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bundled/Crypto/Random/Entropy/Unsafe.hs

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+-- |
+-- Module      : Crypto.Random.Entropy.Unsafe
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : experimental
+-- Portability : Good
+--
+module Crypto.Random.Entropy.Unsafe
+    ( replenish
+    , module Crypto.Random.Entropy.Backend
+    ) where
+
+import Data.Word (Word8)
+import Foreign.Ptr (Ptr, plusPtr)
+import Crypto.Random.Entropy.Backend
+
+-- | Refill the entropy in a buffer
+--
+-- Call each entropy backend in turn until the buffer has
+-- been replenished.
+--
+-- If the buffer cannot be refill after 3 loopings, this will raise
+-- an User Error exception
+replenish :: Int -> [EntropyBackend] -> Ptr Word8 -> IO ()
+replenish _        []       _   = fail "cryptonite: random: cannot get any source of entropy on this system"
+replenish poolSize backends ptr = loop 0 backends ptr poolSize
+  where loop :: Int -> [EntropyBackend] -> Ptr Word8 -> Int -> IO ()
+        loop retry [] p n | n == 0     = return ()
+                          | retry == 3 = error "cryptonite: random: cannot fully replenish"
+                          | otherwise  = loop (retry+1) backends p n
+        loop _     (_:_)  _ 0 = return ()
+        loop retry (b:bs) p n = do
+            r <- gatherBackend b p n
+            loop retry bs (p `plusPtr` r) (n - r)