共享，弱和惰性指针 [英] shared, weak and lazy pointers in C++

问题描述

有人知道 shared_ptr 和 weak_ptr 的实现与懒惰的初始化合作伙伴吗？类的要求是：

Is anyone aware of an implementation of shared_ptr and weak_ptr together with a lazy initialization partner? The requirements of the classes were:

• A lazy_ptr

A weak_lazy_ptr 类有三种可能的状态：尚未构建（不会锁定到 shared_ptr ），构造（将锁定到 shared_ptr ）并销毁（不会锁定到 shared_ptr ）

A weak_lazy_ptr class that has three possible states: not yet constructed (won't lock to a shared_ptr), constructed (will lock to a shared_ptr) and destroyed (won't lock to a shared_ptr)

我创建了一些类，完成前一段时间没有完成这项工作（请参阅CVu文章）在其实现中使用 shared_ptr 和 weak_ptr 。使用共享和弱指针而不是与它们集成的模型的主要问题如下：

I created some classes that didn't do the job completely a while ago (see CVu article here) that used shared_ptr and weak_ptr in their implementation. The main problems with a model that USES shared and weak pointers instead of integrating with them follow:

1. 一旦所有 lazy_ptr 对象超出范围，即使其他客户端持有 shared_ptr 版本

1. Once all lazy_ptr objects go out of scope, any weak references can no longer be locked, even if other clients are holding shared_ptr versions

不能控制不同主题上的对象构建

Construction of objects on different threads can't be controlled

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I'd appreciate any pointers to other attempts to reconcile these problems, or to any work in progress there may be in this area.

推荐答案

我会感谢对其他尝试调解这些问题的任何指示，或任何正在进行的工作。 >

要创建不需要参数的延期构造：

To create deferred construction that requires no parameters:

boost :: bind ; T *>（），param1，param2）将创建一个函数对象，执行 new T（param1，param2）

boost::bind( boost::factory<T*>(), param1, param2 ) will create a function object that performs the equivalent of new T(param1, param2) without needing the parameters at the time of construction.

要创建支持此延迟构造的shared_ptr：

To create a shared_ptr that supports this deferred construction:

使用标准 boost :: shared_ptr （例如，在您的创建类中）捆绑您的工厂，然后您将记录所描述的结果，包括适当的 weak_ptr 功能...

Bundle your factory with the standard boost::shared_ptr (in a class of your creation, for example), and you'llget the results you describe, including the appropriate weak_ptr functionality...

无论任何代码触发延迟构造<客户端应该运行：

Whatever code triggers the deferred construction by the client should run:

your_shared_ptr.reset( your_factory() );

无论代码是否触发对象的销毁都应该执行：

Whatever code triggers the object's destruction should run:

your_shared_ptr.reset();

共享指针将唯一标识为 true 在对象的生命周期。如果你想让尚未构建与销毁区分开，你可以在工厂运行后设置一个bool。

The shared pointer will evauluate to true only during the object's lifetime. And if you want you differentiate "not yet constructed" from "destroyed", you can set a bool after the factory is run.

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