1 // Copyright (c) 2012 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_BASE_BIT_READER_H_
6 #define MEDIA_BASE_BIT_READER_H_
7 
8 #include <stdint.h>
9 #include <string>
10 
11 #include "base/compiler_specific.h"
12 #include "base/macros.h"
13 #include "media/base/bit_reader_core.h"
14 #include "media/base/media_export.h"
15 
16 namespace media {
17 
18 class MEDIA_EXPORT BitReader : private BitReaderCore::ByteStreamProvider {
19  public:
20   // Initialize the reader to start reading at |data|, |size| being size
21   // of |data| in bytes.
22   BitReader(const uint8_t* data, int size);
23   ~BitReader() override;
24 
ReadBits(int num_bits,T * out)25   template<typename T> bool ReadBits(int num_bits, T* out) {
26     return bit_reader_core_.ReadBits(num_bits, out);
27   }
28 
ReadFlag(bool * flag)29   bool ReadFlag(bool* flag) {
30     return bit_reader_core_.ReadFlag(flag);
31   }
32 
33   // Read |num_bits| of binary data into |str|. |num_bits| must be a positive
34   // multiple of 8. This is not efficient for extracting large strings.
35   // If false is returned, |str| may not be valid.
36   bool ReadString(int num_bits, std::string* str);
37 
SkipBits(int num_bits)38   bool SkipBits(int num_bits) {
39     return bit_reader_core_.SkipBits(num_bits);
40   }
41 
bits_available()42   int bits_available() const {
43     return initial_size_ * 8 - bits_read();
44   }
45 
bits_read()46   int bits_read() const {
47     return bit_reader_core_.bits_read();
48   }
49 
50  private:
51   // BitReaderCore::ByteStreamProvider implementation.
52   int GetBytes(int max_n, const uint8_t** out) override;
53 
54   // Total number of bytes that was initially passed to BitReader.
55   const int initial_size_;
56 
57   // Pointer to the next unread byte in the stream.
58   const uint8_t* data_;
59 
60   // Bytes left in the stream.
61   int bytes_left_;
62 
63   BitReaderCore bit_reader_core_;
64 
65   DISALLOW_COPY_AND_ASSIGN(BitReader);
66 };
67 
68 }  // namespace media
69 
70 #endif  // MEDIA_BASE_BIT_READER_H_
71