{
        CPLDebug( "OGR", 
                  "OGRSFDriverRegistrar::ReleaseDataSource(%s)\n"
                  "Datasource reference count is now zero, but some layers\n"
                  "are still referenced ... not closing datasource.",
                  poDS->GetName() );
        return OGRERR_FAILURE;
    }

/* -------------------------------------------------------------------- */
/*      We really want to close this file, and remove it from the       */
/*      shared list.                                                    */
/* -------------------------------------------------------------------- */
    CPLDebug( "OGR", 
              "ReleaseDataSource(%s/%p) dereferenced and now destroying.",
              poDS->GetName(), poDS );

    CPLFree( papszOpenDSRawName[iDS] );
    memmove( papszOpenDSRawName + iDS, papszOpenDSRawName + iDS + 1, 
             sizeof(char *) * (nOpenDSCount - iDS - 1) );
    memmove( papoOpenDS + iDS, papoOpenDS + iDS + 1, 
             sizeof(char *) * (nOpenDSCount - iDS - 1) );
    memmove( papoOpenDSDriver + iDS, papoOpenDSDriver + iDS + 1, 
             sizeof(char *) * (nOpenDSCount - iDS - 1) );

    nOpenDSCount--;

    if( nOpenDSCount == 0 )
    {
        CPLFree( papszOpenDSRawName );
        papszOpenDSRawName = NULL;
        CPLFree( papoOpenDS );
        papoOpenDS = NULL;
        CPLFree( papoOpenDSDriver );
        papoOpenDSDriver = NULL;
    }

    // We are careful to only do the delete poDS after adjusting the
    // table, as if it is a virtual dataset, other removals may happen
    // in the meantime.
    delete poDS;

    return OGRERR_NONE;
}

/************************************************************************/
/*                        OGRReleaseDataSource()                        */
/************************************************************************/

OGRErr OGRReleaseDataSource( OGRDataSourceH hDS )

{
    OGRSFDriverRegistrar::GetRegistrar();
    return poRegistrar->ReleaseDataSource((OGRDataSource *) hDS);
}

/************************************************************************/
/*                         OGRGetOpenDSCount()                          */
/************************************************************************/

int OGRGetOpenDSCount()

{
    OGRSFDriverRegistrar::GetRegistrar();
    return poRegistrar->GetOpenDSCount();
}

/************************************************************************/
/*                             GetOpenDS()                              */
/************************************************************************/

OGRDataSource *OGRSFDriverRegistrar::GetOpenDS( int iDS )

{
    if( iDS < 0 || iDS >= nOpenDSCount )
        return NULL;
    else
        return papoOpenDS[iDS];
}

/************************************************************************/
/*                            OGRGetOpenDS()                            */
/************************************************************************/

OGRDataSourceH OGRGetOpenDS( int iDS )

{
    OGRSFDriverRegistrar::GetRegistrar();
    return (OGRDataSourceH) poRegistrar->GetOpenDS( iDS );
}

/************************************************************************/
/*                           RegisterDriver()                           */
/************************************************************************/

void OGRSFDriverRegistrar::RegisterDriver( OGRSFDriver * poDriver )

{
    int         iDriver;

/* -------------------------------------------------------------------- */
/*      It has no effect to register a driver more than once.           */
/* -------------------------------------------------------------------- */
    for( iDriver = 0; iDriver < nDrivers; iDriver++ )
    {
        if( poDriver == papoDrivers[iDriver] )
            return;
    }                                                   

/* -------------------------------------------------------------------- */
/*      Add to the end of the driver list.                              */
/* -------------------------------------------------------------------- */
    papoDrivers = (OGRSFDriver **)
        CPLRealloc( papoDrivers, (nDrivers+1) * sizeof(void*) );

    papoDrivers[nDrivers++] = poDriver;
}

/************************************************************************/
/*                         OGRRegisterDriver()                          */
/************************************************************************/

void OGRRegisterDriver( OGRSFDriverH hDriver )

{
    OGRSFDriverRegistrar::GetRegistrar()->RegisterDriver( 
        (OGRSFDriver *) hDriver );
}

/************************************************************************/
/*                           GetDriverCount()                           */
/************************************************************************/

int OGRSFDriverRegistrar::GetDriverCount()

{
    return nDrivers;
}

/************************************************************************/
/*                         OGRGetDriverCount()                          */
/************************************************************************/

int OGRGetDriverCount()

{
    if (poRegistrar)
        return poRegistrar->GetDriverCount();

    return 0;
}

/************************************************************************/
/*                             GetDriver()                              */
/************************************************************************/

OGRSFDriver *OGRSFDriverRegistrar::GetDriver( int iDriver )

{
    if( iDriver < 0 || iDriver >= nDrivers )
        return NULL;
    else
        return papoDrivers[iDriver];
}

/************************************************************************/
/*                            OGRGetDriver()                            */
/************************************************************************/

OGRSFDriverH OGRGetDriver( int iDriver )

{
    return (OGRSFDriverH) poRegistrar->GetDriver( iDriver );
}

/************************************************************************/
/*                          GetDriverByName()                           */
/************************************************************************/

OGRSFDriver *OGRSFDriverRegistrar::GetDriverByName( const char * pszName )

{
    for( int i = 0; i < nDrivers; i++ )
    {
        if( papoDrivers[i] != NULL 
            && EQUAL(papoDrivers[i]->GetName(),pszName) )
            return papoDrivers[i];
    }

    return NULL;
}

/************************************************************************/
/*                         OGRGetDriverByName()                         */
/************************************************************************/

OGRSFDriverH OGRGetDriverByName( const char *pszName )

{
    ;
    return (OGRSFDriverH) 
        OGRSFDriverRegistrar::GetRegistrar()->GetDriverByName( pszName );
}

/************************************************************************/
/*                          AutoLoadDrivers()                           */
/************************************************************************/

/**
 * Auto-load GDAL drivers from shared libraries.
 *
 * This function will automatically load drivers from shared libraries.  It
 * searches the "driver path" for .so (or .dll) files that start with the
 * prefix "gdal_X.so".  It then tries to load them and then tries to call
 * a function within them called GDALRegister_X() where the 'X' is the same 
 * as the remainder of the shared library basename, or failing that to 
 * call GDALRegisterMe().  
 *
 * There are a few rules for the driver path.  If the GDAL_DRIVER_PATH
 * environment variable it set, it is taken to be a list of directories
 * to search separated by colons on unix, or semi-colons on Windows.  Otherwise
 * the /usr/local/lib/gdalplugins directory, and (if known) the lib/gdalplugins
 * subdirectory of the gdal home directory are searched. 
 */

void OGRSFDriverRegistrar::AutoLoadDrivers()

{
    char     **papszSearchPath = NULL;
    const char *pszGDAL_DRIVER_PATH = 
        CPLGetConfigOption( "OGR_DRIVER_PATH", NULL );

    if( pszGDAL_DRIVER_PATH == NULL )
        pszGDAL_DRIVER_PATH = 
            CPLGetConfigOption( "GDAL_DRIVER_PATH", NULL );

/* -------------------------------------------------------------------- */
/*      Where should we look for stuff?                                 */
/* -------------------------------------------------------------------- */
    if( pszGDAL_DRIVER_PATH != NULL )
    {
#ifdef WIN32
        papszSearchPath = 
            CSLTokenizeStringComplex( pszGDAL_DRIVER_PATH, ";", TRUE, FALSE );
#else
        papszSearchPath = 
            CSLTokenizeStringComplex( pszGDAL_DRIVER_PATH, ":", TRUE, FALSE );
#endif
    }
    else
    {
#ifdef GDAL_PREFIX
        papszSearchPath = CSLAddString( papszSearchPath,
    #ifdef MACOSX_FRAMEWORK
                                        GDAL_PREFIX "/PlugIns");
    #else
                                        GDAL_PREFIX "/lib/gdalplugins" );
    #endif
#else
        char szExecPath[1024];

        if( CPLGetExecPath( szExecPath, sizeof(szExecPath) ) )
        {
            char szPluginDir[sizeof(szExecPath)+50];
            strcpy( szPluginDir, CPLGetDirname( szExecPath ) );
            strcat( szPluginDir, "\\gdalplugins\\" );
            papszSearchPath = CSLAddString( papszSearchPath, szPluginDir );
        }
        else
        {
            papszSearchPath = CSLAddString( papszSearchPath, 
                                            "/usr/local/lib/gdalplugins" );
        }
#endif 

#ifdef MACOSX_FRAMEWORK
        papszSearchPath = CSLAddString( papszSearchPath, 
                                        "/Library/Application Support/GDAL/PlugIns" );
#endif

    }

/* -------------------------------------------------------------------- */
/*      Scan each directory looking for files starting with gdal_       */
/* -------------------------------------------------------------------- */
    for( int iDir = 0; iDir < CSLCount(papszSearchPath); iDir++ )
    {
        char  **papszFiles = CPLReadDir( papszSearchPath[iDir] );

        for( int iFile = 0; iFile < CSLCount(papszFiles); iFile++ )
        {
            char   *pszFuncName;
            const char *pszFilename;
            const char *pszExtension = CPLGetExtension( papszFiles[iFile] );
            void   *pRegister;

            if( !EQUALN(papszFiles[iFile],"ogr_",4) )
                continue;

            if( !EQUAL(pszExtension,"dll") 
                && !EQUAL(pszExtension,"so") 
                && !EQUAL(pszExtension,"dylib") )
                continue;

            pszFuncName = (char *) CPLCalloc(strlen(papszFiles[iFile])+20,1);
            sprintf( pszFuncName, "RegisterOGR%s", 
                     CPLGetBasename(papszFiles[iFile]) + 4 );
            
            pszFilename = 
                CPLFormFilename( papszSearchPath[iDir], 
                                 papszFiles[iFile], NULL );

            pRegister = CPLGetSymbol( pszFilename, pszFuncName );
            if( pRegister == NULL )
            {
                strcpy( pszFuncName, "GDALRegisterMe" );
                pRegister = CPLGetSymbol( pszFilename, pszFuncName );
            }
            
            if( pRegister != NULL )
            {
                CPLDebug( "OGR", "Auto register %s using %s.", 
                          pszFilename, pszFuncName );

                ((void (*)()) pRegister)();
            }

            CPLFree( pszFuncName );
        }

        CSLDestroy( papszFiles );
    }

    CSLDestroy( papszSearchPath );
}