| /* |
| * 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(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; |
| } |
| |
| } // namespace android |