hexpat-0.12: Text/XML/Expat/IO.hs
{-# LANGUAGE ForeignFunctionInterface #-}
-- hexpat, a Haskell wrapper for expat
-- Copyright (C) 2008 Evan Martin <martine@danga.com>
-- Copyright (C) 2009 Stephen Blackheath <http://blacksapphire.com/antispam>
-- | Low-level interface to Expat. Unless speed is paramount, this should
-- normally be avoided in favour of the interfaces provided by
-- 'Text.XML.Expat.SAX' and 'Text.XML.Expat.Tree'. Basic usage is:
--
-- (1) Make a new parser: 'newParser'.
--
-- (2) Set up callbacks on the parser: 'setStartElementHandler', etc.
--
-- (3) Feed data into the parser: 'parse', 'parse'' or 'parseChunk'.
module Text.XML.Expat.IO (
-- ** Parser Setup
Parser, newParser,
-- ** Parsing
parse, parse', parseChunk, Encoding(..), XMLParseError(..),
getParseLocation,
XMLParseLocation(..),
-- ** Parser Callbacks
StartElementHandler,
EndElementHandler,
CharacterDataHandler,
ExternalEntityRefHandler,
SkippedEntityHandler,
setStartElementHandler,
setEndElementHandler,
setCharacterDataHandler,
setExternalEntityRefHandler,
setSkippedEntityHandler,
setUseForeignDTD,
-- ** Lower-level interface
parseExternalEntityReference,
unsafeParseChunk,
withHandlers,
unsafeSetHandlers,
unsafeReleaseHandlers,
ExpatHandlers,
-- ** Helpers
encodingToString
) where
import Control.Exception (bracket)
import Control.Parallel.Strategies
import Control.Monad
import qualified Data.ByteString as BS
import qualified Data.ByteString.Lazy as BSL
import Data.IORef
import Foreign
import CForeign
-- |Opaque parser type.
type ParserPtr = Ptr ()
data Parser = Parser
{ _parserObj :: ForeignPtr ()
, _startElementHandler :: IORef CStartElementHandler
, _endElementHandler :: IORef CEndElementHandler
, _cdataHandler :: IORef CCharacterDataHandler
, _externalEntityRefHandler :: IORef (Maybe CExternalEntityRefHandler)
, _skippedEntityHandler :: IORef (Maybe CSkippedEntityHandler)
}
instance Show Parser where
showsPrec _ (Parser fp _ _ _ _ _) = showsPrec 0 fp
withParser :: Parser -> (ParserPtr -> IO a) -> IO a
withParser (Parser fp _ _ _ _ _) = withForeignPtr fp
-- |Encoding types available for the document encoding.
data Encoding = ASCII | UTF8 | UTF16 | ISO88591
encodingToString :: Encoding -> String
encodingToString ASCII = "US-ASCII"
encodingToString UTF8 = "UTF-8"
encodingToString UTF16 = "UTF-16"
encodingToString ISO88591 = "ISO-8859-1"
withOptEncoding :: Maybe Encoding -> (CString -> IO a) -> IO a
withOptEncoding Nothing f = f nullPtr
withOptEncoding (Just enc) f = withCString (encodingToString enc) f
parserCreate :: Maybe Encoding -> IO (ParserPtr)
parserCreate a1 =
withOptEncoding a1 $ \a1' ->
parserCreate'_ a1' >>= \res ->
let {res' = id res} in
return (res')
-- | Create a 'Parser'.
newParser :: Maybe Encoding -> IO Parser
newParser enc = do
ptr <- parserCreate enc
fptr <- newForeignPtr parserFree ptr
nullStartH <- newIORef nullCStartElementHandler
nullEndH <- newIORef nullCEndElementHandler
nullCharH <- newIORef nullCCharacterDataHandler
extH <- newIORef Nothing
skipH <- newIORef Nothing
return $ Parser fptr nullStartH nullEndH nullCharH extH skipH
setUseForeignDTD :: Parser -> Bool -> IO ()
setUseForeignDTD p b = withParser p $ \p' -> xmlUseForeignDTD p' b'
where
b' = if b then 1 else 0
-- ByteString.useAsCStringLen is almost what we need, but C2HS wants a CInt
-- instead of an Int.
withBStringLen :: BS.ByteString -> ((CString, CInt) -> IO a) -> IO a
withBStringLen bs f = do
BS.useAsCStringLen bs $ \(str, len) -> f (str, fromIntegral len)
unStatus :: CInt -> Bool
unStatus 0 = False
unStatus _ = True
-- |@parse data@ feeds /lazy/ ByteString data into a 'Parser'. It returns
-- Nothing on success, or Just the parse error.
parse :: Parser -> BSL.ByteString -> IO (Maybe XMLParseError)
parse parser bs = withHandlers parser $ do
ok <- doParseChunks (BSL.toChunks bs)
if ok
then return Nothing
else Just `fmap` getError parser
where
doParseChunks [] = doParseChunk parser BS.empty True
doParseChunks (c:cs) = do
ok <- doParseChunk parser c False
if ok
then doParseChunks cs
else return False
-- |@parse data@ feeds /strict/ ByteString data into a 'Parser'. It returns
-- Nothing on success, or Just the parse error.
parse' :: Parser -> BS.ByteString -> IO (Maybe XMLParseError)
parse' parser bs = withHandlers parser $ do
ok <- doParseChunk parser bs True
if ok
then return Nothing
else Just `fmap` getError parser
-- |@parseChunk data False@ feeds /strict/ ByteString data into a
-- 'Parser'. The end of the data is indicated by passing @True@ for the
-- final parameter. It returns Nothing on success, or Just the parse error.
parseChunk :: Parser
-> BS.ByteString
-> Bool -- ^ True if last chunk
-> IO (Maybe XMLParseError)
parseChunk parser xml final = withHandlers parser $ unsafeParseChunk parser xml final
parseExternalEntityReference :: Parser
-> CString -- ^ context
-> Maybe Encoding -- ^ encoding
-> CStringLen -- ^ text
-> IO Bool
parseExternalEntityReference parser context encoding (text,sz) =
withParser parser $ \p -> do
extp <- withOptEncoding encoding $
xmlExternalEntityParserCreate p context
e <- doParseChunk'_ extp text (fromIntegral sz) 1
parserFree' extp
return $ e == 1
-- | This variant of 'parseChunk' must either be called inside 'withHandlers'
-- (safest), or between 'unsafeSetHandlers' and 'unsafeReleaseHandlers', and
-- this will give you better performance than 'parseChunk' if you process
-- multiple chunks inside.
unsafeParseChunk :: Parser
-> BS.ByteString
-> Bool
-> IO (Maybe XMLParseError)
unsafeParseChunk parser xml final = do
ok <- doParseChunk parser xml final
if ok
then return Nothing
else Just `fmap` getError parser
getError :: Parser -> IO XMLParseError
getError parser = withParser parser $ \p -> do
code <- xmlGetErrorCode p
cerr <- xmlErrorString code
err <- peekCString cerr
loc <- getParseLocation parser
return $ XMLParseError err loc
data ExpatHandlers = ExpatHandlers
(FunPtr CStartElementHandler)
(FunPtr CEndElementHandler)
(FunPtr CCharacterDataHandler)
(Maybe (FunPtr CExternalEntityRefHandler))
(Maybe (FunPtr CSkippedEntityHandler))
unsafeSetHandlers :: Parser -> IO ExpatHandlers
unsafeSetHandlers parser@(Parser _ startRef endRef charRef extRef skipRef) =
do
cStartH <- mkCStartElementHandler =<< readIORef startRef
cEndH <- mkCEndElementHandler =<< readIORef endRef
cCharH <- mkCCharacterDataHandler =<< readIORef charRef
mExtH <- readIORef extRef >>=
maybe (return Nothing)
(\h -> liftM Just $ mkCExternalEntityRefHandler h)
mSkipH <- readIORef skipRef >>=
maybe (return Nothing)
(\h -> liftM Just $ mkCSkippedEntityHandler h)
withParser parser $ \p -> do
xmlSetstartelementhandler p cStartH
xmlSetendelementhandler p cEndH
xmlSetcharacterdatahandler p cCharH
maybe (return ())
(xmlSetExternalEntityRefHandler p)
mExtH
maybe (return ())
(xmlSetSkippedEntityHandler p)
mSkipH
return $ ExpatHandlers cStartH cEndH cCharH mExtH mSkipH
unsafeReleaseHandlers :: ExpatHandlers -> IO ()
unsafeReleaseHandlers (ExpatHandlers cStartH cEndH cCharH mcExtH mcSkipH) = do
freeHaskellFunPtr cStartH
freeHaskellFunPtr cEndH
freeHaskellFunPtr cCharH
maybe (return ()) freeHaskellFunPtr mcExtH
maybe (return ()) freeHaskellFunPtr mcSkipH
-- | 'unsafeParseChunk' is required to be called inside @withHandlers@.
-- Safer than using 'unsafeSetHandlers' / 'unsafeReleaseHandlers'.
withHandlers :: Parser
-> IO a -- ^ Computation where unsafeParseChunk may be used
-> IO a
withHandlers parser code = do
bracket
(unsafeSetHandlers parser)
unsafeReleaseHandlers
(\_ -> code)
-- |Obtain C value from Haskell 'Bool'.
--
cFromBool :: Num a => Bool -> a
cFromBool = fromBool
doParseChunk :: Parser -> BS.ByteString -> Bool -> IO (Bool)
doParseChunk a1 a2 a3 =
withParser a1 $ \a1' ->
withBStringLen a2 $ \(a2'1, a2'2) ->
let {a3' = cFromBool a3} in
doParseChunk'_ a1' a2'1 a2'2 a3' >>= \res ->
let {res' = unStatus res} in
return (res')
-- | Parse error, consisting of message text and error location
data XMLParseError = XMLParseError String XMLParseLocation deriving (Eq, Show)
instance NFData XMLParseError where
rnf (XMLParseError msg loc) = rnf (msg, loc)
-- | Specifies a location of an event within the input text
data XMLParseLocation = XMLParseLocation {
xmlLineNumber :: Int64, -- ^ Line number of the event
xmlColumnNumber :: Int64, -- ^ Column number of the event
xmlByteIndex :: Int64, -- ^ Byte index of event from start of document
xmlByteCount :: Int64 -- ^ The number of bytes in the event
}
deriving (Eq, Show)
instance NFData XMLParseLocation where
rnf (XMLParseLocation lin col ind cou) = rnf (lin, col, ind, cou)
getParseLocation :: Parser -> IO XMLParseLocation
getParseLocation parser = withParser parser $ \p -> do
line <- xmlGetCurrentLineNumber p
col <- xmlGetCurrentColumnNumber p
index <- xmlGetCurrentByteIndex p
count <- xmlGetCurrentByteCount p
return $ XMLParseLocation {
xmlLineNumber = fromIntegral line,
xmlColumnNumber = fromIntegral col,
xmlByteIndex = fromIntegral index,
xmlByteCount = fromIntegral count
}
-- | The type of the \"element started\" callback. The first parameter is the
-- element name; the second are the (attribute, value) pairs. Return True to
-- continue parsing as normal, or False to terminate the parse.
type StartElementHandler = CString -> [(CString, CString)] -> IO Bool
-- | The type of the \"element ended\" callback. The parameter is the element
-- name. Return True to continue parsing as normal, or False to terminate the
-- parse.
type EndElementHandler = CString -> IO Bool
-- | The type of the \"character data\" callback. The parameter is the
-- character data processed. This callback may be called more than once while
-- processing a single conceptual block of text. Return True to continue
-- parsing as normal, or False to terminate the parse.
type CharacterDataHandler = CStringLen -> IO Bool
-- | The type of the \"external entity reference\" callback. See the expat
-- documentation.
type ExternalEntityRefHandler = Parser
-> CString -- context
-> CString -- base
-> CString -- systemID
-> CString -- publicID
-> IO Bool
-- | Set a skipped entity handler. This is called in two situations:
--
-- 1. An entity reference is encountered for which no declaration has been read
-- and this is not an error.
--
-- 2. An internal entity reference is read, but not expanded, because
-- @XML_SetDefaultHandler@ has been called.
type SkippedEntityHandler = CString -- entityName
-> Int -- is a parameter entity?
-> IO Bool
type CStartElementHandler = Ptr () -> CString -> Ptr CString -> IO ()
nullCStartElementHandler :: CStartElementHandler
nullCStartElementHandler _ _ _ = return ()
foreign import ccall safe "wrapper"
mkCStartElementHandler :: CStartElementHandler
-> IO (FunPtr CStartElementHandler)
wrapStartElementHandler :: Parser -> StartElementHandler -> CStartElementHandler
wrapStartElementHandler parser handler = h
where
h _ cname cattrs = do
cattrlist <- peekArray0 nullPtr cattrs
stillRunning <- handler cname (pairwise cattrlist)
unless stillRunning $ stopParser parser
-- | Attach a StartElementHandler to a Parser.
setStartElementHandler :: Parser -> StartElementHandler -> IO ()
setStartElementHandler parser@(Parser _ startRef _ _ _ _) handler =
writeIORef startRef $ wrapStartElementHandler parser handler
type CEndElementHandler = Ptr () -> CString -> IO ()
nullCEndElementHandler :: CEndElementHandler
nullCEndElementHandler _ _ = return ()
foreign import ccall safe "wrapper"
mkCEndElementHandler :: CEndElementHandler
-> IO (FunPtr CEndElementHandler)
wrapEndElementHandler :: Parser -> EndElementHandler -> CEndElementHandler
wrapEndElementHandler parser handler = h
where
h _ cname = do
stillRunning <- handler cname
unless stillRunning $ stopParser parser
-- | Attach an EndElementHandler to a Parser.
setEndElementHandler :: Parser -> EndElementHandler -> IO ()
setEndElementHandler parser@(Parser _ _ endRef _ _ _) handler =
writeIORef endRef $ wrapEndElementHandler parser handler
type CCharacterDataHandler = Ptr () -> CString -> CInt -> IO ()
nullCCharacterDataHandler :: CCharacterDataHandler
nullCCharacterDataHandler _ _ _ = return ()
foreign import ccall safe "wrapper"
mkCCharacterDataHandler :: CCharacterDataHandler
-> IO (FunPtr CCharacterDataHandler)
wrapCharacterDataHandler :: Parser -> CharacterDataHandler -> CCharacterDataHandler
wrapCharacterDataHandler parser handler = h
where
h _ cdata len = do
stillRunning <- handler (cdata, fromIntegral len)
unless stillRunning $ stopParser parser
-- | Attach an CharacterDataHandler to a Parser.
setCharacterDataHandler :: Parser -> CharacterDataHandler -> IO ()
setCharacterDataHandler parser@(Parser _ _ _ charRef _ _) handler =
writeIORef charRef $ wrapCharacterDataHandler parser handler
pairwise :: [a] -> [(a,a)]
pairwise (x1:x2:xs) = (x1,x2) : pairwise xs
pairwise _ = []
stopParser :: Parser -> IO ()
stopParser parser = withParser parser $ \p -> xmlStopParser p 0
------------------------------------------------------------------------------
-- C imports
foreign import ccall unsafe "XML_ParserCreate"
parserCreate'_ :: ((Ptr CChar) -> (IO (Ptr ())))
foreign import ccall unsafe "XML_SetStartElementHandler"
xmlSetstartelementhandler :: ((Ptr ()) -> ((FunPtr ((Ptr ()) -> ((Ptr CChar) -> ((Ptr (Ptr CChar)) -> (IO ()))))) -> (IO ())))
foreign import ccall unsafe "XML_SetEndElementHandler"
xmlSetendelementhandler :: ((Ptr ()) -> ((FunPtr ((Ptr ()) -> ((Ptr CChar) -> (IO ())))) -> (IO ())))
foreign import ccall unsafe "XML_SetCharacterDataHandler"
xmlSetcharacterdatahandler :: ((Ptr ()) -> ((FunPtr ((Ptr ()) -> ((Ptr CChar) -> (CInt -> (IO ()))))) -> (IO ())))
foreign import ccall safe "XML_Parse"
doParseChunk'_ :: ((Ptr ()) -> ((Ptr CChar) -> (CInt -> (CInt -> (IO CInt)))))
foreign import ccall unsafe "XML_UseForeignDTD"
xmlUseForeignDTD :: ParserPtr -- ^ parser
-> CChar -- ^ use foreign DTD? (external entity ref
-- handler will be called with publicID &
-- systemID set to null
-> IO ()
foreign import ccall "&XML_ParserFree" parserFree :: FunPtr (ParserPtr -> IO ())
foreign import ccall "XML_ParserFree" parserFree' :: ParserPtr -> IO ()
type CExternalEntityRefHandler = ParserPtr -- parser
-> Ptr CChar -- context
-> Ptr CChar -- base
-> Ptr CChar -- systemID
-> Ptr CChar -- publicID
-> IO ()
foreign import ccall safe "wrapper"
mkCExternalEntityRefHandler :: CExternalEntityRefHandler
-> IO (FunPtr CExternalEntityRefHandler)
foreign import ccall unsafe "XML_SetExternalEntityRefHandler"
xmlSetExternalEntityRefHandler :: ParserPtr
-> FunPtr CExternalEntityRefHandler
-> IO ()
foreign import ccall unsafe "XML_SetSkippedEntityHandler"
xmlSetSkippedEntityHandler :: ParserPtr
-> FunPtr CSkippedEntityHandler
-> IO ()
foreign import ccall unsafe "XML_ExternalEntityParserCreate"
xmlExternalEntityParserCreate :: ParserPtr
-> CString -- ^ context
-> CString -- ^ encoding
-> IO ParserPtr
type CSkippedEntityHandler = Ptr () -- user data pointer
-> CString -- entity name
-> CInt -- is a parameter entity?
-> IO ()
foreign import ccall safe "wrapper"
mkCSkippedEntityHandler :: CSkippedEntityHandler
-> IO (FunPtr CSkippedEntityHandler)
wrapExternalEntityRefHandler :: Parser
-> ExternalEntityRefHandler
-> CExternalEntityRefHandler
wrapExternalEntityRefHandler parser handler = h
where
h _ context base systemID publicID = do
stillRunning <- handler parser context base systemID publicID
unless stillRunning $ stopParser parser
wrapSkippedEntityHandler :: Parser
-> SkippedEntityHandler
-> CSkippedEntityHandler
wrapSkippedEntityHandler parser handler = h
where
h _ entityName i = do
stillRunning <- handler entityName (fromIntegral i)
unless stillRunning $ stopParser parser
setExternalEntityRefHandler :: Parser -> ExternalEntityRefHandler -> IO ()
setExternalEntityRefHandler parser h =
writeIORef ref $ Just $ wrapExternalEntityRefHandler parser h
where
ref = _externalEntityRefHandler parser
setSkippedEntityHandler :: Parser -> SkippedEntityHandler -> IO ()
setSkippedEntityHandler parser h =
writeIORef ref $ Just $ wrapSkippedEntityHandler parser h
where
ref = _skippedEntityHandler parser
-- Note on word sizes:
--
-- on expat 2.0:
-- XML_GetCurrentLineNumber returns XML_Size
-- XML_GetCurrentColumnNumber returns XML_Size
-- XML_GetCurrentByteIndex returns XML_Index
-- These are defined in expat_external.h
--
-- debian-i386 says XML_Size and XML_Index are 4 bytes.
-- ubuntu-amd64 says XML_Size and XML_Index are 8 bytes.
-- These two systems do NOT define XML_LARGE_SIZE, which would force these types
-- to be 64-bit.
--
-- If we guess the word size too small, it shouldn't matter: We will just discard
-- the most significant part. If we get the word size too large, we will get
-- garbage (very bad).
--
-- So - what I will do is use CLong and CULong, which correspond to what expat
-- is using when XML_LARGE_SIZE is disabled, and give the correct sizes on the
-- two machines mentioned above. At the absolute worst the word size will be too
-- short.
foreign import ccall unsafe "expat.h XML_GetErrorCode" xmlGetErrorCode
:: ParserPtr -> IO CInt
foreign import ccall unsafe "expat.h XML_GetCurrentLineNumber" xmlGetCurrentLineNumber
:: ParserPtr -> IO CULong
foreign import ccall unsafe "expat.h XML_GetCurrentColumnNumber" xmlGetCurrentColumnNumber
:: ParserPtr -> IO CULong
foreign import ccall unsafe "expat.h XML_GetCurrentByteIndex" xmlGetCurrentByteIndex
:: ParserPtr -> IO CLong
foreign import ccall unsafe "expat.h XML_GetCurrentByteCount" xmlGetCurrentByteCount
:: ParserPtr -> IO CInt
foreign import ccall unsafe "expat.h XML_ErrorString" xmlErrorString
:: CInt -> IO CString
foreign import ccall unsafe "expat.h XML_StopParser" xmlStopParser
:: ParserPtr -> CInt -> IO ()