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 <limits.h>
21#include <stdint.h>
22#include <sys/types.h>
23#include <time.h>
24
25#if !defined(_WIN32)
26# include <pthread.h>
27#endif
28
29#include <utils/Errors.h>
30#include <utils/Mutex.h>
31#include <utils/Timers.h>
32
33// ---------------------------------------------------------------------------
34namespace android {
35// ---------------------------------------------------------------------------
36
37/*
38 * Condition variable class.  The implementation is system-dependent.
39 *
40 * Condition variables are paired up with mutexes.  Lock the mutex,
41 * call wait(), then either re-wait() if things aren't quite what you want,
42 * or unlock the mutex and continue.  All threads calling wait() must
43 * use the same mutex for a given Condition.
44 *
45 * On Android and Apple platforms, these are implemented as a simple wrapper
46 * around pthread condition variables.  Care must be taken to abide by
47 * the pthreads semantics, in particular, a boolean predicate must
48 * be re-evaluated after a wake-up, as spurious wake-ups may happen.
49 */
50class Condition {
51public:
52    enum {
53        PRIVATE = 0,
54        SHARED = 1
55    };
56
57    enum WakeUpType {
58        WAKE_UP_ONE = 0,
59        WAKE_UP_ALL = 1
60    };
61
62    Condition();
63    explicit Condition(int type);
64    ~Condition();
65    // Wait on the condition variable.  Lock the mutex before calling.
66    // Note that spurious wake-ups may happen.
67    status_t wait(Mutex& mutex);
68    // same with relative timeout
69    status_t waitRelative(Mutex& mutex, nsecs_t reltime);
70    // Signal the condition variable, allowing one thread to continue.
71    void signal();
72    // Signal the condition variable, allowing one or all threads to continue.
73    void signal(WakeUpType type) {
74        if (type == WAKE_UP_ONE) {
75            signal();
76        } else {
77            broadcast();
78        }
79    }
80    // Signal the condition variable, allowing all threads to continue.
81    void broadcast();
82
83private:
84#if !defined(_WIN32)
85    pthread_cond_t mCond;
86#else
87    void*   mState;
88#endif
89};
90
91// ---------------------------------------------------------------------------
92
93#if !defined(_WIN32)
94
95inline Condition::Condition() : Condition(PRIVATE) {
96}
97inline Condition::Condition(int type) {
98    pthread_condattr_t attr;
99    pthread_condattr_init(&attr);
100#if defined(__linux__)
101    pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
102#endif
103
104    if (type == SHARED) {
105        pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
106    }
107
108    pthread_cond_init(&mCond, &attr);
109    pthread_condattr_destroy(&attr);
110
111}
112inline Condition::~Condition() {
113    pthread_cond_destroy(&mCond);
114}
115inline status_t Condition::wait(Mutex& mutex) {
116    return -pthread_cond_wait(&mCond, &mutex.mMutex);
117}
118inline status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) {
119    struct timespec ts;
120#if defined(__linux__)
121    clock_gettime(CLOCK_MONOTONIC, &ts);
122#else // __APPLE__
123    // Apple doesn't support POSIX clocks.
124    struct timeval t;
125    gettimeofday(&t, NULL);
126    ts.tv_sec = t.tv_sec;
127    ts.tv_nsec = t.tv_usec*1000;
128#endif
129
130    // On 32-bit devices, tv_sec is 32-bit, but `reltime` is 64-bit.
131    int64_t reltime_sec = reltime/1000000000;
132
133    ts.tv_nsec += static_cast<long>(reltime%1000000000);
134    if (reltime_sec < INT64_MAX && ts.tv_nsec >= 1000000000) {
135        ts.tv_nsec -= 1000000000;
136        ++reltime_sec;
137    }
138
139    int64_t time_sec = ts.tv_sec;
140    if (time_sec > INT64_MAX - reltime_sec) {
141        time_sec = INT64_MAX;
142    } else {
143        time_sec += reltime_sec;
144    }
145
146    ts.tv_sec = (time_sec > LONG_MAX) ? LONG_MAX : static_cast<long>(time_sec);
147
148    return -pthread_cond_timedwait(&mCond, &mutex.mMutex, &ts);
149}
150inline void Condition::signal() {
151    pthread_cond_signal(&mCond);
152}
153inline void Condition::broadcast() {
154    pthread_cond_broadcast(&mCond);
155}
156
157#endif // !defined(_WIN32)
158
159// ---------------------------------------------------------------------------
160}; // namespace android
161// ---------------------------------------------------------------------------
162
163#endif // _LIBS_UTILS_CONDITON_H
164