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CXMLFile - A Simple C++ XML Parser

, 19 Mar 2008
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An article on simple and fast C++ XML parser

Introduction

This article is about a simple and fast C++ XML parser class. There is often a need for an effective XML parser that is able to load the XML document, validate it, and browse it. In .NET environment there is a large native support for handling a lot of types of XML documents, but the same native support is missing from the original C++, MFC etc. There is, however, a COM alternative for XML file parsing and handling but it takes some time to learn it, and to use it in the right way.

This article is a simple attempt to make a C++ developer's life a bit easier than it usually is. This is support for handling the well-formed XML documents in the simplest possible way: load it, validate it, and browse it. This supports the following XML elements:

  • A simple TAG element, like <Element>
  • A simple ATTRIBUTE element, like Attribute="Value"
  • A simple TEXT element, like [Text]

Below is an example of a simple XML file that is supported:

    <?xml version="1.0" encoding="ISO-8859-1"?>
    <note>
        <to>Tove</to>
        <from>Jani</from>

        <heading>Reminder</heading>
        <body>Don't forget me this weekend!</body>
    </note>

The presented XML classes are able to load this type of XML document, check if it is well-formed, and browse throughout its content. There are only two classes that provide this functionality.

The first class is called the CXMLFile class, and its main purpose is to load an XML file, validate its structure, and create an XML element collection out of its content. This collection of XML elements will represent the loaded XML file in the system memory. Its easy then to modify the inner struture of this collection, that is, to modify the XML file itself. This class also supports the loading of XML files from the hard-disk or from the memory stream, which is a special usage (ie. on some web server). The CXMLFile class can also output the XML element collection from the system memory to the file on the hard-disk.

The second class is called the CXMLElement class. It is used by the previous class, and will be used by the developer when browsing or modifying the inner structure of an XML file in the system memory, that is, when modifying the inner structure of the XML element collection. It has the basic support for the appending of this collection, and browsing it. It can provide information regarding the name, type or value of the current XML element from the collection.

Background

There are many articles on the CodeProject considering this topic, and this is a small contribution to these articles population. Hope that the readers and developers will find it useful in their everyday work.

Using the Code

It's quite easy to load an XML document from the hard-disk. See an example below:

#include <span class="code-string">"XMLFile.h"</span>

...

_TCHAR lpszXMLFilePath[] = _T("A path to the XML file here...");
CXMLFile xmlFile;
if (xmlFile.LoadFromFile(lpszXMLFilePath))
{
   // Success
}
else
{
   // Error
}

To load an XML document from the memory stream:

...

// lpData and dwDataSize are obtained elsewhere

CXMLFile xmlFile;
if (xmlFile.LoadFromStream(lpData, dwDataSize))
{
    // Success
}
else
{
    // Error
}

To save the XML element collection to the file on the hard-disk, do the following:

if (xmlFile.SaveToFile(lpszXMLFilePath))
{
    // Success
}
else
{
    // Error
}

After the call to LoadFromFile(), a method of the CXMLFile class, the validation and parsing of the custom XML file will be done. If the XML file is well-formed, it will be loaded in the system memory as collection of CXMLElement elements. One can gain access to this collection using another method of the CXMLFile class called GetRoot(). See below:

CXMLEElement* pRoot = xmlFile.GetRoot();

Having the pointer to the root-element of the XML collection in the system memory, there are some things that can be done here. The root-element of the collection is of the CXMLEElement class type. Here are the methods available:

// Returns the name of the current XML element
LPTSTR GetElementName();
// Returns the type of the current XML element
XML_ELEMENT_TYPE GetElementType();
// Returns the number of child elements of the current XML element
int GetChildNumber();
// Returns the first child element of the current XML element
CXMLElement* GetFirstChild();
// Returns the current child element of the current XML element
CXMLElement* GetCurrentChild();
// Returns the next child element of the current XML element
CXMLElement* GetNextChild();
// Returns the last child element of the current XML element
CXMLElement* GetLastChild();
// Sets the value of the current XML element (valid only for attribute elements)
void SetValue(LPTSTR lpszValue);
// Gets the value of the current XML element (valid only for attribute elements)
LPTSTR GetValue();

Modify the inner structure of the XML element collection using the following methods:

// Create the new XML element of the specified type
void Create(LPTSTR lpszElementName, XML_ELEMENT_TYPE type);
// Appends the new XML element to the end of the collection of the current XML element
void AppendChild(CXMLElement* lpXMLChild);

Using the first group of CXMLEElement class methods, one can browse the XML element collection. Using the second group of CXMLEElement class methods, one can create new XML elements of different types and append them to existing ones.

Speaking about the types of XML elements, here are they listed:

XET_TAG // TAG element
XET_ATTRIBUTE // ATTRIBUTE element
XET_TEXT // TEXT element

Points of Interest

I always had a problem with loading XML documents easily and manipulating with them. Now, I have useful classes that decrease my future development time when this type of work is required. I am also able now to easily parse RSS feeds that are used all over the Web. I am planning to extend this basic support to HTML, or XML documents that are not-so-well-formed, soon (when I find some more free time).

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

darkoman
Software Developer (Senior) Elektromehanika d.o.o. Nis
Serbia Serbia
He has a master degree in Computer Science at Faculty of Electronics in Nis (Serbia), and works as a C++/C# application developer for Windows platforms since 2001. He likes traveling, reading and meeting new people and cultures.

Comments and Discussions

 
QuestionProblem with XMLFile.h when compiling with DLL PinmemberGil Goodridge7-May-14 3:43 
QuestionLack of navigation and add/update/delete methods PinmemberAbagian11-Oct-12 13:19 
QuestionNice but very limited PinmemberMark4128-Oct-12 8:10 
Questiondoesnt work in nested tag with same name Pinmemberakazuba23-Aug-12 23:10 
GeneralThanks! Pinmemberliushul13-Jun-12 3:59 
Questionutf-8 Pinmembercedrix572-May-12 21:45 
QuestionMethod to use the code in application [modified] Pinmemberfull_gunjan1-Feb-12 18:06 
Questionit ' urgent Pinmembersamymazine12-Dec-11 14:22 
I am a student in an engineering school. I have a computer project to do which is to: enhance a mp4 video with annotations that are stored in an xml file (mp7).
by your program displays the entire contents of the XML file, for against me I want him m'affiche information stored in specific tags in the xml file.
The project idea is to design an interface to select two files: a. Mp4 and a. Mp7
It should then parse the mp7 looking for a specific tag, previously defined. Mp7 mp4 files and will be given. the
tag annotations to specify a timestamp and a location in the video data.
Then load the video interface. Mp4 in an area of the window, and below there is space to display text from the file previously parsed mp7 (specifically the file will contain an mp7 URL parser that we should go on Web to retrieve information to display).
at first I just want to display the annotations that I set all in my file before I go looking for the internet
I enjoyed your program and I really hope you to help me make my own I await your response
Thank you in advance.............
 
I m realy need your hel MR Darkoman
QuestionXML validation with a DTD file Pinmemberserup11-Sep-11 21:17 
GeneralProblem: please review my code [modified] Pinmemberlinwendong198217-May-11 20:07 
GeneralMy vote of 5 Pinmembersamcsu18-Apr-11 17:20 
GeneraltinyXML PinmemberAs_Sanya15-Dec-10 21:41 
AnswerRe: tinyXML Pinmemberdarkoman29-Dec-10 20:04 
GeneralOne type of tag is not handled... Pinmemberbala66629-Nov-10 23:18 
AnswerRe: One type of tag is not handled... Pinmemberdarkoman12-Dec-10 9:20 
GeneralMy vote of 5 PinmemberRajaManikandan_R23-Sep-10 18:15 
GeneralUsing nested elements with the same names - unable to load file PinmemberGYuval6-Jul-10 21:55 
GeneralA couple of problems PinmemberLEKV16-Feb-10 5:17 
AnswerRe: A couple of problems Pinmemberdarkoman16-Feb-10 9:25 
GeneralRe: A couple of problems PinmemberLEKV16-Feb-10 12:42 
GeneralRe: A couple of problems PinmemberLEKV17-Feb-10 4:44 
Generalnow i saved to file, and Pinmemberliaterez18-Nov-09 3:43 
Generalsorry for confused (- 1 and 4 are the same) Pinmemberliaterez18-Nov-09 3:44 
Generalxml reader performance Pinmemberliaterez17-Nov-09 5:01 
AnswerRe: xml reader performance Pinmemberdarkoman17-Nov-09 10:43 

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