_stream.h"
#include "./cluster.h"
#include "./context.h"
#include "./metablock.h"
#include "./transform.h"
#include "./entropy_encode.h"
#include "./fast_log.h"
#include "./hash.h"
#include "./histogram.h"
#include "./prefix.h"
#include "./utf8_util.h"
#include "./write_bits.h"
namespace brotli {
namespace {
void RecomputeDistancePrefixes(Command* cmds, size_t num_commands,
uint32_t num_direct_distance_codes,
uint32_t distance_postfix_bits) {
if (num_direct_distance_codes == 0 &&
distance_postfix_bits == 0) {
return;
}
for (size_t i = 0; i < num_commands; ++i) {
Command* cmd = &cmds[i];
if (cmd->copy_len_ > 0 && cmd->cmd_prefix_ >= 128) {
PrefixEncodeCopyDistance(cmd->DistanceCode(),
num_direct_distance_codes,
distance_postfix_bits,
&cmd->dist_prefix_,
&cmd->dist_extra_);
}
}
}
bool WriteMetaBlockParallel(const BrotliParams& params,
const uint32_t input_size,
const uint8_t* input_buffer,
const uint32_t prefix_size,
const uint8_t* prefix_buffer,
const bool is_first,
const bool is_last,
size_t* encoded_size,
uint8_t* encoded_buffer) {
if (input_size == 0) {
return false;
}
// Copy prefix + next input block into a continuous area.
uint32_t input_pos = prefix_size;
// CreateBackwardReferences reads up to 3 bytes past the end of input if the
// mask points past the end of input.
// FindMatchLengthWithLimit could do another 8 bytes look-forward.
std::vector<uint8_t> input(prefix_size + input_size + 4 + 8);
memcpy(&input[0], prefix_buffer, prefix_size);
memcpy(&input[input_pos], input_buffer, input_size);
// Since we don't have a ringbuffer, masking is a no-op.
// We use one less bit than the full range because some of the code uses
// mask + 1 as the size of the ringbuffer.
const uint32_t mask = std::numeric_limits<uint32_t>::max() >> 1;
uint8_t prev_byte = input_pos > 0 ? input[(input_pos - 1) & mask] : 0;
uint8_t prev_byte2 = input_pos > 1 ? input[(input_pos - 2) & mask] : 0;
// Decide about UTF8 mode.
static const double kMinUTF8Ratio = 0.75;
bool utf8_mode = IsMostlyUTF8(&input[0], input_pos, mask, input_size,
kMinUTF8Ratio);
// Initialize hashers.
int hash_type = std::min(10, params.quality);
Hashers* hashers = new Hashers();
hashers->Init(hash_type);
// Compute backward references.
size_t last_insert_len = 0;
size_t num_commands = 0;
size_t num_literals = 0;
int dist_cache[4] = { -4, -4, -4, -4 };
Command* commands = static_cast<Command*>(
malloc(sizeof(Command) * ((input_size + 1) >> 1)));
if (commands == 0) {
delete hashers;
return false;
}
CreateBackwardReferences(
input_size, input_pos, is_last,
&input[0], mask,
params.quality,
params.lgwin,
hashers,
hash_type,
dist_cache,
&last_insert_len,
commands,
&num_commands,
&num_literals);
delete hashers;
if (last_insert_len > 0) {
commands[num_commands++] = Command(last_insert_len);
num_literals += last_insert_len;
}
assert(num_commands != 0);
// Build the meta-block.
MetaBlockSplit mb;
uint32_t num_direct_distance_codes =
params.mode == BrotliParams::MODE_FONT ? 12 : 0;
uint32_t distance_postfix_bits =
params.mode == BrotliParams::MODE_FONT ? 1 : 0;
ContextType literal_context_mode = utf8_mode ? CONTEXT_UTF8 : CONTEXT_SIGNED;
RecomputeDistancePrefixes(commands, num_commands,
num_direct_distance_codes,
distance_postfix_bits);
if (params.quality <= 9) {
BuildMetaBlockGreedy(&input[0], input_pos, mask,
commands, num_commands,
&mb);
} else {
BuildMetaBlock(&input[0], input_pos, mask,
prev_byte, prev_byte2,
commands, num_commands,
literal_context_mode,
&mb);
}
// Set up the temporary output storage.
const size_t max_out_size = 2 * input_size + 500;
std::vector<uint8_t> storage(max_out_size);
uint8_t first_byte = 0;
size_t first_byte_bits = 0;
if (is_first) {
if (params.lgwin == 16) {
first_byte = 0;
first_byte_bits = 1;
} else if (params.lgwin == 17) {
first_byte = 1;
first_byte_bits = 7;
} else {
first_byte = static_cast<uint8_t>(((params.lgwin - 17) << 1) | 1);
first_byte_bits = 4;
}
}
storage[0] = static_cast<uint8_t>(first_byte);
size_t storage_ix = first_byte_bits;
// Store the meta-block to the temporary output.
StoreMetaBlock(&input[0], input_pos, input_size, mask,
prev_byte, prev_byte2,
is_last,
num_direct_distance_codes,
distance_postfix_bits,
literal_context_mode,
commands, num_commands,
mb,
&storage_ix, &storage[0]);
free(commands);
// If this is not the last meta-block, store an empty metadata
// meta-block so that the meta-block will end at a byte boundary.
if (!is_last) {
StoreSyncMetaBlock(&storage_ix, &storage[0]);
}
// If the compressed data is too large, fall back to an uncompressed
// meta-block.
size_t output_size = storage_ix >> 3;
if (input_size + 4 < output_size) {
storage[0] = static_cast<uint8_t>(first_byte);
storage_ix = first_byte_bits;
StoreUncompressedMetaBlock(is_last, &input[0], input_pos, mask,
input_size,
&storage_ix, &storage[0]);
output_size = storage_ix >> 3;
}
// Copy the temporary output with size-check to the output.
if (output_size > *encoded_size) {
return false;
}
memcpy(encoded_buffer, &storage[0], output_size);
*encoded_size = output_size;
return true;
}
} // namespace
int BrotliCompressBufferParallel(BrotliParams params,
size_t input_size,
const uint8_t* input_buffer,
size_t* encoded_size,
uint8_t* encoded_buffer) {
if (*encoded_size == 0) {
// Output buffer needs at least one byte.
return 0;
} else if (input_size == 0) {
encoded_buffer[0] = 6;
*encoded_size = 1;
return 1;
}
// Sanitize params.
if (params.lgwin < kMinWindowBits) {
params.lgwin = kMinWindowBits;
} else if (params.lgwin > kMaxWindowBits) {
params.lgwin = kMaxWindowBits;
}
if (params.lgblock == 0) {
params.lgblock = 16;
if (params.quality >= 9 && params.lgwin > params.lgblock) {
params.lgblock = std::min(21, params.lgwin);
}
} else if (params.lgblock < kMinInputBlockBits) {
params.lgblock = kMinInputBlockBits;
} else if (params.lgblock > kMaxInputBlockBits) {
params.lgblock = kMaxInputBlockBits;
}
size_t max_input_block_size = 1 << params.lgblock;
size_t max_prefix_size = 1u << params.lgwin;
std::vector<std::vector<uint8_t> > compressed_pieces;
// Compress block-by-block independently.
for (size_t pos = 0; pos < input_size; ) {
uint32_t input_block_size =
static_cast<uint32_t>(std::min(max_input_block_size, input_size - pos));
uint32_t prefix_size =
static_cast<uint32_t>(std::min(max_prefix_size, pos));
size_t out_size = input_block_size + (input_block_size >> 3) + 1024;
std::vector<uint8_t> out(out_size);
if (!WriteMetaBlockParallel(params,
input_block_size,
&input_buffer[pos],
prefix_size,
&input_buffer[pos - prefix_size],
pos == 0,
pos + input_block_size == input_size,
&out_size,
&out[0])) {
return false;
}
out.resize(out_size);
compressed_pieces.push_back(out);
pos += input_block_size;
}
// Piece together the output.
size_t out_pos = 0;
for (size_t i = 0; i < compressed_pieces.size(); ++i) {
const std::vector<uint8_t>& out = compressed_pieces[i];
if (out_pos + out.size() > *encoded_size) {
return false;
}
memcpy(&encoded_buffer[out_pos], &out[0], out.size());
out_pos += out.size();
}
*encoded_size = out_pos;
return true;
}
} // namespace brotli
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