Loki库读解-为TypeList添足：最远基类、最近基类、类型的排序

发布: 2007-7-01 20:40 | 作者: admin | 来源: | 查看: 19次 | 进入软件测试论坛讨论

相对于TypeList源码，下面代码还是很简单的，就不多说废话了。

#ifndef TYPELIST_ADD_H
#define TYPELIST_ADD_H

//-------------------------------------------------------------------------------
//Loki库自己的SUPERSUBCLASS_STRICT在DevCpp下编译不过，lokiVC6port提供的版本同下。
//-------------------------------------------------------------------------------
#define SUPERSUBCLASS_STRICT_FIX(T, U) \
    (SUPERSUBCLASS(T, U) && \
    !::Loki::Conversion<const T *, const U *>::sameType)

//-------------------------------------------------------------------------------
//-------------------------------------------------------------------------------
template <class TList, class T> struct MostBased;

template <class T>
struct MostBased<NullType, T>
{
typedef T Result;
};

template <class Head, class Tail, class T>
    struct MostBased<Typelist<Head, Tail>, T>
{
private:
    typedef typename MostBased<Tail, T>::Result Candidate;
public:
    typedef typename Select<SUPERSUBCLASS(Head, Candidate),
            Head, Candidate>::Result Result;
};

//-------------------------------------------------------------------------
//-------------------------------------------------------------------------
template <class Tlist, class T> struct NearestBased;

template <class Tlist, class T, class CurNearBase> struct NearestBasedHelper;

template <class Head, class Tail, class T, class CurNearBase>
    struct NearestBasedHelper<Typelist<Head, Tail>, T, CurNearBase>
{
private:
    typedef typename Select< SUPERSUBCLASS_STRICT_FIX(Head, T) &&
                             SUPERSUBCLASS_STRICT_FIX(CurNearBase, Head),
                            Head, CurNearBase>::Result curnearbase;         //搜索处于两个类之间的类
public:
    typedef typename NearestBasedHelper<Tail, T, curnearbase>::Result Result;
};

template <class T, class CurNearBase>
    struct NearestBasedHelper<NullType, T, CurNearBase>
{
    typedef CurNearBase Result;
};

template <class T>                             //保护对空TypeList发生操作。
struct NearestBased<NullType, T>
{
//    typedef T Result;
};

template <class Head, class Tail, class T>
    struct NearestBased<Typelist<Head, Tail>, T>
{
private:
    typedef MostBased<Typelist<Head, Tail>, T>::Result mostbased;   //找到最基类，然后夹杀法。
public:
    typedef typename NearestBasedHelper<Typelist<Head, Tail>, T, mostbased>::Result Result;
};

//-------------------------------------------------------------------------------
//排序完成后，派生类一定在它的基类前面。
//-------------------------------------------------------------------------------
template <class TList> struct Sort;

template <>
struct Sort<NullType>
{
typedef NullType Result;
};

template <class Head, class Tail>
    struct Sort<Typelist<Head, Tail> >
{
private:
    typedef typename MostDerived<Tail, Head>::Result             TheMostDerived;
    typedef typename Replace<Tail, TheMostDerived, Head>::Result L;
public:
    typedef Typelist<TheMostDerived, typename Sort<L>::Result>   Result;

};

#endif