118 lines
4.5 KiB
C
118 lines
4.5 KiB
C
|
/*
|
||
|
* 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_TUNDELAYEDDESTRUCTION_H_
|
||
|
#define THRIFT_ASYNC_TUNDELAYEDDESTRUCTION_H_ 1
|
||
|
|
||
|
#include <cstdlib>
|
||
|
#include <type_traits>
|
||
|
#include <utility>
|
||
|
#include <cassert>
|
||
|
|
||
|
namespace apache { namespace thrift { namespace async {
|
||
|
|
||
|
/**
|
||
|
* A helper class to allow a TDelayedDestruction object to be instantiated on
|
||
|
* the stack.
|
||
|
*
|
||
|
* This class derives from an existing TDelayedDestruction type and makes the
|
||
|
* destructor public again. This allows objects of this type to be declared on
|
||
|
* the stack or directly inside another class. Normally TDelayedDestruction
|
||
|
* objects must be dynamically allocated on the heap.
|
||
|
*
|
||
|
* However, the trade-off is that you lose some of the protections provided by
|
||
|
* TDelayedDestruction::destroy(). TDelayedDestruction::destroy() will
|
||
|
* automatically delay destruction of the object until it is safe to do so.
|
||
|
* If you use TUndelayedDestruction, you become responsible for ensuring that
|
||
|
* you only destroy the object where it is safe to do so. Attempting to
|
||
|
* destroy a TUndelayedDestruction object while it has a non-zero destructor
|
||
|
* guard count will abort the program.
|
||
|
*/
|
||
|
template<typename TDD>
|
||
|
class TUndelayedDestruction : public TDD {
|
||
|
public:
|
||
|
// We want to expose all constructors provided by the parent class.
|
||
|
// C++11 adds constructor inheritance to support this. Unfortunately gcc
|
||
|
// does not implement constructor inheritance yet, so we have to fake it with
|
||
|
// variadic templates.
|
||
|
#if THRIFT_HAVE_CONSTRUCTOR_INHERITANCE
|
||
|
using TDD::TDD;
|
||
|
#else
|
||
|
// We unfortunately can't simulate constructor inheritance as well as I'd
|
||
|
// like.
|
||
|
//
|
||
|
// Ideally we would use std::enable_if<> and std::is_constructible<> to
|
||
|
// provide only constructor methods that are valid for our parent class.
|
||
|
// Unfortunately std::is_constructible<> doesn't work for types that aren't
|
||
|
// destructible. In gcc-4.6 it results in a compiler error. In the latest
|
||
|
// gcc code it looks like it has been fixed to return false. (The language
|
||
|
// in the standard seems to indicate that returning false is the correct
|
||
|
// behavior for non-destructible types, which is unfortunate.)
|
||
|
template<typename ...Args>
|
||
|
explicit TUndelayedDestruction(Args&& ...args)
|
||
|
: TDD(std::forward<Args>(args)...) {}
|
||
|
#endif
|
||
|
|
||
|
/**
|
||
|
* Public destructor.
|
||
|
*
|
||
|
* The caller is responsible for ensuring that the object is only destroyed
|
||
|
* where it is safe to do so. (i.e., when the destructor guard count is 0).
|
||
|
*
|
||
|
* The exact conditions for meeting this may be dependant upon your class
|
||
|
* semantics. Typically you are only guaranteed that it is safe to destroy
|
||
|
* the object directly from the event loop (e.g., directly from a
|
||
|
* TEventBase::LoopCallback), or when the event loop is stopped.
|
||
|
*/
|
||
|
virtual ~TUndelayedDestruction() {
|
||
|
// Crash if the caller is destroying us with outstanding destructor guards.
|
||
|
if (this->getDestructorGuardCount() != 0) {
|
||
|
abort();
|
||
|
}
|
||
|
// Invoke destroy. This is necessary since our base class may have
|
||
|
// implemented custom behavior in destroy().
|
||
|
this->destroy();
|
||
|
}
|
||
|
|
||
|
protected:
|
||
|
/**
|
||
|
* Override our parent's destroy() method to make it protected.
|
||
|
* Callers should use the normal destructor instead of destroy
|
||
|
*/
|
||
|
virtual void destroy() {
|
||
|
this->TDD::destroy();
|
||
|
}
|
||
|
|
||
|
virtual void destroyNow(bool delayed) {
|
||
|
// Do nothing. This will always be invoked from the call to destroy inside
|
||
|
// our destructor.
|
||
|
assert(!delayed);
|
||
|
// prevent unused variable warnings when asserts are compiled out.
|
||
|
(void)delayed;
|
||
|
}
|
||
|
|
||
|
private:
|
||
|
// Forbidden copy constructor and assignment operator
|
||
|
TUndelayedDestruction(TUndelayedDestruction const &) = delete;
|
||
|
TUndelayedDestruction& operator=(TUndelayedDestruction const &) = delete;
|
||
|
};
|
||
|
|
||
|
}}} // apache::thrift::async
|
||
|
|
||
|
#endif // THRIFT_ASYNC_TUNDELAYEDDESTRUCTION_H_
|