From 100fc7dc0c7ce85aad0e413b97a90b98185326ef Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@google.com>
Date: Tue, 25 Sep 2018 18:13:26 -0400
Subject: Give `Algorithm` a `Show` instance

---
 btls.cabal                    |  1 +
 src/BTLS/BoringSSL/Digest.chs |  3 +++
 src/BTLS/BoringSSL/Obj.chs    | 23 +++++++++++++++++++++++
 src/BTLS/Types.hs             | 14 +++++++++++++-
 tests/Data/DigestTests.hs     | 16 +++++++++++++++-
 5 files changed, 55 insertions(+), 2 deletions(-)
 create mode 100644 src/BTLS/BoringSSL/Obj.chs

diff --git a/btls.cabal b/btls.cabal
index cd5a477..0722a9c 100644
--- a/btls.cabal
+++ b/btls.cabal
@@ -78,6 +78,7 @@ library
                      , BTLS.BoringSSL.HKDF
                      , BTLS.BoringSSL.HMAC
                      , BTLS.BoringSSL.Mem
+                     , BTLS.BoringSSL.Obj
                      , BTLS.BoringSSL.Rand
                      , BTLS.Buffer
                      , BTLS.CreateWithFinalizer
diff --git a/src/BTLS/BoringSSL/Digest.chs b/src/BTLS/BoringSSL/Digest.chs
index c919125..793cc68 100644
--- a/src/BTLS/BoringSSL/Digest.chs
+++ b/src/BTLS/BoringSSL/Digest.chs
@@ -19,6 +19,7 @@ module BTLS.BoringSSL.Digest
   , mallocEVPMDCtx
   , evpDigestInitEx, evpDigestUpdate, evpDigestFinalEx
   , evpMaxMDSize
+  , evpMDType
   ) where
 
 import Data.ByteString (ByteString)
@@ -63,6 +64,8 @@ foreign import ccall "&btlsFinalizeEVPMDCtx"
 evpMaxMDSize :: Int
 evpMaxMDSize = {#const EVP_MAX_MD_SIZE#}
 
+{#fun pure EVP_MD_type as evpMDType {`Ptr EVPMD'} -> `Int'#}
+
 instance Storable EVPMDCtx where
   sizeOf _ = {#sizeof EVP_MD_CTX#}
   alignment _ = {#alignof EVP_MD_CTX#}
diff --git a/src/BTLS/BoringSSL/Obj.chs b/src/BTLS/BoringSSL/Obj.chs
new file mode 100644
index 0000000..a337ad5
--- /dev/null
+++ b/src/BTLS/BoringSSL/Obj.chs
@@ -0,0 +1,23 @@
+-- Copyright 2018 Google LLC
+--
+-- Licensed under the Apache License, Version 2.0 (the "License"); you may not
+-- use this file except in compliance with the License. You may obtain a copy of
+-- the License at
+--
+--     https://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+-- WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+-- License for the specific language governing permissions and limitations under
+-- the License.
+
+module BTLS.BoringSSL.Obj
+  ( objNID2SN
+  ) where
+
+import Foreign.C (CString)
+
+#include <openssl/obj.h>
+
+{#fun pure OBJ_nid2sn as objNID2SN {`Int'} -> `CString'#}
diff --git a/src/BTLS/Types.hs b/src/BTLS/Types.hs
index 4a4e518..6abd632 100644
--- a/src/BTLS/Types.hs
+++ b/src/BTLS/Types.hs
@@ -18,13 +18,25 @@ import Data.ByteString (ByteString)
 import qualified Data.ByteString as ByteString
 import qualified Data.ByteString.Base16 as ByteString.Base16
 import qualified Data.ByteString.Char8 as ByteString.Char8
-import Foreign (Ptr)
+import Foreign (Ptr, nullPtr)
+import Foreign.C (peekCString)
+import Foreign.Marshal.Unsafe (unsafeLocalState)
 
 import BTLS.BoringSSL.Base (EVPMD)
+import BTLS.BoringSSL.Digest (evpMDType)
+import BTLS.BoringSSL.Obj (objNID2SN)
 
 -- | A cryptographic hash function.
 newtype Algorithm = Algorithm (Ptr EVPMD)
 
+instance Eq Algorithm where
+  Algorithm a == Algorithm b = evpMDType a == evpMDType b
+
+instance Show Algorithm where
+  show (Algorithm md) =
+    let sn = objNID2SN (evpMDType md) in
+    if sn == nullPtr then "<algorithm>" else unsafeLocalState (peekCString sn)
+
 -- | Context or application-specific information. Equality comparisons on this
 -- type are variable-time.
 newtype AssociatedData = AssociatedData ByteString
diff --git a/tests/Data/DigestTests.hs b/tests/Data/DigestTests.hs
index d56c3d8..cb62b55 100644
--- a/tests/Data/DigestTests.hs
+++ b/tests/Data/DigestTests.hs
@@ -15,13 +15,27 @@
 module Data.DigestTests (tests) where
 
 import Test.Tasty (TestTree, testGroup)
+import Test.Tasty.HUnit ((@?), testCase)
 
+import Data.Digest (md5, sha1, sha224, sha256, sha384, sha512)
 import qualified Data.Digest.MD5Tests
 import qualified Data.Digest.SHA1Tests
 import qualified Data.Digest.SHA2Tests
 
 tests :: TestTree
 tests = testGroup "Data.Digest"
-  [ Data.Digest.MD5Tests.tests
+  [ showTests
+  , Data.Digest.MD5Tests.tests
   , Data.Digest.SHA1Tests.tests
   , Data.Digest.SHA2Tests.tests ]
+
+showTests = testGroup "show"
+  [ testNonEmpty "MD5" (show md5)
+  , testNonEmpty "SHA-1" (show sha1)
+  , testNonEmpty "SHA-224" (show sha224)
+  , testNonEmpty "SHA-256" (show sha256)
+  , testNonEmpty "SHA-384" (show sha384)
+  , testNonEmpty "SHA-512" (show sha512) ]
+  where
+    testNonEmpty description string = testCase description $
+      not (null string) @? "expected: nonempty string\n but got: " ++ show string
-- 
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