Data.Digest: Reify hash algorithms

Eliminate the functional interface for hashing. Hashing now occurs
exclusively through the `hash` function, which accepts a
`Data.Digest.Algorithm`. This makes btls somewhat less extensible, but
it’s the most elegant way to support HMACs.

5 files changed, 51 insertions, 62 deletions

diff --git a/src/Data/Digest.hs b/src/Data/Digest.hs
index 6eebd27..7e88c49 100644
--- a/src/Data/Digest.hs
+++ b/src/Data/Digest.hs
@@ -1,5 +1,48 @@
 module Data.Digest
-  ( Digest
+  ( Algorithm
+  , Digest
+  , hash
+  , md5
+  , sha1
+  , sha224
+  , sha256
+  , sha384
+  , sha512
   ) where
 
-import Data.Digest.Internal (Digest)
\ No newline at end of file
+import Foreign (Ptr)
+
+import Data.Digest.Internal
+
+
+foreign import ccall "openssl/digest.h EVP_md5" evpMd5 :: Ptr EvpMd
+
+md5 :: Algorithm
+md5 = Algorithm evpMd5
+
+
+foreign import ccall "openssl/digest.h EVP_sha1" evpSha1 :: Ptr EvpMd
+
+sha1 :: Algorithm
+sha1 = Algorithm evpSha1
+
+
+foreign import ccall "openssl/digest.h EVP_sha224" evpSha224 :: Ptr EvpMd
+
+foreign import ccall "openssl/digest.h EVP_sha256" evpSha256 :: Ptr EvpMd
+
+foreign import ccall "openssl/digest.h EVP_sha384" evpSha384 :: Ptr EvpMd
+
+foreign import ccall "openssl/digest.h EVP_sha512" evpSha512 :: Ptr EvpMd
+
+sha224 :: Algorithm
+sha224 = Algorithm evpSha224
+
+sha256 :: Algorithm
+sha256 = Algorithm evpSha256
+
+sha384 :: Algorithm
+sha384 = Algorithm evpSha384
+
+sha512 :: Algorithm
+sha512 = Algorithm evpSha512
diff --git a/src/Data/Digest/Internal.hsc b/src/Data/Digest/Internal.hsc
index 73edbd9..a7f19d7 100644
--- a/src/Data/Digest/Internal.hsc
+++ b/src/Data/Digest/Internal.hsc
@@ -31,9 +31,6 @@ data Engine
 -- | The BoringSSL @EVP_MD@ type, representing a hash algorithm.
 data EvpMd
 
--- | A convenience alias for @Ptr EvpMd@.
-type Algo = Ptr EvpMd
-
 -- | The BoringSSL @EVP_MD_CTX@ type, representing the state of a pending
 -- hashing operation.
 data EvpMdCtx
@@ -103,6 +100,9 @@ foreign import ccall "&btlsFinalizeEvpMdCtx"
 
 -- Finally, we're ready to actually implement the hashing interface.
 
+-- | A cryptographic hash function.
+newtype Algorithm = Algorithm (Ptr EvpMd)
+
 -- | The result of a hash operation.
 newtype Digest =
   Digest ByteString
@@ -115,9 +115,9 @@ instance Show Digest where
         hexit (b `shiftR` 4 .&. 0x0f) : hexit (b .&. 0x0f) : xs
       hexit = intToDigit . fromIntegral :: Word8 -> Char
 
--- | Hashes according to the given 'Algo'.
-hash :: Algo -> LazyByteString -> Digest
-hash md bytes =
+-- | Hashes according to the given 'Algorithm'.
+hash :: Algorithm -> LazyByteString -> Digest
+hash (Algorithm md) bytes =
   unsafeLocalState $ do
     ctxFP <- mallocEvpMdCtx
     withForeignPtr ctxFP $ \ctx -> do
diff --git a/src/Data/Digest/Md5.hs b/src/Data/Digest/Md5.hs
deleted file mode 100644
index 194633b..0000000
--- a/src/Data/Digest/Md5.hs
+++ /dev/null
@@ -1,12 +0,0 @@
-module Data.Digest.Md5
-  ( md5
-  ) where
-
-import Data.ByteString.Lazy (ByteString)
-
-import Data.Digest.Internal
-
-foreign import ccall "openssl/digest.h EVP_md5" evpMd5 :: Algo
-
-md5 :: ByteString -> Digest
-md5 = hash evpMd5
diff --git a/src/Data/Digest/Sha1.hs b/src/Data/Digest/Sha1.hs
deleted file mode 100644
index 16101b0..0000000
--- a/src/Data/Digest/Sha1.hs
+++ /dev/null
@@ -1,12 +0,0 @@
-module Data.Digest.Sha1
-  ( sha1
-  ) where
-
-import Data.ByteString.Lazy (ByteString)
-
-import Data.Digest.Internal
-
-foreign import ccall "openssl/digest.h EVP_sha1" evpSha1 :: Algo
-
-sha1 :: ByteString -> Digest
-sha1 = hash evpSha1
diff --git a/src/Data/Digest/Sha2.hs b/src/Data/Digest/Sha2.hs
deleted file mode 100644
index 965686c..0000000
--- a/src/Data/Digest/Sha2.hs
+++ /dev/null
@@ -1,30 +0,0 @@
-module Data.Digest.Sha2
-  ( sha224
-  , sha256
-  , sha384
-  , sha512
-  ) where
-
-import Data.ByteString.Lazy (ByteString)
-
-import Data.Digest.Internal
-
-foreign import ccall "openssl/digest.h EVP_sha224" evpSha224 :: Algo
-
-foreign import ccall "openssl/digest.h EVP_sha256" evpSha256 :: Algo
-
-foreign import ccall "openssl/digest.h EVP_sha384" evpSha384 :: Algo
-
-foreign import ccall "openssl/digest.h EVP_sha512" evpSha512 :: Algo
-
-sha224 :: ByteString -> Digest
-sha224 = hash evpSha224
-
-sha256 :: ByteString -> Digest
-sha256 = hash evpSha256
-
-sha384 :: ByteString -> Digest
-sha384 = hash evpSha384
-
-sha512 :: ByteString -> Digest
-sha512 = hash evpSha512