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
MonoPipeReader(MonoPipe * pipe)26 MonoPipeReader::MonoPipeReader(MonoPipe* pipe) :
27 NBAIO_Source(pipe->mFormat),
28 mPipe(pipe)
29 {
30 }
31
~MonoPipeReader()32 MonoPipeReader::~MonoPipeReader()
33 {
34 }
35
availableToRead()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
read(void * buffer,size_t count)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
76