{- |

Module : $Header$

Description : Base64 character conversions

Copyright : (c) Ian Lynagh, 2005, 2007, Christian Maeder, DFKI GmbH 2008

License : GPLv2 or higher, see LICENSE.txt

Maintainer : Christian.Maeder@dfki.de

Stability : provisional

Portability : portable

base64 character conversions

-}

module ATerm.Base64

( toBase64Int

, toBase64Char

, isBase64Char

, ord0

) where

import Data.Char

{-

toBase64 :: [Char]

toBase64 =

[ 'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P',

'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f',

'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',

'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/'

]

-}

toBase64Int :: Char -> Int

toBase64Int c

| isUpper c = ord c - ordA

| isLower c = ord c - i71

| isDigit c = ord c + i4

| c == '+' = 62

| c == '/' = 63

| otherwise = error "toBase64Int"

toBase64Char :: Int -> Char

toBase64Char i

| i < 26 = chr (ordA + i)

| i < 52 = chr (i71 + i)

| i < 62 = chr (i - i4)

| i == 62 = '+'

| i == 63 = '/'

| otherwise = error "toBase64Char"

isBase64Char :: Char -> Bool

isBase64Char c = isAscii c && (isAlphaNum c || c == '+' || c == '/')

-- a couple of constants

ordA :: Int

ordA = ord 'A'

i71 :: Int

i71 = ord 'a' - 26

ord0 :: Int

ord0 = ord '0'

i4 :: Int

i4 = 52 - ord0