1/*
2 * Copyright (C) 2007 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#ifndef ANDROID_BARRIER_H
18#define ANDROID_BARRIER_H
19
20#include <stdint.h>
21#include <sys/types.h>
22#include <utils/threads.h>
23
24namespace android {
25
26class Barrier
27{
28public:
29    inline Barrier() : state(CLOSED) { }
30    inline ~Barrier() { }
31
32    // Release any threads waiting at the Barrier.
33    // Provides release semantics: preceding loads and stores will be visible
34    // to other threads before they wake up.
35    void open() {
36        Mutex::Autolock _l(lock);
37        state = OPENED;
38        cv.broadcast();
39    }
40
41    // Reset the Barrier, so wait() will block until open() has been called.
42    void close() {
43        Mutex::Autolock _l(lock);
44        state = CLOSED;
45    }
46
47    // Wait until the Barrier is OPEN.
48    // Provides acquire semantics: no subsequent loads or stores will occur
49    // until wait() returns.
50    void wait() const {
51        Mutex::Autolock _l(lock);
52        while (state == CLOSED) {
53            cv.wait(lock);
54        }
55    }
56private:
57    enum { OPENED, CLOSED };
58    mutable     Mutex       lock;
59    mutable     Condition   cv;
60    volatile    int         state;
61};
62
63}; // namespace android
64
65#endif // ANDROID_BARRIER_H
66