3 -- import qualified Data.ByteString.Lazy as BL
4 import qualified Data.ByteString.Char8 as BC
5 import qualified Data.Map.Strict as M
6 import qualified Text.Parsec.ByteString as ParsecBS
7 import Text.ParserCombinators.Parsec
8 import Control.Applicative ((<*))
18 type InfoDict = M.Map BVal BVal
20 instance Show BVal where
21 show (Bint i) = show i
22 show (Bstr s) = "\"" ++ BC.unpack s ++ "\""
23 show (Blist xs) = show xs
24 show (Bdict m) = show m
27 -- >>> import Data.Either
31 -- >>> parse bencStr "Bstr" (BC.pack "4:spam")
33 -- >>> parse bencStr "Bstr" (BC.pack "0:")
35 -- >>> parse bencStr "Bstr" (BC.pack "0:hello")
38 bencStr :: ParsecBS.Parser BC.ByteString
39 bencStr = do _ <- spaces
40 ds <- many1 digit <* char ':'
41 s <- count (read ds) anyChar
46 -- >>> parse bencInt "Bint" (BC.pack "i42e")
48 -- >>> parse bencInt "Bint" (BC.pack "i123e")
50 -- >>> parse bencInt "Bint" (BC.pack "i1e")
52 -- >>> parse bencInt "Bint" (BC.pack "i0e")
54 -- >>> parse bencInt "Bint" (BC.pack "i-1e")
56 -- >>> isLeft $ parse bencInt "Bint" (BC.pack "i01e")
58 -- >>> isLeft $ parse bencInt "Bint" (BC.pack "i00e")
60 -- >>> isLeft $ parse bencInt "Bint" (BC.pack "i002e")
62 bencInt :: ParsecBS.Parser Integer
63 bencInt = do _ <- spaces
64 ds <- between (char 'i') (char 'e') numbers
66 where numbers = do d' <- char '-' <|> digit
69 parseNumber '0' [] = return "0"
70 parseNumber '0' _ = unexpected "numbers cannot be left-padded with zeros"
71 parseNumber '-' [] = unexpected "sign without any digits"
72 parseNumber '-' (d'':_) | d'' == '0' = unexpected "numbers cannot be left-padded with zeros"
73 parseNumber d'' ds'' = return (d'':ds'')
77 -- >>> parse bencList "Blist" (BC.pack "le")
79 -- >>> parse bencList "Blist" (BC.pack "l4:spam4:eggse")
80 -- Right ["spam","eggs"]
81 -- >>> parse bencList "Blist" (BC.pack "l4:spami42ee")
83 -- >>> parse bencList "Blist" (BC.pack "l4:spam4:eggsli42eee")
84 -- Right ["spam","eggs",[42]]
85 bencList :: ParsecBS.Parser [BVal]
86 bencList = do _ <- spaces
87 between (char 'l') (char 'e') (many bencVal)
91 -- >>> parse bencDict "Bdict" (BC.pack "de")
92 -- Right (fromList [])
93 -- >>> parse bencDict "Bdict" (BC.pack "d3:cow3:moo4:spam4:eggse")
94 -- Right (fromList [("cow","moo"),("spam","eggs")])
95 -- >>> parse bencDict "Bdict" (BC.pack "d4:spaml1:a1:bee")
96 -- Right (fromList [("spam",["a","b"])])
97 -- >>> parse bencDict "Bdict" (BC.pack "d9:publisher3:bob17:publisher-webpage15:www.example.com18:publisher.location4:homee")
98 -- Right (fromList [("publisher","bob"),("publisher-webpage","www.example.com"),("publisher.location","home")])
99 bencDict :: ParsecBS.Parser (M.Map BVal BVal)
100 bencDict = between (char 'd') (char 'e') $ M.fromList <$> many kvpair
101 where kvpair = do k <- bencStr
105 bencVal :: ParsecBS.Parser BVal
106 bencVal = Bstr <$> bencStr <|>
108 Blist <$> bencList <|>
111 decode :: BC.ByteString -> Either ParseError BVal
112 decode = parse bencVal "BVal"
114 -- given an input dict or int or string, encode
115 -- it into a bencoded bytestring.
116 -- | encode bencoded-values
118 -- >>> encode (Bstr (BC.pack ""))
120 -- >>> encode (Bstr (BC.pack "spam"))
122 -- >>> encode (Bint 0)
124 -- >>> encode (Bint 42)
126 -- >>> encode (Blist [(Bstr (BC.pack "spam")), (Bstr (BC.pack "eggs"))])
128 -- >>> encode (Blist [])
130 -- >>> encode (Bdict (M.fromList [(Bstr $ BC.pack "spam", Bstr $ BC.pack "eggs")]))
132 encode :: BVal -> String
133 encode (Bstr bs) = let s = BC.unpack bs
134 in show (length s) ++ ":" ++ s
135 encode (Bint i) = "i" ++ show i ++ "e"
136 encode (Blist xs) = "l" ++ encodeList xs ++ "e"
137 where encodeList = foldr ((++) . encode) ""
138 encode (Bdict d) = "d" ++ encodeDict d ++ "e"
139 where encodeDict m = concat [encode k ++ encode (m M.! k) | k <- M.keys m]