Data.Vector.Storable and Data.ByteString

VectorByteString.hs

{-# LANGUAGE ScopedTypeVariables #-}
import Control.Monad ((>=>))
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import qualified Data.ByteString.Unsafe as B
import Data.Vector.Storable (Vector)
import qualified Data.Vector.Storable as V
import Foreign.C.String (CStringLen)
import Foreign.Ptr (castPtr)
import Foreign.Storable (Storable(sizeOf))

packVector :: forall a b. Storable a => Vector a -> (CStringLen -> IO b) -> IO b
packVector v f = V.unsafeWith v aux
  where aux p = f (castPtr p, V.length v * sizeOf (undefined::a))

unsafeWithByteString :: Storable a => Vector a -> (ByteString -> IO b) -> IO b
unsafeWithByteString v f = packVector v (B.unsafePackCStringLen >=> f)

toByteString :: Storable a => Vector a -> IO ByteString
toByteString = flip packVector B.packCStringLen