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Diffstat (limited to 'Codec/MIME/Base64.hs')
| -rw-r--r-- | Codec/MIME/Base64.hs | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/Codec/MIME/Base64.hs b/Codec/MIME/Base64.hs new file mode 100644 index 0000000..f60419b --- /dev/null +++ b/Codec/MIME/Base64.hs @@ -0,0 +1,147 @@ +-------------------------------------------------------------------- +-- | +-- Module : Codec.MIME.Base64 +-- Copyright : (c) 2006-2009, Galois, Inc. +-- License : BSD3 +-- +-- Maintainer: Sigbjorn Finne <sigbjorn.finne@gmail.com> +-- Stability : provisional +-- Portability: portable +-- +-- +-- Base64 decoding and encoding routines, multiple entry +-- points for either depending on use and level of control +-- wanted over the encoded output (and its input form on the +-- decoding side.) +-- +-------------------------------------------------------------------- +module Codec.MIME.Base64 + ( encodeRaw -- :: Bool -> String -> [Word8] + , encodeRawString -- :: Bool -> String -> String + , encodeRawPrim -- :: Bool -> Char -> Char -> [Word8] -> String + + , formatOutput -- :: Int -> Maybe String -> String -> String + + , decode -- :: String -> [Word8] + , decodeToString -- :: String -> String + , decodePrim -- :: Char -> Char -> String -> [Word8] + ) where + +import Data.Bits +import Data.Char +import Data.Word +import Data.Maybe + +encodeRawString :: Bool -> String -> String +encodeRawString trail xs = encodeRaw trail (map (fromIntegral.ord) xs) + +-- | @formatOutput n mbLT str@ formats @str@, splitting it +-- into lines of length @n@. The optional value lets you control what +-- line terminator sequence to use; the default is CRLF (as per MIME.) +formatOutput :: Int -> Maybe String -> String -> String +formatOutput n mbTerm str + | n <= 0 = error ("Codec.MIME.Base64.formatOutput: negative line length " ++ show n) + | otherwise = chop n str + where + crlf :: String + crlf = fromMaybe "\r\n" mbTerm + + chop _ "" = "" + chop i xs = + case splitAt i xs of + (as,"") -> as + (as,bs) -> as ++ crlf ++ chop i bs + +encodeRaw :: Bool -> [Word8] -> String +encodeRaw trail bs = encodeRawPrim trail '+' '/' bs + +-- | @encodeRawPrim@ lets you control what non-alphanum characters to use +-- (The base64url variation uses @*@ and @-@, for instance.) +-- No support for mapping these to multiple characters in the output though. +encodeRawPrim :: Bool -> Char -> Char -> [Word8] -> String +encodeRawPrim trail ch62 ch63 ls = encoder ls + where + trailer xs ys + | not trail = xs + | otherwise = xs ++ ys + f = fromB64 ch62 ch63 + encoder [] = [] + encoder [x] = trailer (take 2 (encode3 f x 0 0 "")) "==" + encoder [x,y] = trailer (take 3 (encode3 f x y 0 "")) "=" + encoder (x:y:z:ws) = encode3 f x y z (encoder ws) + +encode3 :: (Word8 -> Char) -> Word8 -> Word8 -> Word8 -> String -> String +encode3 f a b c rs = + f (low6 (w24 `shiftR` 18)) : + f (low6 (w24 `shiftR` 12)) : + f (low6 (w24 `shiftR` 6)) : + f (low6 w24) : rs + where + w24 :: Word32 + w24 = (fromIntegral a `shiftL` 16) + + (fromIntegral b `shiftL` 8) + + fromIntegral c + +decodeToString :: String -> String +decodeToString str = map (chr.fromIntegral) $ decode str + +decode :: String -> [Word8] +decode str = decodePrim '+' '/' str + +decodePrim :: Char -> Char -> String -> [Word8] +decodePrim ch62 ch63 str = decoder $ takeUntilEnd str + where + takeUntilEnd "" = [] + takeUntilEnd ('=':_) = [] + takeUntilEnd (x:xs) = + case toB64 ch62 ch63 x of + Nothing -> takeUntilEnd xs + Just b -> b : takeUntilEnd xs + +decoder :: [Word8] -> [Word8] +decoder [] = [] +decoder [x] = take 1 (decode4 x 0 0 0 []) +decoder [x,y] = take 1 (decode4 x y 0 0 []) -- upper 4 bits of second val are known to be 0. +decoder [x,y,z] = take 2 (decode4 x y z 0 []) +decoder (x:y:z:w:xs) = decode4 x y z w (decoder xs) + +decode4 :: Word8 -> Word8 -> Word8 -> Word8 -> [Word8] -> [Word8] +decode4 a b c d rs = + (lowByte (w24 `shiftR` 16)) : + (lowByte (w24 `shiftR` 8)) : + (lowByte w24) : rs + where + w24 :: Word32 + w24 = + (fromIntegral a) `shiftL` 18 .|. + (fromIntegral b) `shiftL` 12 .|. + (fromIntegral c) `shiftL` 6 .|. + (fromIntegral d) + +toB64 :: Char -> Char -> Char -> Maybe Word8 +toB64 a b ch + | ch >= 'A' && ch <= 'Z' = Just (fromIntegral (ord ch - ord 'A')) + | ch >= 'a' && ch <= 'z' = Just (26 + fromIntegral (ord ch - ord 'a')) + | ch >= '0' && ch <= '9' = Just (52 + fromIntegral (ord ch - ord '0')) + | ch == a = Just 62 + | ch == b = Just 63 + | otherwise = Nothing + +fromB64 :: Char -> Char -> Word8 -> Char +fromB64 ch62 ch63 x + | x < 26 = chr (ord 'A' + xi) + | x < 52 = chr (ord 'a' + (xi-26)) + | x < 62 = chr (ord '0' + (xi-52)) + | x == 62 = ch62 + | x == 63 = ch63 + | otherwise = error ("fromB64: index out of range " ++ show x) + where + xi :: Int + xi = fromIntegral x + +low6 :: Word32 -> Word8 +low6 x = fromIntegral (x .&. 0x3f) + +lowByte :: Word32 -> Word8 +lowByte x = (fromIntegral x) .&. 0xff + |