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工业自动化软件设计 之四 插件实现 [复制链接]

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离线myer
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只看楼主 倒序阅读 楼主  发表于: 2011-12-02
Qt的插件使用起来非常简单，但是如果在某些平台上，并不想用Qt库，则需要自己实现类似的功能
以下是一个简单的实现：3个宏
1、实现插件：
     定义插件类的头文件：
     class IPlugin{...}
     实现：class IPluginImpl : public IPlugin{...}
     在头文件里声明：Pan_Declare_Plugin(IPlugin)
     在实现文件里：Pan_Export_Plugin(IPlugin, IPluginImpl )
2、load插件：
     在需要load的地方，PanLoadPlugin(IPlugin)，声明一个loadIPlugin函数
     IPlugin*ipulin = loadIPlugin(filename);

3、代码：
宏定义
复制代码
  1. #define Pan_Declare_Plugin(baseclass) extern "C"{\
  2. PAN_EXPORTS baseclass *create_##baseclass();};
  4. #define Pan_Export_Plugin(baseclass, implclass) extern "C"{\
  5.     baseclass *create_##baseclass(){return new implclass;}};
panlibrary.h
复制代码
  1. #pragma once
  3. #ifdef _WIN32
  4. #include <Windows.h>
  5. #include <iostream>
  6. #endif
  8. class PanLibrary
  9. {
  10. public:
  12.     PanLibrary();
  13.     ~PanLibrary();
  15. #ifdef _WIN32
  16.     typedef FARPROC symbol_type;
  17. #else
  18.     typedef void* symbol_type;
  19. #endif
  21.     symbol_type loadEntryPoint(const std::string&);
  23.     bool load(const std::string&);
  25.     symbol_type getSymbol(const std::string&);
  27.     const std::string& getErrorMessage() const;
  29. private:
  31. #ifdef _WIN32
  32.     HINSTANCE _hnd;
  33. #else
  34.     void* _hnd;
  35. #endif
  37.     std::string _err;
  38. };
  40. #define PanLoadPlugin(baseclass)\
  41.     baseclass *load##baseclass(std::string fn)\
  42. {\
  43.     typedef baseclass *(*FUN)(); \
  44.     PanLibrary lib;\
  45.     PanLibrary::symbol_type ret = lib.loadEntryPoint(fn + ":create_" + #baseclass);\
  46.     if(ret)\
  47.     {\
  48.         FUN f = FUN(ret);\
  49.         return f();\
  50.     }\
  51.     return NULL;\
  52. }
panlibrary.cpp
复制代码
  1. #include "panlibrary.h"
  3. #ifndef _WIN32
  4. #   include <dlfcn.h>
  5. #endif
  6. #include <assert.h>
  8. PanLibrary::PanLibrary() : _hnd(0)
  9. {
  10. }
  12. PanLibrary::~PanLibrary()
  13. {
  14.     
  15.     /* Closing the library here can cause a crash at program exit if
  16.     * the application holds references to library resources in global
  17.     * or static variables. Instead, we let the process discard the
  18.     * library.
  19.     printf("asdf");
  20.     if(_hnd != 0)
  21.     {
  22.     #ifdef _WIN32
  23.     FreeLibrary(_hnd);
  24.     #else
  25.     dlclose(_hnd);
  26.     #endif
  27.     }
  28.     */
  29. }
  31. PanLibrary::symbol_type
  32. PanLibrary::loadEntryPoint(const std::string& entryPoint)
  33. {
  34.     std::string::size_type colon = entryPoint.rfind(':');
  35.     if(colon == std::string::npos || colon == entryPoint.size() - 1)
  36.     {
  37.         _err = "invalid entry point format.";
  38.         return 0;
  39.     }
  40.     std::string libName = entryPoint.substr(0, colon);
  41.     std::string funcName = entryPoint.substr(colon + 1);
  42.     std::string lib = libName;
  43. #ifdef _WIN32
  44.     lib += ".dll";
  45. #elif defined(__APPLE__)
  46.     lib = "lib" + libName + ".dylib";
  47. #elif defined(__hpux)
  48.     lib = "lib" + libName + ".sl";
  49. #elif defined(_AIX)
  50.     lib = "lib" + libName + ".a(lib" + libName + ".so" + ")";
  51. #else
  52.     lib = "lib" + libName + ".so";
  53. #endif
  55.     if(!load(lib))
  56.     {
  57.         return 0;
  58.     }
  59.     return getSymbol(funcName);
  60. }
  62. bool
  63. PanLibrary::load(const std::string& lib)
  64. {
  65. #ifdef _WIN32
  66.     _hnd = LoadLibraryA(lib.c_str());
  67.     //_hnd = LoadLibraryA("testplugin.dll");
  68. #else
  70.     int flags = RTLD_NOW | RTLD_GLOBAL;
  71. #ifdef _AIX
  72.     flags |= RTLD_MEMBER;
  73. #endif
  75.     _hnd = dlopen(lib.c_str(), flags);
  76.     if(_hnd == 0)
  77.     {
  78.         //
  79.         // Remember the most recent error in _err.
  80.         //
  81.         const char* err = dlerror();
  83.         if(err)
  84.         {
  85.             _err = err;
  86.         }
  87.     }
  88. #endif
  89.     return _hnd != 0;
  90. }
  92. PanLibrary::symbol_type
  93. PanLibrary::getSymbol(const std::string& name)
  94. {
  95.     assert(_hnd != 0);
  96. #ifdef _WIN32
  97. #  ifdef __BCPLUSPLUS__
  98.     std::string newName = "_" + name;
  99.     return GetProcAddress(_hnd, newName.c_str());
  100. #  else
  101.     return GetProcAddress(_hnd, name.c_str());
  102. #  endif
  103. #else
  104.     symbol_type result = dlsym(_hnd, name.c_str());
  105.     if(result == 0)
  106.     {
  107.         //
  108.         // Remember the most recent error in _err.
  109.         //
  110.         const char* err = dlerror();
  111.         if(err)
  112.         {
  113.             _err = err;
  114.         }
  115.     }
  116.     return result;
  117. #endif
  118. }
  120. const std::string& PanLibrary::getErrorMessage() const
  121. {
  122.     return _err;
  123. }
http://user.qzone.qq.com/56430808
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