mirror of
https://github.com/google/brotli.git
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197 lines
7.5 KiB
C++
197 lines
7.5 KiB
C++
// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// API for Brotli compression
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#ifndef BROTLI_ENC_ENCODE_H_
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#define BROTLI_ENC_ENCODE_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <string>
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#include <vector>
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#include "./command.h"
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#include "./hash.h"
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#include "./ringbuffer.h"
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#include "./static_dict.h"
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#include "./streams.h"
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namespace brotli {
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static const int kMaxWindowBits = 24;
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static const int kMinWindowBits = 10;
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static const int kMinInputBlockBits = 16;
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static const int kMaxInputBlockBits = 24;
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struct BrotliParams {
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BrotliParams()
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: mode(MODE_GENERIC),
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quality(11),
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lgwin(22),
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lgblock(0),
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enable_dictionary(true),
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enable_transforms(false),
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greedy_block_split(false),
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enable_context_modeling(true) {}
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enum Mode {
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// Default compression mode. The compressor does not know anything in
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// advance about the properties of the input.
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MODE_GENERIC = 0,
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// Compression mode for UTF-8 format text input.
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MODE_TEXT = 1,
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// Compression mode used in WOFF 2.0.
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MODE_FONT = 2,
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};
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Mode mode;
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// Controls the compression-speed vs compression-density tradeoffs. The higher
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// the quality, the slower the compression. Range is 0 to 11.
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int quality;
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// Base 2 logarithm of the sliding window size. Range is 10 to 24.
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int lgwin;
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// Base 2 logarithm of the maximum input block size. Range is 16 to 24.
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// If set to 0, the value will be set based on the quality.
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int lgblock;
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// These settings are deprecated and will be ignored.
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// All speed vs. size compromises are controlled by the quality param.
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bool enable_dictionary;
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bool enable_transforms;
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bool greedy_block_split;
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bool enable_context_modeling;
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};
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// An instance can not be reused for multiple brotli streams.
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class BrotliCompressor {
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public:
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explicit BrotliCompressor(BrotliParams params);
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~BrotliCompressor();
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// The maximum input size that can be processed at once.
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size_t input_block_size() const { return 1 << params_.lgblock; }
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// Encodes the data in input_buffer as a meta-block and writes it to
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// encoded_buffer (*encoded_size should be set to the size of
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// encoded_buffer) and sets *encoded_size to the number of bytes that
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// was written. Returns 0 if there was an error and 1 otherwise.
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bool WriteMetaBlock(const size_t input_size,
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const uint8_t* input_buffer,
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const bool is_last,
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size_t* encoded_size,
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uint8_t* encoded_buffer);
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// Writes a metadata meta-block containing the given input to encoded_buffer.
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// *encoded_size should be set to the size of the encoded_buffer.
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// Sets *encoded_size to the number of bytes that was written.
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// Note that the given input data will not be part of the sliding window and
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// thus no backward references can be made to this data from subsequent
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// metablocks.
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bool WriteMetadata(const size_t input_size,
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const uint8_t* input_buffer,
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const bool is_last,
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size_t* encoded_size,
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uint8_t* encoded_buffer);
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// Writes a zero-length meta-block with end-of-input bit set to the
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// internal output buffer and copies the output buffer to encoded_buffer
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// (*encoded_size should be set to the size of encoded_buffer) and sets
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// *encoded_size to the number of bytes written. Returns false if there was
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// an error and true otherwise.
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bool FinishStream(size_t* encoded_size, uint8_t* encoded_buffer);
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// Copies the given input data to the internal ring buffer of the compressor.
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// No processing of the data occurs at this time and this function can be
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// called multiple times before calling WriteBrotliData() to process the
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// accumulated input. At most input_block_size() bytes of input data can be
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// copied to the ring buffer, otherwise the next WriteBrotliData() will fail.
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void CopyInputToRingBuffer(const size_t input_size,
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const uint8_t* input_buffer);
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// Processes the accumulated input data and sets *out_size to the length of
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// the new output meta-block, or to zero if no new output meta-block was
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// created (in this case the processed input data is buffered internally).
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// If *out_size is positive, *output points to the start of the output data.
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// Returns false if the size of the input data is larger than
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// input_block_size() or if there was an error during writing the output.
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// If is_last or force_flush is true, an output meta-block is always created.
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bool WriteBrotliData(const bool is_last, const bool force_flush,
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size_t* out_size, uint8_t** output);
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// Fills the new state with a dictionary for LZ77, warming up the ringbuffer,
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// e.g. for custom static dictionaries for data formats.
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// Not to be confused with the built-in transformable dictionary of Brotli.
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// To decode, use BrotliSetCustomDictionary of the decoder with the same
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// dictionary.
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void BrotliSetCustomDictionary(size_t size, const uint8_t* dict);
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// No-op, but we keep it here for API backward-compatibility.
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void WriteStreamHeader() {}
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private:
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uint8_t* GetBrotliStorage(size_t size);
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bool WriteMetaBlockInternal(const bool is_last,
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const bool utf8_mode,
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size_t* out_size,
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uint8_t** output);
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BrotliParams params_;
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int max_backward_distance_;
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std::unique_ptr<Hashers> hashers_;
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int hash_type_;
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size_t input_pos_;
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std::unique_ptr<RingBuffer> ringbuffer_;
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std::unique_ptr<float[]> literal_cost_;
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size_t literal_cost_mask_;
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size_t cmd_buffer_size_;
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std::unique_ptr<Command[]> commands_;
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int num_commands_;
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int num_literals_;
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int last_insert_len_;
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size_t last_flush_pos_;
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size_t last_processed_pos_;
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int dist_cache_[4];
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int saved_dist_cache_[4];
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uint8_t last_byte_;
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uint8_t last_byte_bits_;
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uint8_t prev_byte_;
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uint8_t prev_byte2_;
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int storage_size_;
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std::unique_ptr<uint8_t[]> storage_;
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};
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// Compresses the data in input_buffer into encoded_buffer, and sets
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// *encoded_size to the compressed length.
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// Returns 0 if there was an error and 1 otherwise.
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int BrotliCompressBuffer(BrotliParams params,
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size_t input_size,
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const uint8_t* input_buffer,
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size_t* encoded_size,
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uint8_t* encoded_buffer);
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// Same as above, but uses the specified input and output classes instead
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// of reading from and writing to pre-allocated memory buffers.
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int BrotliCompress(BrotliParams params, BrotliIn* in, BrotliOut* out);
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// Before compressing the data, sets a custom LZ77 dictionary with
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// BrotliCompressor::BrotliSetCustomDictionary.
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int BrotliCompressWithCustomDictionary(size_t dictsize, const uint8_t* dict,
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BrotliParams params,
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BrotliIn* in, BrotliOut* out);
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} // namespace brotli
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#endif // BROTLI_ENC_ENCODE_H_
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