csrc/enc/encode.h
// Copyright 2013 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.
//
// API for Brotli compression
#ifndef BROTLI_ENC_ENCODE_H_
#define BROTLI_ENC_ENCODE_H_
#include <stddef.h>
#include <stdint.h>
#include <string>
#include <vector>
#include "./command.h"
#include "./hash.h"
#include "./ringbuffer.h"
#include "./static_dict.h"
#include "./streams.h"
namespace brotli {
static const int kMaxWindowBits = 24;
static const int kMinWindowBits = 16;
static const int kMinInputBlockBits = 16;
static const int kMaxInputBlockBits = 24;
struct BrotliParams {
BrotliParams()
: mode(MODE_TEXT),
quality(11),
lgwin(22),
lgblock(0),
enable_dictionary(true),
enable_transforms(false),
greedy_block_split(false),
enable_context_modeling(true) {}
enum Mode {
MODE_TEXT = 0,
MODE_FONT = 1,
};
Mode mode;
// Controls the compression-speed vs compression-density tradeoffs. The higher
// the quality, the slower the compression. Range is 0 to 11.
int quality;
// Base 2 logarithm of the sliding window size. Range is 16 to 24.
int lgwin;
// Base 2 logarithm of the maximum input block size. Range is 16 to 24.
// If set to 0, the value will be set based on the quality.
int lgblock;
// These settings will be respected only if quality > 9.
bool enable_dictionary;
bool enable_transforms;
bool greedy_block_split;
bool enable_context_modeling;
};
// An instance can not be reused for multiple brotli streams.
class BrotliCompressor {
public:
explicit BrotliCompressor(BrotliParams params);
~BrotliCompressor();
// The maximum input size that can be processed at once.
size_t input_block_size() const { return 1 << params_.lgblock; }
// Encodes the data in input_buffer as a meta-block and writes it to
// encoded_buffer (*encoded_size should be set to the size of
// encoded_buffer) and sets *encoded_size to the number of bytes that
// was written. Returns 0 if there was an error and 1 otherwise.
bool WriteMetaBlock(const size_t input_size,
const uint8_t* input_buffer,
const bool is_last,
size_t* encoded_size,
uint8_t* encoded_buffer);
// Writes a metadata meta-block containing the given input to encoded_buffer.
// *encoded_size should be set to the size of the encoded_buffer.
// Sets *encoded_size to the number of bytes that was written.
// Note that the given input data will not be part of the sliding window and
// thus no backward references can be made to this data from subsequent
// metablocks.
bool WriteMetadata(const size_t input_size,
const uint8_t* input_buffer,
const bool is_last,
size_t* encoded_size,
uint8_t* encoded_buffer);
// Writes a zero-length meta-block with end-of-input bit set to the
// internal output buffer and copies the output buffer to encoded_buffer
// (*encoded_size should be set to the size of encoded_buffer) and sets
// *encoded_size to the number of bytes written. Returns false if there was
// an error and true otherwise.
bool FinishStream(size_t* encoded_size, uint8_t* encoded_buffer);
// 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.
void CopyInputToRingBuffer(const size_t input_size,
const uint8_t* input_buffer);
// 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 was
// 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.
// Returns false if the size of the input data is larger than
// input_block_size() or if there was an error during writing the output.
// If is_last or force_flush is true, an output meta-block is always created.
bool WriteBrotliData(const bool is_last, const bool force_flush,
size_t* out_size, uint8_t** output);
// No-op, but we keep it here for API backward-compatibility.
void WriteStreamHeader() {}
private:
// Initializes the hasher with the hashes of dictionary words.
void StoreDictionaryWordHashes(bool enable_transforms);
uint8_t* GetBrotliStorage(size_t size);
bool WriteMetaBlockInternal(const bool is_last,
const bool utf8_mode,
size_t* out_size,
uint8_t** output);
BrotliParams params_;
int max_backward_distance_;
std::unique_ptr<Hashers> hashers_;
int hash_type_;
size_t input_pos_;
std::unique_ptr<RingBuffer> ringbuffer_;
std::unique_ptr<float[]> literal_cost_;
size_t literal_cost_mask_;
size_t cmd_buffer_size_;
std::unique_ptr<Command[]> commands_;
int num_commands_;
int last_insert_len_;
size_t last_flush_pos_;
size_t last_processed_pos_;
int dist_cache_[4];
uint8_t last_byte_;
uint8_t last_byte_bits_;
uint8_t prev_byte_;
uint8_t prev_byte2_;
int storage_size_;
std::unique_ptr<uint8_t[]> storage_;
static StaticDictionary *static_dictionary_;
};
// Compresses the data in input_buffer into encoded_buffer, and sets
// *encoded_size to the compressed length.
// Returns 0 if there was an error and 1 otherwise.
int BrotliCompressBuffer(BrotliParams params,
size_t input_size,
const uint8_t* input_buffer,
size_t* encoded_size,
uint8_t* encoded_buffer);
// Same as above, but uses the specified input and output classes instead
// of reading from and writing to pre-allocated memory buffers.
int BrotliCompress(BrotliParams params, BrotliIn* in, BrotliOut* out);
} // namespace brotli
#endif // BROTLI_ENC_ENCODE_H_