Add Distribution.Compat.MD5

Cabal/Cabal.cabal

@@ -531,6 +531,7 @@ library
     Distribution.Utils.Base62
     Distribution.Compat.CopyFile
     Distribution.Compat.GetShortPathName
+    Distribution.Compat.MD5
     Distribution.Compat.MonadFail
     Distribution.Compat.Prelude
     Distribution.Compat.SnocList

Cabal/Distribution/Compat/MD5.hs

+module Distribution.Compat.MD5 (
+    MD5,
+    showMD5,
+    md5,
+    -- * Binary
+    binaryPutMD5,
+    binaryGetMD5,
+    ) where
+
+import Data.Binary      (Get, Put)
+import Data.Binary.Get  (getWord64le)
+import Data.Binary.Put  (putWord64le)
+import Foreign.Ptr      (castPtr)
+import GHC.Fingerprint  (Fingerprint (..), fingerprintData)
+import Numeric          (showHex)
+import System.IO.Unsafe (unsafeDupablePerformIO)
+
+import qualified Data.ByteString        as BS
+import qualified Data.ByteString.Unsafe as BS
+
+type MD5 = Fingerprint
+
+-- | Show 'MD5' in human readable form
+--
+-- >>> showMD5 (Fingerprint 123 456)
+-- "000000000000007b00000000000001c8"
+--
+-- >>> showMD5 $ md5 $ BS.pack [0..127]
+-- "37eff01866ba3f538421b30b7cbefcac"
+--
+showMD5 :: MD5 -> String
+showMD5 (Fingerprint a b) = pad a' ++ pad b' where
+    a' = showHex a ""
+    b' = showHex b ""
+    pad s = replicate (16 - length s) '0' ++ s
+
+md5 :: BS.ByteString -> MD5
+md5 bs = unsafeDupablePerformIO $ BS.unsafeUseAsCStringLen bs $ \(ptr, len) ->
+    fingerprintData (castPtr ptr) len
+
+binaryPutMD5 :: MD5 -> Put
+binaryPutMD5 (Fingerprint a b) = do
+    putWord64le a
+    putWord64le b
+
+binaryGetMD5 :: Get MD5
+binaryGetMD5 = do
+    a <- getWord64le
+    b <- getWord64le
+    return (Fingerprint a b)

Cabal/Distribution/PackageDescription/Quirks.hs

-{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RankNTypes        #-}
 -- |
 --
 -- @since 2.2.0.0
 module Distribution.PackageDescription.Quirks (patchQuirks) where
 
-import           Prelude ()
-import           Distribution.Compat.Prelude
-import           GHC.Fingerprint (Fingerprint (..), fingerprintData)
-import           Foreign.Ptr (castPtr)
-import           System.IO.Unsafe (unsafeDupablePerformIO)
+import Distribution.Compat.MD5
+import Distribution.Compat.Prelude
+import GHC.Fingerprint             (Fingerprint (..))
+import Prelude ()
 
 import qualified Data.ByteString as BS
-import qualified Data.ByteString.Unsafe as BS
-import qualified Data.Map as Map
+import qualified Data.Map        as Map
 
 -- | Patch legacy @.cabal@ file contents to allow parsec parser to accept
 -- all of Hackage.
@@ -30,13 +28,7 @@ patchQuirks bs = case Map.lookup (BS.take 256 bs, md5 bs) patches of
       where
         output = f bs
 
-md5 :: BS.ByteString -> Fingerprint
-md5 bs = unsafeDupablePerformIO $ BS.unsafeUseAsCStringLen bs $ \(ptr, len) ->
-    fingerprintData (castPtr ptr) len
-
 -- | 'patches' contains first 256 bytes, pre- and post-fingerprints and a patch function.
---
---
 patches :: Map.Map (BS.ByteString, Fingerprint) (Fingerprint, BS.ByteString -> BS.ByteString)
 patches = Map.fromList
     -- http://hackage.haskell.org/package/unicode-transforms-0.3.3