| /* |
| * Copyright (C) 2007 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 ANDROID_BARRIER_H |
| #define ANDROID_BARRIER_H |
| |
| #include <stdint.h> |
| #include <sys/types.h> |
| #include <utils/threads.h> |
| |
| namespace android { |
| |
| class Barrier |
| { |
| public: |
| inline Barrier() : state(CLOSED) { } |
| inline ~Barrier() { } |
| |
| // Release any threads waiting at the Barrier. |
| // Provides release semantics: preceding loads and stores will be visible |
| // to other threads before they wake up. |
| void open() { |
| Mutex::Autolock _l(lock); |
| state = OPENED; |
| cv.broadcast(); |
| } |
| |
| // Reset the Barrier, so wait() will block until open() has been called. |
| void close() { |
| Mutex::Autolock _l(lock); |
| state = CLOSED; |
| } |
| |
| // Wait until the Barrier is OPEN. |
| // Provides acquire semantics: no subsequent loads or stores will occur |
| // until wait() returns. |
| void wait() const { |
| Mutex::Autolock _l(lock); |
| while (state == CLOSED) { |
| cv.wait(lock); |
| } |
| } |
| private: |
| enum { OPENED, CLOSED }; |
| mutable Mutex lock; |
| mutable Condition cv; |
| volatile int state; |
| }; |
| |
| }; // namespace android |
| |
| #endif // ANDROID_BARRIER_H |