{-# LANGUAGE CPP, TypeSynonymInstances #-}

{- |

Module : ./Common/XmlParser.hs

Description : Interface to the Xml Parsing Facility

Copyright : (c) Ewaryst Schulz, DFKI 2009

License : GPLv2 or higher, see LICENSE.txt

Maintainer : ewaryst.schulz@dfki.de

Stability : provisional

Portability : portable

Provides an xml parse function which depends on external libraries.

-}

module Common.XmlParser (XmlParseable (parseXml), readXmlFile) where

import Text.XML.Light

import qualified Data.ByteString.Lazy as BS

#ifdef HEXPAT

import qualified Common.XmlExpat as XE

#else

import Data.ByteString.Lazy.UTF8

#endif

readXmlFile :: FilePath -> IO BS.ByteString

readXmlFile fp = do

bs <- BS.readFile fp

if BS.length bs > 0 then return bs else

fail "Common.XmlParser.readXmlFile: empty file"

{- | This class provides an xml parsing function which is instantiated

by using the hexpat or the XML.Light library, dependent on the haskell

environment. -}

class XmlParseable a where

parseXml :: a -> IO (Either String Element)

#ifdef HEXPAT

instance XmlParseable BS.ByteString where

parseXml = return . XE.parseXml

-- 169MB on Basic/Algebra_I

#else

instance XmlParseable BS.ByteString where

parseXml s = return $ case parseXMLDoc $ toString s of

Just x -> Right x

_ -> Left "parseXMLDoc: parse error"

-- 426MB on Basic/Algebra_I

#endif