68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
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// 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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// Bit reading helpers
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#ifndef BROTLI_DEC_BIT_READER_H_
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#define BROTLI_DEC_BIT_READER_H_
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#include "./types.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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typedef struct {
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uint64_t val_; // pre-fetched bits
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const uint8_t* buf_; // input byte buffer
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size_t len_; // buffer length
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size_t pos_; // byte position in buf_
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int bit_pos_; // current bit-reading position in val_
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int eos_; // bitstream is finished
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int error_; // an error occurred (buffer overflow attempt...)
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} BrotliBitReader;
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void BrotliInitBitReader(BrotliBitReader* const br,
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const uint8_t* const start,
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size_t length);
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// Sets a new data buffer.
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void BrotliBitReaderSetBuffer(BrotliBitReader* const br,
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const uint8_t* const buffer, size_t length);
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// Reads the specified number of bits from Read Buffer.
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// Flags an error in case end_of_stream or n_bits is more than allowed limit.
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// Flags eos if this read attempt is going to cross the read buffer.
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uint32_t BrotliReadBits(BrotliBitReader* const br, int n_bits);
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// Return the prefetched bits, so they can be looked up.
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static BROTLI_INLINE uint32_t BrotliPrefetchBits(BrotliBitReader* const br) {
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return (uint32_t)(br->val_ >> br->bit_pos_);
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}
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// For jumping over a number of bits in the bit stream when accessed with
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// BrotliPrefetchBits and BrotliFillBitWindow.
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static BROTLI_INLINE void BrotliSetBitPos(BrotliBitReader* const br, int val) {
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br->bit_pos_ = val;
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}
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// Advances the Read buffer by 4 bytes to make room for reading next 32 bits.
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void BrotliFillBitWindow(BrotliBitReader* const br);
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif // BROTLI_DEC_BIT_READER_H_
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