modules/sensors/SensorEventQueue.cpp

/*
 * Copyright (C) 2013 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 <hardware/sensors.h>
#include <algorithm>
#include <pthread.h>

#include <linux/input.h>
#include <cutils/atomic.h>
#include <cutils/log.h>

#include "SensorEventQueue.h"

SensorEventQueue::SensorEventQueue(int capacity) {
    mCapacity = capacity;
    mStart = 0;
    mSize = 0;
    mData = new sensors_event_t[mCapacity];
    pthread_cond_init(&mDataAvailableCondition, NULL);
    pthread_cond_init(&mSpaceAvailableCondition, NULL);
    pthread_mutex_init(&mMutex, NULL);
}

SensorEventQueue::~SensorEventQueue() {
    delete[] mData;
    mData = NULL;
    pthread_cond_destroy(&mDataAvailableCondition);
    pthread_cond_destroy(&mSpaceAvailableCondition);
    pthread_mutex_destroy(&mMutex);
}

void SensorEventQueue::lock() {
    pthread_mutex_lock(&mMutex);
}

void SensorEventQueue::unlock() {
    pthread_mutex_unlock(&mMutex);
}

void SensorEventQueue::waitForSpaceAndLock() {
    lock();
    while (mSize >= mCapacity) {
        pthread_cond_wait(&mSpaceAvailableCondition, &mMutex);
    }
}

void SensorEventQueue::waitForDataAndLock() {
    lock();
    while (mSize <= 0) {
        pthread_cond_wait(&mDataAvailableCondition, &mMutex);
    }
}

int SensorEventQueue::getWritableRegion(int requestedLength, sensors_event_t** out) {
    if (mSize >= mCapacity || requestedLength <= 0) {
        *out = NULL;
        return 0;
    }
    // Start writing after the last readable record.
    int firstWritable = (mStart + mSize) % mCapacity;

    int lastWritable = firstWritable + requestedLength - 1;

    // Don't go past the end of the data array.
    if (lastWritable > mCapacity - 1) {
        lastWritable = mCapacity - 1;
    }
    // Don't go into the readable region.
    if (firstWritable < mStart && lastWritable >= mStart) {
        lastWritable = mStart - 1;
    }
    *out = &mData[firstWritable];
    return lastWritable - firstWritable + 1;
}

void SensorEventQueue::markAsWritten(int count) {
    mSize += count;
    if (mSize) {
        pthread_cond_broadcast(&mDataAvailableCondition);
    }
}

int SensorEventQueue::getSize() {
    return mSize;
}

sensors_event_t* SensorEventQueue::peek() {
    if (mSize <= 0) return NULL;
    return &mData[mStart];
}

void SensorEventQueue::dequeue() {
    if (mSize <= 0) return;
    mSize--;
    mStart = (mStart + 1) % mCapacity;
    pthread_cond_broadcast(&mSpaceAvailableCondition);
}