-- |
-- Module      : Foundation.System.Entropy
-- License     : BSD-style
-- Maintainer  : Foundation
-- Stability   : stable
-- Portability : good
--
{-# LANGUAGE CPP #-}
module Foundation.System.Entropy
    ( getEntropy
    ) where


import           Basement.Compat.Base
import           Basement.Types.OffsetSize
import qualified Basement.UArray.Mutable as A
import qualified Basement.UArray as A
import           Control.Exception
import           Foreign.Ptr
import           Foundation.Numerical

import           Foundation.System.Entropy.Common
#ifdef mingw32_HOST_OS
import           Foundation.System.Entropy.Windows
#else
import           Foundation.System.Entropy.Unix
#endif

-- | Get some of the system entropy
getEntropy :: CountOf Word8 -> IO (A.UArray Word8)
getEntropy :: CountOf Word8 -> IO (UArray Word8)
getEntropy n :: CountOf Word8
n@(CountOf Int
x) = do
    m <- CountOf Word8 -> IO (MUArray Word8 (PrimState IO))
forall (prim :: * -> *) ty.
(PrimMonad prim, PrimType ty) =>
CountOf ty -> prim (MUArray ty (PrimState prim))
A.newPinned CountOf Word8
n
    bracket entropyOpen entropyClose $ \EntropyCtx
ctx -> MUArray Word8 (PrimState IO) -> (Ptr Word8 -> IO ()) -> IO ()
forall (prim :: * -> *) ty a.
(PrimMonad prim, PrimType ty) =>
MUArray ty (PrimState prim) -> (Ptr ty -> prim a) -> prim a
A.withMutablePtr MUArray Word8 RealWorld
MUArray Word8 (PrimState IO)
m ((Ptr Word8 -> IO ()) -> IO ()) -> (Ptr Word8 -> IO ()) -> IO ()
forall a b. (a -> b) -> a -> b
$ EntropyCtx -> Int -> Ptr Word8 -> IO ()
loop EntropyCtx
ctx Int
x
    A.unsafeFreeze m
  where
    loop :: EntropyCtx -> Int -> Ptr Word8 -> IO ()
    loop :: EntropyCtx -> Int -> Ptr Word8 -> IO ()
loop EntropyCtx
_   Int
0 Ptr Word8
_ = () -> IO ()
forall a. a -> IO a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
    loop EntropyCtx
ctx Int
i Ptr Word8
p = do
        let chSz :: Int
chSz = Int -> Int -> Int
forall a. Ord a => a -> a -> a
min Int
entropyMaximumSize Int
i
        r <- EntropyCtx -> Ptr Word8 -> Int -> IO Bool
entropyGather EntropyCtx
ctx Ptr Word8
p Int
chSz
        if r
            then loop ctx (i-chSz) (p `plusPtr` chSz)
            else throwIO EntropySystemMissing