Hash digests: Only export primitives for rendering as hex and base32

The old 'digestText16' was really a special case that doesn't belong
in the hashing module proper.

Author: shlevy

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

@@ -10,7 +10,8 @@ module System.Nix.Hash (
   , HNix.hash
   , HNix.hashLazy
 
-  , HNix.printAsBase32
+  , HNix.encodeBase32
+  , HNix.encodeBase16
   ) where
 
 import qualified System.Nix.Internal.Hash as HNix

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

@@ -90,16 +90,13 @@ hashLazy :: forall a.HasDigest a => BSL.ByteString -> Digest a
 hashLazy bsl =
   finalize $ foldl' (update @a) (initialize @a) (BSL.toChunks bsl)
 
-digestText32 :: forall a. NamedAlgo a => Digest a -> T.Text
-digestText32 d = algoName @a <> ":" <> printAsBase32 d
+-- | Encode a Digest in the special Nix base-32 encoding.
+encodeBase32 :: Digest a -> T.Text
+encodeBase32 (Digest bs) = printHashBytes32 bs
 
-digestText16 :: forall a. NamedAlgo a => Digest a -> T.Text
-digestText16 (Digest bs) = algoName @a <> ":" <> T.decodeUtf8 (Base16.encode bs)
-
--- | Convert any Digest to a base32-encoded string.
---   This is not used in producing store path hashes
-printAsBase32 :: Digest a -> T.Text
-printAsBase32 (Digest bs) = printHashBytes32 bs
+-- | Encode a Digest in hex.
+encodeBase16 :: Digest a -> T.Text
+encodeBase16 (Digest bs) = T.decodeUtf8 (Base16.encode bs)
 
 
 instance HasDigest MD5 where

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

@@ -63,7 +63,7 @@ data Path = Path !(Digest PathHashAlgo) !PathName
   deriving (Eq, Ord, Show)
 
 pathToText :: Text -> Path -> Text
-pathToText storeDir (Path h nm) = storeDir <> "/" <> printAsBase32 h <> "-" <> pathNameContents nm
+pathToText storeDir (Path h nm) = storeDir <> "/" <> encodeBase32 h <> "-" <> pathNameContents nm
 
 type PathSet = HashSet Path
 

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

@@ -10,19 +10,20 @@ import qualified Data.HashSet as HS
 import           Data.Text (Text)
 import qualified Data.Text as T
 import           Data.Text.Encoding
-import           System.Nix.Internal.Hash
+import           System.Nix.Hash
 import           System.Nix.Path
 
 makeStorePath :: Text -> Text -> Digest 'SHA256 -> Text -> Path
 makeStorePath storeDir ty h nm = Path storeHash (PathName nm)
   where
     s = T.intercalate ":"
       [ ty
-      , digestText16 h
+      , algoName @'SHA256
+      , encodeBase16 h
       , storeDir
       , nm
       ]
-    storeHash = truncateDigest $ hash $ encodeUtf8 s
+    storeHash = hash $ encodeUtf8 s
 
 makeTextPath :: Text -> Text -> Digest 'SHA256 -> PathSet -> Path
 makeTextPath storeDir nm h refs = makeStorePath storeDir ty h nm

hnix-store-core/tests/Hash.hs

@@ -32,11 +32,11 @@ spec_hash = do
   describe "hashing parity with nix-store" $ do
 
     it "produces (base32 . sha256) of \"nix-output:foo\" the same as Nix does at the moment for placeholder \"foo\"" $
-      shouldBe (printAsBase32 (hash @SHA256 "nix-output:foo"))
+      shouldBe (encodeBase32 (hash @SHA256 "nix-output:foo"))
                "1x0ymrsy7yr7i9wdsqy9khmzc1yy7nvxw6rdp72yzn50285s67j5"
 
     it "produces (base32 . sha1) of \"Hello World\" the same as the thesis" $
-      shouldBe (printAsBase32 (hash @SHA1 "Hello World"))
+      shouldBe (encodeBase32 (hash @SHA1 "Hello World"))
                "s23c9fs0v32pf6bhmcph5rbqsyl5ak8a"
 
     -- The example in question:
@@ -45,5 +45,5 @@ spec_hash = do
       let exampleStr =
             "source:sha256:2bfef67de873c54551d884fdab3055d84d573e654efa79db3"
             <> "c0d7b98883f9ee3:/nix/store:myfile"
-      shouldBe (printAsBase32 @PathHashAlgo (hash exampleStr))
+      shouldBe (encodeBase32 @PathHashAlgo (hash exampleStr))
         "xv2iccirbrvklck36f1g7vldn5v58vck"