OpenSceneGraph/src/osgDB/Registry.cpp

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#include <osg/Notify>
#include <osg/Object>
#include <osg/Image>
#include <osg/Node>
#include <osg/Group>
#include <osg/Geode>
#include <osg/ApplicationUsage>

#include <osgDB/Registry>
#include <osgDB/FileUtils>
#include <osgDB/FileNameUtils>

#include <stdio.h>

#include <algorithm>
#include <set>

using namespace osg;
using namespace osgDB;

class AvailableReaderWriterIterator
{
public:
    AvailableReaderWriterIterator(Registry::ReaderWriterList& rwList):
        _rwList(rwList) {}


    ReaderWriter& operator * () { return *get(); }
    ReaderWriter* operator -> () { return get(); }
    
    bool valid() { return get()!=0; }
    
    void operator ++() 
    {
        _rwUsed.insert(get());
    }
    

protected:

    Registry::ReaderWriterList&     _rwList;
    std::set<ReaderWriter*>         _rwUsed;

    ReaderWriter* get() 
    {
        Registry::ReaderWriterList::iterator itr=_rwList.begin();
        for(;itr!=_rwList.end();++itr)
        {
            if (_rwUsed.find(itr->get())==_rwUsed.end())
            {
                return itr->get();
            }
        }
        return 0;
    }

};

#if 0
    // temporary test of autoregistering, not compiled by default.
    enum Methods
    {
        SET_1,
        SET_2,
        END
    };


    typedef std::pair<Methods,std::string> MethodPair;

    class Proxy
    {
    public:
        Proxy(MethodPair* methods)
        {
            std::cout<<"methods "<<methods<<std::endl;
            for(int i=0;methods[i].first!=END;++i)
            {
                std::cout<<"\t"<<methods[i].first<<"\t"<<methods[i].second<<std::endl;
            }
        }
    };


    static MethodPair methods[] =
    {
        MethodPair(SET_1,"SET_1"),
        MethodPair(SET_2,"SET_2"),
        MethodPair(END,"")
    };

    Proxy myproxy(methods);

#endif

void PrintFilePathList(std::ostream& stream,const FilePathList& filepath)
{
    for(FilePathList::const_iterator itr=filepath.begin();
        itr!=filepath.end();
        ++itr)
    {
        stream << "    "<< *itr<<std::endl;
    }
}

Registry* Registry::instance(bool erase)
{
    static ref_ptr<Registry> s_nodeFactory = new Registry;
    if (erase) 
    {
        s_nodeFactory->closeAllLibraries();
        s_nodeFactory = 0;
    }
    return s_nodeFactory.get(); // will return NULL on erase
}


// definition of the Registry
Registry::Registry()
{
    // comment out because it was causing problems under OSX - causing it to crash osgconv when constucting ostream in osg::notify().
    // notify(INFO) << "Constructing osg::Registry"<<std::endl;

    _createNodeFromImage = false;
    _openingLibrary = false;
    
    _useObjectCacheHint = false;

    initFilePathLists();

    // register file extension alias.
    addFileExtensionAlias("sgi",  "rgb");
    addFileExtensionAlias("rgba", "rgb");
    addFileExtensionAlias("int",  "rgb");
    addFileExtensionAlias("inta", "rgb");
    addFileExtensionAlias("bw",   "rgb");

    addFileExtensionAlias("ivz",   "gz");
    addFileExtensionAlias("ozg",   "gz");
    
#if defined(__DARWIN_OSX__)
    addFileExtensionAlias("jpg",  "qt");
    addFileExtensionAlias("jpe",  "qt");
    addFileExtensionAlias("jpeg", "qt");
    addFileExtensionAlias("tif",  "qt");
    addFileExtensionAlias("tiff", "qt");
    addFileExtensionAlias("gif",  "qt");
    addFileExtensionAlias("png",  "qt");
#else
    addFileExtensionAlias("jpg",  "jpeg");
    addFileExtensionAlias("jpe",  "jpeg");
    addFileExtensionAlias("tif",  "tiff");
#endif

    // remove geo to lwo alias as the new Carbon Graphics GEO format
    // also uses the .geo. It is still possible to load light wave .geo
    // files via loading the lwo plugin explicitly and then doing a readNodeFile.
    //addFileExtensionAlias("geo",  "lwo");
    addFileExtensionAlias("lw",   "lwo");

    addFileExtensionAlias("wrl",   "iv");
    
    // add alias for the text/freetype plugin.
    addFileExtensionAlias("ttf",   "freetype");  // true type
    addFileExtensionAlias("ttc",   "freetype");  // true type
    addFileExtensionAlias("cid",   "freetype");  // Postscript CID-Fonts
    addFileExtensionAlias("cff",   "freetype");  // OpenType
    addFileExtensionAlias("cef",   "freetype");  // OpenType
    addFileExtensionAlias("fon",   "freetype");  // Windows bitmap fonts
    addFileExtensionAlias("fnt",   "freetype");    // Windows bitmap fonts
    
    // wont't add type1 and type2 until resolve extension collision with Peformer binary and ascii files.
    // addFileExtensionAlias("pfb",   "freetype");  // type1 binary
    // addFileExtensionAlias("pfa",   "freetype");  // type2 ascii


    // portable bitmap, greyscale and colour/pixmap image formats
    addFileExtensionAlias("pbm", "pnm");
    addFileExtensionAlias("pgm", "pnm");
    addFileExtensionAlias("ppm", "pnm");
    
}


Registry::~Registry()
{
    // switch off the pager and its associated thread before we clean up 
    // rest of the Registry.
    _databasePager = 0;

    // clean up the SharedStateManager 
    _sharedStateManager = 0;
    
    // object cache clear needed here to prevent crash in unref() of
    // the objects it contains when running the TXP plugin.
    // Not sure why, but perhaps there is is something in a TXP plugin
    // which is deleted the data before its ref count hits zero, perhaps
    // even some issue with objects be allocated by a plugin that is
    // mainted after that plugin is deleted...  Robert Osfield, Jan 2004.
    _objectCache.clear();


    // unload all the plugin before we finally destruct.
    closeAllLibraries();
}

#ifndef WIN32
static osg::ApplicationUsageProxy Registry_e0(osg::ApplicationUsage::ENVIRONMENTAL_VARIABLE,"OSG_FILE_PATH <path>[:path]..","Paths for locating datafiles");
#else
static osg::ApplicationUsageProxy Registry_e0(osg::ApplicationUsage::ENVIRONMENTAL_VARIABLE,"OSG_FILE_PATH <path>[;path]..","Paths for locating datafiles");
#endif

void Registry::initDataFilePathList()
{
    //
    // set up data file paths
    //
    char *ptr;
    if( (ptr = getenv( "OSG_FILE_PATH" )) )
    {
        //notify(DEBUG_INFO) << "OSG_FILE_PATH("<<ptr<<")"<<std::endl;
        setDataFilePathList(ptr);
    }
    else if( (ptr = getenv( "OSGFILEPATH" )) )
    {
        //notify(DEBUG_INFO) << "OSGFILEPATH("<<ptr<<")"<<std::endl;
        setDataFilePathList(ptr);
    }

    //osg::notify(INFO)<<"Data FilePathList"<<std::endl;
    //PrintFilePathList(osg::notify(INFO),getDataFilePathList());
}

#ifndef WIN32
static osg::ApplicationUsageProxy Registry_e1(osg::ApplicationUsage::ENVIRONMENTAL_VARIABLE,"OSG_LIBRARY_PATH <path>[:path]..","Paths for locating libraries/ plugins");
#else
static osg::ApplicationUsageProxy Registry_e1(osg::ApplicationUsage::ENVIRONMENTAL_VARIABLE,"OSG_LIBRARY_PATH <path>[;path]..","Paths for locating libraries/ plugins");
#endif

void Registry::initLibraryFilePathList()
{
    //
    // set up library paths
    //
    char* ptr;
    if( (ptr = getenv( "OSG_LIBRARY_PATH")) )
    {
        //notify(DEBUG_INFO) << "OSG_LIBRARY_PATH("<<ptr<<")"<<std::endl;
        setLibraryFilePathList(ptr);
    }
    else if( (ptr = getenv( "OSG_LD_LIBRARY_PATH")) )
    {
        //notify(DEBUG_INFO) << "OSG_LD_LIBRARY_PATH("<<ptr<<")"<<std::endl;
        setLibraryFilePathList(ptr);
    }

#ifdef __sgi

    convertStringPathIntoFilePathList("/usr/lib32/:/usr/local/lib32/",_libraryFilePath);

    // bloody mess see rld(1) man page
    #if (_MIPS_SIM == _MIPS_SIM_ABI32)


    if( (ptr = getenv( "LD_LIBRARY_PATH" )))
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }

    #elif (_MIPS_SIM == _MIPS_SIM_NABI32)

    if( !(ptr = getenv( "LD_LIBRARYN32_PATH" )))
        ptr = getenv( "LD_LIBRARY_PATH" );

    if( ptr )
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }

    #elif (_MIPS_SIM == _MIPS_SIM_ABI64)

    if( !(ptr = getenv( "LD_LIBRARY64_PATH" )))
        ptr = getenv( "LD_LIBRARY_PATH" );

    if( ptr )
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }
    #endif
    
#elif defined(__CYGWIN__)


    if ((ptr = getenv( "PATH" )))
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }

    convertStringPathIntoFilePathList("/usr/bin/:/usr/local/bin/",_libraryFilePath);
    
#elif defined(WIN32)



    if ((ptr = getenv( "PATH" )))
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }

    convertStringPathIntoFilePathList("C:/Windows/System/",_libraryFilePath);

#elif defined(__DARWIN_OSX__)

    if ((ptr = getenv( "DYLD_LIBRARY_PATH" )) )
    {
        convertStringPathIntoFilePathList(ptr, _libraryFilePath);
    }

#else   

    if( (ptr = getenv( "LD_LIBRARY_PATH" )) )
    {
        convertStringPathIntoFilePathList(ptr,_libraryFilePath);
    }

    convertStringPathIntoFilePathList("/usr/lib/:/usr/local/lib/",_libraryFilePath);

#endif

    //osg::notify(INFO)<<"Library FilePathList"<<std::endl;
    //PrintFilePathList(osg::notify(INFO),getLibraryFilePathList());

}

void Registry::readCommandLine(osg::ArgumentParser& arguments)
{
    // report the usage options.
    if (arguments.getApplicationUsage())
    {
        arguments.getApplicationUsage()->addCommandLineOption("-l <library>","Load the plugin");
        arguments.getApplicationUsage()->addCommandLineOption("-e <extension>","Load the plugin associated with handling files with specified extension");
        arguments.getApplicationUsage()->addCommandLineOption("-O <option_string>","Provide an option string to reader/writers used to load databases");
    }

    std::string value;
    while(arguments.read("-l",value))
    {
        loadLibrary(value);
    }
        
    while(arguments.read("-e",value))
    {
        std::string libName = createLibraryNameForExtension(value);
        loadLibrary(libName);
    }

    while(arguments.read("-O",value))
    {
        setOptions(new osgDB::ReaderWriter::Options(value));
    }
}

void Registry::addDotOsgWrapper(DotOsgWrapper* wrapper)
{
    if (wrapper==0L) return;

    //notify(INFO) << "osg::Registry::addDotOsgWrapper("<<wrapper->getName()<<")"<< std::endl;
    const DotOsgWrapper::Associates& assoc = wrapper->getAssociates();
    
    for(DotOsgWrapper::Associates::const_iterator itr=assoc.begin();
                                                  itr!=assoc.end();
                                                  ++itr)
    {
        //notify(INFO) << "    ("<<*itr<<")"<< std::endl;
    }

    const std::string& name = wrapper->getName();
    const osg::Object* proto = wrapper->getPrototype();

    _objectWrapperMap[name] = wrapper;
    if (wrapper->getReadWriteMode()==DotOsgWrapper::READ_AND_WRITE) _classNameWrapperMap[name] = wrapper;
    
    if (proto)
    {
        std::string libraryName = proto->libraryName();
        std::string compositeName = libraryName + "::" + name;

        _objectWrapperMap[compositeName] = wrapper;
        if (wrapper->getReadWriteMode()==DotOsgWrapper::READ_AND_WRITE) _classNameWrapperMap[compositeName] = wrapper;

        if (dynamic_cast<const Image*>(proto))
        {
            _imageWrapperMap[name] = wrapper;
            _imageWrapperMap[compositeName] = wrapper;
        }
        if (dynamic_cast<const Drawable*>(proto))
        {
              _drawableWrapperMap[name] = wrapper;
              _drawableWrapperMap[compositeName] = wrapper;
        }
        if (dynamic_cast<const StateAttribute*>(proto))
        {
            _stateAttrWrapperMap[name] = wrapper;
            _stateAttrWrapperMap[compositeName] = wrapper;
        }
        if (dynamic_cast<const Node*>(proto))
        {
            _nodeWrapperMap[name] = wrapper;
            _nodeWrapperMap[compositeName] = wrapper;
        }


    }
}

// need to change to delete all instances of wrapper, since we
// now can have a wrapper entered twice with the addition of the
// library::class composite name.
void Registry::eraseWrapper(DotOsgWrapperMap& wrappermap,DotOsgWrapper* wrapper)
{
    typedef std::vector<DotOsgWrapperMap::iterator> EraseList;
    EraseList eraseList;
    for(DotOsgWrapperMap::iterator witr=wrappermap.begin();
        witr!=wrappermap.end();
        ++witr)
    {
        if (witr->second==wrapper) eraseList.push_back(witr);
    }
    for(EraseList::iterator eitr=eraseList.begin();
        eitr!=eraseList.end();
        ++eitr)
    {
        wrappermap.erase(*eitr);
    }
}

void Registry::removeDotOsgWrapper(DotOsgWrapper* wrapper)
{
    if (wrapper==0L) return;

    eraseWrapper(_objectWrapperMap,wrapper);
    eraseWrapper(_classNameWrapperMap,wrapper);
    eraseWrapper(_imageWrapperMap,wrapper);
    eraseWrapper(_drawableWrapperMap,wrapper);
    eraseWrapper(_stateAttrWrapperMap,wrapper);
    eraseWrapper(_nodeWrapperMap,wrapper);
}

void Registry::addReaderWriter(ReaderWriter* rw)
{
    if (rw==0L) return;

    // notify(INFO) << "osg::Registry::addReaderWriter("<<rw->className()<<")"<< std::endl;

    _rwList.push_back(rw);

}


void Registry::removeReaderWriter(ReaderWriter* rw)
{
    if (rw==0L) return;

//    notify(INFO) << "osg::Registry::removeReaderWriter();"<< std::endl;

    ReaderWriterList::iterator rwitr = std::find(_rwList.begin(),_rwList.end(),rw);
    if (rwitr!=_rwList.end())
    {
        _rwList.erase(rwitr);
    }

}


void Registry::addFileExtensionAlias(const std::string mapExt, const std::string toExt)
{
    if (mapExt!=toExt) _extAliasMap[mapExt] = toExt;
}

std::string Registry::createLibraryNameForFile(const std::string& fileName)
{
    std::string ext = getLowerCaseFileExtension(fileName);
    return createLibraryNameForExtension(ext);
}


std::string Registry::createLibraryNameForExtension(const std::string& ext)
{

    ExtensionAliasMap::iterator itr=_extAliasMap.find(ext);
    if (itr!=_extAliasMap.end()) return createLibraryNameForExtension(itr->second);

#if defined(WIN32)
    // !! recheck evolving Cygwin DLL extension naming protocols !! NHV
    #ifdef __CYGWIN__
        return "cygosgdb_"+ext+".dll";
    #elif defined(__MINGW32__)
        return "libosgdb_"+ext+".dll";
    #else
        #ifdef _DEBUG
            return "osgdb_"+ext+"d.dll";
        #else
            return "osgdb_"+ext+".dll";
        #endif
    #endif
#elif macintosh
    return "osgdb_"+ext;
#elif defined(__hpux__)
    // why don't we use PLUGIN_EXT from the makefiles here?
    return "osgdb_"+ext+".sl";
#else
    return "osgdb_"+ext+".so";
#endif

}

std::string Registry::createLibraryNameForNodeKit(const std::string& name)
{
#if defined(WIN32)
    // !! recheck evolving Cygwin DLL extension naming protocols !! NHV
    #ifdef __CYGWIN__ // [
    return "cyg"+name+".dll";
    #elif defined(__MINGW32__)
        return "lib"+name+".dll";
    #else
        #ifdef _DEBUG
            return name+"d.dll";
        #else
            return name+".dll";
        #endif
    #endif
#elif macintosh
    return name;
#elif defined(__hpux__)
    // why don't we use PLUGIN_EXT from the makefiles here?
    return "lib"+name+".sl";
#else
    return "lib"+name+".so";
#endif
}

bool Registry::loadLibrary(const std::string& fileName)
{
    DynamicLibrary* dl = getLibrary(fileName);
    if (dl) return false;

    _openingLibrary=true;

    dl = DynamicLibrary::loadLibrary(fileName);
    _openingLibrary=false;

    if (dl)
    {
        _dlList.push_back(dl);
        return true;
    }
    return false;
}


bool Registry::closeLibrary(const std::string& fileName)
{
    DynamicLibraryList::iterator ditr = getLibraryItr(fileName);
    if (ditr!=_dlList.end())
    {
        _dlList.erase(ditr);
        return true;
    }
    return false;
}

void Registry::closeAllLibraries()
{
    _dlList.clear();
}

Registry::DynamicLibraryList::iterator Registry::getLibraryItr(const std::string& fileName)
{
    DynamicLibraryList::iterator ditr = _dlList.begin();
    for(;ditr!=_dlList.end();++ditr)
    {
        if ((*ditr)->getName()==fileName) return ditr;
    }
    return _dlList.end();
}

DynamicLibrary* Registry::getLibrary(const std::string& fileName)
{
    DynamicLibraryList::iterator ditr = getLibraryItr(fileName);
    if (ditr!=_dlList.end()) return ditr->get();
    else return NULL;
}

ReaderWriter* Registry::getReaderWriterForExtension(const std::string& ext)
{
    // record the existing reader writer.
    std::set<ReaderWriter*> rwOriginal;

    // first attemt one of the installed loaders
    for(ReaderWriterList::iterator itr=_rwList.begin();
        itr!=_rwList.end();
        ++itr)
    {
        rwOriginal.insert(itr->get());
        if((*itr)->acceptsExtension(ext)) return (*itr).get();
    }

    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForExtension(ext);
    notify(INFO) << "Now checking for plug-in "<<libraryName<< std::endl;
    if (loadLibrary(libraryName))
    {
        for(ReaderWriterList::iterator itr=_rwList.begin();
            itr!=_rwList.end();
            ++itr)
        {
            if (rwOriginal.find(itr->get())==rwOriginal.end())
          if((*itr)->acceptsExtension(ext)) return (*itr).get();
        }
    }

    return NULL;

}

struct concrete_wrapper: basic_type_wrapper 
{
    concrete_wrapper(const osg::Object *myobj) : myobj_(myobj) {}
    bool matches(const osg::Object *proto) const
    {
        return myobj_->isSameKindAs(proto);
    }
    const osg::Object *myobj_;
};

osg::Object* Registry::readObjectOfType(const osg::Object& compObj,Input& fr)
{
    return readObjectOfType(concrete_wrapper(&compObj), fr);
}

osg::Object* Registry::readObjectOfType(const basic_type_wrapper &btw,Input& fr)
{
    const char *str = fr[0].getStr();
    if (str==NULL) return NULL;

    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            Object* obj = fr.getObjectForUniqueID(fr[1].getStr());
            if (obj && btw.matches(obj))
            {
                fr+=2;
                return obj;
            }
        }
        else return NULL;

    }

    std::string name = str;
    DotOsgWrapperMap::iterator itr = _objectWrapperMap.find(name);
    if (itr==_objectWrapperMap.end())
    {
        // not found so check if a library::class composite name.
        std::string token = fr[0].getStr();
        std::string::size_type posDoubleColon = token.rfind("::");
        if (posDoubleColon != std::string::npos)
        {
            // we have a composite name so now strip off the library name
            // are try to load it, and then retry the readObject to see
            // if we can recongise the objects.
        
            std::string libraryName = std::string(token,0,posDoubleColon);

            // first try the standard nodekit library.
            std::string nodeKitLibraryName = createLibraryNameForNodeKit(libraryName);
            if (loadLibrary(nodeKitLibraryName)) return readObjectOfType(btw,fr);
            
            // otherwise try the osgdb_ plugin library.
            std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
            if (loadLibrary(pluginLibraryName)) return readObjectOfType(btw,fr);
        }
    }
    else if (fr[1].isOpenBracket())
    {
    
        DotOsgWrapper* wrapper = itr->second.get();
        const osg::Object* proto = wrapper->getPrototype();
        if (proto==NULL)
        {
            osg::notify(osg::WARN)<<"Token "<<fr[0].getStr()<<" read, but has no prototype, cannot load."<< std::endl;
            return NULL;
        }
        
        if (!btw.matches(proto))
        {
            return NULL;
        }

        // record the number of nested brackets move the input iterator
        // over the name { tokens.
        int entry = fr[0].getNoNestedBrackets();
        fr+=2;

        const DotOsgWrapper::Associates& assoc = wrapper->getAssociates();
        osg::Object* obj = proto->cloneType();

        while(!fr.eof() && fr[0].getNoNestedBrackets()>entry)
        {
            bool iteratorAdvanced = false;
            if (fr[0].matchWord("UniqueID") && fr[1].isString())
            {
                fr.regisiterUniqueIDForObject(fr[1].getStr(),obj);
                fr += 2;
                iteratorAdvanced = true;
            }

            // read the local data by iterating through the associate
            // list, mapping the associate names to DotOsgWrapper's which
            // in turn have the appropriate functions.
            for(DotOsgWrapper::Associates::const_iterator aitr=assoc.begin();
                                                          aitr!=assoc.end();
                                                          ++aitr)
            {
                DotOsgWrapperMap::iterator mitr = _objectWrapperMap.find(*aitr);
                if (mitr==_objectWrapperMap.end())
                {
                    // not found so check if a library::class composite name.
                    std::string token = *aitr;
                    std::string::size_type posDoubleColon = token.rfind("::");
                    if (posDoubleColon != std::string::npos)
                    {

                        // we have a composite name so now strip off the library name
                        // are try to load it, and then retry the find to see
                        // if we can recongise the objects.

                        std::string libraryName = std::string(token,0,posDoubleColon);

                        // first try the standard nodekit library.
                        std::string nodeKitLibraryName = createLibraryNameForNodeKit(libraryName);
                        if (loadLibrary(nodeKitLibraryName)) 
                        {
                            mitr = _objectWrapperMap.find(*aitr);
                        }

                        if (mitr==_objectWrapperMap.end())
                        {
                            // otherwise try the osgdb_ plugin library.
                            std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
                            if (loadLibrary(pluginLibraryName))
                            {
                                mitr = _objectWrapperMap.find(*aitr);
                            }
                        }

                    }
                }

                if (mitr!=_objectWrapperMap.end())
                {
                    // get the function to read the data...
                    DotOsgWrapper::ReadFunc rf = mitr->second->getReadFunc();
                    if (rf && (*rf)(*obj,fr)) iteratorAdvanced = true;
                }

            }

            if (!iteratorAdvanced) fr.advanceOverCurrentFieldOrBlock();
        }
        ++fr;                        // step over trailing '}'
        
        return obj;
        
    }
    return 0L;
}

//
// read object from input iterator.
//
osg::Object* Registry::readObject(DotOsgWrapperMap& dowMap,Input& fr)
{
    const char *str = fr[0].getStr();
    if (str==NULL) return NULL;

    std::string name = str;
    DotOsgWrapperMap::iterator itr = dowMap.find(name);
    if (itr==dowMap.end())
    {
        // not found so check if a library::class composite name.
        std::string token = fr[0].getStr();
        std::string::size_type posDoubleColon = token.rfind("::");
        if (posDoubleColon != std::string::npos)
        {
            // we have a composite name so now strip off the library name
            // are try to load it, and then retry the readObject to see
            // if we can recongise the objects.
        
            std::string libraryName = std::string(token,0,posDoubleColon);

            // first try the standard nodekit library.
            std::string nodeKitLibraryName = createLibraryNameForNodeKit(libraryName);
            if (loadLibrary(nodeKitLibraryName)) return readObject(dowMap,fr);
            
            // otherwise try the osgdb_ plugin library.
            std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
            if (loadLibrary(pluginLibraryName)) return readObject(dowMap,fr);
        }
    }
    else if (fr[1].isOpenBracket())
    {
    
        DotOsgWrapper* wrapper = itr->second.get();
        const osg::Object* proto = wrapper->getPrototype();
        if (proto==NULL)
        {
            osg::notify(osg::WARN)<<"Token "<<fr[0].getStr()<<" read, but has no prototype, cannot load."<< std::endl;
            return NULL;
        }

        // record the number of nested brackets move the input iterator
        // over the name { tokens.
        int entry = fr[0].getNoNestedBrackets();
        fr+=2;

        const DotOsgWrapper::Associates& assoc = wrapper->getAssociates();
        osg::Object* obj = proto->cloneType();

        while(!fr.eof() && fr[0].getNoNestedBrackets()>entry)
        {
            bool iteratorAdvanced = false;
            if (fr[0].matchWord("UniqueID") && fr[1].isString())
            {
                fr.regisiterUniqueIDForObject(fr[1].getStr(),obj);
                fr += 2;
                iteratorAdvanced = true;
            }

            // read the local data by iterating through the associate
            // list, mapping the associate names to DotOsgWrapper's which
            // in turn have the appropriate functions.
            for(DotOsgWrapper::Associates::const_iterator aitr=assoc.begin();
                                                          aitr!=assoc.end();
                                                          ++aitr)
            {
                DotOsgWrapperMap::iterator mitr = _objectWrapperMap.find(*aitr);
                if (mitr==_objectWrapperMap.end())
                {
                    // not found so check if a library::class composite name.
                    std::string token = *aitr;
                    std::string::size_type posDoubleColon = token.rfind("::");
                    if (posDoubleColon != std::string::npos)
                    {

                        // we have a composite name so now strip off the library name
                        // are try to load it, and then retry the find to see
                        // if we can recongise the objects.

                        std::string libraryName = std::string(token,0,posDoubleColon);

                        // first try the standard nodekit library.
                        std::string nodeKitLibraryName = createLibraryNameForNodeKit(libraryName);
                        if (loadLibrary(nodeKitLibraryName)) 
                        {
                            mitr = _objectWrapperMap.find(*aitr);
                        }

                        if (mitr==_objectWrapperMap.end())
                        {
                            // otherwise try the osgdb_ plugin library.
                            std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
                            if (loadLibrary(pluginLibraryName))
                            {
                                mitr = _objectWrapperMap.find(*aitr);
                            }
                        }

                    }
                }

                if (mitr!=_objectWrapperMap.end())
                {
                    // get the function to read the data...
                    DotOsgWrapper::ReadFunc rf = mitr->second->getReadFunc();
                    if (rf && (*rf)(*obj,fr)) iteratorAdvanced = true;
                }

            }

            if (!iteratorAdvanced) fr.advanceOverCurrentFieldOrBlock();
        }
        ++fr;                        // step over trailing '}'
        
        return obj;
        
    }

    return 0L;
}

//
// read object from input iterator.
//
Object* Registry::readObject(Input& fr)
{
    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            Object* obj = fr.getObjectForUniqueID(fr[1].getStr());
            if (obj) fr+=2;
            return obj;
        }
        else return NULL;

    }

    return readObject(_objectWrapperMap,fr);
}


//
// read image from input iterator.
//
Image* Registry::readImage(Input& fr)
{
    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            Image* image = dynamic_cast<Image*>(fr.getObjectForUniqueID(fr[1].getStr()));
            if (image) fr+=2;
            return image;
        }
        else return NULL;

    }

    osg::Object* obj = readObject(_imageWrapperMap,fr);
    osg::Image* image = dynamic_cast<Image*>(obj);
    if (image) return image;
    else if (obj) obj->unref();
    
    return NULL;
}


//
// read drawable from input iterator.
//
Drawable* Registry::readDrawable(Input& fr)
{
    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            Drawable* drawable = dynamic_cast<Drawable*>(fr.getObjectForUniqueID(fr[1].getStr()));
            if (drawable) fr+=2;
            return drawable;
        }
        else return NULL;

    }

    osg::Object* obj = readObject(_drawableWrapperMap,fr);
    osg::Drawable* drawable = dynamic_cast<Drawable*>(obj);
    if (drawable) return drawable;
    else if (obj) obj->unref();
    
    return NULL;
}

//
// read drawable from input iterator.
//
StateAttribute* Registry::readStateAttribute(Input& fr)
{

    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            StateAttribute* attribute = dynamic_cast<StateAttribute*>(fr.getObjectForUniqueID(fr[1].getStr()));
            if (attribute) fr+=2;
            return attribute;
        }
        else return NULL;

    }

    return dynamic_cast<StateAttribute*>(readObject(_stateAttrWrapperMap,fr));
}

//
// read node from input iterator.
//
Node* Registry::readNode(Input& fr)
{
    if (fr[0].matchWord("Use"))
    {
        if (fr[1].isString())
        {
            Node* node = dynamic_cast<Node*>(fr.getObjectForUniqueID(fr[1].getStr()));
            if (node) fr+=2;
            return node;
        }
        else return NULL;

    }

    osg::Object* obj = readObject(_nodeWrapperMap,fr);
    osg::Node* node = dynamic_cast<Node*>(obj);
    if (node) return node;
    else if (obj) obj->unref();
    
    return NULL;
}

//
// Write object to output 
//
bool Registry::writeObject(const osg::Object& obj,Output& fw)
{

    if (obj.referenceCount()>1)
    {
        std::string uniqueID;
        if (fw.getUniqueIDForObject(&obj,uniqueID))
        {
            fw.indent() << "Use " << uniqueID << std::endl;
            return true;
        }
    }

    std::string classname = obj.className();
    std::string libraryName = obj.libraryName();
    std::string compositeName = libraryName + "::" + classname;

    // try composite name first
    DotOsgWrapperMap::iterator itr = _classNameWrapperMap.find(compositeName);

    // composite name not found, try simple class name
    if (itr == _classNameWrapperMap.end()) {
        itr = _classNameWrapperMap.find(classname);
    }

    if (itr==_classNameWrapperMap.end())
    {
        // first try the standard nodekit library.
        std::string nodeKitLibraryName = createLibraryNameForNodeKit(obj.libraryName());
        if (loadLibrary(nodeKitLibraryName)) return writeObject(obj,fw);

        // otherwise try the osgdb_ plugin library.
        std::string pluginLibraryName = createLibraryNameForExtension(obj.libraryName());
        if (loadLibrary(pluginLibraryName)) return writeObject(obj,fw);
    }
    else
    {
    
    
        DotOsgWrapper* wrapper = itr->second.get();
        const DotOsgWrapper::Associates& assoc = wrapper->getAssociates();

        if (strcmp(obj.libraryName(),"osg")==0)
        {
            // member of the core osg, so no need to have composite library::class name.
            fw.indent() << wrapper->getName() << " {"<< std::endl;
            fw.moveIn();
        }
        else
        {
            // member of the node kit so must use composite library::class name.
            std::string::size_type posDoubleColon = wrapper->getName().find("::");
            if (posDoubleColon != std::string::npos)
            {
                fw.indent() << wrapper->getName() << " {"<< std::endl;
            }
            else
            {
                fw.indent() << obj.libraryName()<<"::"<< wrapper->getName() << " {"<< std::endl;
            }

            fw.moveIn();
        }


        // write out the unique ID if required.
        if (obj.referenceCount()>1)
        {
            std::string uniqueID;
            fw.createUniqueIDForObject(&obj,uniqueID);
            fw.registerUniqueIDForObject(&obj,uniqueID);
            fw.indent() << "UniqueID " << uniqueID << std::endl;
        }

        // read the local data by iterating through the associate
        // list, mapping the associate names to DotOsgWrapper's which
        // in turn have the appropriate functions.
        for(DotOsgWrapper::Associates::const_iterator aitr=assoc.begin();
                                                      aitr!=assoc.end();
                                                      ++aitr)
        {
            DotOsgWrapperMap::iterator mitr = _objectWrapperMap.find(*aitr);
            if (mitr==_objectWrapperMap.end())
            {
                // not found so check if a library::class composite name.
                std::string token = *aitr;
                std::string::size_type posDoubleColon = token.rfind("::");
                if (posDoubleColon != std::string::npos)
                {

                    // we have a composite name so now strip off the library name
                    // are try to load it, and then retry the find to see
                    // if we can recongise the objects.

                    std::string libraryName = std::string(token,0,posDoubleColon);

                    // first try the standard nodekit library.
                    std::string nodeKitLibraryName = createLibraryNameForNodeKit(libraryName);
                    if (loadLibrary(nodeKitLibraryName)) 
                    {
                        mitr = _objectWrapperMap.find(*aitr);
                    }

                    if (mitr==_objectWrapperMap.end())
                    {
                        // otherwise try the osgdb_ plugin library.
                        std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
                        if (loadLibrary(pluginLibraryName))
                        {
                            mitr = _objectWrapperMap.find(*aitr);
                        }
                    }

                }
            }
            if (mitr!=_objectWrapperMap.end())
            {
                // get the function to read the data...
                DotOsgWrapper::WriteFunc wf = mitr->second->getWriteFunc();
                if (wf) (*wf)(obj,fw);
            }

        }

        fw.moveOut();
        fw.indent() << "}"<< std::endl;

        return true;
    }
    
    return false;
}

//
// read object from specified file.
//
ReaderWriter::ReadResult Registry::readObject(const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::ReadResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::ReadResult rr = itr->readObject(fileName,_options.get());
        if (rr.validObject()) return rr;
        else results.push_back(rr);
    }

    if (!results.empty())
    {
        unsigned int num_FILE_NOT_HANDLED = 0;
        unsigned int num_FILE_NOT_FOUND = 0;
        unsigned int num_ERROR_IN_READING_FILE = 0;

        for(Results::iterator ritr=results.begin();
            ritr!=results.end();
            ++ritr)
        {
            if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_HANDLED) ++num_FILE_NOT_HANDLED;
            else if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND) ++num_FILE_NOT_FOUND;
            else if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE) ++num_ERROR_IN_READING_FILE;
        }
        
        if (num_FILE_NOT_HANDLED!=results.size())
        {
            // we've come across a file not found or error in reading file.
            if (num_ERROR_IN_READING_FILE)
            {
                osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
            else if (num_FILE_NOT_FOUND)
            {
                osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
        }
    }

    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::ReadResult rr = itr->readObject(fileName,_options.get());
            if (rr.validObject()) return rr;
            else results.push_back(rr);
        }
    }
    
    if (results.empty())
    {
        return ReaderWriter::ReadResult("Warning: Could not find plugin to read objects from file \""+fileName+"\".");
    }
    

    return results.front();
}

ReaderWriter::ReadResult Registry::readObject(const std::string& file,bool useObjectCache)
{
    if (useObjectCache)
    {
        // search for entry in the object cache.
        ObjectCache::iterator oitr=_objectCache.find(file);
        if (oitr!=_objectCache.end())
        {
            notify(INFO)<<"returning cached instanced of "<<file<<std::endl;
            osg::Object* object = oitr->second.first.get();
            if (object) return object;
            else return ReaderWriter::ReadResult("Error file does not contain an osg::Object");
        }

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readObject(file);
        if (rr.validObject()) 
        {
            // update cache with new entry.
            notify(INFO)<<"Adding to cache object "<<file<<std::endl;
            addEntryToObjectCache(file,rr.getObject());
        }
        
        return rr;

    }
    else
    {
    
        ObjectCache tmpObjectCache;
        tmpObjectCache.swap(_objectCache);

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readObject(file);

        tmpObjectCache.swap(_objectCache);

        return rr;

    }
}

ReaderWriter::WriteResult Registry::writeObject(const Object& obj,const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::WriteResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::WriteResult rr = itr->writeObject(obj,fileName,_options.get());
        if (rr.success()) return rr;
        else results.push_back(rr);
    }

    // now look for a plug-in to save the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::WriteResult rr = itr->writeObject(obj,fileName,_options.get());
            if (rr.success()) return rr;
            else results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::WriteResult("Warning: Could not find plugin to write objects to file \""+fileName+"\".");
    }

    return results.front();
}

ReaderWriter::ReadResult Registry::readImage(const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::ReadResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::ReadResult rr = itr->readImage(fileName,_options.get());
        if (rr.validImage())  return rr;
        else results.push_back(rr);
    }

    if (!results.empty())
    {
        unsigned int num_FILE_NOT_HANDLED = 0;
        unsigned int num_FILE_NOT_FOUND = 0;
        unsigned int num_ERROR_IN_READING_FILE = 0;

        for(Results::iterator ritr=results.begin();
            ritr!=results.end();
            ++ritr)
        {
            if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_HANDLED) ++num_FILE_NOT_HANDLED;
            else if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND) ++num_FILE_NOT_FOUND;
            else if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE) ++num_ERROR_IN_READING_FILE;
        }
        
        if (num_FILE_NOT_HANDLED!=results.size())
        {
            // we've come across a file not found or error in reading file.
            if (num_ERROR_IN_READING_FILE)
            {
                osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
            else if (num_FILE_NOT_FOUND)
            {
                osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
        }
    }

    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::ReadResult rr = itr->readImage(fileName,_options.get());
            if (rr.validImage()) return rr;
            else results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::ReadResult("Warning: Could not find plugin to read image from file \""+fileName+"\".");
    }

    return results.front();
}


ReaderWriter::ReadResult Registry::readImage(const std::string& file,bool useObjectCache)
{

    if (useObjectCache)
    {
        // search for entry in the object cache.
        ObjectCache::iterator oitr=_objectCache.find(file);
        if (oitr!=_objectCache.end())
        {
            notify(INFO)<< "returning cached instanced of "<<file<<std::endl;
            osg::Image* image = dynamic_cast<osg::Image*>(oitr->second.first.get());
            if (image) return image;
            else return ReaderWriter::ReadResult("Error file not of type osg::Image");
        }

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readImage(file);
        if (rr.validImage()) 
        {
            // update cache with new entry.
            notify(INFO)<<"Adding to cache image "<<file<<std::endl;
            addEntryToObjectCache(file,rr.getObject());
        }
        else
            return ReaderWriter::ReadResult("Warning: file \""+file+"\" not found.");
        
        return rr;

    }
    else
    {
    
        ObjectCache tmpObjectCache;
        tmpObjectCache.swap(_objectCache);

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readImage(file);

        tmpObjectCache.swap(_objectCache);

        return rr;

    }
}



ReaderWriter::WriteResult Registry::writeImage(const Image& image,const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::WriteResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::WriteResult rr = itr->writeImage(image,fileName,_options.get());
        if (rr.success()) return rr;
        else results.push_back(rr);
    }

    // now look for a plug-in to save the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::WriteResult rr = itr->writeImage(image,fileName,_options.get());
            if (rr.success()) return rr;
            else results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::WriteResult("Warning: Could not find plugin to write image to file \""+fileName+"\".");
    }
    
    return results.front();
}

ReaderWriter::ReadResult Registry::readHeightField(const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::ReadResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::ReadResult rr = itr->readHeightField(fileName,_options.get());
        if (rr.validHeightField())  return rr;
        else results.push_back(rr);
    }

    if (!results.empty())
    {
        unsigned int num_FILE_NOT_HANDLED = 0;
        unsigned int num_FILE_NOT_FOUND = 0;
        unsigned int num_ERROR_IN_READING_FILE = 0;

        for(Results::iterator ritr=results.begin();
            ritr!=results.end();
            ++ritr)
        {
            if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_HANDLED) ++num_FILE_NOT_HANDLED;
            else if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND) ++num_FILE_NOT_FOUND;
            else if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE) ++num_ERROR_IN_READING_FILE;
        }
        
        if (num_FILE_NOT_HANDLED!=results.size())
        {
            // we've come across a file not found or error in reading file.
            if (num_ERROR_IN_READING_FILE)
            {
                osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
            else if (num_FILE_NOT_FOUND)
            {
                osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
        }
    }

    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::ReadResult rr = itr->readHeightField(fileName,_options.get());
            if (rr.validHeightField()) return rr;
            else  results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::ReadResult("Warning: Could not find plugin to read HeightField from file \""+fileName+"\".");
    }

    return results.front();
}


ReaderWriter::ReadResult Registry::readHeightField(const std::string& file,bool useObjectCache)
{
    if (useObjectCache)
    {
        // search for entry in the object cache.
        ObjectCache::iterator oitr=_objectCache.find(file);
        if (oitr!=_objectCache.end())
        {
            notify(INFO)<< "returning cached instanced of "<<file<<std::endl;
            osg::HeightField* HeightField = dynamic_cast<osg::HeightField*>(oitr->second.first.get());
            if (HeightField) return HeightField;
            else return ReaderWriter::ReadResult("Error file not of type osg::HeightField");
        }

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readHeightField(file);
        if (rr.validHeightField()) 
        {
            // update cache with new entry.
            notify(INFO)<<"Adding to cache HeightField "<<file<<std::endl;
            addEntryToObjectCache(file,rr.getObject());
        }
        else
            return ReaderWriter::ReadResult("Warning: file \""+file+"\" not found.");
        
        return rr;

    }
    else
    {
    
        ObjectCache tmpObjectCache;
        tmpObjectCache.swap(_objectCache);

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readHeightField(file);

        tmpObjectCache.swap(_objectCache);

        return rr;

    }
}



ReaderWriter::WriteResult Registry::writeHeightField(const HeightField& HeightField,const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::WriteResult> Results;
    Results results;

    // first attempt to load the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::WriteResult rr = itr->writeHeightField(HeightField,fileName,_options.get());
        if (rr.success()) return rr;
        else results.push_back(rr);
    }

    // now look for a plug-in to save the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::WriteResult rr = itr->writeHeightField(HeightField,fileName,_options.get());
            if (rr.success()) return rr;
            else results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::WriteResult("Warning: Could not find plugin to write HeightField to file \""+fileName+"\".");
    }
    
    return results.front();
}



ReaderWriter::ReadResult Registry::readNode(const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::ReadResult> Results;
    Results results;

    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::ReadResult rr = itr->readNode(fileName,_options.get());
        if (rr.validNode())  return rr;
        else results.push_back(rr);
    }

    if (!results.empty())
    {
        unsigned int num_FILE_NOT_HANDLED = 0;
        unsigned int num_FILE_NOT_FOUND = 0;
        unsigned int num_ERROR_IN_READING_FILE = 0;

        for(Results::iterator ritr=results.begin();
            ritr!=results.end();
            ++ritr)
        {
            if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_HANDLED) ++num_FILE_NOT_HANDLED;
            else if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND) ++num_FILE_NOT_FOUND;
            else if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE) ++num_ERROR_IN_READING_FILE;
        }
        
        if (num_FILE_NOT_HANDLED!=results.size())
        {
            // we've come across a file not found or error in reading file.
            if (num_ERROR_IN_READING_FILE)
            {
                osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
            else if (num_FILE_NOT_FOUND)
            {
                osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<fileName<<"\""<<std::endl;
                return NULL;
            }
        }
    }
    
    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    notify(INFO) << "Now checking for plug-in "<<libraryName<< std::endl;
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::ReadResult rr = itr->readNode(fileName,_options.get());
            if (rr.validNode()) return rr;
            else results.push_back(rr);
        }
    }


    // need to sort out.
    bool useObjectCache=true;

    if (_createNodeFromImage)
    {
        ReaderWriter::ReadResult rr = readImage(fileName,useObjectCache);
        if (rr.validImage()) return createGeodeForImage(rr.takeImage());
        //else results.push_back(rr);
    }

    if (results.empty())
    {
        return ReaderWriter::ReadResult("Warning: Could not find plugin to read nodes from file \""+fileName+"\".");
    }

    return results.front();
}

ReaderWriter::ReadResult Registry::readNode(const std::string& file,bool useObjectCache)
{
    if (useObjectCache)
    {
        // search for entry in the object cache.
        ObjectCache::iterator oitr=_objectCache.find(file);
        if (oitr!=_objectCache.end())
        {
            notify(INFO)<< "returning cached instanced of "<<file<<std::endl;
            osg::Node* node = dynamic_cast<osg::Node*>(oitr->second.first.get());
            if (node) return node;
            else return ReaderWriter::ReadResult("Error file not of type osg::Node");
        }

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readNode(file);
        if (rr.validNode()) 
        {
            // update cache with new entry.
            notify(INFO)<<"Adding to cache node "<<file<<std::endl;
            addEntryToObjectCache(file,rr.getObject());
        }
        
        return rr;

    }
    else
    {
    
        ObjectCache tmpObjectCache;
        tmpObjectCache.swap(_objectCache);

        PushAndPopDataPath tmpfile(getFilePath(file));

        ReaderWriter::ReadResult rr = readNode(file);

        tmpObjectCache.swap(_objectCache);

        return rr;

    }
}

ReaderWriter::WriteResult Registry::writeNode(const Node& node,const std::string& fileName)
{
    // record the errors reported by readerwriters.
    typedef std::vector<ReaderWriter::WriteResult> Results;
    Results results;

    // first attempt to write the file from existing ReaderWriter's
    AvailableReaderWriterIterator itr(_rwList);
    for(;itr.valid();++itr)
    {
        ReaderWriter::WriteResult rr = itr->writeNode(node,fileName,_options.get());
        if (rr.success()) return rr;
        else results.push_back(rr);
    }

    // now look for a plug-in to save the file.
    std::string libraryName = createLibraryNameForFile(fileName);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::WriteResult rr = itr->writeNode(node,fileName,_options.get());
            if (rr.success()) return rr;
            else results.push_back(rr);
        }
    }

    if (results.empty())
    {
        return ReaderWriter::WriteResult("Warning: Could not find plugin to write nodes to file \""+fileName+"\".");
    }

    return results.front();
}

void Registry::convertStringPathIntoFilePathList(const std::string& paths,FilePathList& filepath)
{
#if defined(WIN32) && !defined(__CYGWIN__)
    char delimitor = ';';
#else
    char delimitor = ':';
#endif

    if (!paths.empty())
    {
        std::string::size_type start = 0;
        std::string::size_type end;
        while ((end = paths.find_first_of(delimitor,start))!=std::string::npos)
        {
            filepath.push_back(std::string(paths,start,end-start));
            start = end+1;
        }

        filepath.push_back(std::string(paths,start,std::string::npos));
    }
 
}

void Registry::addEntryToObjectCache(const std::string& filename, osg::Object* object, double timestamp)
{
     _objectCache[filename]=ObjectTimeStampPair(object,timestamp);
}

void Registry::updateTimeStampOfObjectsInCacheWithExtenalReferences(double currentTime)
{

    // look for objects with external references and update their time stamp.
    for(ObjectCache::iterator itr=_objectCache.begin();
        itr!=_objectCache.end();
        ++itr)
    {
        // if ref count is greater the 1 the object has an external reference.
        if (itr->second.first->referenceCount()>1)
        {
            // so update it time stamp.
            itr->second.second = currentTime;
        }
    }
}

void Registry::removeExpiredObjectsInCache(double expiryTime)
{
    typedef std::vector<std::string> ObjectsToRemove;
    ObjectsToRemove objectsToRemove;

    // first collect all the exprired entries in the ObjectToRemove list.
    for(ObjectCache::iterator oitr=_objectCache.begin();
        oitr!=_objectCache.end();
        ++oitr)
    {
        if (oitr->second.second<=expiryTime)
        {
            // record the filename of the entry to use as key for deleting
            // afterwards/
            objectsToRemove.push_back(oitr->first);
        }
    }
    
    // remove the entries from the _objectCaache.
    for(ObjectsToRemove::iterator ritr=objectsToRemove.begin();
        ritr!=objectsToRemove.end();
        ++ritr)
    {
        // std::cout<<"Removing from Registry object cache '"<<*ritr<<"'"<<std::endl;
        _objectCache.erase(*ritr);
    }
        
}

void Registry::clearObjectCache()
{
    _objectCache.clear();
}

DatabasePager* Registry::getOrCreateDatabasePager()
{
    if (!_databasePager) _databasePager = new DatabasePager;
    
    return _databasePager.get();
}

SharedStateManager* Registry::getOrCreateSharedStateManager()
{
    if (!_sharedStateManager) _sharedStateManager = new SharedStateManager;
    
    return _sharedStateManager.get();
}