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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) {
}
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(mNumBitsLeft + n, 32u);
mReservoir = (mReservoir >> n) | (x << (32 - n));
mNumBitsLeft += n;
}
size_t ABitReader::numBitsLeft() const {
return mSize * 8 + mNumBitsLeft;
}
const uint8_t *ABitReader::data() const {
CHECK_EQ(mNumBitsLeft % 8, 0u);
return mData - mNumBitsLeft / 8;
}
} // namespace android
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