Core: Internal: mv Base dec -> Base, Hash.decode(Base->DigestWith)

hnix-store-core/src/System/Nix/Hash.hs

@@ -15,7 +15,7 @@ module System.Nix.Hash
 
   , Base.BaseEncoding(..)
   , Hash.encodeDigestWith
-  , Hash.decodeBase
+  , Hash.decodeDigestWith
   )
 where
 

hnix-store-core/src/System/Nix/Internal/Base.hs

@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 module System.Nix.Internal.Base
   ( module System.Nix.Internal.Base
   , Base32.encode
@@ -26,3 +28,18 @@ encodeWith :: BaseEncoding -> Bytes.ByteString -> T.Text
 encodeWith Base16 = T.decodeUtf8 . Base16.encode
 encodeWith NixBase32 = Base32.encode
 encodeWith Base64 = T.decodeUtf8 . Base64.encode
+
+-- | Take the input & @Base@ encoding witness -> decode into @Text@.
+decodeWith :: BaseEncoding -> T.Text -> Either String Bytes.ByteString
+#if MIN_VERSION_base16_bytestring(1,0,0)
+decodeWith Base16 = Base16.decode . T.encodeUtf8
+#else
+decodeWith Base16 = lDecode  -- this tacit sugar simply makes GHC pleased with number of args
+ where
+  lDecode t =
+    case Base16.decode (T.encodeUtf8 t) of
+      (x, "") -> pure $ x
+      _       -> Left $ "Unable to decode base16 string" <> T.unpack t
+#endif
+decodeWith NixBase32 = Base32.decode
+decodeWith Base64 = Base64.decode . T.encodeUtf8

hnix-store-core/src/System/Nix/Internal/Hash.hs

@@ -19,9 +19,6 @@ import qualified Crypto.Hash.SHA1       as SHA1
 import qualified Crypto.Hash.SHA256     as SHA256
 import qualified Crypto.Hash.SHA512     as SHA512
 import qualified Data.ByteString        as BS
-import qualified Data.ByteString.Base16 as Base16
-import qualified System.Nix.Base32      as Base32  -- Nix has own Base32 encoding
-import qualified Data.ByteString.Base64 as Base64
 import           Data.Bits              (xor)
 import qualified Data.ByteString.Lazy   as BSL
 import qualified Data.Hashable          as DataHashable
@@ -29,7 +26,6 @@ import           Data.List              (foldl')
 import           Data.Proxy             (Proxy(Proxy))
 import           Data.Text              (Text)
 import qualified Data.Text              as T
-import qualified Data.Text.Encoding     as T
 import           Data.Word              (Word8)
 import qualified GHC.TypeLits           as Kind
                                         (Nat, KnownNat, natVal)
@@ -37,6 +33,7 @@ import           Data.Coerce            (coerce)
 import           System.Nix.Internal.Base
                                         ( BaseEncoding(Base16,NixBase32,Base64)
                                         , encodeWith
+                                        , decodeWith
                                         )
 
 -- | The universe of supported hash algorithms.
@@ -116,9 +113,9 @@ mkNamedDigest name sriHash =
     _        -> Left $ "Unknown hash name: " <> T.unpack name
   decodeGo :: forall a . (NamedAlgo a, ValidAlgo a) => Text -> Either String (Digest a)
   decodeGo h
-    | size == base16Len = decodeBase Base16 h
-    | size == base32Len = decodeBase NixBase32 h
-    | size == base64Len = decodeBase Base64 h
+    | size == base16Len = decodeDigestWith Base16 h
+    | size == base32Len = decodeDigestWith NixBase32 h
+    | size == base64Len = decodeDigestWith Base64 h
     | otherwise = Left $ T.unpack sriHash <> " is not a valid " <> T.unpack name <> " hash. Its length (" <> show size <> ") does not match any of " <> show [base16Len, base32Len, base64Len]
    where
     size = T.length h
@@ -154,18 +151,8 @@ encodeDigestWith b = encodeWith b . coerce
 
 
 -- | Take BaseEncoding type of the input -> take the input itself -> decodeBase into Digest
-decodeBase :: BaseEncoding -> T.Text -> Either String (Digest a)
-#if MIN_VERSION_base16_bytestring(1,0,0)
-decodeBase Base16 = fmap Digest . Base16.decode . T.encodeUtf8
-#else
-decodeBase Base16 = lDecode  -- this tacit sugar simply makes GHC pleased with number of args
- where
-  lDecode t = case Base16.decode (T.encodeUtf8 t) of
-    (x, "") -> Right $ Digest x
-    _       -> Left $ "Unable to decode base16 string" <> T.unpack t
-#endif
-decodeBase NixBase32 = fmap Digest . Base32.decode
-decodeBase Base64 = fmap Digest . Base64.decode . T.encodeUtf8
+decodeDigestWith :: BaseEncoding -> T.Text -> Either String (Digest a)
+decodeDigestWith b x = Digest <$> decodeWith b x
 
 
 -- | Uses "Crypto.Hash.MD5" from cryptohash-md5.

hnix-store-core/src/System/Nix/Internal/StorePath.hs

@@ -17,7 +17,7 @@ import           System.Nix.Hash                ( HashAlgorithm
                                                 , Digest
                                                 , BaseEncoding(..)
                                                 , encodeDigestWith
-                                                , decodeBase
+                                                , decodeDigestWith
                                                 , SomeNamedDigest
                                                 )
 
@@ -178,7 +178,7 @@ parsePath expectedRoot x =
   let
     (rootDir, fname) = FilePath.splitFileName . Bytes.Char8.unpack $ x
     (digestPart, namePart) = Text.breakOn "-" $ Text.pack fname
-    digest = decodeBase NixBase32 digestPart
+    digest = decodeDigestWith NixBase32 digestPart
     name = makeStorePathName . Text.drop 1 $ namePart
     --rootDir' = dropTrailingPathSeparator rootDir
     -- cannot use ^^ as it drops multiple slashes /a/b/// -> /a/b
@@ -200,7 +200,7 @@ pathParser expectedRoot = do
       <?> "Expecting path separator"
 
   digest <-
-    decodeBase NixBase32
+    decodeDigestWith NixBase32
     <$> Parser.Text.Lazy.takeWhile1 (`elem` Nix.Base32.digits32)
       <?> "Invalid Base32 part"
 

hnix-store-core/tests/Hash.hs

@@ -55,7 +55,7 @@ prop_nixBase32Roundtrip = forAllShrink nonEmptyString genericShrink $
 
 -- | API variants
 prop_nixBase16Roundtrip :: Digest StorePathHashAlgo -> Property
-prop_nixBase16Roundtrip x = pure x === (decodeBase Base16 . encodeDigestWith Base16 $ x)
+prop_nixBase16Roundtrip x = pure x === (decodeDigestWith Base16 . encodeDigestWith Base16 $ x)
 
 -- | Hash encoding conversion ground-truth.
 -- Similiar to nix/tests/hash.sh