// Copyright (C) 2014 The Android Open Source Project // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. #ifndef EMUGL_CONDITION_VARIABLE_H #define EMUGL_CONDITION_VARIABLE_H #include "emugl/common/mutex.h" #include "emugl/common/pod_vector.h" #ifdef _WIN32 #include #else #include #endif namespace emugl { // A class that implements a condition variable, which can be used in // association with a Mutex to blocking-wait for specific conditions. // Useful to implement various synchronization data structures. // For an example, see ::emugl::MessageChannel. class ConditionVariable { public: #ifdef _WIN32 // Default constructor. ConditionVariable(); // Destructor. ~ConditionVariable(); // Wait until the condition variable is signaled. Note that spurious // wakeups are always a possibility, so always check the condition // in a loop, i.e. do: // // while (!condition) { condVar.wait(&lock); } // // instead of: // // if (!condition) { condVar.wait(&lock); } // void wait(Mutex* userLock); // Signal that a condition was reached. This will wake at most one // waiting thread that is blocked on wait(). void signal(); private: PodVector mWaiters; Mutex mLock; #else // !_WIN32 // Note: on Posix systems, make it a naive wrapper around pthread_cond_t. ConditionVariable() { pthread_cond_init(&mCond, NULL); } ~ConditionVariable() { pthread_cond_destroy(&mCond); } void wait(Mutex* userLock) { pthread_cond_wait(&mCond, &userLock->mLock); } void signal() { pthread_cond_signal(&mCond); } private: pthread_cond_t mCond; #endif // !_WIN32 }; } // namespace emugl #endif // EMUGL_CONDITION_VARIABLE_H