Memory Management in RWBasicUString
In typical usage, an RWBasicUString instance owns and manages the memory required to hold an array of RWUChar16 values. Like RWCString, RWBasicUString normally copies input data to an internal buffer. This usage is both safe and convenient.
In some cases, however, such as constant strings or large strings, it may be more efficient to avoid this initial copy by having RWBasicUString use an externally-supplied buffer. Therefore, RWBasicUString can also be constructed with two alternate memory management strategies:
An RWBasicUString instance can reference an external buffer in a read-only fashion. In this case, a client supplies the constructor with a Duration value of Persistent. Any attempt to modify the external buffer causes RWBasicUString to copy its contents to an internal buffer. This strategy is primarily used to treat static arrays or arrays of some other long storage duration as RWBasicUString instances. For example:// At file scope
static RWUChar16 acronym = [ 0x0052, 0x0057, 0x0000 ];
RWBasicUString
getAcronymAsUString()
{
return RWBasicUString(acronym, RWBasicUString::Persistent);
}
An RWBasicUString instance can assume ownership of an external buffer, and use it in a read-write fashion. To pass ownership of a buffer to an RWBasicUString, a client supplies the RWBasicUString constructor with an RWBasicUString::Deallocator object that can be used to deallocate the buffer. (See Creating and Using Deallocators.) This strategy is reminiscent of that offered by std::auto_ptr<T>, except that RWBasicUString implements copy construction and assignment via reference counting. An RWBasicUString mutator modifies the external buffer directly if its capacity is large enough. Otherwise, the mutator copies the buffer's contents to an internal buffer, deallocates the external buffer, then modifies the internal buffer.Note that in both cases, although the client’s choice of constructor determines the initial memory management strategy, RWBasicUString will abandon an externally-supplied buffer in favor of an internal buffer as necessary.
