Where is the XML Editor source code

I am using the Eclipse which version as following:

Eclipse Java EE IDE for Web Developers.

Version:   Indigo   Service   Release   1 
Build id:   20110916-0149 

It includes an XML Editor plugin, my question is: Where is the source code for the XML Editor?
Can anybody give me an URL for getting the source code of the XML Editor?

Whenever you have a question about where the source for a plugin is in Eclipse, you can use a little known hidden feature in Eclipse called the Plugin Spy.

Put your cursor focus on whatever you are interested in inside Eclipse and hit Alt+Shift+F1.

In the case of the XML Editor the result looks like the image below. As you can see, the plugin is org.eclipse.wst.xml.ui, and it even gives you the class to start with (XMLMultiPageEditorPart).

There is some great additional detail on finding and working with Eclipse source here: http://www.vogella.com/articles/EclipseCodeAccess/article.html#swt_spy