140 lines
3.0 KiB
C++
140 lines
3.0 KiB
C++
/*
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* Copyright (C) 2010 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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#include "AmlMpBitReader.h"
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namespace aml_mp {
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AmlMpBitReader::AmlMpBitReader(const uint8_t *data, size_t size)
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: mData(data),
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mSize(size),
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mReservoir(0),
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mNumBitsLeft(0),
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mOverRead(false) {
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}
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AmlMpBitReader::~AmlMpBitReader() {
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}
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bool AmlMpBitReader::fillReservoir() {
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if (mSize == 0) {
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mOverRead = true;
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return false;
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}
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mReservoir = 0;
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size_t i;
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for (i = 0; mSize > 0 && i < 4; ++i) {
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mReservoir = (mReservoir << 8) | *mData;
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++mData;
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--mSize;
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}
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mNumBitsLeft = 8 * i;
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mReservoir <<= 32 - mNumBitsLeft;
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return true;
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}
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uint32_t AmlMpBitReader::getBits(size_t n) {
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uint32_t ret = 0;
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//CHECK(getBitsGraceful(n, &ret));
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getBitsGraceful(n, &ret);
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return ret;
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}
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uint32_t AmlMpBitReader::getBitsWithFallback(size_t n, uint32_t fallback) {
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uint32_t ret = fallback;
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(void)getBitsGraceful(n, &ret);
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return ret;
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}
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bool AmlMpBitReader::getBitsGraceful(size_t n, uint32_t *out) {
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if (n > 32) {
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return false;
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}
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uint32_t result = 0;
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while (n > 0) {
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if (mNumBitsLeft == 0) {
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if (!fillReservoir()) {
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return false;
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}
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}
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size_t m = n;
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if (m > mNumBitsLeft) {
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m = mNumBitsLeft;
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}
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if (32 == m) {
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result = mReservoir;
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mReservoir = 0;
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} else if (m > 0) {
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result = (uint32_t)(result << m) | (mReservoir >> (32 - m));
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mReservoir <<= m;
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}
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mNumBitsLeft -= m;
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n -= m;
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}
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*out = result;
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return true;
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}
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bool AmlMpBitReader::skipBits(size_t n) {
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uint32_t dummy;
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while (n > 32) {
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if (!getBitsGraceful(32, &dummy)) {
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return false;
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}
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n -= 32;
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}
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if (n > 0) {
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return getBitsGraceful(n, &dummy);
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}
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return true;
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}
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void AmlMpBitReader::putBits(uint32_t x, size_t n) {
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if (mOverRead) {
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return;
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}
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//CHECK_LE(n, 32u);
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while (mNumBitsLeft + n > 32) {
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mNumBitsLeft -= 8;
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--mData;
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++mSize;
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}
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mReservoir = (mReservoir >> n) | (x << (32 - n));
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mNumBitsLeft += n;
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}
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size_t AmlMpBitReader::numBitsLeft() const {
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return mSize * 8 + mNumBitsLeft;
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}
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const uint8_t *AmlMpBitReader::data() const {
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return mData - (mNumBitsLeft + 7) / 8;
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}
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} // namespace aml_mp
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