From ff361643054f17373b22d8248f80138cb6ed951f Mon Sep 17 00:00:00 2001
From: Tobias Florek <tob@butter.sh>
Date: Fri, 12 Jun 2015 20:52:15 +0200
Subject: [PATCH] copy withRandomBytes from crypto-random

---
 Crypto/Random.hs | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/Crypto/Random.hs b/Crypto/Random.hs
index d270b82..a8cffcc 100644
--- a/Crypto/Random.hs
+++ b/Crypto/Random.hs
@@ -13,6 +13,7 @@ module Crypto.Random
     , drgNew
     , drgNewTest
     , withDRG
+    , withRandomBytes
     , DRG(..)
     -- * Random abstraction
     , MonadRandom(..)
@@ -22,7 +23,7 @@ module Crypto.Random
 import Crypto.Random.Types
 import Crypto.Random.ChaChaDRG
 import Crypto.Random.Entropy
-import Data.ByteArray (ScrubbedBytes)
+import Data.ByteArray (ByteArray, ScrubbedBytes)
 import Crypto.Internal.Imports
 
 -- | Create a new DRG from system entropy
@@ -38,3 +39,10 @@ drgNew = initialize <$> (getEntropy 40 :: IO ScrubbedBytes)
 -- has been properly randomly generated.
 drgNewTest :: (Word64, Word64, Word64, Word64, Word64) -> ChaChaDRG
 drgNewTest = initializeWords
+
+-- | Generate @len random bytes and mapped the bytes to the function @f.
+--
+-- This is equivalent to use Control.Arrow 'first' with 'randomBytesGenerate'
+withRandomBytes :: (ByteArray ba, DRG g) => g -> Int -> (ba -> a) -> (a, g)
+withRandomBytes rng len f = (f bs, rng')
+  where (bs, rng') = randomBytesGenerate len rng