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62 lines
1.6 KiB
62 lines
1.6 KiB
/*
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* Copyright 2015, The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "AudioSPDIF"
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//#define LOG_NDEBUG 0
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#include <string.h>
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#include <assert.h>
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#include <log/log.h>
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#include "BitFieldParser.h"
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namespace android {
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BitFieldParser::BitFieldParser(uint8_t *data)
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: mData(data)
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, mBitCursor(0)
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{
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}
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BitFieldParser::~BitFieldParser()
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{
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}
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uint32_t BitFieldParser::readBits(uint32_t numBits)
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{
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ALOG_ASSERT(numBits <= 32);
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// Extract some bits from the current byte.
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uint32_t byteCursor = mBitCursor >> 3; // 8 bits per byte
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uint8_t byte = mData[byteCursor];
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uint32_t bitsLeftInByte = 8 - (mBitCursor & 7);
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uint32_t bitsFromByte = (bitsLeftInByte < numBits) ? bitsLeftInByte : numBits;
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uint32_t result = byte >> (bitsLeftInByte - bitsFromByte);
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result &= (1 << bitsFromByte) - 1; // mask
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mBitCursor += bitsFromByte;
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uint32_t bitsRemaining = numBits - bitsFromByte;
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if (bitsRemaining == 0) {
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return result;
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} else {
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// Use recursion to get remaining bits.
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return (result << bitsRemaining) | readBits(bitsRemaining);
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}
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}
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} // namespace android
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