Lucu-0.7.0.2: Network/HTTP/Lucu/Parser.hs
{-# LANGUAGE
BangPatterns
, ScopedTypeVariables
, UnboxedTuples
, UnicodeSyntax
#-}
-- |Yet another parser combinator. This is mostly a subset of
-- "Text.ParserCombinators.Parsec" but there are some differences:
--
-- * This parser works on 'Data.ByteString.Base.LazyByteString'
-- instead of 'Prelude.String'.
--
-- * Backtracking is the only possible behavior so there is no \"try\"
-- action.
--
-- * On success, the remaining string is returned as well as the
-- parser result.
--
-- * You can choose whether to treat reaching EOF (trying to eat one
-- more letter at the end of string) a fatal error or to treat it a
-- normal failure. If a fatal error occurs, the entire parsing
-- process immediately fails without trying any backtracks. The
-- default behavior is to treat EOF fatal.
--
-- In general, you don't have to use this module directly.
module Network.HTTP.Lucu.Parser
( Parser
, ParserResult(..)
, failP
, parse
, parseStr
, anyChar
, eof
, allowEOF
, satisfy
, char
, string
, (<|>)
, choice
, oneOf
, digit
, hexDigit
, notFollowedBy
, many
, manyChar
, many1
, count
, option
, sepBy
, sepBy1
, sp
, ht
, crlf
)
where
import Control.Monad.State.Strict hiding (state)
import qualified Data.ByteString.Lazy as Lazy (ByteString)
import qualified Data.ByteString.Lazy.Char8 as B hiding (ByteString)
import qualified Data.Foldable as Fold
import Data.Int
import qualified Data.Sequence as Seq
import Data.Sequence (Seq, (|>))
-- |@'Parser' a@ is obviously a parser which parses and returns @a@.
newtype Parser a = Parser {
runParser :: State ParserState (ParserResult a)
}
data ParserState
= PST {
pstInput :: Lazy.ByteString
, pstIsEOFFatal :: !Bool
}
deriving (Eq, Show)
data ParserResult a = Success !a
| IllegalInput -- 受理出來ない入力があった
| ReachedEOF -- 限界を越えて讀まうとした
deriving (Eq, Show)
-- (>>=) :: Parser a -> (a -> Parser b) -> Parser b
instance Monad Parser where
p >>= f = Parser $! do saved <- get -- 失敗した時の爲に状態を保存
result <- runParser p
case result of
Success a -> runParser (f a)
IllegalInput -> do put saved -- 状態を復歸
return IllegalInput
ReachedEOF -> do put saved -- 状態を復歸
return ReachedEOF
return !x = Parser $! return $! Success x
fail _ = Parser $! return $! IllegalInput
instance Functor Parser where
fmap f p = p >>= return . f
-- |@'failP'@ is just a synonym for @'Prelude.fail'
-- 'Prelude.undefined'@.
failP :: Parser a
failP = fail undefined
-- |@'parse' p bstr@ parses @bstr@ with @p@ and returns @(# result,
-- remaining #)@.
parse :: Parser a -> Lazy.ByteString -> (# ParserResult a, Lazy.ByteString #)
parse !p input -- input は lazy である必要有り。
= let (!result, state') = runState (runParser p) (PST input True)
in
(# result, pstInput state' #) -- pstInput state' も lazy である必要有り。
-- |@'parseStr' p str@ packs @str@ and parses it.
parseStr :: Parser a -> String -> (# ParserResult a, Lazy.ByteString #)
parseStr !p input -- input は lazy である必要有り。
= parse p (B.pack input)
anyChar :: Parser Char
anyChar = Parser $!
do state@(PST input _) <- get
if B.null input then
return ReachedEOF
else
do put $! state { pstInput = B.tail input }
return (Success $! B.head input)
eof :: Parser ()
eof = Parser $!
do PST input _ <- get
if B.null input then
return $! Success ()
else
return IllegalInput
-- |@'allowEOF' p@ makes @p@ treat reaching EOF a normal failure.
allowEOF :: Parser a -> Parser a
allowEOF !f
= Parser $! do saved@(PST _ isEOFFatal) <- get
put $! saved { pstIsEOFFatal = False }
result <- runParser f
state <- get
put $! state { pstIsEOFFatal = isEOFFatal }
return result
satisfy :: (Char -> Bool) -> Parser Char
satisfy !f
= do c <- anyChar
if f c then
return c
else
failP
char :: Char -> Parser Char
char !c = satisfy (== c)
string :: String -> Parser String
string !str
= let bs = B.pack str
len = B.length bs
in
Parser $!
do st <- get
let (bs', rest) = B.splitAt len $ pstInput st
st' = st { pstInput = rest }
if B.length bs' < len then
return ReachedEOF
else
if bs == bs' then
do put st'
return $ Success str
else
return IllegalInput
infixr 0 <|>
-- |This is the backtracking alternation. There is no non-backtracking
-- equivalent.
(<|>) :: Parser a -> Parser a -> Parser a
(!f) <|> (!g)
= Parser $! do saved <- get -- 状態を保存
result <- runParser f
case result of
Success a -> return $! Success a
IllegalInput -> do put saved -- 状態を復歸
runParser g
ReachedEOF -> if pstIsEOFFatal saved then
do put saved
return ReachedEOF
else
do put saved
runParser g
choice :: [Parser a] -> Parser a
choice = foldl (<|>) failP
oneOf :: [Char] -> Parser Char
oneOf = foldl (<|>) failP . map char
notFollowedBy :: Parser a -> Parser ()
notFollowedBy !p
= Parser $! do saved <- get -- 状態を保存
result <- runParser p
case result of
Success _ -> do put saved -- 状態を復歸
return IllegalInput
IllegalInput -> do put saved -- 状態を復歸
return $! Success ()
ReachedEOF -> do put saved -- 状態を復歸
return $! Success ()
digit :: Parser Char
digit = do c <- anyChar
if c >= '0' && c <= '9' then
return c
else
failP
hexDigit :: Parser Char
hexDigit = do c <- anyChar
if (c >= '0' && c <= '9') ||
(c >= 'a' && c <= 'f') ||
(c >= 'A' && c <= 'F') then
return c
else
failP
many :: forall a. Parser a -> Parser [a]
many !p = Parser $!
do state <- get
let (# result, state' #) = many' state Seq.empty
put state'
return result
where
many' :: ParserState -> Seq a -> (# ParserResult [a], ParserState #)
many' !st !soFar
= case runState (runParser p) st of
(Success a, st') -> many' st' (soFar |> a)
(IllegalInput, _) -> (# Success (Fold.toList soFar), st #)
(ReachedEOF , _) -> if pstIsEOFFatal st then
(# ReachedEOF, st #)
else
(# Success (Fold.toList soFar), st #)
manyChar :: Parser Char -> Parser Lazy.ByteString
manyChar !p = Parser $!
do state <- get
case scan' state 0 of
Success len
-> do let (bs, rest) = B.splitAt len (pstInput state)
state' = state { pstInput = rest }
put state'
return $ Success bs
ReachedEOF
-> if pstIsEOFFatal state then
return ReachedEOF
else
error "internal error"
_ -> error "internal error"
where
scan' :: ParserState -> Int64 -> ParserResult Int64
scan' !st !soFar
= case runState (runParser p) st of
(Success _ , st') -> scan' st' (soFar + 1)
(IllegalInput, _ ) -> Success soFar
(ReachedEOF , _ ) -> if pstIsEOFFatal st then
ReachedEOF
else
Success soFar
many1 :: Parser a -> Parser [a]
many1 !p = do x <- p
xs <- many p
return (x:xs)
count :: Int -> Parser a -> Parser [a]
count !n !p = Parser $! count' n p Seq.empty
-- This implementation is rather ugly but we need to make it
-- tail-recursive to avoid stack overflow.
count' :: Int -> Parser a -> Seq a -> State ParserState (ParserResult [a])
count' 0 _ !soFar = return $! Success $! Fold.toList soFar
count' !n !p !soFar = do saved <- get
result <- runParser p
case result of
Success a -> count' (n-1) p (soFar |> a)
IllegalInput -> do put saved
return IllegalInput
ReachedEOF -> do put saved
return ReachedEOF
-- def may be a _|_
option :: a -> Parser a -> Parser a
option def !p = p <|> return def
sepBy :: Parser a -> Parser sep -> Parser [a]
sepBy !p !sep = sepBy1 p sep <|> return []
sepBy1 :: Parser a -> Parser sep -> Parser [a]
sepBy1 !p !sep
= do x <- p
xs <- many $! sep >> p
return (x:xs)
sp :: Parser Char
sp = char ' '
ht :: Parser Char
ht = char '\t'
crlf :: Parser String
crlf = string "\x0d\x0a"