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1 files changed, 27 insertions, 0 deletions

diff --git a/overlays/spm/server/Crypto/Random/Instances.hs b/overlays/spm/server/Crypto/Random/Instances.hs
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+++ b/overlays/spm/server/Crypto/Random/Instances.hs
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+{-# OPTIONS_GHC -fno-warn-orphans #-}
+
+module Crypto.Random.Instances () where
+
+import Prelude
+import Crypto.Random
+import System.Random
+
+import qualified Data.ByteString as BS
+
+import Data.Bits
+
+
+instance RandomGen ChaChaDRG where
+  split = flip withDRG drgNew
+
+  genWord64 g = withRandomBytes g 8 $ \case
+    (map fromIntegral . BS.unpack -> [b1, b2, b3, b4, b5, b6, b7, b8])
+      ->     b1 `shiftL` 56
+         .|. b2 `shiftL` 48
+         .|. b3 `shiftL` 40
+         .|. b4 `shiftL` 32
+         .|. b5 `shiftL` 24
+         .|. b6 `shiftL` 16
+         .|. b7 `shiftL` 8
+         .|. b8
+    _other -> error "withRandomBytes did not return correct number of bytes"