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{-# LANGUAGE ForeignFunctionInterface #-}
-- |
-- Module : Crypto.Random.Entropy.RDRand
-- License : BSD-style
-- Maintainer : Vincent Hanquez <vincent@snarc.org>
-- Stability : experimental
-- Portability : Good
module Crypto.Random.Entropy.RDRand (
RDRand,
) where
import Crypto.Random.Entropy.Source
import Data.Word (Word8)
import Foreign.C.Types
import Foreign.Ptr
foreign import ccall unsafe "crypton_cpu_has_rdrand"
c_cpu_has_rdrand :: IO CInt
foreign import ccall unsafe "crypton_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)
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