7 -- |Yet another parser combinator. This is mostly a subset of
8 -- "Text.ParserCombinators.Parsec" but there are some differences:
10 -- * This parser works on 'Data.ByteString.Base.LazyByteString'
11 -- instead of 'Prelude.String'.
13 -- * Backtracking is the only possible behavior so there is no \"try\"
16 -- * On success, the remaining string is returned as well as the
19 -- * You can choose whether to treat reaching EOF (trying to eat one
20 -- more letter at the end of string) a fatal error or to treat it a
21 -- normal failure. If a fatal error occurs, the entire parsing
22 -- process immediately fails without trying any backtracks. The
23 -- default behavior is to treat EOF fatal.
25 -- In general, you don't have to use this module directly.
26 module Network.HTTP.Lucu.Parser
61 import Control.Monad.State.Strict hiding (state)
62 import qualified Data.ByteString.Lazy as Lazy (ByteString)
63 import qualified Data.ByteString.Lazy.Char8 as B hiding (ByteString)
64 import qualified Data.Foldable as Fold
66 import qualified Data.Sequence as Seq
67 import Data.Sequence (Seq, (|>))
69 -- |@'Parser' a@ is obviously a parser which parses and returns @a@.
70 newtype Parser a = Parser {
71 runParser :: State ParserState (ParserResult a)
77 pstInput :: Lazy.ByteString
78 , pstIsEOFFatal :: !Bool
83 data ParserResult a = Success !a
84 | IllegalInput -- 受理出來ない入力があった
85 | ReachedEOF -- 限界を越えて讀まうとした
89 -- (>>=) :: Parser a -> (a -> Parser b) -> Parser b
90 instance Monad Parser where
91 p >>= f = Parser $! do saved <- get -- 失敗した時の爲に状態を保存
94 Success a -> runParser (f a)
95 IllegalInput -> do put saved -- 状態を復歸
97 ReachedEOF -> do put saved -- 状態を復歸
99 return !x = Parser $! return $! Success x
100 fail _ = Parser $! return $! IllegalInput
102 instance Functor Parser where
103 fmap f p = p >>= return . f
105 -- |@'failP'@ is just a synonym for @'Prelude.fail'
106 -- 'Prelude.undefined'@.
108 failP = fail undefined
110 -- |@'parse' p bstr@ parses @bstr@ with @p@ and returns @(# result,
112 parse :: Parser a -> Lazy.ByteString -> (# ParserResult a, Lazy.ByteString #)
113 parse !p input -- input は lazy である必要有り。
114 = let (!result, state') = runState (runParser p) (PST input True)
116 (# result, pstInput state' #) -- pstInput state' も lazy である必要有り。
118 -- |@'parseStr' p str@ packs @str@ and parses it.
119 parseStr :: Parser a -> String -> (# ParserResult a, Lazy.ByteString #)
120 parseStr !p input -- input は lazy である必要有り。
121 = parse p (B.pack input)
124 anyChar :: Parser Char
126 do state@(PST input _) <- get
130 do put $! state { pstInput = B.tail input }
131 return (Success $! B.head input)
136 do PST input _ <- get
142 -- |@'allowEOF' p@ makes @p@ treat reaching EOF a normal failure.
143 allowEOF :: Parser a -> Parser a
145 = Parser $! do saved@(PST _ isEOFFatal) <- get
146 put $! saved { pstIsEOFFatal = False }
148 result <- runParser f
151 put $! state { pstIsEOFFatal = isEOFFatal }
156 satisfy :: (Char -> Bool) -> Parser Char
165 char :: Char -> Parser Char
166 char !c = satisfy (== c)
169 string :: String -> Parser String
171 = let bs = B.pack str
176 let (bs', rest) = B.splitAt len $ pstInput st
177 st' = st { pstInput = rest }
178 if B.length bs' < len then
190 -- |This is the backtracking alternation. There is no non-backtracking
192 (<|>) :: Parser a -> Parser a -> Parser a
194 = Parser $! do saved <- get -- 状態を保存
195 result <- runParser f
197 Success a -> return $! Success a
198 IllegalInput -> do put saved -- 状態を復歸
200 ReachedEOF -> if pstIsEOFFatal saved then
208 choice :: [Parser a] -> Parser a
209 choice = foldl (<|>) failP
212 oneOf :: [Char] -> Parser Char
213 oneOf = foldl (<|>) failP . map char
216 notFollowedBy :: Parser a -> Parser ()
218 = Parser $! do saved <- get -- 状態を保存
219 result <- runParser p
221 Success _ -> do put saved -- 状態を復歸
223 IllegalInput -> do put saved -- 状態を復歸
225 ReachedEOF -> do put saved -- 状態を復歸
230 digit = do c <- anyChar
231 if c >= '0' && c <= '9' then
237 hexDigit :: Parser Char
238 hexDigit = do c <- anyChar
239 if (c >= '0' && c <= '9') ||
240 (c >= 'a' && c <= 'f') ||
241 (c >= 'A' && c <= 'F') then
247 many :: forall a. Parser a -> Parser [a]
250 let (# result, state' #) = many' state Seq.empty
254 many' :: ParserState -> Seq a -> (# ParserResult [a], ParserState #)
256 = case runState (runParser p) st of
257 (Success a, st') -> many' st' (soFar |> a)
258 (IllegalInput, _) -> (# Success (Fold.toList soFar), st #)
259 (ReachedEOF , _) -> if pstIsEOFFatal st then
262 (# Success (Fold.toList soFar), st #)
264 manyChar :: Parser Char -> Parser Lazy.ByteString
265 manyChar !p = Parser $!
267 case scan' state 0 of
269 -> do let (bs, rest) = B.splitAt len (pstInput state)
270 state' = state { pstInput = rest }
274 -> if pstIsEOFFatal state then
277 error "internal error"
278 _ -> error "internal error"
280 scan' :: ParserState -> Int64 -> ParserResult Int64
282 = case runState (runParser p) st of
283 (Success _ , st') -> scan' st' (soFar + 1)
284 (IllegalInput, _ ) -> Success soFar
285 (ReachedEOF , _ ) -> if pstIsEOFFatal st then
291 many1 :: Parser a -> Parser [a]
297 count :: Int -> Parser a -> Parser [a]
298 count !n !p = Parser $! count' n p Seq.empty
300 -- This implementation is rather ugly but we need to make it
301 -- tail-recursive to avoid stack overflow.
302 count' :: Int -> Parser a -> Seq a -> State ParserState (ParserResult [a])
303 count' 0 _ !soFar = return $! Success $! Fold.toList soFar
304 count' !n !p !soFar = do saved <- get
305 result <- runParser p
307 Success a -> count' (n-1) p (soFar |> a)
308 IllegalInput -> do put saved
310 ReachedEOF -> do put saved
315 option :: a -> Parser a -> Parser a
316 option def !p = p <|> return def
319 sepBy :: Parser a -> Parser sep -> Parser [a]
320 sepBy !p !sep = sepBy1 p sep <|> return []
323 sepBy1 :: Parser a -> Parser sep -> Parser [a]
326 xs <- many $! sep >> p
338 crlf :: Parser String
339 crlf = string "\x0d\x0a"