blob: 4ea27c01491504c38fa6aaad2d74dc952506762d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
|
/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.mozilla.thirdparty.com.google.android.exoplayer2.extractor;
import org.mozilla.thirdparty.com.google.android.exoplayer2.util.Assertions;
/**
* Wraps a byte array, providing methods that allow it to be read as a Vorbis bitstream.
*
* @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-360002">Vorbis bitpacking
* specification</a>
*/
public final class VorbisBitArray {
private final byte[] data;
private final int byteLimit;
private int byteOffset;
private int bitOffset;
/**
* Creates a new instance that wraps an existing array.
*
* @param data the array to wrap.
*/
public VorbisBitArray(byte[] data) {
this.data = data;
byteLimit = data.length;
}
/**
* Resets the reading position to zero.
*/
public void reset() {
byteOffset = 0;
bitOffset = 0;
}
/**
* Reads a single bit.
*
* @return {@code true} if the bit is set, {@code false} otherwise.
*/
public boolean readBit() {
boolean returnValue = (((data[byteOffset] & 0xFF) >> bitOffset) & 0x01) == 1;
skipBits(1);
return returnValue;
}
/**
* Reads up to 32 bits.
*
* @param numBits The number of bits to read.
* @return An integer whose bottom {@code numBits} bits hold the read data.
*/
public int readBits(int numBits) {
int tempByteOffset = byteOffset;
int bitsRead = Math.min(numBits, 8 - bitOffset);
int returnValue = ((data[tempByteOffset++] & 0xFF) >> bitOffset) & (0xFF >> (8 - bitsRead));
while (bitsRead < numBits) {
returnValue |= (data[tempByteOffset++] & 0xFF) << bitsRead;
bitsRead += 8;
}
returnValue &= 0xFFFFFFFF >>> (32 - numBits);
skipBits(numBits);
return returnValue;
}
/**
* Skips {@code numberOfBits} bits.
*
* @param numBits The number of bits to skip.
*/
public void skipBits(int numBits) {
int numBytes = numBits / 8;
byteOffset += numBytes;
bitOffset += numBits - (numBytes * 8);
if (bitOffset > 7) {
byteOffset++;
bitOffset -= 8;
}
assertValidOffset();
}
/**
* Returns the reading position in bits.
*/
public int getPosition() {
return byteOffset * 8 + bitOffset;
}
/**
* Sets the reading position in bits.
*
* @param position The new reading position in bits.
*/
public void setPosition(int position) {
byteOffset = position / 8;
bitOffset = position - (byteOffset * 8);
assertValidOffset();
}
/**
* Returns the number of remaining bits.
*/
public int bitsLeft() {
return (byteLimit - byteOffset) * 8 - bitOffset;
}
private void assertValidOffset() {
// It is fine for position to be at the end of the array, but no further.
Assertions.checkState(byteOffset >= 0
&& (byteOffset < byteLimit || (byteOffset == byteLimit && bitOffset == 0)));
}
}
|
