Utils.hs

{- arch-tag: Bit utilities main file
Copyright (C) 2004-2005 John Goerzen <jgoerzen@complete.org>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-}

{- |
   Module     : Data.Bits.Utils
   Copyright  : Copyright (C) 2004-2005 John Goerzen
   License    : GNU GPL, version 2 or above

   Maintainer : John Goerzen <jgoerzen@complete.org> 
   Stability  : provisional
   Portability: portable to platforms with rawSystem

  Bit-related utilities

Written by John Goerzen, jgoerzen\@complete.org
-}

module Data.Bits.Utils(getBytes, fromBytes,
                     c2w8, s2w8, w82c, w82s)
where
import Data.Bits
import Data.Word

{- | Returns a list representing the bytes that comprise a data type.

Example:

> getBytes (0x12345678::Int) -> [0x12, 0x34, 0x56, 0x78]
-}
getBytes :: (Integral a, Bounded a, Bits a) => a -> [a]
getBytes input = 
    let getByte _ 0 = []
        getByte x remaining = (x .&. 0xff) : getByte (shiftR x 8) (remaining - 1)
        in
        if (bitSize input `mod` 8) /= 0
           then error "Input data bit size must be a multiple of 8"
           else reverse $ getByte input (bitSize input `div` 8)

{- | The opposite of 'getBytes', this function builds a number based on
its component bytes.

Results are undefined if any components of the input list are > 0xff!

-}

fromBytes :: (Bits a) => [a] -> a
fromBytes input =
    let dofb accum [] = accum
        dofb accum (x:xs) = dofb ((shiftL accum 8) .|. x) xs
        in
        dofb 0 input

{- | Converts a Char to a Word8. -}
c2w8 :: Char -> Word8
c2w8 = fromIntegral . fromEnum

{- | Converts a String to a [Word8]. -}
s2w8 :: String -> [Word8]
s2w8 = map c2w8

{- | Converts a Word8 to a Char. -}
w82c :: Word8 -> Char
w82c = toEnum . fromIntegral

{- | Converts a [Word8] to a String. -}
w82s :: [Word8] -> String
w82s = map w82c