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 // ---------------------------------------------------------------------------
33 namespace 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 */
44 class Condition {
45 public:
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.
signal(WakeUpType type)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
76 private:
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
Condition()88 inline Condition::Condition() {
89 pthread_cond_init(&mCond, NULL);
90 }
Condition(int type)91 inline 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 }
~Condition()102 inline Condition::~Condition() {
103 pthread_cond_destroy(&mCond);
104 }
wait(Mutex & mutex)105 inline status_t Condition::wait(Mutex& mutex) {
106 return -pthread_cond_wait(&mCond, &mutex.mMutex);
107 }
waitRelative(Mutex & mutex,nsecs_t reltime)108 inline 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 }
signal()134 inline 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 }
broadcast()148 inline 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