1 /**
2 * Copyright (C) 2022 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 #include <ImsMediaBitReader.h>
18 #include <ImsMediaTrace.h>
19 #include <string.h>
20
ImsMediaBitReader()21 ImsMediaBitReader::ImsMediaBitReader()
22 {
23 mBuffer = nullptr;
24 mMaxBufferSize = 0;
25 mBytePos = 0;
26 mBitPos = 0;
27 mBitBuffer = 0;
28 mBufferEOF = false;
29 }
30
~ImsMediaBitReader()31 ImsMediaBitReader::~ImsMediaBitReader() {}
32
SetBuffer(uint8_t * pbBuffer,uint32_t nBufferSize)33 void ImsMediaBitReader::SetBuffer(uint8_t* pbBuffer, uint32_t nBufferSize)
34 {
35 mBytePos = 0;
36 mBitPos = 32;
37 mBitBuffer = 0;
38 mBufferEOF = false;
39 mBuffer = pbBuffer;
40 mMaxBufferSize = nBufferSize;
41 }
42
Read(uint32_t nSize)43 uint32_t ImsMediaBitReader::Read(uint32_t nSize)
44 {
45 uint32_t value;
46 if (nSize == 0)
47 return 0;
48 if (mBuffer == nullptr || nSize > 24 || mBufferEOF)
49 {
50 IMLOGE2("[Read] nSize[%d], bBufferEOF[%d]", nSize, mBufferEOF);
51 return 0;
52 }
53
54 // read from byte buffer
55 while ((32 - mBitPos) < nSize)
56 {
57 if (mBytePos >= mMaxBufferSize)
58 {
59 mBufferEOF = true;
60 IMLOGE2("[Read] End of Buffer : nBytePos[%d], nMaxBufferSize[%d]", mBytePos,
61 mMaxBufferSize);
62 return 0;
63 }
64
65 mBitPos -= 8;
66 mBitBuffer <<= 8;
67 mBitBuffer += mBuffer[mBytePos++];
68 }
69
70 // read from bit buffer
71 value = mBitBuffer << mBitPos >> (32 - nSize);
72 mBitPos += nSize;
73 return value;
74 }
75
ReadByteBuffer(uint8_t * pbDst,uint32_t nBitSize)76 void ImsMediaBitReader::ReadByteBuffer(uint8_t* pbDst, uint32_t nBitSize)
77 {
78 uint32_t dst_pos = 0;
79 uint32_t nByteSize;
80 uint32_t nRemainBitSize;
81 nByteSize = nBitSize >> 3;
82 nRemainBitSize = nBitSize & 0x07;
83
84 if (mBitPos == 32)
85 {
86 memcpy(pbDst, mBuffer + mBytePos, nByteSize);
87 mBytePos += nByteSize;
88 dst_pos += nByteSize;
89 }
90 else
91 {
92 for (dst_pos = 0; dst_pos < nByteSize; dst_pos++)
93 {
94 pbDst[dst_pos] = Read(8);
95 }
96 }
97
98 if (nRemainBitSize > 0)
99 {
100 uint32_t v;
101 v = Read(nRemainBitSize);
102 v <<= (8 - nRemainBitSize);
103 pbDst[dst_pos] = (unsigned char)v;
104 }
105 }
106
ReadByUEMode()107 uint32_t ImsMediaBitReader::ReadByUEMode()
108 {
109 uint32_t i = 0;
110 uint32_t j = 0;
111 uint32_t k = 1;
112 uint32_t result = 0;
113
114 while (Read(1) == 0 && mBufferEOF == false)
115 {
116 i++;
117 }
118
119 j = Read(i);
120 result = j - 1 + (k << i);
121 return result;
122 }