Hrm. On the C side the arrays disappear shortly after my call, so just casting wouldn't really work. I settled for the following monstrosity where (cast :: a -> b) is your standard unsafePerformIO/IORef based casting function: peekPackedCString :: CString -> IO PackedString peekPackedCString cs = do i <- findLength cs 0 (arr :: IOUArray Int Char) <- newArray_ (0,i) writeToArr arr i 0 cs (arr' :: UArray Int Char) <- unsafeFreeze arr return (cast arr') where findLength ptr n = do c <- peek ptr if c == 0 then return n else findLength (plusPtr ptr 1) $! n+1 writeToArr arr len pos ptr | pos >= len = return () | otherwise = do c <- peek ptr writeArray arr pos (castCCharToChar c) writeToArr arr len (len+1) (plusPtr ptr 1) it's pretty fast and works only because the type of PackedString is newtype PackedString = PS (UArray Int Char) so the casting gives us what we want. This does seem like something that belongs in the PackedString library or the Foreign.C.String library, though. - Hal -- Hal Daume III | hdaume@isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume
-----Original Message----- From: glasgow-haskell-users-admin@haskell.org [mailto:glasgow-haskell-users-admin@haskell.org] On Behalf Of John Meacham Sent: Thursday, August 21, 2003 3:10 AM To: glasgow-haskell-users@haskell.org Subject: Re: fast CString -> IO PackedString fuction
On Wed, Aug 20, 2003 at 06:48:58PM -0700, Hal Daume wrote:
is there a way to go from a CString to a PackedString w/o going through a normal String in the middle? or should i write my own?
If you can get a wchar_t * out of the app then that can be simply cast to a packedstring, this is quite speedy. if you use mbsrtowcs(3) and friends to do the conversion from char * then you get properly localized text via locale settings for free :) I have used this sort of thing for interfacing haskell to libraries where honoring locale was important in the past. John
-- -------------------------------------------------------------- ------------- John Meacham - California Institute of Technology, Alum. - john@foo.net -------------------------------------------------------------- ------------- _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users