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plugins.h

/* 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.
 *
 * $URL$
 * $Id$
 *
 */

#ifndef BASE_PLUGINS_H
#define BASE_PLUGINS_H

#include "common/array.h"
#include "common/fs.h"
#include "common/str.h"
#include "backends/plugins/elf/version.h"


/**
 * @page pagePlugins An overview of the ScummVM plugin system
 * This is a brief overview of how plugins (dynamically loadable code modules)
 * work in ScummVM. We will explain how to write plugins, how they work internally,
 * and sketch how porters can add support for them in their ports.
 *
 * \section secPluginImpl Implementing a plugin
 * TODO
 *
 * \section secPluginUse Using plugins
 * TODO
 *
 * \section secPluginInternals How plugins work internally
 * TODO
 *
 * \section secPluginBackend How to add support for dynamic plugins to a port
 * TODO
 */



// Plugin versioning

/** Global Plugin API version */
#define PLUGIN_VERSION 1

enum PluginType {
      PLUGIN_TYPE_ENGINE = 0,
      PLUGIN_TYPE_MUSIC,
      /* PLUGIN_TYPE_SCALER, */     // TODO: Add graphics scaler plugins

      PLUGIN_TYPE_MAX
};

// TODO: Make the engine API version depend on ScummVM's version
// because of the backlinking (posibly from the checkout revision)
#define PLUGIN_TYPE_ENGINE_VERSION 1
#define PLUGIN_TYPE_MUSIC_VERSION 1

extern int pluginTypeVersions[PLUGIN_TYPE_MAX];


// Plugin linking

#define STATIC_PLUGIN 1
#define DYNAMIC_PLUGIN 2

#define PLUGIN_ENABLED_STATIC(ID) \
      (ENABLE_##ID && !PLUGIN_ENABLED_DYNAMIC(ID))

#define PLUGIN_ENABLED_DYNAMIC(ID) \
      (ENABLE_##ID && (ENABLE_##ID == DYNAMIC_PLUGIN) && DYNAMIC_MODULES)

// see comments in backends/plugins/elf/elf-provider.cpp
#if defined(USE_ELF_LOADER) && defined(ELF_LOADER_CXA_ATEXIT)
#define PLUGIN_DYNAMIC_DSO_HANDLE \
      uint32 __dso_handle __attribute__((visibility("hidden"))) = 0;
#else
#define PLUGIN_DYNAMIC_DSO_HANDLE
#endif

#ifdef USE_ELF_LOADER
#define PLUGIN_DYNAMIC_BUILD_DATE \
      PLUGIN_EXPORT const char *PLUGIN_getBuildDate() { return gScummVMPluginBuildDate; }
#else
#define PLUGIN_DYNAMIC_BUILD_DATE
#endif

/**
 * REGISTER_PLUGIN_STATIC is a convenience macro which is used to declare
 * the plugin interface for static plugins. Code (such as game engines)
 * which needs to implement a static plugin can simply invoke this macro
 * with a plugin ID, plugin type and PluginObject subclass, and the correct
 * wrapper code will be inserted.
 *
 * @see REGISTER_PLUGIN_DYNAMIC
 */
#define REGISTER_PLUGIN_STATIC(ID,TYPE,PLUGINCLASS) \
      PluginType g_##ID##_type = TYPE; \
      PluginObject *g_##ID##_getObject() { \
            return new PLUGINCLASS(); \
      } \
      void dummyFuncToAllowTrailingSemicolon()

#ifdef DYNAMIC_MODULES

/**
 * REGISTER_PLUGIN_DYNAMIC is a convenience macro which is used to declare
 * the plugin interface for dynamically loadable plugins. Code (such as game engines)
 * which needs to implement a dynamic plugin can simply invoke this macro
 * with a plugin ID, plugin type and PluginObject subclass, and the correct
 * wrapper code will be inserted.
 *
 * @see REGISTER_PLUGIN_STATIC
 */
#define REGISTER_PLUGIN_DYNAMIC(ID,TYPE,PLUGINCLASS) \
      extern "C" { \
            PLUGIN_DYNAMIC_DSO_HANDLE \
            PLUGIN_DYNAMIC_BUILD_DATE \
            PLUGIN_EXPORT int32 PLUGIN_getVersion() { return PLUGIN_VERSION; } \
            PLUGIN_EXPORT int32 PLUGIN_getType() { return TYPE; } \
            PLUGIN_EXPORT int32 PLUGIN_getTypeVersion() { return TYPE##_VERSION; } \
            PLUGIN_EXPORT PluginObject *PLUGIN_getObject() { \
                  return new PLUGINCLASS(); \
            } \
      } \
      void dummyFuncToAllowTrailingSemicolon()

#endif // DYNAMIC_MODULES


// Abstract plugins

/**
 * Abstract base class for the plugin objects which handle plugins 
 * instantiation. Subclasses for this may be used for engine plugins and other
 * types of plugins. An existing PluginObject refers to an executable file
 * loaded in memory and ready to run. The plugin, on the other hand, is just
 * a handle to the file/object, whether it's loaded in memory or not.
 */
00155 class PluginObject {
public:
      virtual ~PluginObject() {}

      /** Returns the name of the plugin. */
      virtual const char *getName() const = 0;
};

/**
 * Abstract base class for the plugin system.
 * Subclasses for this can be used to wrap both static and dynamic
 * plugins. This class refers to a plugin which may or may not be loaded in
 * memory.
 */
00169 class Plugin {
protected:
      PluginObject *_pluginObject;
      PluginType _type;

public:
      Plugin() : _pluginObject(0) {}
      virtual ~Plugin() {
            //if (isLoaded())
                  //unloadPlugin();
      }

//    virtual bool isLoaded() const = 0;  // TODO
      virtual bool loadPlugin() = 0;      // TODO: Rename to load() ?
      virtual void unloadPlugin() = 0;    // TODO: Rename to unload() ?

      /**
       * The following functions query information from the plugin object once
       * it's loaded into memory.
       **/
      PluginType getType() const;
      const char *getName() const;

      /**
       * The getFileName() function gets the name of the plugin file for those
       * plugins that have files (ie. not static). It doesn't require the plugin
       * object to be loaded into memory, unlike getName()
       **/
00197       virtual const char *getFileName() const { return 0; }
};

/** List of Plugin instances. */
typedef Common::Array<Plugin *> PluginList;

/**
 * Convenience template to make it easier defining normal Plugin
 * subclasses. Namely, the PluginSubclass will manage PluginObjects
 * of a type specified via the PO_t template parameter.
 */
template<class PO_t>
00209 class PluginSubclass : public Plugin {
public:
      PO_t *operator->() const {
            return (PO_t *)_pluginObject;
      }

      typedef Common::Array<PluginSubclass *> List;
};

/**
 * Abstract base class for Plugin factories. Subclasses of this
 * are responsible for creating plugin objects, e.g. by loading
 * loadable modules from storage media; by creating "fake" plugins
 * from static code; or whatever other means.
 */
00224 class PluginProvider {
public:
      virtual ~PluginProvider() {}

      /**
       * Return a list of Plugin objects. The caller is responsible for actually
       * loading/unloading them (by invoking the appropriate Plugin methods).
       * Furthermore, the caller is responsible for deleting these objects
       * eventually.
       *
       * @return a list of Plugin instances
       */
      virtual PluginList getPlugins() = 0;

      /**
       * @return whether or not object is a FilePluginProvider.
       */
00241       virtual bool isFilePluginProvider() { return false; }
};

#ifdef DYNAMIC_MODULES

/**
 * Abstract base class for Plugin factories which load binary code from files.
 * Subclasses only have to implement the createPlugin() method, and optionally
 * can overload the other protected methods to achieve custom behavior.
 */
class FilePluginProvider : public PluginProvider {
public:
      /**
       * Return a list of Plugin objects loaded via createPlugin from disk.
       * For this, a list of directories is searched for plugin objects:
       * The current dir and its "plugins" subdirectory (if present), a list
       * of custom search dirs (see addCustomDirectories) and finally the
       * directory specified via the "pluginspath" config variable (if any).
       *
       * @return a list of Plugin instances
       */
      virtual PluginList getPlugins();

      /**
       * @return whether or not object is a FilePluginProvider.
       */
      bool isFilePluginProvider() { return true; }

protected:
      /**
       * Create a Plugin instance from a loadable code module with the specified name.
       * Subclasses of FilePluginProvider have to at least overload this method.
       * If the file is not found, or does not contain loadable code, 0 is returned instead.
       *
       * @param node    the FSNode of the loadable code module
       * @return  a pointer to a Plugin instance, or 0 if an error occurred.
       */
      virtual Plugin *createPlugin(const Common::FSNode &node) const = 0;

      /**
       * Check if the supplied file corresponds to a loadable plugin file in
       * the current platform. Usually, this will just check the file name.
       *
       * @param node    the FSNode of the file to check
       * @return  true if the filename corresponds to a plugin, false otherwise
       */
      virtual bool isPluginFilename(const Common::FSNode &node) const;

      /**
       * Optionally add to the list of directories to be searched for
       * plugins by getPlugins().
       *
       * @param dirs    the reference to the list of directories to be used when
       *          searching for plugins.
       */
      virtual void addCustomDirectories(Common::FSList &dirs) const;
};

#endif // DYNAMIC_MODULES

#define PluginMan PluginManager::instance()

/**
 * Singleton class which manages all plugins, including loading them,
 * managing all Plugin class instances, and unloading them.
 */
00307 class PluginManager {
protected:
      typedef Common::Array<PluginProvider *> ProviderList;

      PluginList _pluginsInMem[PLUGIN_TYPE_MAX];
      ProviderList _providers;

      bool tryLoadPlugin(Plugin *plugin);
      void addToPluginsInMemList(Plugin *plugin);
      
      static PluginManager *_instance;
      PluginManager();

public:
      virtual ~PluginManager();

      static void destroy() { delete _instance; _instance = 0; }
      static PluginManager &instance();

      void addPluginProvider(PluginProvider *pp);

      // Functions used by the uncached PluginManager
      virtual void init()     {}
      virtual void loadFirstPlugin() {}
      virtual bool loadNextPlugin() { return false; }
      virtual bool loadPluginFromGameId(const Common::String &gameId) { return false; } 
      virtual void updateConfigWithFileName(const Common::String &gameId) {} 
      
      // Functions used only by the cached PluginManager
      virtual void loadAllPlugins();
      void unloadAllPlugins();

      void unloadPluginsExcept(PluginType type, const Plugin *plugin, bool deletePlugin = true);

      const PluginList &getPlugins(PluginType t) { return _pluginsInMem[t]; }
};

/** 
 *  Uncached version of plugin manager
 *  Keeps only one dynamic plugin in memory at a time
 **/
00348 class PluginManagerUncached : public PluginManager {
protected:
      friend class PluginManager;
      PluginList _allEnginePlugins;
      PluginList::iterator _currentPlugin;

      PluginManagerUncached() {}
      bool loadPluginByFileName(const Common::String &filename); 

public:
      virtual void init();
      virtual void loadFirstPlugin();
      virtual bool loadNextPlugin();
      virtual bool loadPluginFromGameId(const Common::String &gameId); 
      virtual void updateConfigWithFileName(const Common::String &gameId); 
      
00364       virtual void loadAllPlugins() {}    // we don't allow this
};

#endif

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