randomstr2.hs

{-# LANGUAGE PackageImports #-}

-- Fails with "*** Exception: NeedsInfiniteSeed"

module RandomStr2 where

import           "crypto-api" Crypto.Random
import           "crypto-api" Crypto.Types
import           Data.ByteString.Char8 as B
import           System.Entropy

getGen :: CryptoRandomGen g => Int -> IO g
getGen len = do
    entropy <- getEntropy len
    case newGen entropy of
        Left err -> error (show err)
        Right g' -> return g'

makeStr:: CryptoRandomGen g => ByteLength -> g -> ByteString
makeStr len g =
    case genBytes len g of
        Left err      -> B.empty
        Right (bs, _) -> bs

main :: IO ()
main = do
    let len = 12
    g <- getGen len :: IO SystemRandom
    let str = makeStr len g
    B.putStrLn str