Glenn Kasten | 0106623 | 2012-02-27 11:50:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2012 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #define LOG_TAG "MonoPipeReader" |
| 18 | //#define LOG_NDEBUG 0 |
| 19 | |
| 20 | #include <cutils/compiler.h> |
| 21 | #include <utils/Log.h> |
| 22 | #include "MonoPipeReader.h" |
| 23 | |
| 24 | namespace android { |
| 25 | |
| 26 | MonoPipeReader::MonoPipeReader(MonoPipe* pipe) : |
| 27 | NBAIO_Source(pipe->mFormat), |
| 28 | mPipe(pipe) |
| 29 | { |
| 30 | } |
| 31 | |
| 32 | MonoPipeReader::~MonoPipeReader() |
| 33 | { |
| 34 | } |
| 35 | |
| 36 | ssize_t MonoPipeReader::availableToRead() |
| 37 | { |
| 38 | if (CC_UNLIKELY(!mNegotiated)) { |
| 39 | return NEGOTIATE; |
| 40 | } |
| 41 | ssize_t ret = android_atomic_acquire_load(&mPipe->mRear) - mPipe->mFront; |
| 42 | ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames)); |
| 43 | return ret; |
| 44 | } |
| 45 | |
| 46 | ssize_t MonoPipeReader::read(void *buffer, size_t count) |
| 47 | { |
| 48 | // count == 0 is unlikely and not worth checking for explicitly; will be handled automatically |
| 49 | ssize_t red = availableToRead(); |
| 50 | if (CC_UNLIKELY(red <= 0)) { |
| 51 | return red; |
| 52 | } |
| 53 | if (CC_LIKELY((size_t) red > count)) { |
| 54 | red = count; |
| 55 | } |
| 56 | size_t front = mPipe->mFront & (mPipe->mMaxFrames - 1); |
| 57 | size_t part1 = mPipe->mMaxFrames - front; |
| 58 | if (part1 > (size_t) red) { |
| 59 | part1 = red; |
| 60 | } |
| 61 | if (CC_LIKELY(part1 > 0)) { |
| 62 | memcpy(buffer, (char *) mPipe->mBuffer + (front << mBitShift), part1 << mBitShift); |
| 63 | if (CC_UNLIKELY(front + part1 == mPipe->mMaxFrames)) { |
| 64 | size_t part2 = red - part1; |
| 65 | if (CC_LIKELY(part2 > 0)) { |
| 66 | memcpy((char *) buffer + (part1 << mBitShift), mPipe->mBuffer, part2 << mBitShift); |
| 67 | } |
| 68 | } |
| 69 | android_atomic_release_store(red + mPipe->mFront, &mPipe->mFront); |
| 70 | mFramesRead += red; |
| 71 | } |
| 72 | return red; |
| 73 | } |
| 74 | |
| 75 | } // namespace android |