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(HAVE_PTHREADS)
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 Condition();
52 Condition(int type);
53 ~Condition();
54 // Wait on the condition variable. Lock the mutex before calling.
55 status_t wait(Mutex& mutex);
56 // same with relative timeout
57 status_t waitRelative(Mutex& mutex, nsecs_t reltime);
58 // Signal the condition variable, allowing one thread to continue.
59 void signal();
60 // Signal the condition variable, allowing all threads to continue.
61 void broadcast();
62
63 private:
64 #if defined(HAVE_PTHREADS)
65 pthread_cond_t mCond;
66 #else
67 void* mState;
68 #endif
69 };
70
71 // ---------------------------------------------------------------------------
72
73 #if defined(HAVE_PTHREADS)
74
Condition()75 inline Condition::Condition() {
76 pthread_cond_init(&mCond, NULL);
77 }
Condition(int type)78 inline Condition::Condition(int type) {
79 if (type == SHARED) {
80 pthread_condattr_t attr;
81 pthread_condattr_init(&attr);
82 pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
83 pthread_cond_init(&mCond, &attr);
84 pthread_condattr_destroy(&attr);
85 } else {
86 pthread_cond_init(&mCond, NULL);
87 }
88 }
~Condition()89 inline Condition::~Condition() {
90 pthread_cond_destroy(&mCond);
91 }
wait(Mutex & mutex)92 inline status_t Condition::wait(Mutex& mutex) {
93 return -pthread_cond_wait(&mCond, &mutex.mMutex);
94 }
waitRelative(Mutex & mutex,nsecs_t reltime)95 inline status_t Condition::waitRelative(Mutex& mutex, nsecs_t reltime) {
96 #if defined(HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE)
97 struct timespec ts;
98 ts.tv_sec = reltime/1000000000;
99 ts.tv_nsec = reltime%1000000000;
100 return -pthread_cond_timedwait_relative_np(&mCond, &mutex.mMutex, &ts);
101 #else // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
102 struct timespec ts;
103 #if defined(HAVE_POSIX_CLOCKS)
104 clock_gettime(CLOCK_REALTIME, &ts);
105 #else // HAVE_POSIX_CLOCKS
106 // we don't support the clocks here.
107 struct timeval t;
108 gettimeofday(&t, NULL);
109 ts.tv_sec = t.tv_sec;
110 ts.tv_nsec= t.tv_usec*1000;
111 #endif // HAVE_POSIX_CLOCKS
112 ts.tv_sec += reltime/1000000000;
113 ts.tv_nsec+= reltime%1000000000;
114 if (ts.tv_nsec >= 1000000000) {
115 ts.tv_nsec -= 1000000000;
116 ts.tv_sec += 1;
117 }
118 return -pthread_cond_timedwait(&mCond, &mutex.mMutex, &ts);
119 #endif // HAVE_PTHREAD_COND_TIMEDWAIT_RELATIVE
120 }
signal()121 inline void Condition::signal() {
122 pthread_cond_signal(&mCond);
123 }
broadcast()124 inline void Condition::broadcast() {
125 pthread_cond_broadcast(&mCond);
126 }
127
128 #endif // HAVE_PTHREADS
129
130 // ---------------------------------------------------------------------------
131 }; // namespace android
132 // ---------------------------------------------------------------------------
133
134 #endif // _LIBS_UTILS_CONDITON_H
135