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61 lines
1.6 KiB
61 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 <utils/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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