Reminds me of this code from Data.Binary:
unroll :: Integer -> [Word8] unroll = unfoldr step where step 0 = Nothing step i = Just (fromIntegral i, i `shiftR` 8)
roll :: [Word8] -> Integer roll = foldr unstep 0 where unstep b a = a `shiftL` 8 .|. fromIntegral b
Which is a bit stream-fusion inspired, I must admit.
But better than what is in Codec.Utils:
toBase x = map fromIntegral . reverse . map (flip mod x) . takeWhile (/=0) . iterate (flip div x)
-- | Take a number a convert it to base n as a list of octets.
toOctets :: (Integral a, Integral b) => a -> b -> [Octet] toOctets n x = (toBase n . fromIntegral) x
powersOf n = 1 : (map (*n) (powersOf n))
-- | Take a list of octets (a number expressed in base n) and convert it -- to a number.
fromOctets :: (Integral a, Integral b) => a -> [Octet] -> b fromOctets n x = fromIntegral $ sum $ zipWith (*) (powersOf n) (reverse (map fromIntegral x))
It seems a shame that everyone has to roll their own. Dominic.