From Wang Rui, "I've initially added the XML support of the new native osg format,

using osgDB::XmlParser. The extension for XML-formatted scenes is
.osgx, corresponding to .osgb for binary and .osgt for ascii. It could
either be rendered in osgviewer or edited by common web browsers and
xml editors because of a range of changes to fit the XML syntax. For
example, the recorded class names are slight modified, from
'osg::Geode' to 'osg--Geode'.

To quickly get an XML file:
# ./osgconv cow.osg cow.osgx

The StreamOperator header, InputStreram and OutputStream classes are
modified to be more portable for triple ascii/binary/XML formats. I
also fixed a bug in readImage()/writeImage() to share image objects if
needed.

The ReaderWriterOSG2 class now supports all three formats and
reading/writing scene objects (not nodes or images), thanks to
Torben's advice before.
"

include/osgDB/StreamOperator

@@ -39,6 +39,9 @@ public:
     virtual void writeProperty( const ObjectProperty& prop ) = 0;
     virtual void writeMark( const ObjectMark& mark ) = 0;
     virtual void writeCharArray( const char* s, unsigned int size ) = 0;
+    virtual void writeWrappedString( const std::string& str ) = 0;
+    
+    virtual void flush() { _out->flush(); }
     
 protected:
     std::ostream* _out;
@@ -79,6 +82,10 @@ public:
     virtual void readProperty( ObjectProperty& prop ) = 0;
     virtual void readMark( ObjectMark& mark ) = 0;
     virtual void readCharArray( char* s, unsigned int size ) = 0;
+    virtual void readWrappedString( std::string& str ) = 0;
+    
+    virtual bool matchString( const std::string& str ) { return false; }
+    virtual void advanceToCurrentEndBracket() {}
     
 protected:
     std::istream* _in;