Remove DRBG dependency

1 files changed, 29 insertions, 0 deletions

diff --git a/src/Verismith/Utils.hs b/src/Verismith/Utils.hs
new file mode 100644
index 0000000..1f5dd01
--- /dev/null
+++ b/src/Verismith/Utils.hs
@@ -0,0 +1,29 @@
+{-|
+Module      : Verismith
+Description : Verismith
+Copyright   : (c) 2020, Yann Herklotz
+License     : GPL-3
+Maintainer  : yann [at] yannherklotz [dot] com
+Stability   : experimental
+Portability : POSIX
+-}
+
+module Verismith.Utils
+  (generateByteString)
+where
+
+import System.Random (mkStdGen, newStdGen, randoms)
+import Data.ByteString (ByteString, pack)
+
+generateByteString :: (Maybe Int) -> Int -> Int -> IO [ByteString]
+generateByteString mseed size n = do
+    fmap pack . chunksOf size . take (size * n) . randoms <$>
+      case mseed of
+        Just seed' -> return $ mkStdGen seed'
+        Nothing    -> newStdGen
+  where
+    chunksOf i _ | i <= 0 = error $ "chunksOf, number must be positive, got " ++ show i
+    chunksOf i xs = repeatedly (splitAt i) xs
+    repeatedly _ [] = []
+    repeatedly f as = b : repeatedly f as'
+      where (b, as') = f as