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posix-provider.cpp

/* ScummVM - Graphic Adventure Engine
 *
 * ScummVM is the legal property of its developers, whose names
 * are too numerous to list here. Please refer to the COPYRIGHT
 * file distributed with this source distribution.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * $URL: https://scummvm.svn.sourceforge.net/svnroot/scummvm/scummvm/tags/release-0-11-1/backends/plugins/posix/posix-provider.cpp $
 * $Id: posix-provider.cpp 30944 2008-02-23 22:50:18Z sev $
 *
 */

#if defined(DYNAMIC_MODULES) && defined(UNIX)

#include "backends/plugins/posix/posix-provider.h"
#include "backends/plugins/dynamic-plugin.h"
#include "common/fs.h"

#include <dlfcn.h>
#define PLUGIN_DIRECTORY      "plugins/"


class POSIXPlugin : public DynamicPlugin {
protected:
      void *_dlHandle;
      Common::String _filename;

      virtual VoidFunc findSymbol(const char *symbol) {
            void *func = dlsym(_dlHandle, symbol);
            if (!func)
                  warning("Failed loading symbol '%s' from plugin '%s' (%s)", symbol, _filename.c_str(), dlerror());
      
            // FIXME HACK: This is a HACK to circumvent a clash between the ISO C++
            // standard and POSIX: ISO C++ disallows casting between function pointers
            // and data pointers, but dlsym always returns a void pointer. For details,
            // see e.g. <http://www.trilithium.com/johan/2004/12/problem-with-dlsym/>.
            assert(sizeof(VoidFunc) == sizeof(func));
            VoidFunc tmp;
            memcpy(&tmp, &func, sizeof(VoidFunc));
            return tmp;
      }

public:
      POSIXPlugin(const Common::String &filename)
            : _dlHandle(0), _filename(filename) {}

      bool loadPlugin() {
            assert(!_dlHandle);
            _dlHandle = dlopen(_filename.c_str(), RTLD_LAZY);
      
            if (!_dlHandle) {
                  warning("Failed loading plugin '%s' (%s)", _filename.c_str(), dlerror());
                  return false;
            }
      
            return DynamicPlugin::loadPlugin();
      }
      void unloadPlugin() {
            if (_dlHandle) {
                  if (dlclose(_dlHandle) != 0)
                        warning("Failed unloading plugin '%s' (%s)", _filename.c_str(), dlerror());
                  _dlHandle = 0;
            }
      }
};


POSIXPluginProvider::POSIXPluginProvider() {
}

POSIXPluginProvider::~POSIXPluginProvider() {
}

PluginList POSIXPluginProvider::getPlugins() {
      PluginList pl;
      
      
      // Load dynamic plugins
      // TODO... this is right now just a nasty hack.
      // This should search one or multiple directories for all plugins it can
      // find (to this end, we maybe should use a special prefix/suffix; e.g.
      // instead of libscumm.so, use scumm.engine or scumm.plugin etc.).
      //
      // The list of directories to search could be e.g.:
      // User specified (via config file), ".", "./plugins", "$(prefix)/lib".
      //
      // We also need to add code which ensures what we are looking at is
      // a) a ScummVM engine and b) matches the version of the executable.
      // Hence one more symbol should be exported by plugins which returns
      // the "ABI" version the plugin was built for, and we can compare that
      // to the ABI version of the executable.

      // Load all plugins.
      // Scan for all plugins in this directory
      FilesystemNode dir(PLUGIN_DIRECTORY);
      FSList files;
      if (!dir.getChildren(files, FilesystemNode::kListFilesOnly)) {
            error("Couldn't open plugin directory '%s'", PLUGIN_DIRECTORY);
      }

      for (FSList::const_iterator i = files.begin(); i != files.end(); ++i) {
            Common::String name(i->getName());
            if (name.hasPrefix(PLUGIN_PREFIX) && name.hasSuffix(PLUGIN_SUFFIX)) {
                  pl.push_back(new POSIXPlugin(i->getPath()));
            }
      }
      
      
      return pl;
}


#endif // defined(DYNAMIC_MODULES) && defined(UNIX)

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