/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 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 <osgDB/Archive>

#include <stdio.h>

#include <algorithm>
#include <set>

using namespace osg;
using namespace osgDB;

class Registry::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_registry = new Registry;
    if (erase) 
    {   
        s_registry->destruct();
        s_registry = 0;
    }
    return s_registry.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;

    // add default osga archive extension
    _archiveExtList.push_back("osga");
    
    initFilePathLists();

    // register file extension alias.
    const char* flt_str = getenv("OSG_OPEN_FLIGHT_PLUGIN");
    if (flt_str)
    {
        if (strcmp(flt_str, "new")==0)
        {
            addFileExtensionAlias("flt", "OpenFlight");
        }
    }
    else
    {
    #ifndef COMPILE_WITH_OLD_OPENFLIGHT_PLUGIN_AS_DEFAULT
        addFileExtensionAlias("flt", "OpenFlight");
    #endif
    }

    addFileExtensionAlias("shadow",  "osgShadow");

    addFileExtensionAlias("view",  "osgViewer");

    addFileExtensionAlias("sgi",  "rgb");
    addFileExtensionAlias("rgba", "rgb");
    addFileExtensionAlias("int",  "rgb");
    addFileExtensionAlias("inta", "rgb");
    addFileExtensionAlias("bw",   "rgb");

    addFileExtensionAlias("ivz",   "gz");
    addFileExtensionAlias("ozg",   "gz");
    
#if defined(DARWIN_QUICKTIME)
    addFileExtensionAlias("jpg",  "qt");
    addFileExtensionAlias("jpe",  "qt");
    addFileExtensionAlias("jpeg", "qt");
    addFileExtensionAlias("tif",  "qt");
    addFileExtensionAlias("tiff", "qt");
    addFileExtensionAlias("gif",  "qt");
    addFileExtensionAlias("png",  "qt");
    addFileExtensionAlias("psd",  "qt");
    addFileExtensionAlias("tga",  "qt");
    addFileExtensionAlias("mov",  "qt");
    addFileExtensionAlias("avi",  "qt");
    addFileExtensionAlias("mpg",  "qt");
    addFileExtensionAlias("mpv",  "qt");
    addFileExtensionAlias("dv",   "qt");
    addFileExtensionAlias("mp4",   "qt");
    addFileExtensionAlias("m4v",   "qt");
#else
    addFileExtensionAlias("jpg",  "jpeg");
    addFileExtensionAlias("jpe",  "jpeg");
    addFileExtensionAlias("tif",  "tiff");

    // really need to decide this at runtime...
    #if defined(USE_XINE)
        addFileExtensionAlias("mov",  "xine");
        addFileExtensionAlias("mpg",  "xine");
        addFileExtensionAlias("mpv",  "xine");
        addFileExtensionAlias("dv",   "xine");
        addFileExtensionAlias("avi",  "xine");
        addFileExtensionAlias("wmv",  "xine");
    #endif

#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");

    #if defined(USE_VRML)
        addFileExtensionAlias("wrl",   "vrml");    
    #elif defined(USE_INVENTOR)
        addFileExtensionAlias("wrl",   "iv");
    #endif
    
    // 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()
{
    destruct();
}

void Registry::destruct()
{
    // 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.
    clearObjectCache();
    clearArchiveCache();
    

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

#if !defined(WIN32) || defined(__CYGWIN__)
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

#include <iostream>

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

    osgDB::appendPlatformSpecificResourceFilePaths(filepath);
    setDataFilePathList(filepath);
    
}

void Registry::setDataFilePathList(const std::string& paths)
{
    _dataFilePath.clear(); 
    convertStringPathIntoFilePathList(paths,_dataFilePath);
}

void Registry::setLibraryFilePathList(const std::string& paths) { _libraryFilePath.clear(); convertStringPathIntoFilePathList(paths,_libraryFilePath); }

#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);
    }
    
    appendPlatformSpecificLibraryFilePaths(_libraryFilePath);

}


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 Uniform*>(proto))
        {
            _uniformWrapperMap[name] = wrapper;
            _uniformWrapperMap[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(_uniformWrapperMap,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)
{
    _extAliasMap[mapExt] = toExt;
}

bool Registry::readPluginAliasConfigurationFile( const std::string& file )
{
    std::string fileName = osgDB::findDataFile( file );
    if (fileName.empty())
    {
        osg::notify( osg::WARN) << "Can't find plugin alias config file \"" << file << "\"." << std::endl;
        return false;
    }

    std::ifstream ifs;
    ifs.open( fileName.c_str() );
    if (!ifs.good())
    {
        osg::notify( osg::WARN) << "Can't open plugin alias config file \"" << fileName << "\"." << std::endl;
        return false;
    }

    int lineNum( 0 );
    while (ifs.good())
    {
        std::string raw;
        ++lineNum;
        std::getline( ifs, raw );
        std::string ln = trim( raw );
        if (ln.empty()) continue;
        if (ln[0] == '#') continue;

        std::string::size_type spIdx = ln.find_first_of( " \t" );
        if (spIdx == ln.npos)
        {
            // mapExt and toExt must be on the same line, separated by a space.
            osg::notify( osg::WARN) << file << ", line " << lineNum << ": Syntax error: missing space in \"" << raw << "\"." << std::endl;
            continue;
        }

        const std::string mapExt = trim( ln.substr( 0, spIdx ) );
        const std::string toExt = trim( ln.substr( spIdx+1 ) );
        addFileExtensionAlias( mapExt, toExt );
    }
    return true;
}

std::string Registry::trim( const std::string& str )
{
    if (!str.size()) return str;
    std::string::size_type first = str.find_first_not_of( " \t" );
    std::string::size_type last = str.find_last_not_of( "  \t\r\n" );
    if ((first==str.npos) || (last==str.npos)) return std::string( "" );
    return str.substr( first, last-first+1 );
}


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() && ext != itr->second) return createLibraryNameForExtension(itr->second);

#ifdef OSG_JAVA_BUILD
    static std::string prepend = "java";
#else
    static std::string prepend = "";
#endif

#if defined(WIN32)
    // !! recheck evolving Cygwin DLL extension naming protocols !! NHV
    #ifdef __CYGWIN__
        return "cyg"+prepend+"osgdb_"+ext+".dll";
    #elif defined(__MINGW32__)
        return "lib"+prepend+"osgdb_"+ext+".dll";
    #else
        #ifdef _DEBUG
            return prepend+"osgdb_"+ext+"d.dll";
        #else
            return prepend+"osgdb_"+ext+".dll";
        #endif
    #endif
#elif macintosh
    return prepend+"osgdb_"+ext;
#elif defined(__hpux__)
    // why don't we use PLUGIN_EXT from the makefiles here?
    return prepend+"osgdb_"+ext+".sl";
#else
    return prepend+"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 
{
    virtual ~concrete_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 drawable from input iterator.
//
Uniform* Registry::readUniform(Input& fr)
{

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

    }

    return dynamic_cast<Uniform*>(readObject(_uniformWrapperMap,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.writeUseID( uniqueID );
            return true;
        }
    }

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

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

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

        // otherwise try the osgdb_ plugin library.
        std::string pluginLibraryName = createLibraryNameForExtension(libraryName);
        if (loadLibrary(pluginLibraryName)) return writeObject(obj,fw);

        // otherwise try simple class name
        if (itr == _classNameWrapperMap.end()) 
            itr = _classNameWrapperMap.find(classname);
    }

    if (itr!=_classNameWrapperMap.end())
    { 
        DotOsgWrapper* wrapper = itr->second.get();
        const DotOsgWrapper::Associates& assoc = wrapper->getAssociates();

        if (libraryName=="osg")
        {
            // member of the core osg, so no need to have composite library::class name.
            fw.writeBeginObject( wrapper->getName() );
        }
        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.writeBeginObject( wrapper->getName() );
            }
            else
            {
                fw.writeBeginObject( libraryName + "::" + wrapper->getName() );
            }
        }
        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.writeUniqueID( uniqueID );
        }

        // 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.writeEndObject();

        return true;
    }
    
    return false;
}



struct Registry::ReadObjectFunctor : public Registry::ReadFunctor
{
    ReadObjectFunctor(const std::string& filename, const ReaderWriter::Options* options):ReadFunctor(filename,options) {}

    virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw) const { return rw.readObject(_filename, _options); }    
    virtual bool isValid(ReaderWriter::ReadResult& readResult) const { return readResult.validObject(); }
    virtual bool isValid(osg::Object* object) const { return object!=0;  }
};

struct Registry::ReadImageFunctor : public Registry::ReadFunctor
{
    ReadImageFunctor(const std::string& filename, const ReaderWriter::Options* options):ReadFunctor(filename,options) {}

    virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw)const  { return rw.readImage(_filename, _options); }    
    virtual bool isValid(ReaderWriter::ReadResult& readResult) const { return readResult.validImage(); }
    virtual bool isValid(osg::Object* object) const { return dynamic_cast<osg::Image*>(object)!=0;  }
};

struct Registry::ReadHeightFieldFunctor : public Registry::ReadFunctor
{
    ReadHeightFieldFunctor(const std::string& filename, const ReaderWriter::Options* options):ReadFunctor(filename,options) {}

    virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw) const { return rw.readHeightField(_filename, _options); }    
    virtual bool isValid(ReaderWriter::ReadResult& readResult) const { return readResult.validHeightField(); }
    virtual bool isValid(osg::Object* object) const { return dynamic_cast<osg::HeightField*>(object)!=0;  }
};

struct Registry::ReadNodeFunctor : public Registry::ReadFunctor
{
    ReadNodeFunctor(const std::string& filename, const ReaderWriter::Options* options):ReadFunctor(filename,options) {}

    virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw) const { return rw.readNode(_filename, _options); }    
    virtual bool isValid(ReaderWriter::ReadResult& readResult) const { return readResult.validNode(); }
    virtual bool isValid(osg::Object* object) const { return dynamic_cast<osg::Node*>(object)!=0;  }

};

struct Registry::ReadArchiveFunctor : public Registry::ReadFunctor
{
    ReadArchiveFunctor(const std::string& filename, ReaderWriter::ArchiveStatus status, unsigned int indexBlockSizeHint, const ReaderWriter::Options* options):
        ReadFunctor(filename,options),
        _status(status),
        _indexBlockSizeHint(indexBlockSizeHint) {}
        
    ReaderWriter::ArchiveStatus _status;
    unsigned int _indexBlockSizeHint;

    virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw) const { return rw.openArchive(_filename, _status, _indexBlockSizeHint, _options); }
    virtual bool isValid(ReaderWriter::ReadResult& readResult) const { return readResult.validArchive(); }
    virtual bool isValid(osg::Object* object) const { return dynamic_cast<osgDB::Archive*>(object)!=0;  }

};

void Registry::addArchiveExtension(const std::string ext)
{
    for(ArchiveExtensionList::iterator aitr=_archiveExtList.begin();
        aitr!=_archiveExtList.end();
        ++aitr)
    {
        if ( (*aitr) == ext)   // extension already in archive extension list
            return;
    }
    _archiveExtList.push_back(ext);
};

ReaderWriter::ReadResult Registry::read(const ReadFunctor& readFunctor)
{
    for(ArchiveExtensionList::iterator aitr=_archiveExtList.begin();
        aitr!=_archiveExtList.end();
        ++aitr)
    {
        std::string archiveName = "." + (*aitr);

        std::string::size_type positionArchive = readFunctor._filename.find(archiveName+'/');
        if (positionArchive==std::string::npos) positionArchive = readFunctor._filename.find(archiveName+'\\');
        if (positionArchive!=std::string::npos)
        {
            std::string archiveName(readFunctor._filename.substr(0,positionArchive+5));
            std::string fileName(readFunctor._filename.substr(positionArchive+6,std::string::npos));
            osg::notify(osg::INFO)<<"Contains archive : "<<readFunctor._filename<<std::endl;
            osg::notify(osg::INFO)<<"         archive : "<<archiveName<<std::endl;
            osg::notify(osg::INFO)<<"         filename : "<<fileName<<std::endl;
        
            ReaderWriter::ReadResult result = openArchiveImplementation(archiveName,ReaderWriter::READ, 4096, readFunctor._options);
        
            if (!result.validArchive()) return result;

            osgDB::Archive* archive = result.getArchive();
        
            osg::ref_ptr<ReaderWriter::Options> options = new ReaderWriter::Options;
            options->setDatabasePath(archiveName);

            return archive->readObject(fileName,options.get());
        }
    }

    // if filename contains archive
    // then get archive name
    // if archive name is not in the cache then do an openArchive on
    // that archive name
    // use that archive to read the file.

    if (containsServerAddress(readFunctor._filename))
    {
        std::string serverName = getServerAddress(readFunctor._filename);
        std::string serverFile = getServerFileName(readFunctor._filename);
        osg::notify(osg::INFO)<<"Contains sever address : "<<serverName<<std::endl;
        osg::notify(osg::INFO)<<"         file name on server : "<<serverFile<<std::endl;

        if (serverName.empty())
        {
            return ReaderWriter::ReadResult("Warning: Server address invalid.");
        }
        
        if (serverFile.empty())
        {
            return ReaderWriter::ReadResult("Warning: Server file name invalid.");
        }

        ReaderWriter* rw = getReaderWriterForExtension("net");
        if (rw)
        {
            std::string& filename = const_cast<std::string&>(readFunctor._filename);
            filename = serverName+':'+serverFile;
            return readFunctor.doRead(*rw);
        }
        else
        {
            return  ReaderWriter::ReadResult("Warning: Could not find the .net plugin to read from server.");
        }
    }
    
    // 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 = readFunctor.doRead(*itr);
        if (readFunctor.isValid(rr)) 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;

        Results::iterator ritr;
        for(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())
        {
            for(ritr=results.begin(); ritr!=results.end(); ++ritr)
            {
                if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE)
                {
                    osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<readFunctor._filename<<"\""<<std::endl;
                    return *ritr;
                }
            }

            for(ritr=results.begin(); ritr!=results.end(); ++ritr)
            {
                if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND)
                {
                    osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<readFunctor._filename<<"\""<<std::endl;
                    return *ritr;
                }
            }
        }
    }

    results.clear();

    // now look for a plug-in to load the file.
    std::string libraryName = createLibraryNameForFile(readFunctor._filename);
    if (loadLibrary(libraryName))
    {
        for(;itr.valid();++itr)
        {
            ReaderWriter::ReadResult rr = readFunctor.doRead(*itr);
            if (readFunctor.isValid(rr)) 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;

        Results::iterator ritr;
        for(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())
        {
            for(ritr=results.begin(); ritr!=results.end(); ++ritr)
            {
                if (ritr->status()==ReaderWriter::ReadResult::ERROR_IN_READING_FILE)
                {
                    osg::notify(osg::NOTICE)<<"Warning: error reading file \""<<readFunctor._filename<<"\""<<std::endl;
                    return *ritr;
                }
            }

            for(ritr=results.begin(); ritr!=results.end(); ++ritr)
            {
                if (ritr->status()==ReaderWriter::ReadResult::FILE_NOT_FOUND)
                {
                    osg::notify(osg::NOTICE)<<"Warning: could not find file \""<<readFunctor._filename<<"\""<<std::endl;
                    return *ritr;
                }
            }
        }
    }
    else
    {
        return ReaderWriter::ReadResult("Warning: Could not find plugin to read objects from file \""+readFunctor._filename+"\".");
    }

    return results.front();
}

ReaderWriter::ReadResult Registry::readImplementation(const ReadFunctor& readFunctor, bool useObjectCache)
{
    std::string file(readFunctor._filename);

    if (useObjectCache)
    {
        // search for entry in the object cache.
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
            ObjectCache::iterator oitr=_objectCache.find(file);
            if (oitr!=_objectCache.end())
            {
                notify(INFO)<<"returning cached instanced of "<<file<<std::endl;
                if (readFunctor.isValid(oitr->second.first.get())) return ReaderWriter::ReadResult(oitr->second.first.get(), ReaderWriter::ReadResult::FILE_LOADED_FROM_CACHE);
                else return ReaderWriter::ReadResult("Error file does not contain an osg::Object");
            }
        }
        
        ReaderWriter::ReadResult rr = read(readFunctor);
        if (rr.validObject()) 
        {
            // update cache with new entry.
            notify(INFO)<<"Adding to object cache "<<file<<std::endl;
            addEntryToObjectCache(file,rr.getObject());
        }
        else
        {
            notify(INFO)<<"No valid object found for "<<file<<std::endl;
        }

        return rr;

    }
    else
    {
        ObjectCache tmpObjectCache;
        
        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
            tmpObjectCache.swap(_objectCache);
        }
        
        ReaderWriter::ReadResult rr = read(readFunctor);

        {
            OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
            tmpObjectCache.swap(_objectCache);
        }
        
        return rr;
    }
}


ReaderWriter::ReadResult Registry::openArchiveImplementation(const std::string& fileName, ReaderWriter::ArchiveStatus status, unsigned int indexBlockSizeHint, const ReaderWriter::Options* options)
{
    osgDB::Archive* archive = getFromArchiveCache(fileName);
    if (archive) return archive;

    ReaderWriter::ReadResult result = readImplementation(ReadArchiveFunctor(fileName, status, indexBlockSizeHint, options),false);

    // default to using chaching archive if no options structure provided, but if options are provided use archives
    // only if supplied.
    if (result.validArchive() &&
        (!options || (options->getObjectCacheHint() & ReaderWriter::Options::CACHE_ARCHIVES)) )
    {
        addToArchiveCache(fileName,result.getArchive());
    }
    return result;
}


ReaderWriter::ReadResult Registry::readObjectImplementation(const std::string& fileName,const ReaderWriter::Options* options)
{
    return readImplementation(ReadObjectFunctor(fileName, options),
                              options ? (options->getObjectCacheHint()&ReaderWriter::Options::CACHE_OBJECTS)!=0: false);
}

ReaderWriter::WriteResult Registry::writeObjectImplementation(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+"\".");
    }

    if (results.front().message().empty())
    {
        switch(results.front().status())
        {
            case(ReaderWriter::WriteResult::FILE_NOT_HANDLED): results.front().message() = "Warning: Write to \""+fileName+"\" not supported."; break;
            case(ReaderWriter::WriteResult::ERROR_IN_WRITING_FILE): results.front().message() = "Warning: Error in writing to \""+fileName+"\"."; break;
            default: break;
        }
    }

    return results.front();
}



ReaderWriter::ReadResult Registry::readImageImplementation(const std::string& fileName,const ReaderWriter::Options* options)
{
    return readImplementation(ReadImageFunctor(fileName, options),
                              options ? (options->getObjectCacheHint()&ReaderWriter::Options::CACHE_IMAGES)!=0: false);
}

ReaderWriter::WriteResult Registry::writeImageImplementation(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);
    }

    results.clear();

    // 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+"\".");
    }
    
    if (results.front().message().empty())
    {
        switch(results.front().status())
        {
            case(ReaderWriter::WriteResult::FILE_NOT_HANDLED): results.front().message() = "Warning: Write to \""+fileName+"\" not supported."; break;
            case(ReaderWriter::WriteResult::ERROR_IN_WRITING_FILE): results.front().message() = "Warning: Error in writing to \""+fileName+"\"."; break;
            default: break;
        }
    }

    return results.front();
}


ReaderWriter::ReadResult Registry::readHeightFieldImplementation(const std::string& fileName,const ReaderWriter::Options* options)
{
    return readImplementation(ReadHeightFieldFunctor(fileName, options),
                              options ? (options->getObjectCacheHint()&ReaderWriter::Options::CACHE_HEIGHTFIELDS)!=0: false);
}

ReaderWriter::WriteResult Registry::writeHeightFieldImplementation(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);
    }

    results.clear();

    // 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+"\".");
    }

    if (results.front().message().empty())
    {
        switch(results.front().status())
        {
            case(ReaderWriter::WriteResult::FILE_NOT_HANDLED): results.front().message() = "Warning: Write to \""+fileName+"\" not supported."; break;
            case(ReaderWriter::WriteResult::ERROR_IN_WRITING_FILE): results.front().message() = "Warning: Error in writing to \""+fileName+"\"."; break;
            default: break;
        }
    }
    
    return results.front();
}


ReaderWriter::ReadResult Registry::readNodeImplementation(const std::string& fileName,const ReaderWriter::Options* options)
{
    return readImplementation(ReadNodeFunctor(fileName, options),
                              options ? (options->getObjectCacheHint()&ReaderWriter::Options::CACHE_NODES)!=0: false);
}

ReaderWriter::WriteResult Registry::writeNodeImplementation(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);
    }

    results.clear();

    // 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+"\".");
    }

    if (results.front().message().empty())
    {
        switch(results.front().status())
        {
            case(ReaderWriter::WriteResult::FILE_NOT_HANDLED): results.front().message() = "Warning: Write to \""+fileName+"\" not supported."; break;
            case(ReaderWriter::WriteResult::ERROR_IN_WRITING_FILE): results.front().message() = "Warning: Error in writing to \""+fileName+"\"."; break;
            default: break;
        }
    }

    return results.front();
}


void Registry::addEntryToObjectCache(const std::string& filename, osg::Object* object, double timestamp)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
    _objectCache[filename]=ObjectTimeStampPair(object,timestamp);
}
osg::Object* Registry::getFromObjectCache(const std::string& fileName)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
    ObjectCache::iterator itr = _objectCache.find(fileName);
    if (itr!=_objectCache.end()) return itr->second.first.get();
    else return 0;
}

void Registry::updateTimeStampOfObjectsInCacheWithExtenalReferences(double currentTime)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);

    // 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)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);

    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()
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);
    _objectCache.clear();
}

void Registry::addToArchiveCache(const std::string& fileName, osgDB::Archive* archive)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_archiveCacheMutex);
    _archiveCache[fileName] = archive;
}

/** Remove archive from cache.*/
void Registry::removeFromArchiveCache(const std::string& fileName)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_archiveCacheMutex);
    ArchiveCache::iterator itr = _archiveCache.find(fileName);
    if (itr!=_archiveCache.end()) 
    {
        _archiveCache.erase(itr);
    }
}

osgDB::Archive* Registry::getFromArchiveCache(const std::string& fileName)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_archiveCacheMutex);
    ArchiveCache::iterator itr = _archiveCache.find(fileName);
    if (itr!=_archiveCache.end()) return itr->second.get();
    else return 0;
}

void Registry::clearArchiveCache()
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_archiveCacheMutex);
    _archiveCache.clear();
}

void Registry::releaseGLObjects(osg::State* state)
{
    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_objectCacheMutex);

    for(ObjectCache::iterator itr = _objectCache.begin();
        itr != _objectCache.end();
        ++itr)
    {
        osg::Object* object = itr->second.first.get();
        object->releaseGLObjects(state);
    }
}

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

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