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This is a small XML parser, based purely on STL. There are two main classes XmlStream and XmlParser. XmlParser.h contains most of the parsing code. It has several state variable, which can be split up into two categories:

Buffer state - Shows where we are parsing from
Parsing state - Shows what we have found

XmlParser makes extensive use of offsets to keep track of its state. This is done by design. In order to maximize speed it does not do any string copies.

To start parsing declare an instance of the class XmlStream and setup the buffer that you want to parse. An example is included in Parser.cpp. Call parse in XmlStream, passing in a pointer to the buffer and the buffers length. You will see screen output showing what has been found. This is simple debug output and can be turned off.

XmlNotify is used as an interface class to notify a subscriber of nodes and elements being found. There is a pointer to a subscriber in the XmlStream class. The subscriber can be set using setSubscriber.

Notice that no XML document declaration is included nor is a schema included. If those exist in your buffer don't send them to the parser. Later, the ability to remove these, will added in the code to step through these. so this is a non-validating parser. There is one bug in the parser. When an empty node is encountered it will be reported as an element this will be fixed later. An example of this is included in the sample code.

If you have any suggestions or improvements let me know.

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David Hubbard

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multiple entries of the same name

14 Jul '03 - 11:58

thanks for the great XML tools, they are very easy to use.

I would like to have a table represented in XML but this implementation of the parser doesn't handle multiple entries of the same name, for example:

<HOST>
<NAME>cod</NAME>
<DNSNAME>cod.somecorp.com</DNSNAME>
<NIC>
   <MAC>0040f4612820</MAC>
   <IP>192.168.172.54</IP>
   <IP>192.168.173.54</IP>
</NIC>
</HOST>
<HOST>
<NAME>drum</NAME>
<DNSNAME>drum.somecorp.com</DNSNAME>
<NIC>
   <IP>192.168.172.47</IP>
</NIC>
</HOST>

in this example the <HOST> and <IP> tags both have multiple entries.   the XMLDialog displays the host cod for both entries, and only 1 IP address, it would be nice to be able to address these in the read/write methods like:

"HOST[0]:NIC:IP[1]","192.168.173.54"

--Ben Burnett

Re: multiple entries of the same name

14 Oct '05 - 17:47

I found the same problem, and believe it is related to this code in XmlStream.cpp:

// if new parse cur position is in the last parser
// last tag position we are done with the node
char * curPos = parserNode.getCurPos();
char * lastCurPos = parser.getLastTagPos();
if ( curPos >= lastCurPos )
{
break;
}

This code seems to assume that if you hit the end of a node at a certain level of XML heirarchy, you also must be done with that entire heirarchical level altogether. (When first </HOST> is hit, there won't be any more <HOST> entries to follow).

I simply removed that code and allowed the above parser.parse() method to do what it does, and that seemed to fix the problem.

I don't quite know if this will introduce other issues, though.

- MikeG

-- modified at 23:47 Friday 14th October, 2005

Nodes have the same name BUG

Ken Lee

9 Apr '03 - 20:43

I found a bug... when nearby nodes have the same name, the next node will be ignore ex: will only found the first node "n0"
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Re: Nodes have the same name BUG

Ken Lee

9 Apr '03 - 20:52

sorry... example code here... <Node id="n0"> <Node id="n1"> <Element id="e1"/> </Node> </Node>
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pretty print of stream

7 Feb '03 - 18:00

in generell i find my way of prettyprinting a bit more easier to read:

stringstream strm;
strm
            << "<Contacts>" << endl

            << "<Contact/>" << endl

            << initContact( "Joe Blow", 100 )
            << initContact( "Mary Jane", 400, true, true )

            << "</Contacts>" << endl
;

another question:
even its a examples, i find it better to return some string, which is streamed, instead to write directly to the stream.

this method safes an unneccesary argument,
can be reused easier,
ok only disadvantage: creating temporarily a string for returning. but i think its ok, because the entries are all pretty small...

---------------------
string initContact ( LPCTSTR cname, long id,
                       bool hasAttributes = false,
                       bool showToDo = false )
{
      stringstream strm;

     if ( hasAttributes )
          strm << "<Contact language=\"english\" hasEmail=\"false\">" << endl;
     else
          strm << "<Contact>" << endl;
      strm
            << "<name>" << cname << "</name>" << endl
            << "<id>" << id << "</id>" << endl
      ;

     if ( showToDo )
     {
            strm
                  << "<ToDo>" << endl
                  << "<Item></Item>" << endl
                  << "<Item/>" << endl
                  << "<Item>Call</Item>" << endl
                  << "<Item>Say Hello</Item>" << endl
                  << "<Item>Take Notes</Item>" << endl
                  << "<Item>HangUp</Item>" << endl
                  << "</ToDo>" << endl
            ;
     }

     strm << "</Contact>" << endl;
      return( strm.str() );
}

attributes

7 Feb '03 - 17:56

to be valid XML u should enclose all attribs with ": strm << "<Contact language=\"english\" hasEmail=\"false\">" << endl; cu george.
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Bug fix for null nodes

2 Jan '03 - 10:06

Parser will 'kick out' of a parent node when a subnode is a null node entry:

<Skin Name="CMX">
<Information>
   <Author>John Doe</Author>
   <Copyright>2003</Copyright>
</Information>
<Resource Type="Font" Name="SmallFont" File="Font10.fnt"/>
<Resource Type="Font" Name="NormalFont" File="Font16.fnt"/>
<Resource Type="Font" Name="GameText" File="GameText.fnt"/>
<Resource Type="Image" Name="Title" File="TitleScr.jpg"/>
<Resource Type="Image" Name="MenuBack" File="MenuScr.jpg"/>
</Skin>

This will kick out on the first "Resource" node.

The problem lies in xmlparser.h, the routine 'parse()':

          // if null tag no data or last tag
          if ( hasNullTag() )
          {
               // update cur position
               _current   = _firstTagEnd + idTagRightLength;

               // done so show success
               return true;
          }

needs to change to:

          // if null tag no data or last tag
          if ( hasNullTag() )
          {
               // update cur position
               _current   = _firstTagEnd + idTagRightLength;
               _lastTagStart = _current;
               _lastTagEnd   = _current;

               // done so show success
               return true;
          }

and the parser will work properly.

Re: Bug fix for null nodes

6 Jan '03 - 5:04

Strange... The fix does work, after a fashion, but there seems to be no rhyme or reason as to whether a null tag is considered a node or an element. I've modified my code not to worry about it, but if anybody can figure this out, I'd greatly appreciate it.
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Anoying bug for an xml parser

21 Nov '02 - 20:42

I've got an xml file with standard header and comments like this: <?xml version="1.0" ?> <!-- Ok ? --> <!-- Ok --> <Tag currentTag="0"> ... The parser fails reading the xml file because of the header and comments. Well, good job anyway. I'm working on the fix, I'll post it when done. Yarp http://www.senosoft.com/
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Re: Anoying bug for an xml parser

21 Nov '02 - 21:17

So here'a partial fix:

  bool hasNullTag ()
  {
    // get beginning of first tag
    char * firstTagBegin = _buffer + _firstTagStart;
    // get end of first tag
    char * firstTagEnd = _buffer + _firstTagEnd - 1;
 
    // if null tag marker
    if (( *firstTagBegin == '<' && *(firstTagBegin+1) == '?' ) ||
        ( *firstTagBegin == '<' && *(firstTagBegin+1) == '!' ) ||
        ( *firstTagEnd == '/' && *(firstTagEnd+1) == '>' ))
      return true;
    else
      return false;
  }

Not perfect since the XmlNotify class is still called but this is easy to fix too:
Each time a _subscriber is called just test if the parsed name isn't "?" or "!". I recall that the _subscriber is called by XmlStream to notify the caller for the xml parsing result.

Yarp
http://www.senosoft.com/

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This is a small non-validating XML parser based purely on STL

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