StringMemoryPassthru

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template<typename From, typename To, int32 DefaultConversionSize>  
auto StringMemoryPassthru  
(  
    To * Buffer,  
    int32 BufferSize,  
    int32 SourceLength  
)  
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template<typename From, typename To, int32 DefaultConversionSize> auto StringMemoryPassthru (     To * Buffer,     int32 BufferSize,     int32 SourceLength )

Remarks

Allows the efficient conversion of strings by means of a temporary memory buffer only when necessary. Intended to be used when you have an API which populates a buffer with some string representation which is ultimately going to be stored in another representation, but where you don't want to do a conversion or create a temporary buffer for that string if it's not necessary.

Intended use:

// Populates the buffer Str with StrLen characters. void SomeAPI(APICharType* Str, int32 StrLen);

void Func(DestChar* Buffer, int32 BufferSize) { // Create a passthru. This takes the buffer (and its size) which will ultimately hold the string, as well as the length of the // string that's being converted, which must be known in advance. // An explicit template argument is also passed to indicate the character type of the source string. // Buffer must be correctly typed for the destination string type. auto Passthru = StringMemoryPassthru(Buffer, BufferSize, SourceLength);

// Passthru.Get() returns an APICharType buffer pointer which is guaranteed to be SourceLength characters in size. // It's possible, and in fact intended, for Get() to return the same pointer as Buffer if DestChar and APICharType are // compatible string types. If this is the case, SomeAPI will write directly into Buffer. If the string types are not // compatible, Get() will return a pointer to some temporary memory which allocated by and owned by the passthru. SomeAPI(Passthru.Get(), SourceLength);

// If the string types were not compatible, then the passthru used temporary storage, and we need to write that back to Buffer. // We do that with the Apply call. If the string types were compatible, then the data was already written to Buffer directly // and so Apply is a no-op. Passthru.Apply();

// Now Buffer holds the data output by SomeAPI, already converted if necessary. }