4 files changed, 8 insertions, 18 deletions
diff --git a/src/BTLS/Cast.hs b/src/BTLS/Cast.hs
index 6f29469..a467c90 100644
--- a/src/BTLS/Cast.hs
+++ b/src/BTLS/Cast.hs
@@ -15,7 +15,11 @@
 module BTLS.Cast where
 
 import Foreign (Ptr)
+import Foreign.C.Types
 import Unsafe.Coerce (unsafeCoerce)
 
+asCUCharBuf :: Ptr CChar -> Ptr CUChar
+asCUCharBuf = unsafeCoerce
+
 asVoidPtr :: Ptr a -> Ptr ()
 asVoidPtr = unsafeCoerce
diff --git a/src/Codec/Crypto/HKDF.hs b/src/Codec/Crypto/HKDF.hs
index 8c1db0a..4547a52 100644
--- a/src/Codec/Crypto/HKDF.hs
+++ b/src/Codec/Crypto/HKDF.hs
@@ -19,13 +19,12 @@ module Codec.Crypto.HKDF
 
 import qualified Data.ByteString as ByteString
 import qualified Data.ByteString.Unsafe as ByteString
-import Foreign (Ptr, Storable(peek), alloca, allocaArray)
-import Foreign.C.Types
+import Foreign (Storable(peek), alloca, allocaArray)
 import Foreign.Marshal.Unsafe (unsafeLocalState)
-import Unsafe.Coerce (unsafeCoerce)
 
 import BTLS.BoringSSL.Digest (evpMaxMDSize)
 import BTLS.BoringSSL.HKDF
+import BTLS.Cast (asCUCharBuf)
 import BTLS.Types
   (AssociatedData(AssociatedData), Salt(Salt), SecretKey(SecretKey), noSalt)
 import Data.Digest.Internal (Algorithm(Algorithm))
@@ -63,6 +62,3 @@ expand (Algorithm md) (AssociatedData info) outLen (SecretKey secret) =
             (asCUCharBuf pSecret) (fromIntegral secretLen)
             (asCUCharBuf pInfo) (fromIntegral infoLen)
       SecretKey <$> ByteString.packCStringLen (pOutKey, outLen)
-
-asCUCharBuf :: Ptr CChar -> Ptr CUChar
-asCUCharBuf = unsafeCoerce
diff --git a/src/Data/Digest.hs b/src/Data/Digest.hs
index 2d06389..03026fb 100644
--- a/src/Data/Digest.hs
+++ b/src/Data/Digest.hs
@@ -22,13 +22,11 @@ module Data.Digest
   ) where
 
 import qualified Data.ByteString.Lazy as ByteString.Lazy
-import Foreign (Ptr)
-import Foreign.C.Types
 import Foreign.Marshal.Unsafe (unsafeLocalState)
-import Unsafe.Coerce (unsafeCoerce)
 
 import BTLS.BoringSSL.Base
 import BTLS.BoringSSL.Digest
+import BTLS.Cast (asCUCharBuf)
 import Data.Digest.Internal
 
 type LazyByteString = ByteString.Lazy.ByteString
@@ -56,6 +54,3 @@ hash (Algorithm md) =
       -- we're going to cheat and let Haskell reinterpret-cast 'mdOut' to 'Ptr
       -- CUChar.
       evpDigestFinalEx ctx (asCUCharBuf mdOut) pOutSize
-
-    asCUCharBuf :: Ptr CChar -> Ptr CUChar
-    asCUCharBuf = unsafeCoerce
diff --git a/src/Data/HMAC.hs b/src/Data/HMAC.hs
index 29b6ce0..a6b72fe 100644
--- a/src/Data/HMAC.hs
+++ b/src/Data/HMAC.hs
@@ -21,13 +21,11 @@ module Data.HMAC
 import Data.ByteString (ByteString)
 import qualified Data.ByteString.Lazy as ByteString.Lazy
 import qualified Data.ByteString.Unsafe as ByteString
-import Foreign (Ptr)
-import Foreign.C.Types
 import Foreign.Marshal.Unsafe (unsafeLocalState)
-import Unsafe.Coerce (unsafeCoerce)
 
 import BTLS.BoringSSL.Base
 import BTLS.BoringSSL.HMAC
+import BTLS.Cast (asCUCharBuf)
 import BTLS.ConstantTimeEquals (constantTimeEquals)
 import BTLS.Types (SecretKey(SecretKey))
 import Data.Digest.Internal
@@ -65,6 +63,3 @@ hmac (Algorithm md) (SecretKey key) =
     -- in Data.Digest, we'll let Haskell reinterpret-cast the buffers.
     update ctx buf len = hmacUpdate ctx (asCUCharBuf buf) len
     finalize ctx hmacOut pOutSize = hmacFinal ctx (asCUCharBuf hmacOut) pOutSize
-
-    asCUCharBuf :: Ptr CChar -> Ptr CUChar
-    asCUCharBuf = unsafeCoerce