141 lines
3.6 KiB
C++
141 lines
3.6 KiB
C++
/*
|
|
* Copyright (C) 2015 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 "ring.h"
|
|
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <atomic>
|
|
|
|
namespace android {
|
|
|
|
RingBuffer::RingBuffer(size_t size)
|
|
: mSize(size),
|
|
mData((sensors_event_t *)malloc(sizeof(sensors_event_t) * mSize)),
|
|
mReadPos(0),
|
|
mWritePos(0) {
|
|
}
|
|
|
|
RingBuffer::~RingBuffer() {
|
|
free(mData);
|
|
mData = NULL;
|
|
}
|
|
|
|
ssize_t RingBuffer::write(const sensors_event_t *ev, size_t size) {
|
|
Mutex::Autolock autoLock(mLock);
|
|
|
|
size_t numAvailableToRead = mWritePos - mReadPos;
|
|
size_t numAvailableToWrite = mSize - numAvailableToRead;
|
|
|
|
if (size > numAvailableToWrite) {
|
|
size = numAvailableToWrite;
|
|
}
|
|
|
|
size_t writePos = (mWritePos % mSize);
|
|
size_t copy = mSize - writePos;
|
|
|
|
if (copy > size) {
|
|
copy = size;
|
|
}
|
|
|
|
memcpy(&mData[writePos], ev, copy * sizeof(sensors_event_t));
|
|
|
|
if (size > copy) {
|
|
memcpy(mData, &ev[copy], (size - copy) * sizeof(sensors_event_t));
|
|
}
|
|
|
|
mWritePos += size;
|
|
|
|
if (numAvailableToRead == 0 && size > 0) {
|
|
mNotEmptyCondition.broadcast();
|
|
}
|
|
|
|
return size;
|
|
}
|
|
|
|
ssize_t RingBuffer::read(sensors_event_t *ev, size_t size) {
|
|
Mutex::Autolock autoLock(mLock);
|
|
|
|
size_t numAvailableToRead;
|
|
for (;;) {
|
|
numAvailableToRead = mWritePos - mReadPos;
|
|
if (numAvailableToRead > 0) {
|
|
break;
|
|
}
|
|
|
|
mNotEmptyCondition.wait(mLock);
|
|
}
|
|
|
|
if (size > numAvailableToRead) {
|
|
size = numAvailableToRead;
|
|
}
|
|
|
|
size_t readPos = (mReadPos % mSize);
|
|
size_t copy = mSize - readPos;
|
|
|
|
if (copy > size) {
|
|
copy = size;
|
|
}
|
|
|
|
memcpy(ev, &mData[readPos], copy * sizeof(sensors_event_t));
|
|
|
|
if (size > copy) {
|
|
memcpy(&ev[copy], mData, (size - copy) * sizeof(sensors_event_t));
|
|
}
|
|
|
|
mReadPos += size;
|
|
|
|
return size;
|
|
}
|
|
|
|
LockfreeBuffer::LockfreeBuffer(void* buf, size_t size)
|
|
: mData((sensors_event_t *)buf), mSize(size/sizeof(sensors_event_t)),
|
|
mWritePos(0), mCounter(1) {
|
|
memset(mData, 0, size);
|
|
}
|
|
|
|
LockfreeBuffer::~LockfreeBuffer() {
|
|
memset(mData, 0, mSize*sizeof(sensors_event_t));
|
|
}
|
|
|
|
void LockfreeBuffer::write(const sensors_event_t *ev, size_t size) {
|
|
if (!mSize) {
|
|
return;
|
|
}
|
|
|
|
while(size--) {
|
|
// part before reserved0 field
|
|
memcpy(&mData[mWritePos], ev, offsetof(sensors_event_t, reserved0));
|
|
// part after reserved0 field
|
|
memcpy(reinterpret_cast<char *>(&mData[mWritePos]) + offsetof(sensors_event_t, timestamp),
|
|
reinterpret_cast<const char *>(ev) + offsetof(sensors_event_t, timestamp),
|
|
sizeof(sensors_event_t) - offsetof(sensors_event_t, timestamp));
|
|
// barrier before writing the atomic counter
|
|
std::atomic_thread_fence(std::memory_order_release);
|
|
mData[mWritePos].reserved0 = mCounter++;
|
|
// barrier after writing the atomic counter
|
|
std::atomic_thread_fence(std::memory_order_release);
|
|
++ev;
|
|
|
|
if (++mWritePos >= mSize) {
|
|
mWritePos = 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
} // namespace android
|
|
|