Initial commit

bundled/Crypto/Random/Entropy/Backend.hs

@@ -0,0 +1,57 @@
+-- |
+-- Module      : Crypto.Random.Entropy.Backend
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : stable
+-- Portability : good
+--
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ExistentialQuantification #-}
+module Crypto.Random.Entropy.Backend
+    ( EntropyBackend
+    , supportedBackends
+    , gatherBackend
+    ) where
+
+import Foreign.Ptr
+import Data.Proxy
+import Data.Word (Word8)
+import Crypto.Random.Entropy.Source
+#ifdef SUPPORT_RDRAND
+import Crypto.Random.Entropy.RDRand
+#endif
+#ifdef WINDOWS
+import Crypto.Random.Entropy.Windows
+#else
+import Crypto.Random.Entropy.Unix
+#endif
+
+-- | All supported backends 
+supportedBackends :: [IO (Maybe EntropyBackend)]
+supportedBackends =
+    [
+#ifdef SUPPORT_RDRAND
+    openBackend (Proxy :: Proxy RDRand),
+#endif
+#ifdef WINDOWS
+    openBackend (Proxy :: Proxy WinCryptoAPI)
+#else
+    openBackend (Proxy :: Proxy DevRandom), openBackend (Proxy :: Proxy DevURandom)
+#endif
+    ]
+
+-- | Any Entropy Backend
+data EntropyBackend = forall b . EntropySource b => EntropyBackend b
+
+-- | Open a backend handle
+openBackend :: EntropySource b => Proxy b -> IO (Maybe EntropyBackend)
+openBackend b = fmap EntropyBackend `fmap` callOpen b
+  where callOpen :: EntropySource b => Proxy b -> IO (Maybe b)
+        callOpen _ = entropyOpen
+
+-- | Gather randomness from an open handle
+gatherBackend :: EntropyBackend -- ^ An open Entropy Backend
+              -> Ptr Word8      -- ^ Pointer to a buffer to write to
+              -> Int            -- ^ number of bytes to write
+              -> IO Int         -- ^ return the number of bytes actually written
+gatherBackend (EntropyBackend backend) ptr n = entropyGather backend ptr n