# Pastebin lbu13Vm0
import Data.ByteString (ByteString)
import Data.ByteString.Unsafe (unsafeUseAsCStringLen)
import Data.Vector.Storable (Vector, unsafeFreeze)
import Data.Vector.Storable.Mutable (MVector(MVector), unsafeNew)
import Foreign (copyArray, withForeignPtr)
import Foreign.C (CChar)

bsToVec :: ByteString -> IO (Vector CChar)
bsToVec bs = unsafeUseAsCStringLen bs $ \(ptr, n) -> do
    v@(MVector _ foreignPtr) <- unsafeNew n
    withForeignPtr foreignPtr $ \ptr' -> copyArray ptr' ptr n
    unsafeFreeze v