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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ABitReader.h"
#include <media/stagefright/foundation/ADebug.h>
namespace android {
ABitReader::ABitReader(const uint8_t *data, size_t size)
: mData(data),
mSize(size),
mReservoir(0),
mNumBitsLeft(0) {
}
ABitReader::~ABitReader() {
}
void ABitReader::fillReservoir() {
CHECK_GT(mSize, 0u);
mReservoir = 0;
size_t i;
for (i = 0; mSize > 0 && i < 4; ++i) {
mReservoir = (mReservoir << 8) | *mData;
++mData;
--mSize;
}
mNumBitsLeft = 8 * i;
mReservoir <<= 32 - mNumBitsLeft;
}
uint32_t ABitReader::getBits(size_t n) {
CHECK_LE(n, 32u);
uint32_t result = 0;
while (n > 0) {
if (mNumBitsLeft == 0) {
fillReservoir();
}
size_t m = n;
if (m > mNumBitsLeft) {
m = mNumBitsLeft;
}
result = (result << m) | (mReservoir >> (32 - m));
mReservoir <<= m;
mNumBitsLeft -= m;
n -= m;
}
return result;
}
void ABitReader::skipBits(size_t n) {
while (n > 32) {
getBits(32);
n -= 32;
}
if (n > 0) {
getBits(n);
}
}
void ABitReader::putBits(uint32_t x, size_t n) {
CHECK_LE(n, 32u);
while (mNumBitsLeft + n > 32) {
mNumBitsLeft -= 8;
--mData;
++mSize;
}
mReservoir = (mReservoir >> n) | (x << (32 - n));
mNumBitsLeft += n;
}
size_t ABitReader::numBitsLeft() const {
return mSize * 8 + mNumBitsLeft;
}
const uint8_t *ABitReader::data() const {
return mData - (mNumBitsLeft + 7) / 8;
}
NALBitReader::NALBitReader(const uint8_t *data, size_t size)
: ABitReader(data, size),
mNumZeros(0) {
}
bool NALBitReader::atLeastNumBitsLeft(size_t n) const {
// check against raw size and reservoir bits first
size_t numBits = numBitsLeft();
if (n > numBits) {
return false;
}
ssize_t numBitsRemaining = n - mNumBitsLeft;
size_t size = mSize;
const uint8_t *data = mData;
int32_t numZeros = mNumZeros;
while (size > 0 && numBitsRemaining > 0) {
bool isEmulationPreventionByte = (numZeros >= 2 && *data == 3);
if (*data == 0) {
++numZeros;
} else {
numZeros = 0;
}
if (!isEmulationPreventionByte) {
numBitsRemaining -= 8;
}
++data;
--size;
}
return (numBitsRemaining <= 0);
}
void NALBitReader::fillReservoir() {
CHECK_GT(mSize, 0u);
mReservoir = 0;
size_t i = 0;
while (mSize > 0 && i < 4) {
bool isEmulationPreventionByte = (mNumZeros >= 2 && *mData == 3);
if (*mData == 0) {
++mNumZeros;
} else {
mNumZeros = 0;
}
// skip emulation_prevention_three_byte
if (!isEmulationPreventionByte) {
mReservoir = (mReservoir << 8) | *mData;
++i;
}
++mData;
--mSize;
}
mNumBitsLeft = 8 * i;
mReservoir <<= 32 - mNumBitsLeft;
}
} // namespace android
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