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{-# OPTIONS_GHC -funbox-strict-fields #-}
-- | Support module for the POSIX writev system call.
module Network.Socket.Posix.IOVec
( IOVec(..)
, withIOVec
) where
import Foreign.Marshal.Array (allocaArray)
import Network.Socket.Imports
#include <sys/types.h>
#include <sys/uio.h>
data IOVec = IOVec
{ iovBase :: !(Ptr Word8)
, iovLen :: !CSize
}
instance Storable IOVec where
sizeOf _ = (#const sizeof(struct iovec))
alignment _ = alignment (0 :: CInt)
peek p = do
base <- (#peek struct iovec, iov_base) p
len <- (#peek struct iovec, iov_len) p
return $ IOVec base len
poke p iov = do
(#poke struct iovec, iov_base) p (iovBase iov)
(#poke struct iovec, iov_len) p (iovLen iov)
-- | @withIOVec cs f@ executes the computation @f@, passing as argument a pair
-- consisting of a pointer to a temporarily allocated array of pointers to
-- IOVec made from @cs@ and the number of pointers (@length cs@).
-- /Unix only/.
withIOVec :: [(Ptr Word8, Int)] -> ((Ptr IOVec, Int) -> IO a) -> IO a
withIOVec [] f = f (nullPtr, 0)
withIOVec cs f =
allocaArray csLen $ \aPtr -> do
zipWithM_ pokeIov (ptrs aPtr) cs
f (aPtr, csLen)
where
csLen = length cs
ptrs = iterate (`plusPtr` sizeOf (IOVec nullPtr 0))
pokeIov ptr (sPtr, sLen) = poke ptr $ IOVec sPtr (fromIntegral sLen)
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