插件式结构设计(PluginsPattern)

// MainProgram.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "IPlugin.h" //for the IPlugin abstract base //convenience typedef for the pointers to the 2 functions we expect to find in the plugins typedef IPlugin* (*PLUGIN_FACTORY)(); typedef void (*PLUGIN_CLEANUP)(IPlugin*); int main(int argc, char* argv[]) { //get the program's directory char dir [MAX_PATH]; ::GetModuleFileName (NULL, dir, MAX_PATH); //eliminate the file name (to get just the directory) char* p = ::strrchr (dir, '\\'); *(p + 1) = 0; //find all DLLs in the plugins subdirectory char search_parms [MAX_PATH]; ::strcpy_s (search_parms, MAX_PATH, dir); ::strcat_s (search_parms, MAX_PATH, "plugins\\*.dll"); WIN32_FIND_DATA find_data; HANDLE h_find = ::FindFirstFile (search_parms, &find_data); BOOL f_ok = TRUE; while (h_find != INVALID_HANDLE_VALUE && f_ok) { //load each DLL and determine whether it is exporting the functions we care about char plugin_full_name [MAX_PATH]; ::strcpy_s (plugin_full_name, MAX_PATH, dir); ::strcat_s (plugin_full_name, MAX_PATH, "plugins\\"); ::strcat_s (plugin_full_name, MAX_PATH, find_data.cFileName); HMODULE h_mod = ::LoadLibrary (plugin_full_name); if (h_mod != NULL) { PLUGIN_FACTORY p_factory_function = (PLUGIN_FACTORY) ::GetProcAddress (h_mod, "Create_Plugin"); PLUGIN_CLEANUP p_cleanup_function = (PLUGIN_CLEANUP) ::GetProcAddress (h_mod, "Release_Plugin"); if (p_factory_function != NULL && p_cleanup_function != NULL) { //yes, this DLL exposes the 2 functions we need, it is a plugin we can use! //invoke the factory to create the plugin object IPlugin* p_plugin = (*p_factory_function) (); //show which plugin it is, and let the plugin do the processing printf ("Now working with plugin: %s\n", p_plugin ->Get_Name ()); p_plugin ->Process_Data (); //done, cleanup the plugin by invoking its cleanup function (*p_cleanup_function) (p_plugin); } ::FreeLibrary (h_mod); } //go for the next DLL f_ok = ::FindNextFile (h_find, &find_data); } return 0; }