Add C.D.Compat.Binary.{encodeFile,decodeFileOrFail'}

Cabal/Distribution/Compat/Binary.hs

@@ -9,11 +9,12 @@
 
 module Distribution.Compat.Binary
        ( decodeOrFailIO
+       , decodeFileOrFail'
 #if __GLASGOW_HASKELL__ >= 708 || MIN_VERSION_binary(0,7,0)
        , module Data.Binary
 #else
        , Binary(..)
-       , decode, encode
+       , decode, encode, encodeFile
 #endif
        ) where
 
@@ -33,15 +34,21 @@ import Data.ByteString.Lazy (ByteString)
 
 import Data.Binary
 
+-- | Lazily reconstruct a value previously written to a file.
+decodeFileOrFail' :: Binary a => FilePath -> IO (Either String a)
+decodeFileOrFail' f = either (Left . snd) Right `fmap` decodeFileOrFail f
+
 #else
 
 import Data.Binary.Get
 import Data.Binary.Put
+import qualified Data.ByteString.Lazy as BSL
 
 import Distribution.Compat.Binary.Class
 import Distribution.Compat.Binary.Generic ()
 
--- | Decode a value from a lazy ByteString, reconstructing the original structure.
+-- | Decode a value from a lazy ByteString, reconstructing the
+-- original structure.
 --
 decode :: Binary a => ByteString -> a
 decode = runGet get
@@ -52,6 +59,14 @@ encode :: Binary a => a -> ByteString
 encode = runPut . put
 {-# INLINE encode #-}
 
+-- | Lazily reconstruct a value previously written to a file.
+decodeFileOrFail' :: Binary a => FilePath -> IO (Either String a)
+decodeFileOrFail' f = decodeOrFailIO =<< BSL.readFile f
+
+-- | Lazily serialise a value to a file
+encodeFile :: Binary a => FilePath -> a -> IO ()
+encodeFile f = BSL.writeFile f . encode
+
 #endif
 
 decodeOrFailIO :: Binary a => ByteString -> IO (Either String a)