1 -- | |
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2 -- Module : Codec.Binary.Base64 |
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3 -- Copyright : (c) 2007 Magnus Therning |
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4 -- License : BSD3 |
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5 -- |
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6 -- Implemented as specified in RFC 4648 |
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7 -- (<http://tools.ietf.org/html/rfc4648>). |
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8 -- |
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9 -- Further documentation and information can be found at |
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10 -- <http://www.haskell.org/haskellwiki/Library/Data_encoding>. |
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11 module Codec.Binary.Base64 |
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12 ( encode |
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13 , decode |
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14 , decode' |
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15 , chop |
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16 , unchop |
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17 ) where |
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18 |
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19 import Control.Monad |
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20 import Data.Array |
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21 import Data.Bits |
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22 import Data.Maybe |
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23 import Data.Word |
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24 import qualified Data.Map as M |
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25 |
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26 -- {{{1 enc/dec map |
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27 _encMap = |
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28 [ (0, 'A'), (1, 'B'), (2, 'C'), (3, 'D'), (4, 'E') |
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29 , (5, 'F') , (6, 'G'), (7, 'H'), (8, 'I'), (9, 'J') |
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30 , (10, 'K'), (11, 'L'), (12, 'M'), (13, 'N'), (14, 'O') |
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31 , (15, 'P'), (16, 'Q'), (17, 'R'), (18, 'S'), (19, 'T') |
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32 , (20, 'U'), (21, 'V'), (22, 'W'), (23, 'X'), (24, 'Y') |
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33 , (25, 'Z'), (26, 'a'), (27, 'b'), (28, 'c'), (29, 'd') |
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34 , (30, 'e'), (31, 'f'), (32, 'g'), (33, 'h'), (34, 'i') |
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35 , (35, 'j'), (36, 'k'), (37, 'l'), (38, 'm'), (39, 'n') |
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36 , (40, 'o'), (41, 'p'), (42, 'q'), (43, 'r'), (44, 's') |
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37 , (45, 't'), (46, 'u'), (47, 'v'), (48, 'w'), (49, 'x') |
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38 , (50, 'y'), (51, 'z'), (52, '0'), (53, '1'), (54, '2') |
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39 , (55, '3'), (56, '4'), (57, '5'), (58, '6'), (59, '7') |
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40 , (60, '8'), (61, '9'), (62, '+'), (63, '/') ] |
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41 |
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42 -- {{{1 encodeArray |
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43 encodeArray :: Array Word8 Char |
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44 encodeArray = array (0, 64) _encMap |
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45 |
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46 -- {{{1 decodeMap |
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47 decodeMap :: M.Map Char Word8 |
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48 decodeMap = M.fromList [(snd i, fst i) | i <- _encMap] |
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49 |
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50 -- {{{1 encode |
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51 -- | Encode data. |
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52 encode :: [Word8] |
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53 -> String |
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54 encode = let |
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55 pad n = take n $ repeat 0 |
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56 enc [] = "" |
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57 enc l@[o] = (++ "==") . take 2 .enc $ l ++ pad 2 |
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58 enc l@[o1, o2] = (++ "=") . take 3 . enc $ l ++ pad 1 |
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59 enc (o1:o2:o3:os) = let |
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60 i1 = o1 `shiftR` 2 |
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61 i2 = (o1 `shiftL` 4 .|. o2 `shiftR` 4) .&. 0x3f |
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62 i3 = (o2 `shiftL` 2 .|. o3 `shiftR` 6) .&. 0x3f |
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63 i4 = o3 .&. 0x3f |
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64 in (foldr (\ i s -> (encodeArray ! i) : s) "" [i1, i2, i3, i4]) ++ enc os |
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65 in enc |
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66 |
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67 -- {{{1 decode |
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68 -- | Decode data (lazy). |
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69 decode' :: String |
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70 -> [Maybe Word8] |
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71 decode' = let |
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72 pad n = take n $ repeat $ Just 0 |
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73 dec [] = [] |
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74 dec l@[Just eo1, Just eo2] = take 1 . dec $ l ++ pad 2 |
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75 dec l@[Just eo1, Just eo2, Just eo3] = take 2 . dec $ l ++ pad 1 |
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76 dec (Just eo1:Just eo2:Just eo3:Just eo4:eos) = let |
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77 o1 = eo1 `shiftL` 2 .|. eo2 `shiftR` 4 |
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78 o2 = eo2 `shiftL` 4 .|. eo3 `shiftR` 2 |
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79 o3 = eo3 `shiftL` 6 .|. eo4 |
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80 in Just o1:Just o2:Just o3:(dec eos) |
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81 dec _ = [Nothing] |
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82 in |
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83 dec . map (flip M.lookup decodeMap) . takeWhile (/= '=') |
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84 |
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85 -- | Decode data (strict). |
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86 decode :: String |
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87 -> Maybe [Word8] |
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88 decode = sequence . decode' |
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89 |
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90 -- {{{1 chop |
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91 -- | Chop up a string in parts. |
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92 -- |
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93 -- The length given is rounded down to the nearest multiple of 4. |
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94 -- |
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95 -- /Notes:/ |
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96 -- |
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97 -- * PEM requires lines that are 64 characters long. |
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98 -- |
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99 -- * MIME requires lines that are at most 76 characters long. |
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100 chop :: Int -- ^ length of individual lines |
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101 -> String |
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102 -> [String] |
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103 chop n "" = [] |
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104 chop n s = let |
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105 enc_len | n < 4 = 4 |
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106 | otherwise = n `div` 4 * 4 |
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107 in (take enc_len s) : chop n (drop enc_len s) |
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108 |
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109 -- {{{1 unchop |
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110 -- | Concatenate the strings into one long string. |
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111 unchop :: [String] |
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112 -> String |
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113 unchop = foldr (++) "" |
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