Introduction

Essential Tools Module User's Guide
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11.1 Introduction

To support better resource control, the Tools Module includes scope guard classes that implement the C++ idiom "Resource Acquisition Is Initialization" (RAII). These classes provide a simple mechanism to allow an object to take ownership of a resource and to release that resource, thus avoiding potentially unsafe or verbose error handing code.

The RAII idiom is useful when writing exception-safe code, but also simplifies resource cleanup when control flow gets complicated. The C++ Standard Library class template std::auto_ptr<> is another implementation of this same idiom written to manage the cleanup of a heap-allocated object.

The basic concept is to acquire a resource in the constructor, and to leverage the C++ language's guarantee that the destructor of a successfully-constructed object will be called.

Using the RAII idiom, the program performs an action when control flow leaves the current scope. Typically, the action to be performed is to undo a previous action in the event that an exception occurs.

Table 23 lists classes and functions in this group.

Table 23: Scope guard classes

Class	Description
*RWScopeGuard*	Typedef for *RWScopeGuardImp*.
*RWTRefHolder*	Reference wrapper object used with scope guards.
*RWScopeGuardImp*	This class and its derived classes implement the scope guard.

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