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/*
* Copyright (C) 2012 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.
*/
#define LOG_TAG "MonoPipe"
//#define LOG_NDEBUG 0
#include <cutils/atomic.h>
#include <cutils/compiler.h>
#include <utils/Log.h>
#include "MonoPipe.h"
#include "roundup.h"
namespace android {
MonoPipe::MonoPipe(size_t maxFrames, NBAIO_Format format, bool writeCanBlock) :
NBAIO_Sink(format),
mMaxFrames(roundup(maxFrames)),
mBuffer(malloc(mMaxFrames * Format_frameSize(format))),
mFront(0),
mRear(0),
mWriteCanBlock(writeCanBlock)
{
}
MonoPipe::~MonoPipe()
{
free(mBuffer);
}
ssize_t MonoPipe::availableToWrite() const
{
if (CC_UNLIKELY(!mNegotiated)) {
return NEGOTIATE;
}
ssize_t ret = mMaxFrames - (mRear - android_atomic_acquire_load(&mFront));
ALOG_ASSERT((0 <= ret) && (ret <= mMaxFrames));
return ret;
}
ssize_t MonoPipe::write(const void *buffer, size_t count)
{
if (CC_UNLIKELY(!mNegotiated)) {
return NEGOTIATE;
}
size_t totalFramesWritten = 0;
while (count > 0) {
size_t avail = availableToWrite();
size_t written = avail;
if (CC_LIKELY(written > count)) {
written = count;
}
size_t rear = mRear & (mMaxFrames - 1);
size_t part1 = mMaxFrames - rear;
if (part1 > written) {
part1 = written;
}
if (CC_LIKELY(part1 > 0)) {
memcpy((char *) mBuffer + (rear << mBitShift), buffer, part1 << mBitShift);
if (CC_UNLIKELY(rear + part1 == mMaxFrames)) {
size_t part2 = written - part1;
if (CC_LIKELY(part2 > 0)) {
memcpy(mBuffer, (char *) buffer + (part1 << mBitShift), part2 << mBitShift);
}
}
android_atomic_release_store(written + mRear, &mRear);
totalFramesWritten += written;
}
if (!mWriteCanBlock) {
break;
}
count -= written;
buffer = (char *) buffer + (written << mBitShift);
// Simulate blocking I/O by sleeping at different rates, depending on a throttle.
// The throttle tries to keep the pipe about 5/8 full on average, with a slight jitter.
uint64_t ns;
enum {
THROTTLE_VERY_FAST, // pipe is (nearly) empty, fill quickly
THROTTLE_FAST, // pipe is normal, fill at slightly faster rate
THROTTLE_NOMINAL, // pipe is normal, fill at nominal rate
THROTTLE_SLOW, // pipe is normal, fill at slightly slower rate
THROTTLE_VERY_SLOW, // pipe is (nearly) full, fill slowly
} throttle;
avail -= written;
// FIXME cache these values to avoid re-computation
if (avail >= (mMaxFrames * 3) / 4) {
throttle = THROTTLE_VERY_FAST;
} else if (avail >= mMaxFrames / 2) {
throttle = THROTTLE_FAST;
} else if (avail >= (mMaxFrames * 3) / 8) {
throttle = THROTTLE_NOMINAL;
} else if (avail >= mMaxFrames / 4) {
throttle = THROTTLE_SLOW;
} else {
throttle = THROTTLE_VERY_SLOW;
}
if (written > 0) {
// FIXME cache these values also
switch (throttle) {
case THROTTLE_VERY_FAST:
default:
ns = written * ( 500000000 / Format_sampleRate(mFormat));
break;
case THROTTLE_FAST:
ns = written * ( 750000000 / Format_sampleRate(mFormat));
break;
case THROTTLE_NOMINAL:
ns = written * (1000000000 / Format_sampleRate(mFormat));
break;
case THROTTLE_SLOW:
ns = written * (1100000000 / Format_sampleRate(mFormat));
break;
case THROTTLE_VERY_SLOW:
ns = written * (1250000000 / Format_sampleRate(mFormat));
break;
}
} else {
ns = mMaxFrames * (250000000 / Format_sampleRate(mFormat));
}
if (ns > 999999999) {
ns = 999999999;
}
struct timespec sleep;
sleep.tv_sec = 0;
sleep.tv_nsec = ns;
nanosleep(&sleep, NULL);
}
mFramesWritten += totalFramesWritten;
return totalFramesWritten;
}
} // namespace android
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