Introduced CMake option OSG_PROVIDE_READFILE option that defaults to ON, but when switched to OFF disables the building of the osgDB::read*File() methods,

forcing users to use osgDB::readRef*File() methods.  The later is preferable as it closes a potential threading bug when using paging databases in conjunction
with the osgDB::Registry Object Cache.  This threading bug occurs when one thread gets an object from the Cache via an osgDB::read*File() call where only
a pointer to the object is passed back, so taking a reference to the object is delayed till it gets reassigned to a ref_ptr<>, but at the same time another
thread calls a flush of the Object Cache deleting this object as it's referenceCount is now zero.  Using osgDB::readREf*File() makes sure the a ref_ptr<> is
passed back and the referenceCount never goes to zero.

To ensure the OSG builds when OSG_PROVIDE_READFILE is to OFF the many cases of osgDB::read*File() usage had to be replaced with a ref_ptr<> osgDB::readRef*File()
usage.  The avoid this change causing lots of other client code to be rewritten to handle the use of ref_ptr<> in place of C pointer I introduced a serious of
templte methods in various class to adapt ref_ptr<> to the underly C pointer to be passed to old OSG API's, example of this is found in include/osg/Group:

    bool addChild(Node* child); // old method which can only be used with a Node*

    tempalte<class T> bool addChild(const osg::ref_ptr<T>& child) { return addChild(child.get()); } // adapter template method

These changes together cover 149 modified files, so it's a large submission. This extent of changes are warrent to make use of the Object Cache
and multi-threaded loaded more robust.



git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@15164 16af8721-9629-0410-8352-f15c8da7e697

src/osgDB/InputStream.cpp

@@ -320,7 +320,7 @@ InputStream& InputStream::operator>>( osg::BoundingSphered& bs)
 
 
 
-osg::Array* InputStream::readArray()
+osg::ref_ptr<osg::Array> InputStream::readArray()
 {
     osg::ref_ptr<osg::Array> array = NULL;
 
@@ -571,10 +571,10 @@ osg::Array* InputStream::readArray()
     if ( getException() ) return NULL;
     _arrayMap[id] = array;
 
-    return array.release();
+    return array;
 }
 
-osg::PrimitiveSet* InputStream::readPrimitiveSet()
+osg::ref_ptr<osg::PrimitiveSet> InputStream::readPrimitiveSet()
 {
     osg::ref_ptr<osg::PrimitiveSet> primitive = NULL;
 
@@ -663,10 +663,10 @@ osg::PrimitiveSet* InputStream::readPrimitiveSet()
     }
 
     if ( getException() ) return NULL;
-    return primitive.release();
+    return primitive;
 }
 
-osg::Image* InputStream::readImage(bool readFromExternal)
+osg::ref_ptr<osg::Image> InputStream::readImage(bool readFromExternal)
 {
     std::string className = "osg::Image";
     if ( _fileVersion>94 )  // ClassName property is only supported in 3.1.4 and higher
@@ -858,17 +858,17 @@ osg::Image* InputStream::readImage(bool readFromExternal)
     }
     else
     {
-        image = static_cast<osg::Image*>( readObjectFields("osg::Object", id, image.get()) );
+        image = readObjectFieldsOfType<osg::Image>("osg::Object", id, image.get());
         if ( image.valid() )
         {
             image->setFileName( name );
             image->setWriteHint( (osg::Image::WriteHint)writeHint );
         }
     }
-    return image.release();
+    return image;
 }
 
-osg::Object* InputStream::readObject( osg::Object* existingObj )
+osg::ref_ptr<osg::Object> InputStream::readObject( osg::Object* existingObj )
 {
     std::string className;
     unsigned int id = 0;
@@ -880,23 +880,23 @@ osg::Object* InputStream::readObject( osg::Object* existingObj )
     }
 
     *this >> BEGIN_BRACKET >> PROPERTY("UniqueID") >> id;
-    if ( getException() ) return NULL;
+    if ( getException() ) return 0;
 
     IdentifierMap::iterator itr = _identifierMap.find( id );
     if ( itr!=_identifierMap.end() )
     {
         advanceToCurrentEndBracket();
-        return itr->second.get();
+        return itr->second;
     }
 
     osg::ref_ptr<osg::Object> obj = readObjectFields( className, id, existingObj );
 
     advanceToCurrentEndBracket();
 
-    return obj.release();
+    return obj;
 }
 
-osg::Object* InputStream::readObjectFields( const std::string& className, unsigned int id, osg::Object* existingObj )
+osg::ref_ptr<osg::Object> InputStream::readObjectFields( const std::string& className, unsigned int id, osg::Object* existingObj )
 {
     ObjectWrapper* wrapper = Registry::instance()->getObjectWrapperManager()->findWrapper( className );
     if ( !wrapper )
@@ -927,7 +927,7 @@ osg::Object* InputStream::readObjectFields( const std::string& className, unsign
             _fields.pop_back();
         }
     }
-    return obj.release();
+    return obj;
 }
 
 void InputStream::readSchema( std::istream& fin )