hi,
my problem is as follows:
I have a c-function "bla()" which gets a stream for reading ( FILE *rx ).
Within "bla()" alternating a c-function "getlineC()" and a haskell-function
"getlineHS()" should read a line from stream rx and print it.
void bla ( FILE *rx ) {
char *line
for ( ;; ) {
line = getlineC( rx );
printf ( "%s\n", line );
free( line );
line = getlineHs( rx );
printf ( "%s\n", line );
}
}
How do i pass the stream FILE *rx to the haskell-function properly?
I tried to pass FILE *rx as a Ptr Cfile and converting it back into
something of type Handle in getlineHS,
\begin{code}
module Cfile ( getLineHs ) where
import IO
import Foreign ( Ptr )
import Foreign.C.Types ( CFile, CInt )
import Foreign.C.String ( CString, newCString )
import System.Posix.IO ( fdToHandle )
foreign export ccall "getLineHs" getLineHs :: Ptr CFile -> IO (CString)
getLineHs :: Ptr CFile -> IO (CString)
getLineHs file
= do
hdl <- getInStream file
hGetLine hdl >>= newCString
foreign import ccall "stdio.h fileno" cfileno :: Ptr CFile -> IO CInt
getInStream :: Ptr CFile -> IO (Handle)
getInStream f = cfileno f >>= fdToHandle . fromIntegral
\end{code}
but this doesn't work (i seem to lose the file position indicator)
and i get the following error:
Fail: end of file
Action: hGetLine
Handle: {loc=