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 
SensorEventQueue(int capacity)24 SensorEventQueue::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 
~SensorEventQueue()33 SensorEventQueue::~SensorEventQueue() {
34     delete[] mData;
35     mData = NULL;
36     pthread_cond_destroy(&mSpaceAvailableCondition);
37 }
38 
getWritableRegion(int requestedLength,sensors_event_t ** out)39 int 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 
markAsWritten(int count)61 void SensorEventQueue::markAsWritten(int count) {
62     mSize += count;
63 }
64 
getSize()65 int SensorEventQueue::getSize() {
66     return mSize;
67 }
68 
peek()69 sensors_event_t* SensorEventQueue::peek() {
70     if (mSize == 0) return NULL;
71     return &mData[mStart];
72 }
73 
dequeue()74 void 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.
waitForSpace(pthread_mutex_t * mutex)84 bool 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