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1 /*
2  * Copyright (C) 2010 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef A_BIT_READER_H_
18 
19 #define A_BIT_READER_H_
20 
21 #include <media/stagefright/foundation/ABase.h>
22 
23 #include <sys/types.h>
24 #include <stdint.h>
25 
26 namespace android {
27 
28 class ABitReader {
29 public:
30     ABitReader(const uint8_t *data, size_t size);
31     virtual ~ABitReader();
32 
33     uint32_t getBits(size_t n);
34     void skipBits(size_t n);
35 
36     void putBits(uint32_t x, size_t n);
37 
38     size_t numBitsLeft() const;
39 
40     const uint8_t *data() const;
41 
42 protected:
43     const uint8_t *mData;
44     size_t mSize;
45 
46     uint32_t mReservoir;  // left-aligned bits
47     size_t mNumBitsLeft;
48 
49     virtual void fillReservoir();
50 
51     DISALLOW_EVIL_CONSTRUCTORS(ABitReader);
52 };
53 
54 class NALBitReader : public ABitReader {
55 public:
56     NALBitReader(const uint8_t *data, size_t size);
57 
58     bool atLeastNumBitsLeft(size_t n) const;
59 
60 private:
61     int32_t mNumZeros;
62 
63     virtual void fillReservoir();
64 
65     DISALLOW_EVIL_CONSTRUCTORS(NALBitReader);
66 };
67 
68 }  // namespace android
69 
70 #endif  // A_BIT_READER_H_
71