{-# LANGUAGE TypeSynonymInstances #-} module Text.XML.Light.Lexer where import Text.XML.Light.Types import Data.Char (chr,isSpace) import Numeric (readHex) import qualified Data.ByteString as S import qualified Data.ByteString.Lazy as L import qualified Data.Text as TS import qualified Data.Text.Lazy as TL class XmlSource s where uncons :: s -> Maybe (Char,s) instance XmlSource String where uncons (c:s) = Just (c,s) uncons "" = Nothing instance XmlSource S.ByteString where uncons bs = f `fmap` S.uncons bs where f (c,s) = (chr (fromEnum c), s) instance XmlSource L.ByteString where uncons bs = f `fmap` L.uncons bs where f (c,s) = (chr (fromEnum c), s) instance XmlSource TS.Text where uncons = TS.uncons instance XmlSource TL.Text where uncons = TL.uncons linenumber :: XmlSource s => Integer -> s -> LString linenumber n s = case uncons s of Nothing -> [] Just ('\r', s') -> case uncons s' of Just ('\n',s'') -> next s'' _ -> next s' Just ('\n', s') -> next s' Just (c , s') -> (n,c) : linenumber n s' where next s' = n' `seq` ((n,'\n'):linenumber n' s') where n' = n + 1 -- | This type may be used to provide a custom scanning function -- for extracting characters. data Scanner s = Scanner (Maybe (Char,s)) (s -> Maybe (Char,s)) -- | This type may be used to provide a custom scanning function -- for extracting characters. customScanner :: (s -> Maybe (Char,s)) -> s -> Scanner s customScanner next s = Scanner (next s) next instance XmlSource (Scanner s) where uncons (Scanner this next) = do (c,s1) <- this return (c, Scanner (next s1) next) -- Lexer ----------------------------------------------------------------------- type LChar = (Line,Char) type LString = [LChar] data Token = TokStart Line QName [Attr] Bool -- is empty? | TokEnd Line QName | TokCRef String | TokText CData deriving Show tokens :: XmlSource source => source -> [Token] tokens = tokens' . linenumber 1 tokens' :: LString -> [Token] tokens' ((_,'<') : c@(_,'!') : cs) = special c cs tokens' ((_,'<') : cs) = tag (dropSpace cs) -- we are being nice here tokens' [] = [] tokens' cs@((l,_):_) = let (as,bs) = breakn ('<' ==) cs in map cvt (decode_text as) ++ tokens' bs -- XXX: Note, some of the lines might be a bit inacuarate where cvt (TxtBit x) = TokText CData { cdLine = Just l , cdVerbatim = CDataText , cdData = x } cvt (CRefBit x) = case cref_to_char x of Just c -> TokText CData { cdLine = Just l , cdVerbatim = CDataText , cdData = [c] } Nothing -> TokCRef x special :: LChar -> LString -> [Token] special _ ((_,'-') : (_,'-') : cs) = skip cs where skip ((_,'-') : (_,'-') : (_,'>') : ds) = tokens' ds skip (_ : ds) = skip ds skip [] = [] -- unterminated comment special c ((_,'[') : (_,'C') : (_,'D') : (_,'A') : (_,'T') : (_,'A') : (_,'[') : cs) = let (xs,ts) = cdata cs in TokText CData { cdLine = Just (fst c), cdVerbatim = CDataVerbatim, cdData = xs } : tokens' ts where cdata ((_,']') : (_,']') : (_,'>') : ds) = ([],ds) cdata ((_,d) : ds) = let (xs,ys) = cdata ds in (d:xs,ys) cdata [] = ([],[]) special c cs = let (xs,ts) = munch "" 0 cs in TokText CData { cdLine = Just (fst c) , cdVerbatim = CDataRaw , cdData = '<':'!':(reverse xs) } : tokens' ts where munch acc nesting ((_,'>') : ds) | nesting == (0::Int) = ('>':acc,ds) | otherwise = munch ('>':acc) (nesting-1) ds munch acc nesting ((_,'<') : ds) = munch ('<':acc) (nesting+1) ds munch acc n ((_,x) : ds) = munch (x:acc) n ds munch acc _ [] = (acc,[]) -- unterminated DTD markup --special c cs = tag (c : cs) -- invalid specials are processed as tags qualName :: LString -> (QName,LString) qualName xs = let (as,bs) = breakn endName xs (q,n) = case break (':'==) as of (q1,_:n1) -> (Just q1, n1) _ -> (Nothing, as) in (QName { qURI = Nothing, qPrefix = q, qName = n }, bs) where endName x = isSpace x || x == '=' || x == '>' || x == '/' tag :: LString -> [Token] tag ((p,'/') : cs) = let (n,ds) = qualName (dropSpace cs) in TokEnd p n : case ds of (_,'>') : es -> tokens' es -- tag was not properly closed... _ -> tokens' ds tag [] = [] tag cs = let (n,ds) = qualName cs (as,b,ts) = attribs (dropSpace ds) in TokStart (fst (head cs)) n as b : ts attribs :: LString -> ([Attr], Bool, [Token]) attribs cs = case cs of (_,'>') : ds -> ([], False, tokens' ds) (_,'/') : ds -> ([], True, case ds of (_,'>') : es -> tokens' es -- insert missing > ... _ -> tokens' ds) (_,'?') : (_,'>') : ds -> ([], True, tokens' ds) -- doc ended within a tag.. [] -> ([],False,[]) _ -> let (a,cs1) = attrib cs (as,b,ts) = attribs cs1 in (a:as,b,ts) attrib :: LString -> (Attr,LString) attrib cs = let (ks,cs1) = qualName cs (vs,cs2) = attr_val (dropSpace cs1) in ((Attr ks (decode_attr vs)),dropSpace cs2) attr_val :: LString -> (String,LString) attr_val ((_,'=') : cs) = string (dropSpace cs) attr_val cs = ("",cs) dropSpace :: LString -> LString dropSpace = dropWhile (isSpace . snd) -- | Match the value for an attribute. For malformed XML we do -- our best to guess the programmer's intention. string :: LString -> (String,LString) string ((_,'"') : cs) = break' ('"' ==) cs -- Allow attributes to be enclosed between ' '. string ((_,'\'') : cs) = break' ('\'' ==) cs -- Allow attributes that are not enclosed by anything. string cs = breakn eos cs where eos x = isSpace x || x == '>' || x == '/' break' :: (a -> Bool) -> [(b,a)] -> ([a],[(b,a)]) break' p xs = let (as,bs) = breakn p xs in (as, case bs of [] -> [] _ : cs -> cs) breakn :: (a -> Bool) -> [(b,a)] -> ([a],[(b,a)]) breakn p l = (map snd as,bs) where (as,bs) = break (p . snd) l decode_attr :: String -> String decode_attr cs = concatMap cvt (decode_text cs) where cvt (TxtBit x) = x cvt (CRefBit x) = case cref_to_char x of Just c -> [c] Nothing -> '&' : x ++ ";" data Txt = TxtBit String | CRefBit String deriving Show decode_text :: [Char] -> [Txt] decode_text xs@('&' : cs) = case break (';' ==) cs of (as,_:bs) -> CRefBit as : decode_text bs _ -> [TxtBit xs] decode_text [] = [] decode_text cs = let (as,bs) = break ('&' ==) cs in TxtBit as : decode_text bs cref_to_char :: [Char] -> Maybe Char cref_to_char cs = case cs of '#' : ds -> num_esc ds "lt" -> Just '<' "gt" -> Just '>' "amp" -> Just '&' "apos" -> Just '\'' "quot" -> Just '"' _ -> Nothing num_esc :: String -> Maybe Char num_esc cs = case cs of 'x' : ds -> check (readHex ds) _ -> check (reads cs) where check [(n,"")] = cvt_char n check _ = Nothing cvt_char :: Int -> Maybe Char cvt_char x | fromEnum (minBound :: Char) <= x && x <= fromEnum (maxBound::Char) = Just (toEnum x) | otherwise = Nothing