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