/******************************************************************************
 * $Id: ogrsfdriverregistrar.cpp 27044 2014-03-16 23:41:27Z rouault $
 *
 * Project:  OpenGIS Simple Features Reference Implementation
 * Purpose:  The OGRSFDriverRegistrar class implementation.
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 1999,  Les Technologies SoftMap Inc.
 * Copyright (c) 2008-2012, Even Rouault <even dot rouault at mines-paris dot org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "ogrsf_frmts.h"
#include "ogr_api.h"
#include "ogr_p.h"
#include "cpl_multiproc.h"
#include "swq.h"

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

CPL_CVSID("$Id: ogrsfdriverregistrar.cpp 27044 2014-03-16 23:41:27Z rouault $");

static void *hDRMutex = NULL;
static OGRSFDriverRegistrar * volatile poRegistrar = NULL;

static const char *pszUpdatableINST_DATA = 
"__INST_DATA_TARGET:                                                                                                                                      ";
/************************************************************************/
/*                         OGRSFDriverRegistrar                         */
/************************************************************************/

/**
 * \brief Constructor
 *
 * Normally the driver registrar is constucted by the 
 * OGRSFDriverRegistrar::GetRegistrar() accessor which ensures singleton
 * status.  
 */

OGRSFDriverRegistrar::OGRSFDriverRegistrar()

{
    CPLAssert( poRegistrar == NULL );
    nDrivers = 0;
    papoDrivers = NULL;

    nOpenDSCount = 0;
    papszOpenDSRawName = NULL;
    papoOpenDS = NULL;
    papoOpenDSDriver = NULL;
    panOpenDSPID = NULL;

/* -------------------------------------------------------------------- */
/*      We want to push a location to search for data files             */
/*      supporting GDAL/OGR such as EPSG csv files, S-57 definition     */
/*      files, and so forth.  The static pszUpdateableINST_DATA         */
/*      string can be updated within the shared library or              */
/*      executable during an install to point installed data            */
/*      directory.  If it isn't burned in here then we use the          */
/*      INST_DATA macro (setup at configure time) if                    */
/*      available. Otherwise we don't push anything and we hope         */
/*      other mechanisms such as environment variables will have        */
/*      been employed.                                                  */
/* -------------------------------------------------------------------- */
    if( CPLGetConfigOption( "GDAL_DATA", NULL ) != NULL )
    {
        CPLPushFinderLocation( CPLGetConfigOption( "GDAL_DATA", NULL ) );
    }
    else if( pszUpdatableINST_DATA[19] != ' ' )
    {
        CPLPushFinderLocation( pszUpdatableINST_DATA + 19 );
    }
    else
    {
#ifdef INST_DATA
        CPLPushFinderLocation( INST_DATA );
#endif
    }
}

/************************************************************************/
/*                       ~OGRSFDriverRegistrar()                        */
/************************************************************************/

OGRSFDriverRegistrar::~OGRSFDriverRegistrar()

{
    for( int i = 0; i < nDrivers; i++ )
    {
        delete papoDrivers[i];
    }
    nDrivers = 0;
    CPLFree( papoDrivers );
    papoDrivers = NULL;

    poRegistrar = NULL; /* equivalent to this = NULL; */
}

/************************************************************************/
/*                           OGRCleanupAll()                            */
/************************************************************************/

/**
 * \brief Cleanup all OGR related resources. 
 *
 * This function will destroy the OGRSFDriverRegistrar along with all registered
 * drivers, and then cleanup long lived OSR (OGRSpatialReference) and CPL
 * resources.  This may be called in an application when OGR services are
 * no longer needed.  It is not normally required, but by freeing all
 * dynamically allocated memory it can make memory leak testing easier.
 * 
 * In addition to destroying the OGRDriverRegistrar, this function also calls:
 * - OSRCleanup()
 * - CPLFinderClean()
 * - VSICleanupFileManager()
 * - CPLFreeConfig()
 * - CPLCleanupTLS()
 */
void OGRCleanupAll()

{
    {
        // We don't want to hold the mutex while CPL level mutex services
        // are being destroyed ... just long enough to avoid conflict while
        // cleaning up OGR and OSR services.
        CPLMutexHolderD( &hDRMutex );
    
        if( poRegistrar != NULL )
            delete poRegistrar;
        OSRCleanup();
    }

    CPLDestroyMutex( hDRMutex );
    hDRMutex = NULL;

    CPLFinderClean();
    VSICleanupFileManager();
    CPLFreeConfig();
    CPLCleanupTLS();
}


/************************************************************************/
/*                            GetRegistrar()                            */
/************************************************************************/

/**
 * \brief Fetch registrar.
 *
 * This static method should be used to fetch the singleton 
 * registrar.  It will create a registrar if there is not already
 * one in existance.
 *
 * @return the current driver registrar.
 */

OGRSFDriverRegistrar *OGRSFDriverRegistrar::GetRegistrar()

{
    if( poRegistrar == NULL )
    {
        CPLMutexHolderD( &hDRMutex );

        if( poRegistrar == NULL )
            poRegistrar = new OGRSFDriverRegistrar();
    }
   
    CPLAssert( NULL != poRegistrar );
    return poRegistrar;
}

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

OGRDataSource *OGRSFDriverRegistrar::Open( const char * pszName,
                                           int bUpdate,
                                           OGRSFDriver ** ppoDriver )

{
    OGRDataSource       *poDS;

#ifdef HAVE_READLINK
    char szPointerFilename[2048];
    int  bHasRetried = FALSE;
#endif

    if( ppoDriver != NULL )
        *ppoDriver = NULL;

    GetRegistrar();
    
    CPLErrorReset();

    CPLAcquireMutex( hDRMutex, 0.1 );

#ifdef HAVE_READLINK
retry:
#endif
    for( int iDriver = 0; iDriver < poRegistrar->nDrivers; iDriver++ )
    {
        OGRSFDriver *poDriver = poRegistrar->papoDrivers[iDriver];

        CPLReleaseMutex( hDRMutex );

        poDS = poDriver->Open( pszName, bUpdate );
        if( poDS != NULL )
        {
            if( ppoDriver != NULL )
                *ppoDriver = poDriver;

            poDS->Reference();
            if( poDS->GetDriver() == NULL )
                poDS->m_poDriver = poDriver;

            CPLDebug( "OGR", "OGROpen(%s/%p) succeeded as %s.", 
                      pszName, poDS, poDS->GetDriver()->GetName() );
            
            return poDS;
        }

        if( CPLGetLastErrorType() == CE_Failure )
            return NULL;

        CPLAcquireMutex( hDRMutex, 0.1 );
    }

#ifdef HAVE_READLINK
    if (!bHasRetried)
    {
        /* If someone creates a file with "ln -sf /vsicurl/http://svn.osgeo.org/gdal/trunk/autotest/ogr/data/poly.shp my_remote_poly.shp" */
        /* we will be able to open it by passing my_remote_poly.shp */
        /* This helps a lot for OGR based readers that only provide file explorers to open datasources */
        int nBytes = readlink(pszName, szPointerFilename, sizeof(szPointerFilename));
        if (nBytes != -1)
        {
            szPointerFilename[MIN(nBytes, (int)sizeof(szPointerFilename)-1)] = 0;
            pszName = szPointerFilename;
            bHasRetried = TRUE;
            goto retry;
        }
    }
#endif

    CPLReleaseMutex( hDRMutex );

    CPLDebug( "OGR", "OGROpen(%s) failed.", pszName );
            
    return NULL;
}

/************************************************************************/
/*                              OGROpen()                               */
/************************************************************************/

OGRDataSourceH OGROpen( const char *pszName, int bUpdate,
                        OGRSFDriverH *pahDriverList )

{
    VALIDATE_POINTER1( pszName, "OGROpen", NULL );

    if (poRegistrar)
        return (OGRDataSourceH) 
            poRegistrar->Open( pszName, bUpdate, 
                               (OGRSFDriver **) pahDriverList );

    return NULL;
}

/************************************************************************/
/*                             OpenShared()                             */
/************************************************************************/

OGRDataSource *
OGRSFDriverRegistrar::OpenShared( const char * pszName, int bUpdate,
                                  OGRSFDriver ** ppoDriver )

{
    OGRDataSource       *poDS;

    if( ppoDriver != NULL )
        *ppoDriver = NULL;

    CPLErrorReset();

/* -------------------------------------------------------------------- */
/*      First try finding an existing open dataset matching exactly     */
/*      on the original datasource raw name used to open the            */
/*      datasource.                                                     */
/*                                                                      */
/*      NOTE: It is an error, but currently we ignore the bUpdate,      */
/*      and return whatever is open even if it is read-only and the     */
/*      application requested update access.                            */
/* -------------------------------------------------------------------- */
    {
        int iDS;
        CPLMutexHolderD( &hDRMutex );
        GIntBig nThisPID = CPLGetPID();
        
        for( iDS = 0; iDS < nOpenDSCount; iDS++ )
        {
            poDS = papoOpenDS[iDS];
            
            if( strcmp( pszName, papszOpenDSRawName[iDS]) == 0 
                && nThisPID == panOpenDSPID[iDS] )
            {
                poDS->Reference();
                
                if( ppoDriver != NULL )
                    *ppoDriver = papoOpenDSDriver[iDS];
                return poDS;
            }
        }

/* -------------------------------------------------------------------- */
/*      If that doesn't match, try matching on the name returned by     */
/*      the datasource itself.                                          */
/* -------------------------------------------------------------------- */
        for( iDS = 0; iDS < nOpenDSCount; iDS++ )
        {
            poDS = papoOpenDS[iDS];
            
            if( strcmp( pszName, poDS->GetName()) == 0 
                && nThisPID == panOpenDSPID[iDS] )
            {
                poDS->Reference();
                
                if( ppoDriver != NULL )
                    *ppoDriver = papoOpenDSDriver[iDS];
                return poDS;
            }
        }
    }

/* -------------------------------------------------------------------- */
/*      We don't have the datasource.  Open it normally.                */
/* -------------------------------------------------------------------- */
    OGRSFDriver *poTempDriver = NULL;

    poDS = Open( pszName, bUpdate, &poTempDriver );

    if( poDS == NULL )
        return poDS;

/* -------------------------------------------------------------------- */
/*      We don't have this datasource already.  Grow our list to        */
/*      hold the new datasource.                                        */
/* -------------------------------------------------------------------- */
    {
        CPLMutexHolderD( &hDRMutex );

        papszOpenDSRawName = (char **) 
            CPLRealloc( papszOpenDSRawName, sizeof(char*) * (nOpenDSCount+1) );
    
        papoOpenDS = (OGRDataSource **) 
            CPLRealloc( papoOpenDS, sizeof(char*) * (nOpenDSCount+1) );
    
        papoOpenDSDriver = (OGRSFDriver **) 
            CPLRealloc( papoOpenDSDriver, sizeof(char*) * (nOpenDSCount+1) );

        panOpenDSPID = (GIntBig *) 
            CPLRealloc( panOpenDSPID, sizeof(GIntBig) * (nOpenDSCount+1) );

        papszOpenDSRawName[nOpenDSCount] = CPLStrdup( pszName );
        papoOpenDS[nOpenDSCount] = poDS;
        papoOpenDSDriver[nOpenDSCount] = poTempDriver;
        panOpenDSPID[nOpenDSCount] = CPLGetPID();

        nOpenDSCount++;
    }

    if( ppoDriver != NULL )
        *ppoDriver = poTempDriver;

    return poDS;
}

/************************************************************************/
/*                           OGROpenShared()                            */
/************************************************************************/

OGRDataSourceH OGROpenShared( const char *pszName, int bUpdate,
                              OGRSFDriverH *pahDriverList )

{
    VALIDATE_POINTER1( pszName, "OGROpenShared", NULL );

    OGRSFDriverRegistrar::GetRegistrar();
    return (OGRDataSourceH)
        poRegistrar->OpenShared( pszName, bUpdate, 
                                 (OGRSFDriver **) pahDriverList );
}

/************************************************************************/
/*                         ReleaseDataSource()                          */
/************************************************************************/

OGRErr OGRSFDriverRegistrar::ReleaseDataSource( OGRDataSource * poDS )

{
    {
        CPLMutexHolderD( &hDRMutex );

        int iDS;

        for( iDS = 0; iDS < nOpenDSCount; iDS++ )
        {
            if( poDS == papoOpenDS[iDS] )
                break;
        }

        if( iDS == nOpenDSCount )
        {
            CPLDebug( "OGR", 
                      "ReleaseDataSource(%s/%p) on unshared datasource!\n"
                      "Deleting directly.", 
                      poDS->GetName(), poDS );
            delete poDS;
            return OGRERR_FAILURE;
        }

        if( poDS->GetRefCount() > 0 )
            poDS->Dereference();

        if( poDS->GetRefCount() > 0 )
        {
            CPLDebug( "OGR", 
                      "ReleaseDataSource(%s/%p) ... just dereferencing.",
                      poDS->GetName(), poDS );
            return OGRERR_NONE;
        }

        if( poDS->GetSummaryRefCount() > 0 )
        {
            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) );
        memmove( panOpenDSPID + iDS, panOpenDSPID + iDS + 1, 
                 sizeof(GIntBig) * (nOpenDSCount - iDS - 1) );

        nOpenDSCount--;

        if( nOpenDSCount == 0 )
        {
            CPLFree( papszOpenDSRawName );
            papszOpenDSRawName = NULL;
            CPLFree( papoOpenDS );
            papoOpenDS = NULL;
            CPLFree( papoOpenDSDriver );
            papoOpenDSDriver = NULL;
            CPLFree( panOpenDSPID );
            panOpenDSPID = 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.  We are also careful to do this         */
/*      outside the mutex protected loop as destroying a dataset can    */
/*      take quite a while.                                             */
/* -------------------------------------------------------------------- */
    delete poDS;

    return OGRERR_NONE;
}

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

OGRErr OGRReleaseDataSource( OGRDataSourceH hDS )

{
    VALIDATE_POINTER1( hDS, "OGRReleaseDataSource", OGRERR_INVALID_HANDLE );

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

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

int OGRGetOpenDSCount()

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

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

OGRDataSource *OGRSFDriverRegistrar::GetOpenDS( int iDS )

{
    CPLMutexHolderD( &hDRMutex );

    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 )

{
    CPLMutexHolderD( &hDRMutex );
    int         iDriver;

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

        /* Same name but different pointer. Likely a second call to OGRRegisterAll() */
        /* We delete the new driver */
        if (EQUAL(poDriver->GetName(), papoDrivers[iDriver]->GetName()))
        {
            delete poDriver;
            return;
        }
    }

/* -------------------------------------------------------------------- */
/*      Skip and destroy drivers in the black list.                     */
/* -------------------------------------------------------------------- */
    char** papszSkipDrivers =
            CSLTokenizeStringComplex(CPLGetConfigOption("OGR_SKIP", ""), ",", FALSE, FALSE);
    char** iter = papszSkipDrivers;
    while(*iter)
    {
        if (strcmp(*iter, poDriver->GetName()) == 0)
        {
            CSLDestroy(papszSkipDrivers);
            delete poDriver;
            return;
        }
        iter ++;
    }
    CSLDestroy(papszSkipDrivers);

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

    papoDrivers[nDrivers++] = poDriver;
}

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

void OGRRegisterDriver( OGRSFDriverH hDriver )

{
    VALIDATE_POINTER0( hDriver, "OGRRegisterDriver" );

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

/************************************************************************/
/*                          DeregisterDriver()                          */
/************************************************************************/

void OGRSFDriverRegistrar::DeregisterDriver( OGRSFDriver * poDriver )

{
    CPLMutexHolderD( &hDRMutex );
    int         i;

    for( i = 0; i < nDrivers; i++ )
    {
        if( poDriver == papoDrivers[i] )
            break;
    }

    if (i == nDrivers)
        return;

    while( i < nDrivers-1 )
    {
        papoDrivers[i] = papoDrivers[i+1];
        i++;
    }
    nDrivers--;
}

/************************************************************************/
/*                        OGRDeregisterDriver()                         */
/************************************************************************/

void OGRDeregisterDriver( OGRSFDriverH hDriver )

{
    VALIDATE_POINTER0( hDriver, "OGRDeregisterDriver" );

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

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

int OGRSFDriverRegistrar::GetDriverCount()

{
    return nDrivers;
}

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

int OGRGetDriverCount()

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

    return 0;
}

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

OGRSFDriver *OGRSFDriverRegistrar::GetDriver( int iDriver )

{
    CPLMutexHolderD( &hDRMutex );

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

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

OGRSFDriverH OGRGetDriver( int iDriver )

{
    VALIDATE_POINTER1( poRegistrar, "OGRGetDriver", NULL );

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

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

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

{
    CPLMutexHolderD( &hDRMutex );

    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 )

{
    VALIDATE_POINTER1( pszName, "OGRGetDriverByName", NULL );

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

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

/**
 * \brief 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 "ogr_X.so".  It then tries to load them and then tries to call
 * a function within them called RegisterOGRX() 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.  
 * 
 * Auto loading can be completely disabled by setting the GDAL_DRIVER_PATH
 * config option to "disable".
 *
 * If that is not set the following defaults are used:
 *
 * <ul>
 * <li> Linux/Unix: &lt;prefix&gt;/lib/gdalplugins is searched or
 * /usr/local/lib/gdalplugins if the install prefix is not known.
 * <li> MacOSX: &lt;prefix&gt;/PlugIns is searched, or /usr/local/lib/gdalplugins if
 * the install prefix is not known.  Also, the framework directory
 * /Library/Application Support/GDAL/PlugIns is searched.
 * <li> Win32: &lt;prefix&gt;/lib/gdalplugins if the prefix is known (normally it
 * is not), otherwise the gdalplugins subdirectory of the directory containing
 * the currently running executable is used. 
 * </ul>
 */

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 );

/* -------------------------------------------------------------------- */
/*      Allow applications to completely disable this search by         */
/*      setting the driver path to the special string "disable".        */
/* -------------------------------------------------------------------- */
    if( pszGDAL_DRIVER_PATH != NULL && EQUAL(pszGDAL_DRIVER_PATH,"disable")) 
    {
        CPLDebug( "GDAL", "OGRSFDriverRegistrar::AutoLoadDrivers() disabled." );
        return;
    }

/* -------------------------------------------------------------------- */
/*      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
#define num2str(x) str(x)
#define str(x) #x 
        papszSearchPath = CSLAddString( papszSearchPath, 
                                        "/Library/Application Support/GDAL/"
                                        num2str(GDAL_VERSION_MAJOR) "."
                                        num2str(GDAL_VERSION_MINOR) "/PlugIns" );
#endif

    }

/* -------------------------------------------------------------------- */
/*      Format the ABI version specific subdirectory to look in.        */
/* -------------------------------------------------------------------- */
    CPLString osABIVersion;

    osABIVersion.Printf( "%d.%d", GDAL_VERSION_MAJOR, GDAL_VERSION_MINOR );

/* -------------------------------------------------------------------- */
/*      Scan each directory looking for files starting with ogr_        */
/* -------------------------------------------------------------------- */
    for( int iDir = 0; iDir < CSLCount(papszSearchPath); iDir++ )
    {
        char **papszFiles = NULL;
        VSIStatBufL sStatBuf;
        CPLString osABISpecificDir =
            CPLFormFilename( papszSearchPath[iDir], osABIVersion, NULL );
        
        if( VSIStatL( osABISpecificDir, &sStatBuf ) != 0 )
            osABISpecificDir = papszSearchPath[iDir];

        papszFiles = CPLReadDir( osABISpecificDir );

        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( osABISpecificDir,
                                 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 );
}

