/*****************************************************************************
 * modules_plugin.h : Plugin management functions used by the core application.
 *****************************************************************************
 * Copyright (C) 2001 VideoLAN
 * $Id: modules_plugin.h.in,v 1.10 2003/07/01 12:50:56 sam Exp $
 *
 * Authors: Samuel Hocevar <sam@zoy.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*****************************************************************************
 * Inline functions for handling dynamic modules
 *****************************************************************************/

/*****************************************************************************
 * module_load: load a dynamic library
 *****************************************************************************
 * This function loads a dynamically linked library using a system dependant
 * method, and returns a non-zero value on error, zero otherwise.
 *****************************************************************************/
static int module_load( const MYCHAR * psz_filename, module_handle_t * handle )
{
#ifdef SYS_BEOS
    *handle = load_add_on( psz_filename );
    return( *handle < 0 );

#elif defined(WIN32) || defined(UNDER_CE)
    *handle = LoadLibrary( psz_filename );
    return( *handle == NULL );

#elif defined(RTLD_NOW)
    /* static is OK, we are called atomically */
    static vlc_bool_t b_kde = VLC_FALSE;

#   if defined(SYS_LINUX)
    /* XXX HACK #1 - we should NOT open modules with RTLD_GLOBAL, or we
     * are going to get namespace collisions when two modules have common
     * public symbols, but ALSA is being a pest here. */
    if( strstr( psz_filename, "alsa_plugin" ) )
    {
        *handle = dlopen( psz_filename, RTLD_NOW | RTLD_GLOBAL );
        return( *handle == NULL );
    }
#   endif
    /* XXX HACK #2 - the ugly KDE workaround. It seems that libkdewhatever
     * causes dlopen() to segfault if libstdc++ is not loaded in the caller,
     * so we just load libstdc++. Bwahahaha! ph34r! -- Sam. */
    /* Update: FYI, this is Debian bug #180505, and seems to be fixed. */
    if( !b_kde && !strstr( psz_filename, "kde" ) )
    {
        dlopen( "libstdc++.so.6", RTLD_NOW )
         || dlopen( "libstdc++.so.5", RTLD_NOW )
         || dlopen( "libstdc++.so.4", RTLD_NOW )
         || dlopen( "libstdc++.so.3", RTLD_NOW );
        b_kde = VLC_TRUE;
    }

    *handle = dlopen( psz_filename, RTLD_NOW );
    return( *handle == NULL );

#else
    *handle = dlopen( psz_filename, DL_LAZY );
    return( *handle == NULL );

#endif
}

/*****************************************************************************
 * module_unload: unload a dynamic library
 *****************************************************************************
 * This function unloads a previously opened dynamically linked library
 * using a system dependant method. No return value is taken in consideration,
 * since some libraries sometimes refuse to close properly.
 *****************************************************************************/
static void module_unload( module_handle_t handle )
{
#ifdef SYS_BEOS
    unload_add_on( handle );

#elif defined(WIN32) || defined(UNDER_CE)
    FreeLibrary( handle );

#else
    dlclose( handle );

#endif
    return;
}

/*****************************************************************************
 * module_getsymbol: get a symbol from a dynamic library
 *****************************************************************************
 * This function queries a loaded library for a symbol specified in a
 * string, and returns a pointer to it. We don't check for dlerror() or
 * similar functions, since we want a non-NULL symbol anyway.
 *****************************************************************************/
static void * _module_getsymbol( module_handle_t handle,
                                 const char * psz_function )
{
#ifdef SYS_BEOS
    void * p_symbol;
    if( B_OK == get_image_symbol( handle, psz_function,
                                  B_SYMBOL_TYPE_TEXT, &p_symbol ) )
    {
        return p_symbol;
    }
    else
    {
        return NULL;
    }

#elif defined( UNDER_CE )
    wchar_t psz_real[256];
    MultiByteToWideChar( CP_ACP, 0, psz_function, -1, psz_real, 256 );

    return (void *)GetProcAddress( handle, psz_real );

#elif defined( WIN32 )
    return (void *)GetProcAddress( handle, (MYCHAR*)psz_function );

#else
    return dlsym( handle, psz_function );

#endif
}

static void * module_getsymbol( module_handle_t handle,
                                const char * psz_function )
{
    void * p_symbol = _module_getsymbol( handle, psz_function );

    /* MacOS X dl library expects symbols to begin with "_". So do
     * some other operating systems. That's really lame, but hey, what
     * can we do ? */
    if( p_symbol == NULL )
    {
        char *psz_call = malloc( strlen( psz_function ) + 2 );

        strcpy( psz_call + 1, psz_function );
        psz_call[ 0 ] = '_';
        p_symbol = _module_getsymbol( handle, psz_call );
        free( psz_call );
    }

    return p_symbol;
}

/*****************************************************************************
 * module_error: wrapper for dlerror()
 *****************************************************************************
 * This function returns the error message of the last module operation. It
 * returns the string "failed" on systems which do not have a dlerror() like
 * function. psz_buffer can be used to store temporary data, it is guaranteed
 * to be kept intact until the return value of module_error has been used.
 *****************************************************************************/
static const char * module_error( char *psz_buffer )
{
#if defined(SYS_BEOS)
    return "failed";

#elif defined(UNDER_CE)
    wchar_t psz_tmp[256];

    int i, i_error = GetLastError();

    FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                   NULL, i_error, MAKELANGID (LANG_NEUTRAL, SUBLANG_DEFAULT),
                   (LPTSTR) psz_tmp, 256, NULL );

    /* Go to the end of the string */
    for( i = 0;
         psz_tmp[i] && psz_tmp[i] != L'\r' && psz_tmp[i] != L'\n';
         i++ ) {};

    if( psz_tmp[i] )
    {
        swprintf( psz_tmp + i, L" (error %i)", i_error );
        psz_tmp[ 255 ] = L'\0';
    }

    WideCharToMultiByte( CP_ACP, WC_DEFAULTCHAR, psz_tmp, -1,
                         psz_buffer, 256, NULL, NULL );

    return psz_buffer;

#elif defined(WIN32)
    int i, i_error = GetLastError();

    FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                   NULL, i_error, MAKELANGID (LANG_NEUTRAL, SUBLANG_DEFAULT),
                   (LPTSTR) psz_buffer, 256, NULL );

    /* Go to the end of the string */
    for( i = 0;
         psz_buffer[i] && psz_buffer[i] != '\r' && psz_buffer[i] != '\n';
         i++ ) {};

    if( psz_buffer[i] )
    {
        snprintf( psz_buffer + i, 256 - i, " (error %i)", i_error );
        psz_buffer[ 255 ] = '\0';
    }

    return psz_buffer;

#else
    return dlerror();

#endif
}

/*****************************************************************************
 * STORE_SYMBOLS: store known symbols into p_symbols for plugin access.
 *****************************************************************************/