// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Note: ported from Chromium commit head: e5a9a62
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#ifndef VP9_BOOL_DECODER_H_
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#define VP9_BOOL_DECODER_H_
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#include <stddef.h>
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#include <stdint.h>
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#include <memory>
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#include "base/macros.h"
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namespace media {
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class BitReader;
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class Vp9BoolDecoder {
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public:
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Vp9BoolDecoder();
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~Vp9BoolDecoder();
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// |data| is the input buffer with |size| bytes.
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// Returns true if read first marker bit successfully.
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bool Initialize(const uint8_t* data, size_t size);
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// Returns true if none of the reads since the last Initialize() call has
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// gone beyond the end of available data.
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bool IsValid() const { return valid_; }
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// Reads one bit. B(p).
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// If the read goes beyond the end of buffer, the return value is undefined.
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bool ReadBool(int prob);
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// Reads a literal. L(n).
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// If the read goes beyond the end of buffer, the return value is undefined.
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uint8_t ReadLiteral(int bits);
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// Consumes padding bits up to end of data. Returns true if no
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// padding bits or they are all zero.
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bool ConsumePaddingBits();
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private:
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// The highest 8 bits of BigBool is actual "bool value". The remain bits
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// are optimization of prefill buffer.
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using BigBool = size_t;
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// The size of "bool value" used for boolean decoding defined in spec.
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const int kBoolSize = 8;
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const int kBigBoolBitSize = sizeof(BigBool) * 8;
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bool Fill();
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std::unique_ptr<BitReader> reader_;
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// Indicates if none of the reads since the last Initialize() call has gone
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// beyond the end of available data.
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bool valid_ = true;
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BigBool bool_value_ = 0;
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// Need to fill at least |count_to_fill_| bits. Negative value means extra
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// bits pre-filled.
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int count_to_fill_ = 0;
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unsigned int bool_range_ = 0;
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DISALLOW_COPY_AND_ASSIGN(Vp9BoolDecoder);
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};
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} // namespace media
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#endif // VP9_BOOL_DECODER_H_
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