异步线程任务封装可以参考Chrome中Callback和tuple实现。

Callback.h

#ifndef __callback_h__
#define __callback_h__

#pragma once

#include "base/tuple.h"

#include "raw_scoped_refptr_mismatch_checker.h"

// Callback跟Task很像, 但没有参数限制, 实质上是面向对象的函数指针.
//
// Callbacks被设计和Tuples共同工作. 有一系列的辅助函数和类用于对使用者隐藏
// Tuple的细节. 用户代码只需要和CallbackRunner基类打交道, CallbackRunner只
// 有Run方法, 通过New*函数创建. 这样用户不必关心哪个类实现了回调, 只需要知
// 道参数个数以及类型.
//
// 这些实现是通过CallbackImpl完成的, CallbackImpl派生自CallbackStorage, 具体
// 的存储类型对用户透明, 用户只需要调用即可.
//
// 注意callbacks目前不能取消或者放弃自己的操作, 现在是在上层进行处理的.
// callback中的指针在调用结束前都必须是有效的.
//
// 类似Task, 一旦回调执行结束, 回调执行者负责删除回调指针.
//
// 客户端用法示例:
//     void Object::DoStuff(int, string);
//     Callback2<int, string>::Type* callback =
//       NewCallback(obj, &Object::DoStuff);
//     callback->Run(5, string("hello"));
//     delete callback;
// 或者直接使用元组:
//     CallbackRunner<Tuple2<int, string> >* callback =
//       NewCallback(obj, &Object::DoStuff);
//     callback->RunWithParams(MakeTuple(5, string("hello")));
//
// 有一个不带参数有返回值的版本. 示例:
//     int Object::GetNextInt();
//     CallbackWithReturnValue<int>::Type* callback =
//       NewCallbackWithReturnValue(obj, &Object::GetNextInt);
//     int next_int = callback->Run();
//     delete callback;


// 所有Callbacks的基类, 存储对象方法指针.
template<class T, typename Method>
class CallbackStorage
{
public:
    CallbackStorage(T* obj, Method meth) : obj_(obj), meth_(meth) {}

protected:
    T* obj_;
    Method meth_;
};

// Interface that is exposed to the consumer, that does the actual calling
// of the method.
template<typename Params>
class CallbackRunner
{
public:
    typedef Params TupleType;

    virtual ~CallbackRunner() {}
    virtual void RunWithParams(const Params& params) = 0;

    // Convenience functions so callers don't have to deal with Tuples.
    inline void Run()
    {
        RunWithParams(Tuple0());
    }

    template<typename Arg1>
    inline void Run(const Arg1& a)
    {
        RunWithParams(Params(a));
    }

    template<typename Arg1, typename Arg2>
    inline void Run(const Arg1& a, const Arg2& b)
    {
        RunWithParams(Params(a, b));
    }

    template<typename Arg1, typename Arg2, typename Arg3>
    inline void Run(const Arg1& a, const Arg2& b, const Arg3& c)
    {
        RunWithParams(Params(a, b, c));
    }

    template<typename Arg1, typename Arg2, typename Arg3, typename Arg4>
    inline void Run(const Arg1& a, const Arg2& b, const Arg3& c, const Arg4& d)
    {
        RunWithParams(Params(a, b, c, d));
    }

    template<typename Arg1, typename Arg2, typename Arg3,
        typename Arg4, typename Arg5>
        inline void Run(const Arg1& a, const Arg2& b, const Arg3& c,
        const Arg4& d, const Arg5& e)
    {
        RunWithParams(Params(a, b, c, d, e));
    }
};

template<class T, typename Method, typename Params>
class CallbackImpl : public CallbackStorage<T, Method>,
    public CallbackRunner<Params>
{
public:
    CallbackImpl(T* obj, Method meth) : CallbackStorage<T, Method>(obj, meth) {}
    virtual void RunWithParams(const Params& params)
    {
        // use "this->" to force C++ to look inside our templatized base class; see
        // Effective C++, 3rd Ed, item 43, p210 for details.
        DispatchToMethod(this->obj_, this->meth_, params);
    }
};

// 0-arg implementation
struct Callback0
{
    typedef CallbackRunner<Tuple0> Type;
};

template<class T>
typename Callback0::Type* NewCallback(T* object, void (T::*method)())
{
    return new CallbackImpl<T, void (T::*)(), Tuple0 >(object, method);
}

// 1-arg implementation
template<typename Arg1>
struct Callback1
{
    typedef CallbackRunner<Tuple1<Arg1> > Type;
};

template<class T, typename Arg1>
typename Callback1<Arg1>::Type* NewCallback(T* object, void (T::*method)(Arg1))
{
    return new CallbackImpl<T, void (T::*)(Arg1), Tuple1<Arg1> >(object, method);
}

// 2-arg implementation
template<typename Arg1, typename Arg2>
struct Callback2
{
    typedef CallbackRunner<Tuple2<Arg1, Arg2> > Type;
};

template<class T, typename Arg1, typename Arg2>
typename Callback2<Arg1, Arg2>::Type* NewCallback(
    T* object, void (T::*method)(Arg1, Arg2))
{
    return new CallbackImpl<T, void (T::*)(Arg1, Arg2),
        Tuple2<Arg1, Arg2> >(object, method);
}

// 3-arg implementation
template<typename Arg1, typename Arg2, typename Arg3>
struct Callback3
{
    typedef CallbackRunner<Tuple3<Arg1, Arg2, Arg3> > Type;
};

template<class T, typename Arg1, typename Arg2, typename Arg3>
typename Callback3<Arg1, Arg2, Arg3>::Type* NewCallback(
    T* object, void (T::*method)(Arg1, Arg2, Arg3))
{
    return new CallbackImpl<T,  void (T::*)(Arg1, Arg2, Arg3),
        Tuple3<Arg1, Arg2, Arg3> >(object, method);
}

// 4-arg implementation
template<typename Arg1, typename Arg2, typename Arg3, typename Arg4>
struct Callback4
{
    typedef CallbackRunner<Tuple4<Arg1, Arg2, Arg3, Arg4> > Type;
};

template<class T, typename Arg1, typename Arg2, typename Arg3, typename Arg4>
typename Callback4<Arg1, Arg2, Arg3, Arg4>::Type* NewCallback(
    T* object, void (T::*method)(Arg1, Arg2, Arg3, Arg4))
{
    return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4),
        Tuple4<Arg1, Arg2, Arg3, Arg4> >(object, method);
}

// 5-arg implementation
template<typename Arg1, typename Arg2, typename Arg3,
typename Arg4, typename Arg5>
struct Callback5
{
    typedef CallbackRunner<Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> > Type;
};

template<class T, typename Arg1, typename Arg2,
typename Arg3, typename Arg4, typename Arg5>
typename Callback5<Arg1, Arg2, Arg3, Arg4, Arg5>::Type* NewCallback(
    T* object, void (T::*method)(Arg1, Arg2, Arg3, Arg4, Arg5))
{
    return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4, Arg5),
        Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> >(object, method);
}

// An UnboundMethod is a wrapper for a method where the actual object is
// provided at Run dispatch time.
template<class T, class Method, class Params>
class UnboundMethod
{
public:
    UnboundMethod(Method m, const Params& p) : m_(m), p_(p)
    {
        COMPILE_ASSERT((MethodUsesScopedRefptrCorrectly<Method, Params>::value),
            badunboundmethodparams);
    }
    void Run(T* obj) const
    {
        DispatchToMethod(obj, m_, p_);
    }

private:
    Method m_;
    Params p_;
};

// 无参数带返回值版本.
template<typename ReturnValue>
struct CallbackWithReturnValue
{
    class Type
    {
    public:
        virtual ~Type() {}
        virtual ReturnValue Run() = 0;
    };
};

template<class T, typename Method, typename ReturnValue>
class CallbackWithReturnValueImpl : public CallbackStorage<T, Method>,
    public CallbackWithReturnValue<ReturnValue>::Type
{
public:
    CallbackWithReturnValueImpl(T* obj, Method meth)
        : CallbackStorage<T, Method>(obj, meth) {}

    virtual ReturnValue Run()
    {
        return (this->obj_->*(this->meth_))();
    }

protected:
    virtual ~CallbackWithReturnValueImpl() {}
};

template<class T, typename ReturnValue>
typename CallbackWithReturnValue<ReturnValue>::Type*
NewCallbackWithReturnValue(T* object, ReturnValue (T::*method)())
{
    return new CallbackWithReturnValueImpl<T, ReturnValue (T::*)(),
        ReturnValue>(object, method);
}

#endif //__callback_h__

chrome自己实现tuple

#ifndef __tuple_h__
#define __tuple_h__

#pragma once

// 元组(Tuple)是一种概念上与std::pair类似的通用模板容器.
// Tuple0到Tuple6对应容器中元素个数. 带有0-6个参数的MakeTuple()函数能够方便
// 的构造对应的元组对象. DispatchToMethod和DispatchToFunction带有函数指针或
// 者对象实例和成员函数指针, 解包元组为参数进行函数调用.
//
// 元组的元素通过值拷贝存储.
//
// 用法示例:
//     // These two methods of creating a Tuple are identical.
//     Tuple2<int, const char*> tuple_a(1, "wee");
//     Tuple2<int, const char*> tuple_b = MakeTuple(1, "wee");
//
//     void SomeFunc(int a, const char* b) {}
//     DispatchToFunction(&SomeFunc, tuple_a); // SomeFunc(1, "wee")
//     DispatchToFunction(
//       &SomeFunc, MakeTuple(10, "foo")); // SomeFunc(10, "foo")
//
//     struct { void SomeMeth(int a, int b, int c) {} } foo;
//     DispatchToMethod(&foo, &Foo::SomeMeth, MakeTuple(1, 2, 3));
//     //foo->SomeMeth(1, 2, 3);

// Traits ----------------------------------------------------------------------
//
// A simple traits class for tuple arguments.
//
// ValueType: the bare, nonref version of a type (same as the type for nonrefs).
// RefType: the ref version of a type (same as the type for refs).
// ParamType: what type to pass to functions (refs should not be constified).
template<class P>
struct TupleTraits
{
    typedef P ValueType;
    typedef P& RefType;
    typedef const P& ParamType;
};

template<class P>
struct TupleTraits<P&>
{
    typedef P ValueType;
    typedef P& RefType;
    typedef P& ParamType;
};

template<class P>
struct TupleTypes {};

// Tuple -----------------------------------------------------------------------
//
// This set of classes is useful for bundling 0 or more heterogeneous data types
// into a single variable.  The advantage of this is that it greatly simplifies
// function objects that need to take an arbitrary number of parameters; see
// RunnableMethod and IPC::MessageWithTuple.
//
// Tuple0 is supplied to act as a 'void' type.  It can be used, for example,
// when dispatching to a function that accepts no arguments (see the
// Dispatchers below).
// Tuple1<A> is rarely useful.  One such use is when A is non-const ref that you
// want filled by the dispatchee, and the tuple is merely a container for that
// output (a "tier").  See MakeRefTuple and its usages.
struct Tuple0
{
    typedef Tuple0 ValueTuple;
    typedef Tuple0 RefTuple;
    typedef Tuple0 ParamTuple;
};

template<class A>
struct Tuple1
{
public:
    typedef A TypeA;

    Tuple1() {}
    explicit Tuple1(typename TupleTraits<A>::ParamType a) : a(a) {}

    A a;
};

template<class A, class B>
struct Tuple2
{
public:
    typedef A TypeA;
    typedef B TypeB;

    Tuple2() {}
    Tuple2(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b)
        : a(a), b(b) {}

    A a;
    B b;
};

template<class A, class B, class C>
struct Tuple3
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;

    Tuple3() {}
    Tuple3(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c)
        : a(a), b(b), c(c){}

    A a;
    B b;
    C c;
};

template<class A, class B, class C, class D>
struct Tuple4
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;
    typedef D TypeD;

    Tuple4() {}
    Tuple4(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c,
        typename TupleTraits<D>::ParamType d)
        : a(a), b(b), c(c), d(d) {}

    A a;
    B b;
    C c;
    D d;
};

template<class A, class B, class C, class D, class E>
struct Tuple5
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;
    typedef D TypeD;
    typedef E TypeE;

    Tuple5() {}
    Tuple5(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c,
        typename TupleTraits<D>::ParamType d,
        typename TupleTraits<E>::ParamType e)
        : a(a), b(b), c(c), d(d), e(e) {}

    A a;
    B b;
    C c;
    D d;
    E e;
};

template<class A, class B, class C, class D, class E, class F>
struct Tuple6
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;
    typedef D TypeD;
    typedef E TypeE;
    typedef F TypeF;

    Tuple6() {}
    Tuple6(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c,
        typename TupleTraits<D>::ParamType d,
        typename TupleTraits<E>::ParamType e,
        typename TupleTraits<F>::ParamType f)
        : a(a), b(b), c(c), d(d), e(e), f(f) {}

    A a;
    B b;
    C c;
    D d;
    E e;
    F f;
};

template<class A, class B, class C, class D, class E, class F, class G>
struct Tuple7
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;
    typedef D TypeD;
    typedef E TypeE;
    typedef F TypeF;
    typedef G TypeG;

    Tuple7() {}
    Tuple7(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c,
        typename TupleTraits<D>::ParamType d,
        typename TupleTraits<E>::ParamType e,
        typename TupleTraits<F>::ParamType f,
        typename TupleTraits<G>::ParamType g)
        : a(a), b(b), c(c), d(d), e(e), f(f), g(g) {}

    A a;
    B b;
    C c;
    D d;
    E e;
    F f;
    G g;
};

template<class A, class B, class C, class D, class E, class F, class G,
class H>
struct Tuple8
{
public:
    typedef A TypeA;
    typedef B TypeB;
    typedef C TypeC;
    typedef D TypeD;
    typedef E TypeE;
    typedef F TypeF;
    typedef G TypeG;
    typedef H TypeH;

    Tuple8() {}
    Tuple8(typename TupleTraits<A>::ParamType a,
        typename TupleTraits<B>::ParamType b,
        typename TupleTraits<C>::ParamType c,
        typename TupleTraits<D>::ParamType d,
        typename TupleTraits<E>::ParamType e,
        typename TupleTraits<F>::ParamType f,
        typename TupleTraits<G>::ParamType g,
        typename TupleTraits<H>::ParamType h)
        : a(a), b(b), c(c), d(d), e(e), f(f), g(g), h(h) {}

    A a;
    B b;
    C c;
    D d;
    E e;
    F f;
    G g;
    H h;
};

// Tuple types ----------------------------------------------------------------
//
// Allows for selection of ValueTuple/RefTuple/ParamTuple without needing the
// definitions of class types the tuple takes as parameters.
template<>
struct TupleTypes< Tuple0 >
{
    typedef Tuple0 ValueTuple;
    typedef Tuple0 RefTuple;
    typedef Tuple0 ParamTuple;
};

template<class A>
struct TupleTypes< Tuple1<A> >
{
    typedef Tuple1<typename TupleTraits<A>::ValueType> ValueTuple;
    typedef Tuple1<typename TupleTraits<A>::RefType> RefTuple;
    typedef Tuple1<typename TupleTraits<A>::ParamType> ParamTuple;
};

template<class A, class B>
struct TupleTypes< Tuple2<A, B> >
{
    typedef Tuple2<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType> ValueTuple;
    typedef Tuple2<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType> RefTuple;
    typedef Tuple2<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType> ParamTuple;
};

template<class A, class B, class C>
struct TupleTypes< Tuple3<A, B, C> >
{
    typedef Tuple3<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType> ValueTuple;
    typedef Tuple3<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType> RefTuple;
    typedef Tuple3<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType> ParamTuple;
};

template<class A, class B, class C, class D>
struct TupleTypes< Tuple4<A, B, C, D> >
{
    typedef Tuple4<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType,
        typename TupleTraits<D>::ValueType> ValueTuple;
    typedef Tuple4<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType,
        typename TupleTraits<D>::RefType> RefTuple;
    typedef Tuple4<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType,
        typename TupleTraits<D>::ParamType> ParamTuple;
};

template<class A, class B, class C, class D, class E>
struct TupleTypes< Tuple5<A, B, C, D, E> >
{
    typedef Tuple5<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType,
        typename TupleTraits<D>::ValueType,
        typename TupleTraits<E>::ValueType> ValueTuple;
    typedef Tuple5<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType,
        typename TupleTraits<D>::RefType,
        typename TupleTraits<E>::RefType> RefTuple;
    typedef Tuple5<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType,
        typename TupleTraits<D>::ParamType,
        typename TupleTraits<E>::ParamType> ParamTuple;
};

template<class A, class B, class C, class D, class E, class F>
struct TupleTypes< Tuple6<A, B, C, D, E, F> >
{
    typedef Tuple6<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType,
        typename TupleTraits<D>::ValueType,
        typename TupleTraits<E>::ValueType,
        typename TupleTraits<F>::ValueType> ValueTuple;
    typedef Tuple6<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType,
        typename TupleTraits<D>::RefType,
        typename TupleTraits<E>::RefType,
        typename TupleTraits<F>::RefType> RefTuple;
    typedef Tuple6<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType,
        typename TupleTraits<D>::ParamType,
        typename TupleTraits<E>::ParamType,
        typename TupleTraits<F>::ParamType> ParamTuple;
};

template<class A, class B, class C, class D, class E, class F, class G>
struct TupleTypes< Tuple7<A, B, C, D, E, F, G> >
{
    typedef Tuple7<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType,
        typename TupleTraits<D>::ValueType,
        typename TupleTraits<E>::ValueType,
        typename TupleTraits<F>::ValueType,
        typename TupleTraits<G>::ValueType> ValueTuple;
    typedef Tuple7<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType,
        typename TupleTraits<D>::RefType,
        typename TupleTraits<E>::RefType,
        typename TupleTraits<F>::RefType,
        typename TupleTraits<G>::RefType> RefTuple;
    typedef Tuple7<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType,
        typename TupleTraits<D>::ParamType,
        typename TupleTraits<E>::ParamType,
        typename TupleTraits<F>::ParamType,
        typename TupleTraits<G>::ParamType> ParamTuple;
};

template<class A, class B, class C, class D, class E, class F, class G,
class H>
struct TupleTypes< Tuple8<A, B, C, D, E, F, G, H> >
{
    typedef Tuple8<typename TupleTraits<A>::ValueType,
        typename TupleTraits<B>::ValueType,
        typename TupleTraits<C>::ValueType,
        typename TupleTraits<D>::ValueType,
        typename TupleTraits<E>::ValueType,
        typename TupleTraits<F>::ValueType,
        typename TupleTraits<G>::ValueType,
        typename TupleTraits<H>::ValueType> ValueTuple;
    typedef Tuple8<typename TupleTraits<A>::RefType,
        typename TupleTraits<B>::RefType,
        typename TupleTraits<C>::RefType,
        typename TupleTraits<D>::RefType,
        typename TupleTraits<E>::RefType,
        typename TupleTraits<F>::RefType,
        typename TupleTraits<G>::RefType,
        typename TupleTraits<H>::RefType> RefTuple;
    typedef Tuple8<typename TupleTraits<A>::ParamType,
        typename TupleTraits<B>::ParamType,
        typename TupleTraits<C>::ParamType,
        typename TupleTraits<D>::ParamType,
        typename TupleTraits<E>::ParamType,
        typename TupleTraits<F>::ParamType,
        typename TupleTraits<G>::ParamType,
        typename TupleTraits<H>::ParamType> ParamTuple;
};

// Tuple creators -------------------------------------------------------------
//
// Helper functions for constructing tuples while inferring the template
// argument types.
inline Tuple0 MakeTuple()
{
    return Tuple0();
}

template<class A>
inline Tuple1<A> MakeTuple(const A& a)
{
    return Tuple1<A>(a);
}

template<class A, class B>
inline Tuple2<A, B> MakeTuple(const A& a, const B& b)
{
    return Tuple2<A, B>(a, b);
}

template<class A, class B, class C>
inline Tuple3<A, B, C> MakeTuple(const A& a, const B& b, const C& c)
{
    return Tuple3<A, B, C>(a, b, c);
}

template<class A, class B, class C, class D>
inline Tuple4<A, B, C, D> MakeTuple(const A& a, const B& b, const C& c,
                                    const D& d)
{
    return Tuple4<A, B, C, D>(a, b, c, d);
}

template<class A, class B, class C, class D, class E>
inline Tuple5<A, B, C, D, E> MakeTuple(const A& a, const B& b, const C& c,
                                       const D& d, const E& e)
{
    return Tuple5<A, B, C, D, E>(a, b, c, d, e);
}

template<class A, class B, class C, class D, class E, class F>
inline Tuple6<A, B, C, D, E, F> MakeTuple(const A& a, const B& b, const C& c,
                                          const D& d, const E& e, const F& f)
{
    return Tuple6<A, B, C, D, E, F>(a, b, c, d, e, f);
}

template<class A, class B, class C, class D, class E, class F, class G>
inline Tuple7<A, B, C, D, E, F, G> MakeTuple(const A& a, const B& b, const C& c,
                                             const D& d, const E& e, const F& f,
                                             const G& g)
{
    return Tuple7<A, B, C, D, E, F, G>(a, b, c, d, e, f, g);
}

template<class A, class B, class C, class D, class E, class F, class G,
class H>
    inline Tuple8<A, B, C, D, E, F, G, H> MakeTuple(const A& a, const B& b,
    const C& c, const D& d,
    const E& e, const F& f,
    const G& g, const H& h)
{
    return Tuple8<A, B, C, D, E, F, G, H>(a, b, c, d, e, f, g, h);
}

// The following set of helpers make what Boost refers to as "Tiers" - a tuple
// of references.
template<class A>
inline Tuple1<A&> MakeRefTuple(A& a)
{
    return Tuple1<A&>(a);
}

template<class A, class B>
inline Tuple2<A&, B&> MakeRefTuple(A& a, B& b)
{
    return Tuple2<A&, B&>(a, b);
}

template<class A, class B, class C>
inline Tuple3<A&, B&, C&> MakeRefTuple(A& a, B& b, C& c)
{
    return Tuple3<A&, B&, C&>(a, b, c);
}

template<class A, class B, class C, class D>
inline Tuple4<A&, B&, C&, D&> MakeRefTuple(A& a, B& b, C& c, D& d)
{
    return Tuple4<A&, B&, C&, D&>(a, b, c, d);
}

template<class A, class B, class C, class D, class E>
inline Tuple5<A&, B&, C&, D&, E&> MakeRefTuple(A& a, B& b, C& c, D& d, E& e)
{
    return Tuple5<A&, B&, C&, D&, E&>(a, b, c, d, e);
}

template<class A, class B, class C, class D, class E, class F>
inline Tuple6<A&, B&, C&, D&, E&, F&> MakeRefTuple(A& a, B& b, C& c, D& d, E& e,
                                                   F& f)
{
    return Tuple6<A&, B&, C&, D&, E&, F&>(a, b, c, d, e, f);
}

template<class A, class B, class C, class D, class E, class F, class G>
inline Tuple7<A&, B&, C&, D&, E&, F&, G&> MakeRefTuple(A& a, B& b, C& c, D& d,
                                                       E& e, F& f, G& g)
{
    return Tuple7<A&, B&, C&, D&, E&, F&, G&>(a, b, c, d, e, f, g);
}

template<class A, class B, class C, class D, class E, class F, class G,
class H>
    inline Tuple8<A&, B&, C&, D&, E&, F&, G&, H&> MakeRefTuple(A& a, B& b, C& c,
    D& d, E& e, F& f,
    G& g, H& h)
{
    return Tuple8<A&, B&, C&, D&, E&, F&, G&, H&>(a, b, c, d, e, f, g, h);
}

// Dispatchers ----------------------------------------------------------------
//
// Helper functions that call the given method on an object, with the unpacked
// tuple arguments.  Notice that they all have the same number of arguments,
// so you need only write:
//   DispatchToMethod(object, &Object::method, args);
// This is very useful for templated dispatchers, since they don't need to know
// what type |args| is.

// Non-Static Dispatchers with no out params.
template<class ObjT, class Method>
inline void DispatchToMethod(ObjT* obj, Method method, const Tuple0& arg)
{
    (obj->*method)();
}

template<class ObjT, class Method, class A>
inline void DispatchToMethod(ObjT* obj, Method method, const A& arg)
{
    (obj->*method)(arg);
}

template<class ObjT, class Method, class A>
inline void DispatchToMethod(ObjT* obj, Method method, const Tuple1<A>& arg)
{
    (obj->*method)(arg.a);
}

template<class ObjT, class Method, class A, class B>
inline void DispatchToMethod(ObjT* obj,
                             Method method,
                             const Tuple2<A, B>& arg)
{
    (obj->*method)(arg.a, arg.b);
}

template<class ObjT, class Method, class A, class B, class C>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple3<A, B, C>& arg)
{
    (obj->*method)(arg.a, arg.b, arg.c);
}

template<class ObjT, class Method, class A, class B, class C, class D>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple4<A, B, C, D>& arg)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d);
}

template<class ObjT, class Method, class A, class B, class C, class D, class E>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple5<A, B, C, D, E>& arg)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d, arg.e);
}

template<class ObjT, class Method, class A, class B, class C, class D, class E,
class F>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<A, B, C, D, E, F>& arg)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f);
}

template<class ObjT, class Method, class A, class B, class C, class D, class E,
class F, class G>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple7<A, B, C, D, E, F, G>& arg)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f, arg.g);
}

// Static Dispatchers with no out params.
template<class Function>
inline void DispatchToFunction(Function function, const Tuple0& arg)
{
    (*function)();
}

template<class Function, class A>
inline void DispatchToFunction(Function function, const A& arg)
{
    (*function)(arg);
}

template<class Function, class A>
inline void DispatchToFunction(Function function, const Tuple1<A>& arg)
{
    (*function)(arg.a);
}

template<class Function, class A, class B>
inline void DispatchToFunction(Function function, const Tuple2<A, B>& arg)
{
    (*function)(arg.a, arg.b);
}

template<class Function, class A, class B, class C>
inline void DispatchToFunction(Function function, const Tuple3<A, B, C>& arg)
{
    (*function)(arg.a, arg.b, arg.c);
}

template<class Function, class A, class B, class C, class D>
inline void DispatchToFunction(Function function,
                               const Tuple4<A, B, C, D>& arg)
{
    (*function)(arg.a, arg.b, arg.c, arg.d);
}

template<class Function, class A, class B, class C, class D, class E>
inline void DispatchToFunction(Function function,
                               const Tuple5<A, B, C, D, E>& arg)
{
    (*function)(arg.a, arg.b, arg.c, arg.d, arg.e);
}

template<class Function, class A, class B, class C, class D, class E, class F>
inline void DispatchToFunction(Function function,
                               const Tuple6<A, B, C, D, E, F>& arg)
{
    (*function)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f);
}

template<class Function, class A, class B, class C, class D, class E, class F,
class G>
    inline void DispatchToFunction(Function function,
    const Tuple7<A, B, C, D, E, F, G>& arg)
{
    (*function)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f, arg.g);
}

template<class Function, class A, class B, class C, class D, class E, class F,
class G, class H>
    inline void DispatchToFunction(Function function,
    const Tuple8<A, B, C, D, E, F, G, H>& arg)
{
    (*function)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f, arg.g, arg.h);
}

// Dispatchers with 0 out param (as a Tuple0).
template<class ObjT, class Method>
inline void DispatchToMethod(ObjT* obj,
                             Method method,
                             const Tuple0& arg, Tuple0*)
{
    (obj->*method)();
}

template<class ObjT, class Method, class A>
inline void DispatchToMethod(ObjT* obj, Method method, const A& arg, Tuple0*)
{
    (obj->*method)(arg);
}

template<class ObjT, class Method, class A>
inline void DispatchToMethod(ObjT* obj,
                             Method method,
                             const Tuple1<A>& arg, Tuple0*)
{
    (obj->*method)(arg.a);
}

template<class ObjT, class Method, class A, class B>
inline void DispatchToMethod(ObjT* obj,
                             Method method,
                             const Tuple2<A, B>& arg, Tuple0*)
{
    (obj->*method)(arg.a, arg.b);
}

template<class ObjT, class Method, class A, class B, class C>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple3<A, B, C>& arg, Tuple0*)
{
    (obj->*method)(arg.a, arg.b, arg.c);
}

template<class ObjT, class Method, class A, class B, class C, class D>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple4<A, B, C, D>& arg, Tuple0*)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d);
}

template<class ObjT, class Method, class A, class B, class C, class D, class E>
inline void DispatchToMethod(ObjT* obj, Method method,
                             const Tuple5<A, B, C, D, E>& arg, Tuple0*)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d, arg.e);
}

template<class ObjT, class Method, class A, class B, class C, class D, class E,
class F>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<A, B, C, D, E, F>& arg, Tuple0*)
{
    (obj->*method)(arg.a, arg.b, arg.c, arg.d, arg.e, arg.f);
}

// Dispatchers with 1 out param.
template<class ObjT, class Method,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple0& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(&out->a);
}

template<class ObjT, class Method, class InA,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const InA& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in, &out->a);
}

template<class ObjT, class Method, class InA,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple1<InA>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, &out->a);
}

template<class ObjT, class Method, class InA, class InB,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple2<InA, InB>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, in.b, &out->a);
}

template<class ObjT, class Method, class InA, class InB, class InC,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple3<InA, InB, InC>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, in.b, in.c, &out->a);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple4<InA, InB, InC, InD>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, &out->a);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class InE, class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple5<InA, InB, InC, InD, InE>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, &out->a);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE, class InF,
class OutA>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<InA, InB, InC, InD, InE, InF>& in,
    Tuple1<OutA>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, in.f, &out->a);
}

// Dispatchers with 2 out params.
template<class ObjT, class Method,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple0& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(&out->a, &out->b);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const InA& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in, &out->a, &out->b);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple1<InA>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, &out->a, &out->b);
}

template<class ObjT, class Method, class InA, class InB,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple2<InA, InB>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, in.b, &out->a, &out->b);
}

template<class ObjT, class Method, class InA, class InB, class InC,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple3<InA, InB, InC>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, in.b, in.c, &out->a, &out->b);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple4<InA, InB, InC, InD>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, &out->a, &out->b);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple5<InA, InB, InC, InD, InE>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, &out->a, &out->b);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE, class InF,
class OutA, class OutB>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<InA, InB, InC, InD, InE, InF>& in,
    Tuple2<OutA, OutB>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, in.f, &out->a, &out->b);
}

// Dispatchers with 3 out params.
template<class ObjT, class Method,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple0& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(&out->a, &out->b, &out->c);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const InA& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple1<InA>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method, class InA, class InB,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple2<InA, InB>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, in.b, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method, class InA, class InB, class InC,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple3<InA, InB, InC>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, in.b, in.c, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple4<InA, InB, InC, InD>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple5<InA, InB, InC, InD, InE>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, &out->a, &out->b, &out->c);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE, class InF,
class OutA, class OutB, class OutC>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<InA, InB, InC, InD, InE, InF>& in,
    Tuple3<OutA, OutB, OutC>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, in.f, &out->a, &out->b, &out->c);
}

// Dispatchers with 4 out params.
template<class ObjT, class Method,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple0& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(&out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const InA& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in, &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple1<InA>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method, class InA, class InB,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple2<InA, InB>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, in.b, &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method, class InA, class InB, class InC,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple3<InA, InB, InC>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, in.b, in.c, &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple4<InA, InB, InC, InD>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple5<InA, InB, InC, InD, InE>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e,
        &out->a, &out->b, &out->c, &out->d);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE, class InF,
class OutA, class OutB, class OutC, class OutD>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<InA, InB, InC, InD, InE, InF>& in,
    Tuple4<OutA, OutB, OutC, OutD>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, in.f,
        &out->a, &out->b, &out->c, &out->d);
}

// Dispatchers with 5 out params.
template<class ObjT, class Method,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple0& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(&out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const InA& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in, &out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method, class InA,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple1<InA>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, &out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method, class InA, class InB,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple2<InA, InB>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, in.b, &out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method, class InA, class InB, class InC,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple3<InA, InB, InC>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, in.b, in.c, &out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method, class InA, class InB, class InC, class InD,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple4<InA, InB, InC, InD>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, &out->a, &out->b, &out->c, &out->d,
        &out->e);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple5<InA, InB, InC, InD, InE>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e,
        &out->a, &out->b, &out->c, &out->d, &out->e);
}

template<class ObjT, class Method,
class InA, class InB, class InC, class InD, class InE, class InF,
class OutA, class OutB, class OutC, class OutD, class OutE>
    inline void DispatchToMethod(ObjT* obj, Method method,
    const Tuple6<InA, InB, InC, InD, InE, InF>& in,
    Tuple5<OutA, OutB, OutC, OutD, OutE>* out)
{
    (obj->*method)(in.a, in.b, in.c, in.d, in.e, in.f,
        &out->a, &out->b, &out->c, &out->d, &out->e);
}

#endif //__tuple_h__