On 01 September 2004 10:16, Bayley, Alistair wrote:

I want to call a foreign C function that takes a UTF-8 encoded string as one of its arguments (and there's also a version of the function that receives UTF-16). Can someone point me to documentation or examples of how this would be done? AFAICT (reading the FFI spec) marshalling a String to a CString is locale-dependent, whereas I know that I want UTF-8/16.

Also, if a C function returns a UTF-8 (or UTF-16) encoded string, how do I marshall this reliably into a Haskell String?

Can I use the UTF-16 functions directly with CWStrings? (I'm not sure exactly what wchar_t is, as it's apparently dependent on the locale at compile-time, and could be 8, 16, or 32 bits).

Your best bet is to marshal it yourself. We're a bit behind in this area: 6.2.x doesn't have CAString and CWString, and CString is just char*. The HEAD has CAString and CWString, and will hopefully follow the FFI spec by the time we release 6.4 (we still have to do the locale encoding/decoding between CString and String, IIRC). In any case, none of this allows you to specify a UTF-8 conversion. wchar_t varies from platform to platform: on Windows it is 16 bits, on Linux with glibc it is 32 bits, for example. CWString is only useful for talking to C interfaces that are expressed in terms of wchar_t. Cheers, Simon