From 021932a9ee2a81435b0a341030f68730dd9abd3b Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@google.com>
Date: Fri, 21 Sep 2018 14:19:10 -0400
Subject: Start using base16-bytestring in btls
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We’re already using it in tests, so eliminate some hand-rolled
hexification code.
---
 btls.cabal        |  1 +
 src/BTLS/Types.hs | 14 ++++++--------
 src/Data/HMAC.hs  |  4 ++--
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/btls.cabal b/btls.cabal
index 1ff34f0..9d27272 100644
--- a/btls.cabal
+++ b/btls.cabal
@@ -88,6 +88,7 @@ library
   -- in OpenSSL.
   extra-libraries:     btls_crypto
   build-depends:       base >=4.9 && <4.10
+                     , base16-bytestring >=0.1.1.6 && <0.2
                      , bytestring >=0.10 && <0.11
                      , monad-loops >=0.4.3 && <0.5
                      , transformers >=0.5.2 && <0.6
diff --git a/src/BTLS/Types.hs b/src/BTLS/Types.hs
index 44b29bc..4a4e518 100644
--- a/src/BTLS/Types.hs
+++ b/src/BTLS/Types.hs
@@ -14,11 +14,10 @@
 
 module BTLS.Types where
 
-import Data.Bits (Bits((.&.)), shiftR)
 import Data.ByteString (ByteString)
 import qualified Data.ByteString as ByteString
-import Data.Char (intToDigit)
-import Data.Word (Word8)
+import qualified Data.ByteString.Base16 as ByteString.Base16
+import qualified Data.ByteString.Char8 as ByteString.Char8
 import Foreign (Ptr)
 
 import BTLS.BoringSSL.Base (EVPMD)
@@ -39,11 +38,7 @@ newtype Digest = Digest ByteString
   deriving (Eq, Ord)
 
 instance Show Digest where
-  show (Digest d) = ByteString.foldr showHexPadded [] d
-    where
-      showHexPadded b xs =
-        hexit (b `shiftR` 4 .&. 0x0f) : hexit (b .&. 0x0f) : xs
-      hexit = intToDigit . fromIntegral :: Word8 -> Char
+  show (Digest d) = showHex d
 
 -- | A salt. Equality comparisons on this type are variable-time.
 newtype Salt = Salt ByteString
@@ -57,3 +52,6 @@ noSalt = Salt ByteString.empty
 -- this type are variable-time.
 newtype SecretKey = SecretKey ByteString
   deriving (Eq, Ord, Show)
+
+showHex :: ByteString -> String
+showHex = ByteString.Char8.unpack . ByteString.Base16.encode
\ No newline at end of file
diff --git a/src/Data/HMAC.hs b/src/Data/HMAC.hs
index c6edca3..d8c36f1 100644
--- a/src/Data/HMAC.hs
+++ b/src/Data/HMAC.hs
@@ -59,7 +59,7 @@ import BTLS.BoringSSL.HMAC
 import BTLS.BoringSSL.Mem (cryptoMemcmp)
 import BTLS.Buffer (onBufferOfMaxSize)
 import BTLS.Result (Error, check)
-import BTLS.Types (Algorithm(Algorithm), Digest(Digest), SecretKey(SecretKey))
+import BTLS.Types (Algorithm(Algorithm), SecretKey(SecretKey), showHex)
 import Data.Digest (md5, sha1, sha224, sha256, sha384, sha512)
 
 -- | A hash-based message authentication code. Equality comparisons on this type
@@ -74,7 +74,7 @@ instance Eq HMAC where
           (==0) <$> cryptoMemcmp a' b' size
 
 instance Show HMAC where
-  show (HMAC m) = show (Digest m)
+  show (HMAC m) = showHex m
 
 -- | Creates an HMAC according to the given 'Algorithm'.
 hmac :: Algorithm -> SecretKey -> Lazy.ByteString -> Either [Error] HMAC
-- 
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