Expose encoders/decoders for Maybe

Author: ruhatch

binary/src/Cardano/Binary/FromCBOR.hs

@@ -13,6 +13,7 @@ module Cardano.Binary.FromCBOR
   , enforceSize
   , matchSize
   , module D
+  , fromCBORMaybe
   )
 where
 
@@ -298,15 +299,15 @@ instance FromCBOR a => FromCBOR (NonEmpty a) where
     Just xs -> Right xs
 
 instance FromCBOR a => FromCBOR (Maybe a) where
-  fromCBOR = decodeMaybe fromCBOR
+  fromCBOR = fromCBORMaybe fromCBOR
 
-decodeMaybe :: D.Decoder s a -> D.Decoder s (Maybe a)
-decodeMaybe decoder = do
+fromCBORMaybe :: D.Decoder s a -> D.Decoder s (Maybe a)
+fromCBORMaybe fromCBORA = do
   n <- D.decodeListLen
   case n of
     0 -> return Nothing
     1 -> do
-      !x <- decoder
+      !x <- fromCBORA
       return (Just x)
     _ -> cborError $ DecoderErrorUnknownTag "Maybe" (fromIntegral n)
 

binary/src/Cardano/Binary/ToCBOR.hs

@@ -14,6 +14,7 @@ module Cardano.Binary.ToCBOR
   ( ToCBOR(..)
   , withWordSize
   , module E
+  , toCBORMaybe
 
     -- * Size of expressions
   , Range(..)
@@ -584,12 +585,15 @@ instance ToCBOR a => ToCBOR (NonEmpty a) where
   encodedSizeExpr size _ = size (Proxy @[a]) -- MN TODO make 0 count impossible
 
 instance ToCBOR a => ToCBOR (Maybe a) where
-  toCBOR Nothing  = E.encodeListLen 0
-  toCBOR (Just x) = E.encodeListLen 1 <> toCBOR x
+  toCBOR = toCBORMaybe toCBOR
 
   encodedSizeExpr size _ =
     szCases [Case "Nothing" 1, Case "Just" (1 + size (Proxy @a))]
 
+toCBORMaybe :: (a -> Encoding) -> Maybe a -> Encoding
+toCBORMaybe encodeA = \case
+  Nothing -> E.encodeListLen 0
+  Just x  -> E.encodeListLen 1 <> encodeA x
 
 encodeContainerSkel
   :: (Word -> E.Encoding)