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 _LIBS_UTILS_CONDITION_H
18#define _LIBS_UTILS_CONDITION_H
19
20#include <stdint.h>
21#include <sys/types.h>
22#include <time.h>
23
24#if !defined(_WIN32)
25# include <pthread.h>
26#endif
27
28#include <utils/Errors.h>
29#include <utils/Mutex.h>
30#include <utils/Timers.h>
31
32// ---------------------------------------------------------------------------
33namespace android {
34// ---------------------------------------------------------------------------
35
36/*
37 * Condition variable class.  The implementation is system-dependent.
38 *
39 * Condition variables are paired up with mutexes.  Lock the mutex,
40 * call wait(), then either re-wait() if things aren't quite what you want,
41 * or unlock the mutex and continue.  All threads calling wait() must
42 * use the same mutex for a given Condition.
43 */
44class Condition {
45public:
46    enum {
47        PRIVATE = 0,
48        SHARED = 1
49    };
50
51    enum WakeUpType {
52        WAKE_UP_ONE = 0,
53        WAKE_UP_ALL = 1
54    };
55
56    Condition();
57    Condition(int type);
58    ~Condition();
59    // Wait on the condition variable.  Lock the mutex before calling.
60    status_t wait(Mutex& mutex);
61    // same with relative timeout
62    status_t waitRelative(Mutex& mutex, nsecs_t reltime);
63    // Signal the condition variable, allowing exactly one thread to continue.
64    void signal();
65    // Signal the condition variable, allowing one or all threads to continue.
66    void signal(WakeUpType type) {
67        if (type == WAKE_UP_ONE) {
68            signal();
69        } else {
70            broadcast();
71        }
72    }
73    // Signal the condition variable, allowing all threads to continue.
74    void broadcast();
75
76private:
77#if !defined(_WIN32)
78    pthread_cond_t mCond;
79#else
80    void*   mState;
81#endif
82};
83
84// ---------------------------------------------------------------------------
85
86#if !defined(_WIN32)
87
88inline Condition::Condition() {
89    pthread_cond_init(&mCond, NULL);
90}
91inline Condition::Condition(int type) {
92    if (type == SHARED) {
93        pthread_condattr_t attr;
94        pthread_condattr_init(&attr);
95        pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
96        pthread_cond_init(&mCond, &attr);
97        pthread_condattr_destroy(&attr);
98    } else {
99        pthread_cond_init(&mCond, NULL);
100    }
101}
102inline Condition::~Condition() {
103    pthread_cond_destroy(&mCond);
104}
105inline status_t Condition::wait(Mutex& mutex) {
106    return -pthread_cond_wait(&mCond, &mutex.mMutex);
107}
108inline status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) {
109#if defined(HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE)
110    struct timespec ts;
111    ts.tv_sec  = reltime/1000000000;
112    ts.tv_nsec = reltime%1000000000;
113    return -pthread_cond_timedwait_relative_np(&mCond, &mutex.mMutex, &ts);
114#else // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
115    struct timespec ts;
116#if defined(__linux__)
117    clock_gettime(CLOCK_REALTIME, &ts);
118#else // __APPLE__
119    // we don't support the clocks here.
120    struct timeval t;
121    gettimeofday(&t, NULL);
122    ts.tv_sec = t.tv_sec;
123    ts.tv_nsec= t.tv_usec*1000;
124#endif
125    ts.tv_sec += reltime/1000000000;
126    ts.tv_nsec+= reltime%1000000000;
127    if (ts.tv_nsec >= 1000000000) {
128        ts.tv_nsec -= 1000000000;
129        ts.tv_sec  += 1;
130    }
131    return -pthread_cond_timedwait(&mCond, &mutex.mMutex, &ts);
132#endif // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
133}
134inline void Condition::signal() {
135    /*
136     * POSIX says pthread_cond_signal wakes up "one or more" waiting threads.
137     * However bionic follows the glibc guarantee which wakes up "exactly one"
138     * waiting thread.
139     *
140     * man 3 pthread_cond_signal
141     *   pthread_cond_signal restarts one of the threads that are waiting on
142     *   the condition variable cond. If no threads are waiting on cond,
143     *   nothing happens. If several threads are waiting on cond, exactly one
144     *   is restarted, but it is not specified which.
145     */
146    pthread_cond_signal(&mCond);
147}
148inline void Condition::broadcast() {
149    pthread_cond_broadcast(&mCond);
150}
151
152#endif // !defined(_WIN32)
153
154// ---------------------------------------------------------------------------
155}; // namespace android
156// ---------------------------------------------------------------------------
157
158#endif // _LIBS_UTILS_CONDITON_H
159