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| 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef MEDIA_FILTERS_VP9_BOOL_DECODER_H_ |
| 6 #define MEDIA_FILTERS_VP9_BOOL_DECODER_H_ |
| 7 |
| 8 #include <stddef.h> |
| 9 #include <stdint.h> |
| 10 |
| 11 #include <memory> |
| 12 |
| 13 #include "base/macros.h" |
| 14 #include "media/base/media_export.h" |
| 15 |
| 16 namespace media { |
| 17 |
| 18 class BitReader; |
| 19 |
| 20 class MEDIA_EXPORT Vp9BoolDecoder { |
| 21 public: |
| 22 Vp9BoolDecoder(); |
| 23 ~Vp9BoolDecoder(); |
| 24 |
| 25 // |data| is the input buffer with |size| bytes. |
| 26 // Returns true if read first marker bit successfully. |
| 27 bool Initialize(const uint8_t* data, size_t size); |
| 28 |
| 29 // Returns true if none of the reads since the last Initialize() call has |
| 30 // gone beyond the end of available data. |
| 31 bool IsValid() const { return valid_; } |
| 32 |
| 33 // Reads one bit. B(p). |
| 34 // If the read goes beyond the end of buffer, the return value is undefined. |
| 35 bool ReadBool(int prob); |
| 36 |
| 37 // Reads a literal. L(n). |
| 38 // If the read goes beyond the end of buffer, the return value is undefined. |
| 39 uint8_t ReadLiteral(int bits); |
| 40 |
| 41 // Consumes padding bits up to end of data. Returns true if no |
| 42 // padding bits or they are all zero. |
| 43 bool ConsumePaddingBits(); |
| 44 |
| 45 private: |
| 46 // The highest 8 bits of BigBool is actual "bool value". The remain bits |
| 47 // are optimization of prefill buffer. |
| 48 using BigBool = size_t; |
| 49 // The size of "bool value" used for boolean decoding defined in spec. |
| 50 const int kBoolSize = 8; |
| 51 const int kBigBoolBitSize = sizeof(BigBool) * 8; |
| 52 |
| 53 bool Fill(); |
| 54 |
| 55 std::unique_ptr<BitReader> reader_; |
| 56 |
| 57 // Indicates if none of the reads since the last Initialize() call has gone |
| 58 // beyond the end of available data. |
| 59 bool valid_ = true; |
| 60 |
| 61 BigBool bool_value_ = 0; |
| 62 |
| 63 // Need to fill at least |count_to_fill_| bits. Negative value means extra |
| 64 // bits pre-filled. |
| 65 int count_to_fill_ = 0; |
| 66 unsigned int bool_range_ = 0; |
| 67 |
| 68 DISALLOW_COPY_AND_ASSIGN(Vp9BoolDecoder); |
| 69 }; |
| 70 |
| 71 } // namespace media |
| 72 |
| 73 #endif // MEDIA_FILTERS_VP9_BOOL_DECODER_H_ |
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