1/*
2 * Copyright 2015, 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//#define LOG_NDEBUG 0
19
20#include <string.h>
21#include <assert.h>
22
23#include <utils/Log.h>
24#include "BitFieldParser.h"
25
26namespace android {
27
28BitFieldParser::BitFieldParser(uint8_t *data)
29 : mData(data)
30 , mBitCursor(0)
31{
32}
33
34BitFieldParser::~BitFieldParser()
35{
36}
37
38uint32_t BitFieldParser::readBits(uint32_t numBits)
39{
40    ALOG_ASSERT(numBits <= 32);
41
42    // Extract some bits from the current byte.
43    uint32_t byteCursor = mBitCursor >> 3; // 8 bits per byte
44    uint8_t byte = mData[byteCursor];
45
46    uint32_t bitsLeftInByte = 8 - (mBitCursor & 7);
47    uint32_t bitsFromByte = (bitsLeftInByte < numBits) ? bitsLeftInByte : numBits;
48    uint32_t result = byte >> (bitsLeftInByte - bitsFromByte);
49    result &= (1 << bitsFromByte) - 1; // mask
50    mBitCursor += bitsFromByte;
51
52    uint32_t bitsRemaining = numBits - bitsFromByte;
53    if (bitsRemaining == 0) {
54        return result;
55    } else {
56        // Use recursion to get remaining bits.
57        return (result << bitsRemaining) | readBits(bitsRemaining);
58    }
59}
60
61}  // namespace android
62