OpenSceneGraph/include/osgDB/Registry

/* -*-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.
*/

#ifndef OSGDB_REGISTRY
#define OSGDB_REGISTRY 1

#include <OpenThreads/ReentrantMutex>

#include <osg/ref_ptr>
#include <osg/ArgumentParser>
#include <osg/KdTree>

#include <osgDB/DynamicLibrary>
#include <osgDB/ReaderWriter>
#include <osgDB/Options>
#include <osgDB/DotOsgWrapper>
#include <osgDB/ObjectWrapper>
#include <osgDB/FileCache>
#include <osgDB/SharedStateManager>
#include <osgDB/ImageProcessor>

#include <vector>
#include <map>
#include <string>

extern "C"
{
    typedef void (* CPluginFunction) (void);
}

namespace osgDB {

/** basic structure for custom runtime inheritance checking */
struct basic_type_wrapper {
    virtual ~basic_type_wrapper() {}
    virtual bool matches(const osg::Object *proto) const = 0;
};

/** a class template that checks inheritance between a given
    Object's class and a class defined at compile time through
        the template parameter T.
        This is used in conjunction with readObjectOfType() to
        specify an abstract class as reference type.
**/
template<class T>
struct type_wrapper: basic_type_wrapper {
    bool matches(const osg::Object *proto) const
    {
        return dynamic_cast<const T*>(proto) != 0;
    }
};

/**
    Registry is a singleton factory which stores
    the reader/writers which are linked in
    at runtime for reading non-native file formats.

    The RegisterReaderWriterProxy can be used to automatically
    register at runtime a reader/writer with the Registry.
*/
class OSGDB_EXPORT Registry : public osg::Referenced
{
    public:



        
        static Registry* instance(bool erase = false);

        /** read the command line arguments.*/
        void readCommandLine(osg::ArgumentParser& commandLine);

        /** register an .fileextension alias to mapExt toExt, the later
          * should the the extension name of the readerwriter plugin library.
          * For example to map .tif files to the tiff loader, use
          * addExtAlias("tif","tiff") which will enable .tif to be read
          * by the libdb_tiff readerwriter plugin.*/
        void addFileExtensionAlias(const std::string mapExt, const std::string toExt);

        /** Reads a file that configures extension mappings. File is ASCII text
          * and each line contains the parameters to the addFileExtensionAlias
          * method. Lines can be commented out with an initial '#' character.*/
        bool readPluginAliasConfigurationFile( const std::string& file );

        typedef std::map< std::string, std::string> MimeTypeExtensionMap;

        /** Registers a mapping of a mime-type to an extension. A process fetching data
          * over HTTP can use this facility to determine the proper ReaderWriter to use
          * when there is no filename extension to rely upon.
          */
        void addMimeTypeExtensionMapping(const std::string fromMimeType, const std::string toExt);
        MimeTypeExtensionMap& getMimeTypeExtensionMap() { return _mimeTypeExtMap; }
        const MimeTypeExtensionMap& getMimeTypeExtensionMap() const { return _mimeTypeExtMap; }

        void addReaderWriter(ReaderWriter* rw);
        void removeReaderWriter(ReaderWriter* rw);

        void addImageProcessor(ImageProcessor* ip);
        void removeImageProcessor(ImageProcessor* ip);

        /** create the platform specific library name associated with file.*/
        std::string createLibraryNameForFile(const std::string& fileName);

        /** create the platform specific library name associated with file extension.*/
        std::string createLibraryNameForExtension(const std::string& ext);

        /** create the platform specific library name associated with nodekit library name.*/
        std::string createLibraryNameForNodeKit(const std::string& name);


        enum LoadStatus {
            NOT_LOADED = 0,
            PREVIOUSLY_LOADED,
            LOADED
        };

        /** find the library in the OSG_LIBRARY_PATH and load it.*/
        LoadStatus loadLibrary(const std::string& fileName);
        
        /** close the attached library with specified name.*/
        bool closeLibrary(const std::string& fileName);
        
        /** close all libraries.*/
        void closeAllLibraries();

        typedef std::vector< osg::ref_ptr<ReaderWriter> > ReaderWriterList;

        /** get a reader writer which handles specified extension.*/
        ReaderWriter* getReaderWriterForExtension(const std::string& ext);

        /** gets a reader/writer that handles the extension mapped to by one of
          * the registered mime-types. */
        ReaderWriter* getReaderWriterForMimeType(const std::string& mimeType);
        
        /** get list of all registered ReaderWriters.*/
        ReaderWriterList& getReaderWriterList() { return _rwList; }

        /** get const list of all registered ReaderWriters.*/
        const ReaderWriterList& getReaderWriterList() const { return _rwList; }
 

        typedef std::vector< osg::ref_ptr<ImageProcessor> > ImageProcessorList;

        /** get a image processor if available.*/
        ImageProcessor* getImageProcessor();

        /** get a image processor which is associated specified extension.*/
        ImageProcessor* getImageProcessorForExtension(const std::string& ext);

        /** get list of all registered ImageProcessors.*/
        ImageProcessorList& getImageProcessorList() { return _ipList; }

        /** get const list of all registered ImageProcessors.*/
        const ImageProcessorList& getImageProcessorList() const { return _ipList; }


        typedef class osgDB::FindFileCallback FindFileCallback;
        typedef class osgDB::ReadFileCallback ReadFileCallback;
        typedef class osgDB::WriteFileCallback WriteFileCallback;
        typedef class osgDB::FileLocationCallback FileLocationCallback;

        /** Set the Registry callback to use in place of the default findFile calls.*/
        void setFindFileCallback( FindFileCallback* cb) { _findFileCallback = cb; }

        /** Get the findFile callback.*/
        FindFileCallback* getFindFileCallback() { return _findFileCallback.get(); }

        /** Get the const findFile callback.*/
        const FindFileCallback* getFindFileCallback() const { return _findFileCallback.get(); }


        std::string findDataFile(const std::string& fileName, const Options* options, CaseSensitivity caseSensitivity)
        {
            if (options && options->getFindFileCallback()) return options->getFindFileCallback()->findDataFile(fileName, options, caseSensitivity);
            else if (_findFileCallback.valid()) return _findFileCallback->findDataFile(fileName, options, caseSensitivity);
            else return findDataFileImplementation(fileName, options, caseSensitivity);
        }
        std::string findDataFileImplementation(const std::string& fileName, const Options* options, CaseSensitivity caseSensitivity);

        std::string findLibraryFile(const std::string& fileName, const Options* options, CaseSensitivity caseSensitivity)
        {
            if (options && options->getFindFileCallback()) return options->getFindFileCallback()->findLibraryFile(fileName, options, caseSensitivity);
            else if (_findFileCallback.valid()) return _findFileCallback->findLibraryFile(fileName, options, caseSensitivity);
            else return findLibraryFileImplementation(fileName, options, caseSensitivity);
        }
        std::string findLibraryFileImplementation(const std::string& fileName, const Options* options, CaseSensitivity caseSensitivity);



        /** Set the Registry callback to use in place of the default readFile calls.*/
        void setReadFileCallback( ReadFileCallback* cb) { _readFileCallback = cb; }

        /** Get the readFile callback.*/
        ReadFileCallback* getReadFileCallback() { return _readFileCallback.get(); }
        
        /** Get the const readFile callback.*/
        const ReadFileCallback* getReadFileCallback() const { return _readFileCallback.get(); }


        ReaderWriter::ReadResult openArchive(const std::string& fileName,ReaderWriter::ArchiveStatus status, unsigned int indexBlockSizeHint, const Options* options)
        {
            if (options && options->getReadFileCallback()) return options->getReadFileCallback()->openArchive(fileName, status, indexBlockSizeHint, options);
            else if (_readFileCallback.valid()) return _readFileCallback->openArchive(fileName, status, indexBlockSizeHint, options);
            else return openArchiveImplementation(fileName, status, indexBlockSizeHint, options);
        }
        ReaderWriter::ReadResult openArchiveImplementation(const std::string& fileName, ReaderWriter::ArchiveStatus status, unsigned int indexBlockSizeHint, const Options* options);

        ReaderWriter::ReadResult readObject(const std::string& fileName,const Options* options, bool buildKdTreeIfRequired=true)
        {
            ReaderWriter::ReadResult result;
            if (options && options->getReadFileCallback()) result = options->getReadFileCallback()->readObject(fileName,options);
            else if (_readFileCallback.valid()) result = _readFileCallback->readObject(fileName,options);
            else result = readObjectImplementation(fileName,options);

            if (buildKdTreeIfRequired) _buildKdTreeIfRequired(result, options);

            return result;
        }
        ReaderWriter::ReadResult readObjectImplementation(const std::string& fileName,const Options* options);

        ReaderWriter::ReadResult readImage(const std::string& fileName,const Options* options)
        {
            if (options && options->getReadFileCallback()) return options->getReadFileCallback()->readImage(fileName,options);
            else if (_readFileCallback.valid()) return _readFileCallback->readImage(fileName,options);
            else return readImageImplementation(fileName,options);
        }
        ReaderWriter::ReadResult readImageImplementation(const std::string& fileName,const Options* options);

        ReaderWriter::ReadResult readHeightField(const std::string& fileName,const Options* options)
        {
            if (options && options->getReadFileCallback()) return options->getReadFileCallback()->readHeightField(fileName,options);
            else if (_readFileCallback.valid()) return _readFileCallback->readHeightField(fileName,options);
            else return readHeightFieldImplementation(fileName,options);
        }
        ReaderWriter::ReadResult readHeightFieldImplementation(const std::string& fileName,const Options* options);

        ReaderWriter::ReadResult readNode(const std::string& fileName,const Options* options, bool buildKdTreeIfRequired=true)
        {
            ReaderWriter::ReadResult result;
            if (options && options->getReadFileCallback()) result = options->getReadFileCallback()->readNode(fileName,options);
            else if (_readFileCallback.valid()) result = _readFileCallback->readNode(fileName,options);
            else result = readNodeImplementation(fileName,options);

            if (buildKdTreeIfRequired) _buildKdTreeIfRequired(result, options);

            return result;
        }
        ReaderWriter::ReadResult readNodeImplementation(const std::string& fileName,const Options* options);

        ReaderWriter::ReadResult readShader(const std::string& fileName,const Options* options)
        {
            if (options && options->getReadFileCallback()) return options->getReadFileCallback()->readShader(fileName,options);
            if (_readFileCallback.valid()) return _readFileCallback->readShader(fileName,options);
            else return readShaderImplementation(fileName,options);
        }
        ReaderWriter::ReadResult readShaderImplementation(const std::string& fileName,const Options* options);


        /** Set the Registry callback to use in place of the default writeFile calls.*/
        void setWriteFileCallback( WriteFileCallback* cb) { _writeFileCallback = cb; }

        /** Get the writeFile callback.*/
        WriteFileCallback* getWriteFileCallback() { return _writeFileCallback.get(); }
        
        /** Get the const writeFile callback.*/
        const WriteFileCallback* getWriteFileCallback() const { return _writeFileCallback.get(); }


        ReaderWriter::WriteResult writeObject(const osg::Object& obj, const std::string& fileName,const Options* options)
        {
            if (options && options->getWriteFileCallback()) return options->getWriteFileCallback()->writeObject(obj,fileName,options);
            else if (_writeFileCallback.valid()) return _writeFileCallback->writeObject(obj,fileName,options);
            else return writeObjectImplementation(obj,fileName,options);
        }
        ReaderWriter::WriteResult writeObjectImplementation(const osg::Object& obj, const std::string& fileName,const Options* options);

        ReaderWriter::WriteResult writeImage(const osg::Image& obj, const std::string& fileName,const Options* options)
        {
            if (options && options->getWriteFileCallback()) return options->getWriteFileCallback()->writeImage(obj,fileName,options);
            else if (_writeFileCallback.valid()) return _writeFileCallback->writeImage(obj,fileName,options);
            else return writeImageImplementation(obj,fileName,options);
        }
        ReaderWriter::WriteResult writeImageImplementation(const osg::Image& obj, const std::string& fileName,const Options* options);

        ReaderWriter::WriteResult writeHeightField(const osg::HeightField& obj, const std::string& fileName,const Options* options)
        {
            if (options && options->getWriteFileCallback()) return options->getWriteFileCallback()->writeHeightField(obj,fileName,options);
            else if (_writeFileCallback.valid()) return _writeFileCallback->writeHeightField(obj,fileName,options);
            else return writeHeightFieldImplementation(obj,fileName,options);
        }
        ReaderWriter::WriteResult writeHeightFieldImplementation(const osg::HeightField& obj, const std::string& fileName,const Options* options);

        ReaderWriter::WriteResult writeNode(const osg::Node& node, const std::string& fileName,const Options* options)
        {
            if (options && options->getWriteFileCallback()) return options->getWriteFileCallback()->writeNode(node,fileName,options);
            else if (_writeFileCallback.valid()) return _writeFileCallback->writeNode(node,fileName,options);
            else return writeNodeImplementation(node,fileName,options);
        }
        ReaderWriter::WriteResult writeNodeImplementation(const osg::Node& node, const std::string& fileName,const Options* options);
        
        ReaderWriter::WriteResult writeShader(const osg::Shader& obj, const std::string& fileName,const Options* options)
        {
            if (options && options->getWriteFileCallback()) return options->getWriteFileCallback()->writeShader(obj,fileName,options);
            else if (_writeFileCallback.valid()) return _writeFileCallback->writeShader(obj,fileName,options);
            else return writeShaderImplementation(obj,fileName,options);
        }
        ReaderWriter::WriteResult writeShaderImplementation(const osg::Shader& obj, const std::string& fileName,const Options* options);
        

        inline void _buildKdTreeIfRequired(ReaderWriter::ReadResult& result, const Options* options)
        {
            bool doKdTreeBuilder = (options && options->getBuildKdTreesHint()!=Options::NO_PREFERENCE) ?
                options->getBuildKdTreesHint() == Options::BUILD_KDTREES :
                _buildKdTreesHint == Options::BUILD_KDTREES;

            if (doKdTreeBuilder && _kdTreeBuilder.valid() && result.validNode()) 
            {
                osg::ref_ptr<osg::KdTreeBuilder> builder = _kdTreeBuilder->clone();
                result.getNode()->accept(*builder);
            }
        }

        /** Set the callback to use inform to the DatabasePager whether a file is located on local or remote file system.*/
        void setFileLocationCallback( FileLocationCallback* cb) { _fileLocationCallback = cb; }

        /** Get the callback to use inform to the DatabasePager whether a file is located on local or remote file system.*/
        FileLocationCallback* getFileLocationCallback() const { return _fileLocationCallback.get(); }



        /** Set whether the KdTrees should be built for geometry in the loader model. */
        void setBuildKdTreesHint(Options::BuildKdTreesHint hint) { _buildKdTreesHint = hint; }

        /** Get whether the KdTrees should be built for geometry in the loader model. */
        Options::BuildKdTreesHint getBuildKdTreesHint() const { return _buildKdTreesHint; }

        /** Set the KdTreeBuilder visitor that is used to build KdTree on loaded models.*/
        void setKdTreeBuilder(osg::KdTreeBuilder* builder) { _kdTreeBuilder = builder; }

        /** Get the KdTreeBuilder visitor that is used to build KdTree on loaded models.*/
        osg::KdTreeBuilder* getKdTreeBuilder() { return _kdTreeBuilder.get(); }


        /** Set the FileCache that is used to manage local storage of files downloaded from the internet.*/
        void setFileCache(FileCache* fileCache) { _fileCache = fileCache; }

        /** Get the FileCache that is used to manage local storage of files downloaded from the internet.*/
        FileCache* getFileCache() { return _fileCache.get(); }

        /** Get the const FileCache that is used to manage local storage of files downloaded from the internet.*/
        const FileCache* getFileCache() const { return _fileCache.get(); }


        /** Set the password map to be used by plugins when access files from secure locations.*/
        void setAuthenticationMap(AuthenticationMap* authenticationMap) { _authenticationMap = authenticationMap; }

        /** Get the password map to be used by plugins when access files from secure locations.*/
        AuthenticationMap* getAuthenticationMap() { return _authenticationMap.get(); }

        /** Get the password map to be used by plugins when access files from secure locations.*/
        const AuthenticationMap* getAuthenticationMap() const { return _authenticationMap.get(); }


        void setCreateNodeFromImage(bool flag) { _createNodeFromImage = flag; }
        bool getCreateNodeFromImage() const { return _createNodeFromImage; }
        

        void setOptions(Options* opt) { _options = opt; }
        Options* getOptions() { return _options.get(); }
        const Options*  getOptions() const { return _options.get(); }


        /** initialize both the Data and Library FilePaths, by default called by the 
          * constructor, so it should only be required if you want to force
          * the re-reading of environmental variables.*/
        void initFilePathLists() { initDataFilePathList(); initLibraryFilePathList(); }
        
        /** initialize the Data FilePath by reading the OSG_FILE_PATH environmental variable.*/
        void initDataFilePathList();

        /** Set the data file path using a list of paths stored in a FilePath, which is used when search for data files.*/
        void setDataFilePathList(const FilePathList& filepath) { _dataFilePath = filepath; }

        /** Set the data file path using a single string delimited either with ';' (Windows) or ':' (All other platforms), which is used when search for data files.*/
        void setDataFilePathList(const std::string& paths);

        /** get the data file path which is used when search for data files.*/
        FilePathList& getDataFilePathList() { return _dataFilePath; }

        /** get the const data file path which is used when search for data files.*/
        const FilePathList& getDataFilePathList() const { return _dataFilePath; }

        /** initialize the Library FilePath by reading the OSG_LIBRARY_PATH 
          * and the appropriate system environmental variables*/
        void initLibraryFilePathList();

        /** Set the library file path using a list of paths stored in a FilePath, which is used when search for data files.*/
        void setLibraryFilePathList(const FilePathList& filepath) { _libraryFilePath = filepath; }

        /** Set the library file path using a single string delimited either with ';' (Windows) or ':' (All other platforms), which is used when search for data files.*/
        void setLibraryFilePathList(const std::string& paths);

        /** get the library file path which is used when search for library (dso/dll's) files.*/
        FilePathList& getLibraryFilePathList() { return _libraryFilePath; }
        
        /** get the const library file path which is used when search for library (dso/dll's) files.*/
        const FilePathList& getLibraryFilePathList() const { return _libraryFilePath; }

        /** For each object in the cache which has an reference count greater than 1 
          * (and therefore referenced by elsewhere in the application) set the time stamp
          * for that object in the cache to specified time.
          * This would typically be called once per frame by applications which are doing database paging,
          * and need to prune objects that are no longer required.
          * The time used is taken from the FrameStamp::getReferenceTime().*/
        void updateTimeStampOfObjectsInCacheWithExternalReferences(const osg::FrameStamp& frameStamp);

        /** Removed object in the cache which have a time stamp at or before the specified expiry time.
          * This would typically be called once per frame by applications which are doing database paging,
          * and need to prune objects that are no longer required, and called after the a called
          * after the call to updateTimeStampOfObjectsInCacheWithExternalReferences(frameStamp).*/
        void removeExpiredObjectsInCache(const osg::FrameStamp& frameStamp);

        /** set hint to viewer code calling removeExpiredObjectsInCache to specify how long it should give before expiring objects in Registry cache,*/
        void setExpiryDelay(double expiryDelay) { _expiryDelay = expiryDelay; }

        double getExpiryDelay() const { return _expiryDelay; }


        /** Remove all objects in the cache regardless of having external references or expiry times.*/ 
        void clearObjectCache();

        /** Add a filename,object,timestamp triple to the Registry::ObjectCache.*/
        void addEntryToObjectCache(const std::string& filename, osg::Object* object, double timestamp = 0.0);

        /** Remove Object from cache.*/
        void removeFromObjectCache(const std::string& fileName);

        /** Get an Object from the object cache*/
        osg::Object* getFromObjectCache(const std::string& fileName);
        
        /** Get an ref_ptr<Object> from the object cache*/
        osg::ref_ptr<osg::Object> getRefFromObjectCache(const std::string& fileName);


        
        /** Add archive to archive cache so that future calls reference this archive.*/
        void addToArchiveCache(const std::string& fileName, osgDB::Archive* archive);

        /** Remove Archive from cache.*/
        void removeFromArchiveCache(const std::string& fileName);
        
        /** Get an Archive from the archive cache.*/
        osgDB::Archive* getFromArchiveCache(const std::string& fileName);

        /** Get an ref_ptr<Archive> from the archive cache.*/
        osg::ref_ptr<osgDB::Archive> getRefFromArchiveCache(const std::string& fileName);
        
        /** Remove all archives from the archive cache.*/
        void clearArchiveCache();
        
         /** If State is non-zero, this function releases OpenGL objects for
           * the specified graphics context. Otherwise, releases OpenGL objexts
           * for all graphics contexts. */
        void releaseGLObjects(osg::State* state=0);

        /** get the attached library with specified name.*/
        DynamicLibrary*              getLibrary(const std::string& fileName);

        /** Set the SharedStateManager.*/
        void setSharedStateManager(SharedStateManager* SharedStateManager) { _sharedStateManager = SharedStateManager; }

        /** Get the SharedStateManager, creating one if one is not already created.*/
        SharedStateManager* getOrCreateSharedStateManager();
        
        /** Get the SharedStateManager. Return 0 if no SharedStateManager has been assigned.*/
        SharedStateManager* getSharedStateManager() { return _sharedStateManager.get(); }

        /** Add an Archive extension.*/
        void addArchiveExtension(const std::string ext);
        
        /** registers a protocol */
        void registerProtocol(const std::string& protocol);
        
        /** returns true, if named protocol is registered */
        bool isProtocolRegistered(const std::string& protocol);

        /** Get the ObjectWrapperManager that is used to store all the ObjectWrappers. */
        ObjectWrapperManager* getObjectWrapperManager() { return _objectWrapperManager.get(); }

        /** Get the ObjectWrapperManager that is used to store all the ObjectWrappers. */
        DeprecatedDotOsgWrapperManager* getDeprecatedDotOsgObjectWrapperManager() { return _deprecatedDotOsgWrapperManager.get(); }

        typedef std::vector< std::string> ArchiveExtensionList;
        const ArchiveExtensionList& getArchiveExtensions() const { return _archiveExtList; }

    protected:

        virtual ~Registry();

        typedef std::vector< osg::ref_ptr<DynamicLibrary> >             DynamicLibraryList;
        typedef std::map< std::string, std::string>                     ExtensionAliasMap;
        
        typedef std::pair<osg::ref_ptr<osg::Object>, double >           ObjectTimeStampPair;
        typedef std::map<std::string, ObjectTimeStampPair >             ObjectCache;
        typedef std::map<std::string, osg::ref_ptr<osgDB::Archive> >    ArchiveCache;
        
        typedef std::set<std::string>                                   RegisteredProtocolsSet;

        /** constructor is private, as its a singleton, preventing
            construction other than via the instance() method and
            therefore ensuring only one copy is ever constructed*/
        Registry();

        /** get the attached library with specified name.*/
        DynamicLibraryList::iterator getLibraryItr(const std::string& fileName);

        Options::BuildKdTreesHint     _buildKdTreesHint;
        osg::ref_ptr<osg::KdTreeBuilder>            _kdTreeBuilder;
        
        osg::ref_ptr<FileCache>                     _fileCache;
        
        osg::ref_ptr<AuthenticationMap>             _authenticationMap;
        
        bool                                        _createNodeFromImage;
        
        RegisteredProtocolsSet                      _registeredProtocols;

    public:
        /** Functor used in internal implementations.*/
        struct ReadFunctor
        {
            ReadFunctor(const std::string& filename, const Options* options):
                _filename(filename),
                _options(options) {}

            virtual ~ReadFunctor() {}
            virtual ReaderWriter::ReadResult doRead(ReaderWriter& rw) const = 0;
            virtual bool isValid(ReaderWriter::ReadResult& readResult) const = 0;
            virtual bool isValid(osg::Object* object) const = 0;

            std::string _filename;
            const Options* _options;
        };

   protected:
   
        void destruct();
   
        // forward declare helper classes
        struct ReadObjectFunctor;
        struct ReadImageFunctor;
        struct ReadHeightFieldFunctor;
        struct ReadNodeFunctor;
        struct ReadArchiveFunctor;
        struct ReadShaderFunctor;
        
        // make helper classes friends to get round VS6.0 "issues"
        friend struct ReadFunctor;
        friend struct ReadObjectFunctor;
        friend struct ReadImageFunctor;
        friend struct ReadHeightFieldFunctor;
        friend struct ReadNodeFunctor;
        friend struct ReadArchiveFunctor;
        friend struct ReadShaderFunctor;

        ReaderWriter::ReadResult read(const ReadFunctor& readFunctor);
        ReaderWriter::ReadResult readImplementation(const ReadFunctor& readFunctor,Options::CacheHintOptions cacheHint);


        // forward declare helper class
        class AvailableReaderWriterIterator;
        friend class AvailableReaderWriterIterator;
        class AvailableArchiveIterator;
        friend class AvailableArchiveIterator;


        osg::ref_ptr<FindFileCallback>      _findFileCallback;
        osg::ref_ptr<ReadFileCallback>      _readFileCallback;
        osg::ref_ptr<WriteFileCallback>     _writeFileCallback;
        osg::ref_ptr<FileLocationCallback>  _fileLocationCallback;

        OpenThreads::ReentrantMutex _pluginMutex;
        ReaderWriterList            _rwList;
        ImageProcessorList          _ipList;
        DynamicLibraryList          _dlList;

        OpenThreads::ReentrantMutex _archiveCacheMutex;
        ArchiveCache                _archiveCache;

        bool _openingLibrary;
    
        // map to alias to extensions to plugins.
        ExtensionAliasMap  _extAliasMap;

        // maps mime-types to extensions.
        MimeTypeExtensionMap _mimeTypeExtMap;

        // Utility: Removes whitespace from both ends of a string.
        static std::string trim( const std::string& str );
        
        // options to pass to reader writers.
        osg::ref_ptr<Options>     _options;
        
        FilePathList                            _dataFilePath;
        FilePathList                            _libraryFilePath;

        double                                  _expiryDelay;
        ObjectCache                             _objectCache;
        OpenThreads::Mutex                      _objectCacheMutex;
        

        ArchiveExtensionList                    _archiveExtList;

        osg::ref_ptr<SharedStateManager>        _sharedStateManager;

        osg::ref_ptr<ObjectWrapperManager>      _objectWrapperManager;
        osg::ref_ptr<DeprecatedDotOsgWrapperManager> _deprecatedDotOsgWrapperManager;
};

/** read the command line arguments.*/
inline void readCommandLine(osg::ArgumentParser& parser)
{
    Registry::instance()->readCommandLine(parser);
}

/** Proxy class for automatic registration of reader/writers with the Registry.*/
template<class T>
class RegisterReaderWriterProxy
{
    public:
        RegisterReaderWriterProxy()
        {
            if (Registry::instance())
            {
                _rw = new T;
                Registry::instance()->addReaderWriter(_rw.get());
            }
        }

        ~RegisterReaderWriterProxy()
        {
            if (Registry::instance())
            {
                Registry::instance()->removeReaderWriter(_rw.get());
            }
        }
        
        T* get() { return _rw.get(); }
        
    protected:
        osg::ref_ptr<T> _rw;
};


/** Proxy class for automatic registration of reader/writers with the Registry.*/
template<class T>
class RegisterImageProcessorProxy
{
    public:
        RegisterImageProcessorProxy()
        {
            if (Registry::instance())
            {
                _rw = new T;
                Registry::instance()->addImageProcessor(_rw.get());
            }
        }

        ~RegisterImageProcessorProxy()
        {
            if (Registry::instance())
            {
                Registry::instance()->removeImageProcessor(_rw.get());
            }
        }

        T* get() { return _rw.get(); }

    protected:
        osg::ref_ptr<T> _rw;
};

struct PluginFunctionProxy
{
    PluginFunctionProxy(CPluginFunction function) { (function)(); }
};

#define USE_OSGPLUGIN(ext) \
    extern "C" void osgdb_##ext(void); \
    static osgDB::PluginFunctionProxy proxy_##ext(osgdb_##ext);

#define USE_DOTOSGWRAPPER(classname) \
    extern "C" void dotosgwrapper_##classname(void); \
    static osgDB::PluginFunctionProxy proxy_dotosgwrapper_##classname(dotosgwrapper_##classname);

#define USE_DOTOSGWRAPPER_LIBRARY(libname) \
    extern "C" void dotosgwrapper_library_##libname(void); \
    static osgDB::PluginFunctionProxy proxy_dotosgwrapper_library_##libname(dotosgwrapper_library_##libname);

#define USE_SERIALIZER_WRAPPER(classname) \
    extern "C" void wrapper_serializer_##classname(void); \
    static osgDB::PluginFunctionProxy proxy_serializer_##classname(wrapper_serializer_##classname);

#define USE_SERIALIZER_WRAPPER_LIBRARY(libname) \
    extern "C" void wrapper_serializer_library_##libname(void); \
    static osgDB::PluginFunctionProxy proxy_serializer_library_##libname(wrapper_serializer_library_##libname);

#define USE_COMPRESSOR_WRAPPER(classname) \
    extern "C" void wrapper_serializer_##classname(void); \
    static osgDB::PluginFunctionProxy proxy_compressor_##classname(wrapper_compressor_##classname);

#define REGISTER_OSGPLUGIN(ext, classname) \
    extern "C" void osgdb_##ext(void) {} \
    static osgDB::RegisterReaderWriterProxy<classname> g_proxy_##classname;

#define REGISTER_OSGIMAGEPROCESSOR(ext, classname) \
    extern "C" void osgdb_##ext(void) {} \
    static osgDB::RegisterImageProcessorProxy<classname> g_proxy_##classname;

}

#endif