system-uuid-1.1.0: System/UUID/FromForeign.hs

{-| Utilities for fetching the results from foreign functions. 
 -}

{-# LANGUAGE ForeignFunctionInterface
  #-}

module System.UUID.FromForeign
  ( runAndRead
  ) where


import Data.UUID

import Foreign.C
import Foreign.ForeignPtr
import Foreign


{-| Allocates a pointer to capture the output of a foreign function, runs the
    function and interprets the sixteen bytes following the pointer as a UUID.
 -}
runAndRead                  ::  (Ptr CChar -> IO ()) -> IO UUID 
runAndRead procedure         =  do
  fp                        <-  mallocForeignPtrArray 16
  withForeignPtr fp procedure 
  withForeignPtr fp $ peek . castPtr