1 /*
2  * Copyright 2014, 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 #define LOG_TAG "AudioSPDIF"
18 
19 #include <string.h>
20 #include <assert.h>
21 
22 #include <utils/Log.h>
23 #include <audio_utils/spdif/FrameScanner.h>
24 
25 namespace android {
26 
27 FrameScanner::FrameScanner(int dataType,
28             const uint8_t *syncBytes,
29             uint32_t syncLength,
30             uint32_t headerLength)
31  : mBytesSkipped(0)
32  , mSyncBytes(syncBytes)
33  , mSyncLength(syncLength)
34  , mHeaderLength(headerLength)
35  , mCursor(0)
36  , mFormatDumpCount(0)
37  , mSampleRate(0)
38  , mRateMultiplier(1)
39  , mFrameSizeBytes(0)
40  , mDataType(dataType)
41  , mDataTypeInfo(0)
42 {
43 }
44 
45 FrameScanner::~FrameScanner()
46 {
47 }
48 
49 // State machine that scans for headers in a byte stream.
50 // @return true if we have detected a complete and valid header.
51 bool FrameScanner::scan(uint8_t byte)
52 {
53     bool result = false;
54     ALOGV("FrameScanner: byte = 0x%02X, mCursor = %d", byte, mCursor);
55     assert(mCursor < sizeof(mHeaderBuffer));
56     if (mCursor < mSyncLength) {
57         // match sync word
58         if (byte == mSyncBytes[mCursor]) {
59             mHeaderBuffer[mCursor++] = byte;
60         } else {
61             mBytesSkipped += 1; // skip unsynchronized data
62             mCursor = 0;
63         }
64     } else if (mCursor < mHeaderLength) {
65         // gather header for parsing
66         mHeaderBuffer[mCursor++] = byte;
67         if (mCursor >= mHeaderLength) {
68             if (parseHeader()) {
69                 result = true;
70             } else {
71                 ALOGE("FrameScanner: ERROR - parseHeader() failed.");
72             }
73             mCursor = 0;
74         }
75     }
76     return result;
77 }
78 
79 }  // namespace android
80