1 /*
2 * Copyright (C) 2017 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 "RingBuffer.h"
18
19 #include <stdlib.h>
20 #include <string.h>
21
22 namespace android {
23
RingBuffer(size_t size)24 RingBuffer::RingBuffer(size_t size)
25 : mSize(size),
26 mData((sensors_event_t *)malloc(sizeof(sensors_event_t) * mSize)),
27 mReadPos(0),
28 mWritePos(0) {
29 }
30
~RingBuffer()31 RingBuffer::~RingBuffer() {
32 free(mData);
33 mData = NULL;
34 }
35
write(const sensors_event_t * ev,size_t size)36 ssize_t RingBuffer::write(const sensors_event_t *ev, size_t size) {
37 Mutex::Autolock autoLock(mLock);
38
39 size_t numAvailableToRead = mWritePos - mReadPos;
40 size_t numAvailableToWrite = mSize - numAvailableToRead;
41
42 if (size > numAvailableToWrite) {
43 size = numAvailableToWrite;
44 }
45
46 size_t writePos = (mWritePos % mSize);
47 size_t copy = mSize - writePos;
48
49 if (copy > size) {
50 copy = size;
51 }
52
53 memcpy(&mData[writePos], ev, copy * sizeof(sensors_event_t));
54
55 if (size > copy) {
56 memcpy(mData, &ev[copy], (size - copy) * sizeof(sensors_event_t));
57 }
58
59 mWritePos += size;
60
61 if (numAvailableToRead == 0 && size > 0) {
62 mNotEmptyCondition.broadcast();
63 }
64
65 return size;
66 }
67
read(sensors_event_t * ev,size_t size)68 ssize_t RingBuffer::read(sensors_event_t *ev, size_t size) {
69 Mutex::Autolock autoLock(mLock);
70
71 size_t numAvailableToRead;
72 for (;;) {
73 numAvailableToRead = mWritePos - mReadPos;
74 if (numAvailableToRead > 0) {
75 break;
76 }
77
78 mNotEmptyCondition.wait(mLock);
79 }
80
81 if (size > numAvailableToRead) {
82 size = numAvailableToRead;
83 }
84
85 size_t readPos = (mReadPos % mSize);
86 size_t copy = mSize - readPos;
87
88 if (copy > size) {
89 copy = size;
90 }
91
92 memcpy(ev, &mData[readPos], copy * sizeof(sensors_event_t));
93
94 if (size > copy) {
95 memcpy(&ev[copy], mData, (size - copy) * sizeof(sensors_event_t));
96 }
97
98 mReadPos += size;
99
100 return size;
101 }
102
103 } // namespace android
104
105