1 files changed, 21 insertions, 0 deletions

diff --git a/haskell/Data/Primitive/ByteArray/Util.hs b/haskell/Data/Primitive/ByteArray/Util.hs
index 1776286..de944e7 100644
--- a/haskell/Data/Primitive/ByteArray/Util.hs
+++ b/haskell/Data/Primitive/ByteArray/Util.hs
@@ -9,10 +9,16 @@
 {-# LANGUAGE TypeOperators         #-}
 module Data.Primitive.ByteArray.Util where
 
+import GHC.Exts (Ptr(..))
 import GHC.TypeLits
 import Control.Monad.Primitive
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Unsafe as B
+import Data.Primitive.Addr
 import Data.Primitive.Types
 import Data.Primitive.ByteArray
+import Data.Word
+import Foreign.Ptr
 
 newtype Offset (n :: Nat) = Offset Int
 
@@ -43,3 +49,18 @@ readAtByte :: forall a m n.
                ) => MutableByteArray (PrimState m) -> Offset n -> m a
 readAtByte buf (Offset offset) = readByteArray buf (div offset $ (sizeOf (undefined :: a)))
 {-# INLINE readAtByte #-}
+
+writeStringAt :: PrimMonad m => MutableByteArray s -> Int -> B.ByteString -> m (Ptr a)
+writeStringAt src o bsname = do
+    (p,cnt) <- unsafeIOToPrim $ B.unsafeUseAsCStringLen bsname return
+    let nptr = ptr (mutableByteArrayContents src) `plusPtr` o
+    copyAddr (adr nptr) (adr p) cnt
+    writeOffAddr (adr nptr) cnt (0 :: Word8)
+    return nptr
+
+ptr :: Addr -> Ptr a
+ptr (Addr a) = Ptr a
+
+adr :: Ptr a -> Addr
+adr (Ptr a) = Addr a
+