1/*
2 * Copyright (C) 2013 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#include <hardware/sensors.h>
18#include <algorithm>
19#include <pthread.h>
20#include <cutils/log.h>
21
22#include "SensorEventQueue.h"
23
24SensorEventQueue::SensorEventQueue(int capacity) {
25    mCapacity = capacity;
26
27    mStart = 0;
28    mSize = 0;
29    mData = new sensors_event_t[mCapacity];
30    pthread_cond_init(&mSpaceAvailableCondition, NULL);
31}
32
33SensorEventQueue::~SensorEventQueue() {
34    delete[] mData;
35    mData = NULL;
36    pthread_cond_destroy(&mSpaceAvailableCondition);
37}
38
39int SensorEventQueue::getWritableRegion(int requestedLength, sensors_event_t** out) {
40    if (mSize == mCapacity || requestedLength <= 0) {
41        *out = NULL;
42        return 0;
43    }
44    // Start writing after the last readable record.
45    int firstWritable = (mStart + mSize) % mCapacity;
46
47    int lastWritable = firstWritable + requestedLength - 1;
48
49    // Don't go past the end of the data array.
50    if (lastWritable > mCapacity - 1) {
51        lastWritable = mCapacity - 1;
52    }
53    // Don't go into the readable region.
54    if (firstWritable < mStart && lastWritable >= mStart) {
55        lastWritable = mStart - 1;
56    }
57    *out = &mData[firstWritable];
58    return lastWritable - firstWritable + 1;
59}
60
61void SensorEventQueue::markAsWritten(int count) {
62    mSize += count;
63}
64
65int SensorEventQueue::getSize() {
66    return mSize;
67}
68
69sensors_event_t* SensorEventQueue::peek() {
70    if (mSize == 0) return NULL;
71    return &mData[mStart];
72}
73
74void SensorEventQueue::dequeue() {
75    if (mSize == 0) return;
76    if (mSize == mCapacity) {
77        pthread_cond_broadcast(&mSpaceAvailableCondition);
78    }
79    mSize--;
80    mStart = (mStart + 1) % mCapacity;
81}
82
83// returns true if it waited, or false if it was a no-op.
84bool SensorEventQueue::waitForSpace(pthread_mutex_t* mutex) {
85    bool waited = false;
86    while (mSize == mCapacity) {
87        waited = true;
88        pthread_cond_wait(&mSpaceAvailableCondition, mutex);
89    }
90    return waited;
91}
92