[Mono-dev] Specifying MarshallAs for [Out] StringBuilder

[Kornél Pál]

> I understood that I have to use a StringBuilder with a large enough
> buffer. But what I don't understand is how do I get access to the
> underlying pointer from the StringBuilder ? Are you suggesting that I
> don't rely on Mono's marshalling of stringbuilder<->read-write_string
> but instead write my own marshaller; something like this ?

You cannot obtain that pointer using public methods. But note that that 
pointer would be UTF-16 and you need some other encoding so you couldn't use 
it directly even if you had it.

>  // 3. Read back string and fill in the stringbuilder
>  sb.Length = 0;
>  sb.Append (do some encoding stuff with PtrToString on the buffer);

You only need to do this if you want to replace the contents of the 
StringBuilder. If you just need the string you don't need a StringBuilder, 
simply return a string.

Kornél