callback的实现

Callback.h

继承层次

• CallBack实现类

SimpleRefCount	CallbackImplBase	CallbackImpl	FunctorCallbackImpl
			MemPtrCallbackImpl
			BoundFunctorCallbackImpl
			TwoBoundFunctorCallbackImpl
			ThreeBoundFunctorCallbackImpl

• Callback封装类
  • CallbackBase
    封装Ptr<CallbackImplBase> m_impl
  • Callback
    CallbackBase的子类。根据传入的不同实参，构造不同类型的callback。
    

模板整体说明

• CallbackImpl:有不同的特化子模板
  • 根据重载（）操作符时需要的形参类型个数将Ti～Tk特化为empty类,调用是根据传入的模板形参个数匹配相应的模板
  • R：回调返回值
• FunctorCallbackImpl：CallbackImpl没有默认值,
  • T:泛函的类型（配套的，包括泛函返回类型，泛函形参类型）
• MemPtrCallbackImpl:CallbackImpl
  • OBJ_PTR：object的类型
  • MEM_PTR：object成员泛函的类型（包括泛函返回类型，泛函形参类型）

• BoundFunctorCallbackImpl: CallbackImpl

  • T:泛函类型
  • R:回调返回值
  • Tx：绑定的类型
  • 回调时，总有一个类型为Tx的值作为回调的形参

• CallBack:T1~T9:默认值为empty类

• MakeCallback<>模板函数:根据传入不同的形参，实例化不同版本

  • 形参：泛函指针
    • 根据传入的普通泛函涉及的类型个数（返回值类型，形参类型个数）匹配不同回调形参个数的模板
  • 形参：类成员泛函指针，类对象指针
    • 根据传入的类成员泛函的涉及的类型（返回值类型，形参类型个数）匹配不同回调形参的模板
  • 形参：泛函指针，绑定的值（1~3个）

CallbackTraits

• 模板1
  c++
template <typename T>
struct CallbackTraits;

• 将指针转化为引用，用于MemPtrCallBackImpl
  c++
template <typename T>
struct CallbackTraits<T *>
{
static T & GetReference (T * const p){
return *p; }
};


CallbackImplBase

class CallbackImplBase : public SimpleRefCount<CallbackImplBase>

{

public:

  virtual ~CallbackImplBase () {}

 // Equality test

  virtual bool IsEqual (Ptr<const CallbackImplBase> other) const = 0;

};

CallbackImpl

通过重载函数操作符"()"实现
- 模板声明,该模板限定了最多能传入9个形参给callback

template <typename R, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8, typename T9>

class CallbackImpl;

• 无参数特化模板

template <typename R>

class CallbackImpl<R,empty,empty,empty,empty,empty,empty,empty,empty,empty> : public CallbackImplBase {

public:

  virtual ~CallbackImpl () {}

  virtual R operator() (void) = 0;      //!< Abstract operator

};

• 将模板形参T2~T9特例话为空
  这是将基类模板中模板形参T2到T9特化为empty类型的一个例子（部分特化）

template <typename R, typename T1>

class CallbackImpl<R,T1,empty,empty,empty,empty,empty,empty,empty,empty> : public CallbackImplBase {

public:

  virtual ~CallbackImpl () {}

  virtual R operator() (T1) = 0;        //!< Abstract operator

};

• 其他类似
• CallbackImpl的定义

template <typename R, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8, typename T9>

class CallbackImpl : public CallbackImplBase {

public:

  virtual ~CallbackImpl () {}

  virtual R operator() (T1, T2, T3, T4, T5, T6, T7, T8, T9) = 0;  //!< Abstract operator

};

FunctorCallbackImpl

CallbackImpl with functors
R:回调返回类型；
T :m_functor类型，T是一个函数指针的类型（包括函数形参列表，以及函数返回类型。而处于兼容性考虑，T应该是这样的类型 R(*)(T1,T2.......)

template <typename T, typename R, typename T1, typename T2, typename T3, typename T4,typename T5, typename T6, typename T7, typename T8, typename T9>

class FunctorCallbackImpl : public CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> {

public:

FunctorCallbackImpl (T const &functor):m_functor(functor){}

virtual ~FunctorCallbackImpl () {}

//无输入参数的回调,

R operator() (void) {return m_functor (); }

//带一个形参的回调

 R operator() (T1 a1) {return m_functor (a1);  }

// 其他形参个数的回调类似

.......

virtual bool IsEqual (Ptr<const CallbackImplBase> other) const{

FunctorCallbackImpl<T,R,T1,T2,T3,T4,T5,T6,T7,T8,T9>const *otherDerived =dynamic_cast<FunctorCallbackImpl<T,R,T1,T2,T3,T4,T5,T6,T7,T8,T9> const *> (PeekPointer (other));//把其他类型的CallbackImpl转换成FunctorCallbackImpl类

if (otherDerived == 0){return false;}

else if (otherDerived->m_functor != m_functor){

    return false;}

return true;

}

private:

  T m_functor;         //!< the functor

};

MemPtrCallbackImpl

CallbackImpl for pointer to member functions
模板形参MEM_PTR：类成员泛函的类型（涉及泛函返回类型，形参类型表等）

template <typename OBJ_PTR, typename MEM_PTR, typename R, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8, typename T9>

class MemPtrCallbackImpl : public CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> {

public:

MemPtrCallbackImpl (OBJ_PTR const&objPtr, MEM_PTR memPtr)

    : m_objPtr (objPtr), m_memPtr (memPtr) {}

  virtual ~MemPtrCallbackImpl () {}

  //无形参成员函数回调实现

  R operator() (void) {

 return ((CallbackTraits<OBJ_PTR>::GetReference (m_objPtr)).*m_memPtr)();//将m_objPtr转换成引用并调用其成员函数(*m_memPtr)

 //其他参数个数的成员函数的回调实现类似

 }

 .......

 virtual bool IsEqual (Ptr<const CallbackImplBase> other) const {

 MemPtrCallbackImpl<OBJ_PTR,MEM_PTR,R,T1,T2,T3,T4,T5,T6,T7,T8,T9> const *otherDerived=dynamic_cast<MemPtrCallbackImpl<OBJ_PTR,MEM_PTR,R,T1,T2,T3,T4,T5,T6,T7,T8,T9> const *> (PeekPointer (other));

if (otherDerived == 0){  return false;  }

else if (otherDerived->m_objPtr != m_objPtr||therDerived->m_memPtr != m_memPtr){return false;}

return true;

}

private:

  OBJ_PTR const m_objPtr;     //!< the object pointer

  MEM_PTR m_memPtr;        //!< the member function pointer

};

BoundFunctorCallbackImpl

CallbackImpl for functors with first argument bound at construction

 template <typename T, typename R, typename TX, typename T1, typename T2, typename T3, typename T4,typename T5, typename T6, typename T7, typename T8>

class BoundFunctorCallbackImpl : public CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,empty> {

public:

template <typename FUNCTOR, typename ARG>

  BoundFunctorCallbackImpl (FUNCTOR functor, ARG a)

    : m_functor (functor), m_a (a) {}

  virtual ~BoundFunctorCallbackImpl () {}

//没有可变类型形参的函数调用

R operator() (void) {    return m_functor (m_a);  }

//有一个Arg的函数回调

R operator() (T1 a1) {  return m_functor (m_a,a1);  }

//其他Arg个数的模板类似

virtual bool IsEqual (Ptr<const CallbackImplBase> other) const{

//实现和上面类似，先转换，然后比较

}

private:

  T m_functor;    //!< The functor

  typename TypeTraits<TX>::ReferencedType m_a;  //!< the bound argument

};

TwoBoundFunctorCallbackImpl

CallbackImpl for functors with first two arguments bound at construction

template <typename T, typename R, typename TX1, typename TX2, typename T1, typename T2, typename T3, typename T4,typename T5, typename T6, typename T7>

class TwoBoundFunctorCallbackImpl : public CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,empty,empty> {

....

private:

  T m_functor;              //!< The functor

  typename TypeTraits<TX1>::ReferencedType m_a1;  //!< first bound argument

  typename TypeTraits<TX2>::ReferencedType m_a2;  //!< second bound argument

};

}

ThreeBoundFunctorCallbackImpl

和上述类似

CallbackBase

class CallbackBase {

public:

  CallbackBase () : m_impl () {}

   Ptr<CallbackImplBase> GetImpl (void) const { return m_impl; }

protected:

CallbackBase (Ptr<CallbackImplBase> impl) : m_impl (impl) {}

  Ptr<CallbackImplBase> m_impl;         //!< the pimpl

   static std::string Demangle (const std::string& mangled);

   //符号重组？这个干什么的呢？

};

CallBack类

• 模板的示例化具有POD语义：需要的内存是自动管理的，并且允许用户传递一个CallBack实例
• 模板使用pimpl idiom,传递CallBack类的值并将实现传递给其pimpl指针
• CallbackImpl和 FunctorCallbackImpl的子类可用于任何functor-type，而 MemPtrCallbackImpl 可用于某一个类的成员函数指针
• 通过reference list implementation实现CallBack类的值语义
  ####Callback的构造函数
• 空构造函数
  Callback () {}
• 根据 Ptr构建Callback
  c++
Callback (Ptr<CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> > const &impl): CallbackBase (impl){}

• 内置类型为FunctorCallbackImpl
  创建一个FunctorCallbackImpl的实例（第一参数特化为iFUNCTOR类型，其他分别是R，T1等）。创建Create模板函数的此FunctorCallbackImpl的实例，给函数传入实参functor，创建对应的Ptr的关于FunctorCallbackImpl的实例，将此Ptr对象作为CallBackBase类的构造函数实参

template <typename FUNCTOR>

  Callback (FUNCTOR const &functor, bool, bool)

 : CallbackBase(Create<FunctorCallbackImpl<FUNCTOR,R,T1,T2,T3,T4,T5,T6,T7,T8,T9> > (functor)){}

• 内置类型为MemPtrCallbackImpl
  实例化MemPtrCallbackImpl，创建一个此类型的ptr，传给Create函数的实参为objPtr和memPtr

template <typename OBJ_PTR, typename MEM_PTR>

 Callback (OBJ_PTR const &objPtr, MEM_PTR memPtr)：CallbackBase (Create<MemPtrCallbackImpl<OBJ_PTR,MEM_PTR,R,T1,T2,T3,T4,T5,T6,T7,T8,T9> > (objPtr, memPtr)){}

Callback的绑定

• Bind
  • 构造一个绑定第一个Arg的回调
  • 实例化一个BoundFunctorCallbackImpl，实例化传入的模板实参解释
    • Callback<R,T1,T2,T3,T4,T5,T6,T7,T8,T9>：BoundFunctorCallbackImpl内置泛函类型
    • R：回调的返回类型
    • T1:绑定的类型
    • T2～T9:其他可控的函调形参类型
  • 创建上述BoundFunctorCallbackImpl实例类的一个对象
    • 传给类的构造函数的实参：(*this):BoundFunctorCallbackImpl的内部泛函
    • a :绑定的值
  • 创建Ptr>对象impl
    • 传给Ptr构造函数的实参：上面创建的BoundFunctorCallbackImpl实例类临时对象和false
  • 以impl为实参构建Callback对象

template <typename T>

Callback<R,T2,T3,T4,T5,T6,T7,T8,T9> Bind (T a) {

    Ptr<CallbackImpl<R,T2,T3,T4,T5,T6,T7,T8,T9,empty> > impl =

      Ptr<CallbackImpl<R,T2,T3,T4,T5,T6,T7,T8,T9,empty> > (

        new BoundFunctorCallbackImpl<

          Callback<R,T1,T2,T3,T4,T5,T6,T7,T8,T9>,

          R,T1,T2,T3,T4,T5,T6,T7,T8,T9> (*this, a), false);

    return Callback<R,T2,T3,T4,T5,T6,T7,T8,T9> (impl);

  }

• 绑定前两个
  实现与Bind类似

template <typename TX1, typename TX2>

Callback<R,T3,T4,T5,T6,T7,T8,T9> TwoBind (TX1 a1, TX2 a2){..}

• 绑定前三个

  实现与上面类似

template <typename TX1, typename TX2, typename TX3>

  Callback<R,T4,T5,T6,T7,T8,T9> ThreeBind (TX1 a1, TX2 a2, TX3 a3){...}

Callback的其他成员函数函数

template<typename R,typename T1 = empty, typename T2 = empty,typename T3 = empty, typename T4 = empty,typename T5 = empty, typename T6 = empty,typename T7 = empty, typename T8 = empty,typename T9 = empty>

class Callback : public CallbackBase {

public:

bool IsNull (void) const {

   return (DoPeekImpl () == 0) ? true : false;

 }

 void Nullify (void) {

    m_impl = 0;

  }

  //无输入参数的回调

 R operator() (void) const {

    return (*(DoPeekImpl ()))();

  }

  //输入一个参数的回调

  R operator() (T1 a1) const {

    return (*(DoPeekImpl ()))(a1);

  }

 // 其他输入参数个数的回调与上述类似

 bool IsEqual (const CallbackBase &other) const {

    return m_impl->IsEqual (other.GetImpl ());

  }

  //如果other能转换成我这种类型，返回true

   bool CheckType (const CallbackBase & other) const {

    return DoCheckType (other.GetImpl ());

  }

  void Assign (const CallbackBase &other) {

    DoAssign (other.GetImpl ());

  }

  private:

  CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> *DoPeekImpl (void) const {

    return static_cast<CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> *> (PeekPointer (m_impl));

  }

  //如果other能转换成我这种类型，返回true

  bool DoCheckType (Ptr<const CallbackImplBase> other) const {

    if (other != 0 && dynamic_cast<const CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> *> (PeekPointer (other)) != 0)

    {  return true; //不为空且能转换    }

    else if (other == 0){ return true; //传入的Ptr为空 }

    else{   return false; }

  }

  void DoAssign (Ptr<const CallbackImplBase> other) {

    if (!DoCheckType (other))

      {

        Ptr<CallbackImpl<R,T1,T2,T3,T4,T5,T6,T7,T8,T9> > expected;

        NS_FATAL_ERROR (....);

      }

    m_impl = const_cast<CallbackImplBase *> (PeekPointer (other));

  }

}

MakeCallback模板函数

针对不同形参个数的函数指针的 MakeCallback函数模板

template <typename R>

Callback<R> MakeCallback (R (*fnPtr)()) {

  return Callback<R> (fnPtr, true, true);

}

template <typename R, typename T1>

Callback<R,T1> MakeCallback (R (*fnPtr)(T1)) {

  return Callback<R,T1> (fnPtr, true, true);

}

//其他类型函数指针的MakeCallback类似

针对不同形参个数的类成员函数指针的 MakeCallback函数模板

template <typename T, typename OBJ, typename R>

Callback<R> MakeCallback (R (T::*memPtr)(void), OBJ objPtr) {

  return Callback<R> (objPtr, memPtr);

}//const版本类似

template <typename T, typename OBJ, typename R, typename T1>

Callback<R,T1> MakeCallback (R (T::*memPtr)(T1), OBJ objPtr) {

  return Callback<R,T1> (objPtr, memPtr);

}

//其他类似

• != 符号的重载

• MakeNullCallback的定义

• MakeBoundCallback的定义（包括绑定一个，两个等）

  CallBack类的和属性系统相关的东西

class CallbackValue : public AttributeValue

{

public:

CallbackValue ();

 CallbackValue (const CallbackBase &base);

 virtual ~CallbackValue ();

 void Set (CallbackBase base);

 template <typename T>

  bool GetAccessor (T &value) const;

  virtual Ptr<AttributeValue> Copy (void) const;

  virtual std::string SerializeToString (Ptr<const AttributeChecker> checker) const;

  virtual bool DeserializeFromString (std::string value, Ptr<const AttributeChecker> checker);

  private:

  CallbackBase m_value;                 //!< the CallbackBase

};

ATTRIBUTE_ACCESSOR_DEFINE (Callback);

ATTRIBUTE_CHECKER_DEFINE (Callback);

//Assign和CheckType函数是callback的成员函数。因此T应该也是一张callback又是哪里定义的

template <typename T>

bool CallbackValue::GetAccessor (T &value) const

{

  if (value.CheckType (m_value))

    {

      value.Assign (m_value);

      return true;

    }

  return false;

}

Callback.cc

• CallbackValue类成员函数的一些定义
• 定义和Callback相关的checker

ATTRIBUTE_CHECKER_IMPLEMENT (Callback);