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bundled/Crypto/Random/Entropy/RDRand.hs

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+-- |
+-- Module      : Crypto.Random.Entropy.RDRand
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : experimental
+-- Portability : Good
+--
+{-# LANGUAGE ForeignFunctionInterface #-}
+module Crypto.Random.Entropy.RDRand
+    ( RDRand
+    ) where
+
+import Foreign.Ptr
+import Foreign.C.Types
+import Data.Word (Word8)
+import Crypto.Random.Entropy.Source
+
+foreign import ccall unsafe "cryptonite_cpu_has_rdrand"
+   c_cpu_has_rdrand :: IO CInt
+
+foreign import ccall unsafe "cryptonite_get_rand_bytes"
+  c_get_rand_bytes :: Ptr Word8 -> CInt -> IO CInt
+
+-- | Fake handle to Intel RDRand entropy CPU instruction
+data RDRand = RDRand
+
+instance EntropySource RDRand where
+    entropyOpen     = rdrandGrab
+    entropyGather _ = rdrandGetBytes
+    entropyClose  _ = return ()
+
+rdrandGrab :: IO (Maybe RDRand)
+rdrandGrab = supported `fmap` c_cpu_has_rdrand
+  where supported 0 = Nothing
+        supported _ = Just RDRand
+
+rdrandGetBytes :: Ptr Word8 -> Int -> IO Int
+rdrandGetBytes ptr sz = fromIntegral `fmap` c_get_rand_bytes ptr (fromIntegral sz)