callback的实现

Callback.h

继承层次

• CallBack实现类

基类	第一层子类	第二层子类	第三层子类
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);