NewLC - Building an XML Parser Generator for Symbian (Part 4) - Comments

Re: Building an XML Parser Generator for Symbian (Part 4)

Varsha4u — Mon, 07 Jul 2008 14:21:52 +0200

Hi Paul,

I have been trying to use the SyExpat.zip available from your previous post, but when I build the project it gives me numerous errors similar to what venki_kv have been receiving. I'm using the SyExpat.zip with UIQ3.3 which is based off Symbian OS v9.3 with Carbide v1.3.

Please let me know if I need to do any modifications.

Thanks in Advance,
Varsha.

Re: Building an XML Parser Generator for Symbian (Part 4)

venki_kv — Thu, 22 May 2008 08:47:43 +0200

Hai Paul
I have been trying to use SyExpat Lib on Symbian V9.2. But i am unable to compile it. Any idea why its not generating the DLL?
Here is my error console output

mwldsym2.exe: Undefined symbol: '__declspec(dllimport) _XML_ParserFree (__imp__XML_ParserFree)'
mwldsym2.exe: referenced from 'CExpatParserBase::~CExpatParserBase(void) (??1CExpatParserBase@@UAE@XZ)' in SyExpat.cpp:304
mwldsym2.exe: Note: symbol '_XML_ParserFree' found in 'xmlparse.o';
mwldsym2.exe: your project may need the DLL import library instead of a static library

Thanks in advance,

Building an XML Parser Generator for Symbian (Part 4)

Andrew Chung — Thu, 08 Feb 2007 02:15:58 +0100

I dug through this and even the latest SyExpat from toddsoftware.com has the same defualt namespace issue. I have fixed this by making a few slight changes to code in SyExpat.cpp. Three functions have been modified and their new forms are included here. Changes from the original are in bold.

I've also put this up as a page on my web site so that copy/paste of the code is easier. Pardon the horrible page. I'm just throwing the information up.

static void StartNamespaceHandler(void *userData, const XML_Char *aPrefix, const XML_Char *aURI) TPtrC prefix; if (aPrefix != NULL) prefix.Set(TPtrC(RECAST_FROM_XML_CHAR(aPrefix))); const TPtrC uri(RECAST_FROM_XML_CHAR(aURI)); MSyDeclHandler* handler = RECAST_TO_DECL_HANDLER(userData); if (handler != NULL) handler->StartNamespace(prefix, uri);

static void EndNamespaceHandler(void *userData, const XML_Char* aPrefix) TPtrC prefix; if (aPrefix != NULL) prefix.Set(TPtrC(RECAST_FROM_XML_CHAR(aPrefix)));

MSyDeclHandler* handler = RECAST_TO_DECL_HANDLER(userData); if (handler != NULL) handler->EndNamespace(prefix);

static void SplitElementName(const TText* aName, TQualified& aItem) TPtrC tmp(aName); //URI + sep + local_name + sep + prefix. const TInt EndURI = tmp.Find(KSeperator); if (EndURI != KErrNotFound) aItem.iURI.Set(tmp.Ptr(), EndURI); tmp.Set(aName + EndURI + KSeperator.BufferSize); const TInt EndLocalName = tmp.Find(KSeperator); if (EndLocalName != KErrNotFound) aItem.iLocalName.Set(tmp.Ptr(), EndLocalName); tmp.Set(tmp.Ptr() + EndLocalName + KSeperator.BufferSize); aItem.iPrefix.Set(tmp); else aItem.iLocalName.Set(tmp); // We couldn't find the seperator for the prefix // we will assume this is the default prefix of '' else ; // as there is no namespace information we assume we only have a local name so do nothing aItem.iLocalName.Set(tmp);

The changes in the start and end namespace handler fix the issue of the KERN-EXEC 3 or NULL pointer error. The fix in the SplitElement fixes an issue where the local name returned in the StartElement handler is incorrect. The splitelement function is looking for a string in the form of: [URI]\n[LocalName]\n[Prefix]. If there is no prefix the check for the second \n fails. In this case we really want to save the correct LocaName, which happens to be the rest of the string.

> Building an XML Parser Generator for Symbian (Part 4)

Twm Davies — Fri, 11 Aug 2006 18:58:48 +0200

I found a problem with writing attribute values. The writer only encodes entities for character content and not attribute values. This often leads to invalid XML output when < & and other characters are present in text being stores as an attribute. I've patched Sygen.cpp so that it generates valid XML and also made it deal with line feeds and tabs in attributes, which also need to be encoded as entities. Some silly XML file formats store line feeds within attributes, which is not elegent but is valid XML.

I have the patch to contribute back to this useful project. Who do I send it to?

> Building an XML Parser Generator for Symbian (Part 4)

swapna.saroja — Mon, 07 Aug 2006 13:57:01 +0200

Hi Paul, I have the same problem like Ashish. If i try to parse a XML document with a default namespace for eg: xmlns="some:namespace:etc", the parser goes in KERN-EXEC 3. It works if you specify the prefix for eg: xmlnsQ = "urn:dvb:ipdc:esgbs:2005"). Hope you can help me on this.

Thank you

Building an XML Parser Generator for Symbian (Part 4)

Anonymous — Tue, 27 Jun 2006 14:37:42 +0200

Hi Paul i am trying to use SyExpat. But it crashing inside function XML_Parse defined in xmlparse.c it is crashing on this line errorCode = processor(parser, bufferPtr, parseEndPtr, &bufferPtr); with panic code KERN-EXEC 3

I am using ParseFile example supplied along with SyExpat.

can any body please help me in making parser run.

Regards,

Saurabh

> Building an XML Parser Generator for Symbian (Part 4)

Dario Consoli — Sat, 22 Apr 2006 13:03:43 +0200

Hi Paul. I have the same problem like Ashish. If you try to parse a XML document with a default namespace (I mean xmlns="some:namespace:etc"), the parser goes in KERN-EXEC 3. It works if you specify the prefix (I mean xmlns:ns1="some:namespace:etc"). Hope you can give us some advice. Thank you

> Building an XML Parser Generator for Symbian (Part 4)

Max — Sat, 01 Apr 2006 12:29:45 +0200

Hi,

did anyone manage to build for Symbian 9.1 or is there any public available download of the precompiled dll?

Regards Max

> Building an XML Parser Generator for Symbian (Part 4)

Twm Davies — Mon, 16 Jan 2006 22:02:06 +0100

Good job on porting this expat. I've found it very useful However if the parser cannot be created due to OOM then it access violates when accessing iParser (it is null);

I added the lines in bold and it fixed the problem - a leave is generated to halt the operation on OOM.

void CExpatParserBase::BaseConstructL(const TDesC& aEncoding)

const TDesC& tmp = KSeperator;

const TChar c = tmp[0];

iParser = XML_ParserCreateNS( RECAST_TO_XML_CHAR(aEncoding.Ptr()), c);

if(!iParser)

User::Leave(KErrNoMemory);

TExpatDocumentHandlers* docHandlers = new (ELeave)

TExpatDocumentHandlers;

docHandlers->iDeclHandler = NULL;

docHandlers->iDocHandler = NULL;

> Building an XML Parser Generator for Symbian (Part 4)

Ashish Chopra — Thu, 22 Dec 2005 10:26:41 +0100

hi Paul

I must say that you've done a commendable job in providing the C++ wrapper over Expat so that the integration in Symbian is made easier.

There is a small issue, though. I was trying to use SyExpat code from www.toddsoftware.com. I kept encountering a Â‘Access Violation in EUSER.DLL' error whenever i tried to parse a certain XML document.

After a long debugging session, it turned out that in file "./lib/xmlparse.c" line no 2970, a call is made to the C++ wrapper as

if (attId && startNamespaceDeclHandler) startNamespaceDeclHandler(handlerArg, prefix->name, prefix->binding ? uri : 0);

the function called, in file "./Symbian/SyExpat.cpp" line no. 227, is

static void StartNamespaceHandler(void *userData, const XML_Char *aPrefix, const XML_Char *aURI)

if a default namespace is mentioned in XML document under the format xmlns="urn:namspace", then the code crashes with the access violation error mentioned above. This happens due to the fact that the "aPrefix" parameter in the function call is returned to be NULL in this case, resulting in access of a NULL pointer when "aPrefix" is tried to recast in next line: const TPtr prefix(RECAST_FROM_XML_CHAR(aPrefix))

In conclusion, it seems that although default namespace handling exists in code of Expat, the same is not ported correctly over C++ wrapper classes.

Can you please suggest what sort of changes should be made in the C++ code, so that this error is handled. I'm using Symbian SDK 8.0a.

hope to hear from you soon

thanks

Ashish

> Building an XML Parser Generator for Symbian (Part 4)

Anonymous — Thu, 22 Dec 2005 09:35:09 +0100

Hi Ashish,

Would it be possible for you to email me an example XML file showing the error?

Thanks

Paul (paul at toddsoftware.com)

> Possible bug in the SyExpat.cpp

Ashish Chopra — Thu, 22 Dec 2005 09:21:51 +0100

hi Paul

I must say that you've done a commendable job in providing the C++ wrapper over Expat so that the integration in Symbian is made easier.

There is a small issue, though. I was trying to use SyExpat code from www.toddsoftware.com. I kept encountering a Â‘Access Violation in EUSER.DLL' error whenever i tried to parse a certain XML document.

After a long debugging session, it turned out that in file "./lib/xmlparse.c" line no 2970, a call is made to the C++ wrapper as

if (attId && startNamespaceDeclHandler) startNamespaceDeclHandler(handlerArg, prefix->name, prefix->binding ? uri : 0);

the function called, in file "./Symbian/SyExpat.cpp" line no. 227, is

static void StartNamespaceHandler(void *userData, const XML_Char *aPrefix, const XML_Char *aURI)

if a default namespace is mentioned in XML document under the format xmlns="urn:namspace", then the code crashes with the access violation error mentioned above. This happens due to the fact that the "aPrefix" parameter in the function call is returned to be NULL in this case, resulting in access of a NULL pointer when "aPrefix" is tried to recast in next line:

const TPtrC prefix(RECAST_FROM_XML_CHAR(aPrefix))

In conclusion, it seems that although default namespace handling exists in code of Expat, the same is not ported correctly over C++ wrapper classes.

Can you please suggest what sort of changes should be made in the C++ code, so that this error is handled. I'm using Symbian SDK 8.0a.

hope to hear from you soon

thanks

Ashish

> Building an XML Parser Generator for Symbian (Part 4)

Micky Menezes — Wed, 01 Dec 2004 13:48:49 +0100

Hi, Please note ResumeParser form expat 1.95.8 is not available in the same.

so, I have added following in the SyExpat.cpp

EXPORT_C TSyExpatStatus CExpatParserBase::Resume()

return (TSyExpatStatus)XML_ResumeParser(REINTERPRET_CAST(XML_Parser,iParser));

Thanks and Regards, Micky

> Building an XML Parser Generator for Symbian (Part 4)

PaulT — Fri, 19 Nov 2004 17:53:43 +0100

A number of bugs were recently addressed as I think I might have put the wrong files on NewLC.

The latest version can always downloaded from toddsoftware.com

Paul

Building an XML Parser Generator for Symbian (Part 4)

paul — Wed, 10 Nov 2004 18:29:31 +0100

This article presents the generator class that makes the structure of the XML you are generating easier to understand and as such it can be easily understood and debugged as the code naturally maps to the XML format.
read more