开发C封装API面向对象的C ++ code [英] Developing C wrapper API for Object-Oriented C++ code

问题描述

我希望开发一组C的API，将环绕我们现有的C ++ API访问我们的核心逻辑（写在面向对象的C ++）的。这将主要是胶水的API，可以让我们的C ++的逻辑是由其他语言的使用。有什么好的教程，书籍或参与引进围绕面向对象的C ++？

I'm looking to develop a set of C APIs that will wrap around our existing C++ APIs to access our core logic (written in object-oriented C++). This will essentially be a glue API that allows our C++ logic to be usable by other languages. What are some good tutorials, books, or best-practices that introduce the concepts involved in wrapping C around object-oriented C++?

推荐答案

这是不是太难做手工，但将取决于您的接口的大小。
在那里我做的情况下，它是从纯C code内能够使用我们的C ++库，因而SWIG是没有太大的帮助。 （嗯，也许痛饮可用于做到这一点，但我没有痛饮大师，似乎不平凡）

This is not too hard to do by hand, but will depend on the size of your interface. The cases where I've done it were to enable use of our C++ library from within pure C code, and thus SWIG was not much help. (Well maybe SWIG can be used to do this, but I'm no SWIG guru and it seemed non-trivial)

所有我们落得这样做是：

All we ended up doing was:

1. 的每一个对象在C传递有关的不透明句柄。


2. 构造函数和析构函数被包裹在纯函数


3. 的成员函数是纯函数。


4. 其他建宏被映射到C当量在可能的情况。

所以像这样（C ++头）一类

So a class like this (C++ header)

class MyClass
{
  public:
  explicit MyClass( std::string & s );
  ~MyClass();
  int doSomething( int j );
}

将映射到一个C接口这样的（C头）：

Would map to a C interface like this (C header):

struct HMyClass; // An opaque type that we'll use as a handle
typedef struct HMyClass HMyClass;
HMyClass * myStruct_create( const char * s );
void myStruct_destroy( HMyClass * v );
int myStruct_doSomething( HMyClass * v, int i );

该接口的实现是这样的（C ++源）

The implementation of the interface would look like this (C++ source)

#include "MyClass.h"

extern "C" 
{
  HMyClass * myStruct_create( const char * s )
  {
    return reinterpret_cast<HMyClass*>( new MyClass( s ) );
  }
  void myStruct_destroy( HMyClass * v )
  {
    delete reinterpret_cast<MyClass*>(v);
  }
  int myStruct_doSomething( HMyClass * v, int i )
  {
    return reinterpret_cast<MyClass*>(v)->doSomething(i);
  }
}

我们从原来的类派生我们的不透明句柄，以避免任何需要的铸造和（这似乎并没有与我目前的编译工作）。我们必须使处理结构作为C不支持类。

We derive our opaque handle from the original class to avoid needing any casting, and (This didn't seem to work with my current complier). We have to make the handle a struct as C doesn't support classes.

所以这给了我们基本的C接口。如果你想表明您可以集成异常处理的一种方式更完整的示例，那么你可以尝试在github上我的code：的 https://gist.github.com/mikeando/5394166

So that gives us the basic C interface. If you want a more complete example showing one way that you can integrate exception handling, then you can try my code on github : https://gist.github.com/mikeando/5394166

有趣的部分现在已经确保您获得所有必需的C ++库链接到你更大的库正确。海湾合作委员会（或铛），这意味着刚刚在干嘛用G ++的最后链接阶段。

The fun part is now ensuring that you get all the required C++ libraries linked into you larger library correctly. For gcc (or clang) that means just doing the final link stage using g++.

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