rocksdb/thrift/lib/cpp/async/TEventBaseManager.h

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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 THRIFT_ASYNC_TEVENTBASEMANAGER_H
#define THRIFT_ASYNC_TEVENTBASEMANAGER_H 1
#include "thrift/lib/cpp/concurrency/ThreadLocal.h"
namespace apache { namespace thrift { namespace async {
class TEventBase;
/**
* Manager for per-thread TEventBase objects.
* This class will find or create a TEventBase for the current
* thread, associated with thread-specific storage for that thread.
* Although a typical application will generally only have one
* TEventBaseManager, there is no restriction on multiple instances;
* the TEventBases belong to one instance are isolated from those of
* another.
*/
class TEventBaseManager {
public:
TEventBaseManager() {}
~TEventBaseManager() {}
/**
* Get the TEventBase for this thread, or create one if none exists yet.
*
* If no TEventBase exists for this thread yet, a new one will be created and
* returned. May throw std::bad_alloc if allocation fails.
*/
TEventBase* getEventBase() const {
// localStore_.get() will never return NULL.
// InfoManager::allocate() will throw an exception instead if it cannot
// allocate a new EventBaseInfo or TEventBase.
return localStore_.get()->eventBase;
}
/**
* Get the TEventBase for this thread.
*
* Returns NULL if no TEventBase has been created for this thread yet.
*/
TEventBase* getExistingEventBase() const {
EventBaseInfo* info = localStore_.getNoAlloc();
if (info == NULL) {
return NULL;
}
return info->eventBase;
}
/**
* Set the TEventBase to be used by this thread.
*
* This may only be called if no TEventBase has been defined for this thread
* yet. If a TEventBase is already defined for this thread, a
* TLibraryException is thrown. std::bad_alloc may also be thrown if
* allocation fails while setting the TEventBase.
*
* This should typically be invoked by the code that will call loop() on the
* TEventBase, to make sure the TEventBaseManager points to the correct
* TEventBase that is actually running in this thread.
*/
void setEventBase(TEventBase *eventBase, bool takeOwnership);
/**
* Clear the TEventBase for this thread.
*
* This can be used if the code driving the TEventBase loop() has finished
* the loop and new events should no longer be added to the TEventBase.
*/
void clearEventBase();
private:
struct EventBaseInfo {
EventBaseInfo(TEventBase *evb, bool owned)
: eventBase(evb),
owned(owned) {}
TEventBase *eventBase;
bool owned;
};
class InfoManager {
public:
EventBaseInfo* allocate();
void destroy(EventBaseInfo* info);
void replace(EventBaseInfo* oldInfo, EventBaseInfo* newInfo) {
if (oldInfo != newInfo) {
destroy(oldInfo);
}
}
};
// Forbidden copy constructor and assignment opererator
TEventBaseManager(TEventBaseManager const &);
TEventBaseManager& operator=(TEventBaseManager const &);
concurrency::ThreadLocal<EventBaseInfo, InfoManager> localStore_;
};
}}} // apache::thrift::async
#endif // THRIFT_ASYNC_TEVENTBASEMANAGER_H