Rule.hs

{-|
Module      : Graphics.Autom.Rule
Description : Helper functions for working with rules
Copyright   : (c) Christopher Howard, 2016
License     : GPL-3
Maintainer  : ch.howard@zoho.com

These helper functions can be useful when choosing rule values.
-}
module Graphics.Autom.Rule where

import Prelude (($), flip, fromIntegral)
import Data.Word (Word8, Word32)
import Data.Bits ((.&.), shift, (.|.))

-- |Concatenates four 8-bit values.
fromQuad :: Word8 -> Word8 -> Word8 -> Word8 -> Word32
fromQuad n3 n2 n1 n0 = n3' .|. n2' .|. n1' .|. n0'
    where n3' = shift (fromIntegral n3 :: Word32) 24
          n2' = shift (fromIntegral n2 :: Word32) 16
          n1' = shift (fromIntegral n1 :: Word32) 8
          n0' = fromIntegral n0 :: Word32

-- |Splits a 32-bit value into four 8-bit values.
toQuad :: Word32 -> (Word8, (Word8, (Word8, Word8)))
toQuad x = (y3, (y2, (y1, y0)))
  where y3 = fromIntegral $ flip shift (-24) (x .&. 0xFF000000)
        y2 = fromIntegral $ flip shift (-16) (x .&. 0xFF0000)
        y1 = fromIntegral $ flip shift (-8) (x .&. 0xFF00)
        y0 = fromIntegral $ x .&. 0xFF