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-- |
-- 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
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