chromium之tuple

// A Tuple is a generic templatized container, similar in concept to std::pair.
// There are classes Tuple0 to Tuple6, cooresponding to the number of elements
// it contains.  The convenient MakeTuple() function takes 0 to 6 arguments,
// and will construct and return the appropriate Tuple object.  The functions
// DispatchToMethod and DispatchToFunction take a function pointer or instance
// and method pointer, and unpack a tuple into arguments to the call.
//
// Tuple elements are copied by value, and stored in the tuple.  See the unit
// tests for more details of how/when the values are copied.
//
// Example usage:
//   // 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);

Tuple是一个通用的模板化容器，类似std::pair的概念。

转换函数MakeTuple接收0-6个参数，并返回一个Tuple对象

DispatchToFunction 接收一个函数指针，并解压一个tuple作为函数指针的参数，并调用

//   void SomeFunc(int a, const char* b) { }
//   DispatchToFunction(&SomeFunc, tuple_a);  // SomeFunc(1, "wee")

DispatchToMethod 接收一个实例、实例的方法指针，并解压一个tuple作为函数指针的参数，并调用

//   struct { void SomeMeth(int a, int b, int c) { } } foo;
//   DispatchToMethod(&foo, &Foo::SomeMeth, MakeTuple(1, 2, 3));

---

看看代码

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 A>
struct Tuple1 {
 public:
  typedef A TypeA;
  typedef Tuple1<typename TupleTraits<A>::ValueType> ValueTuple;
  typedef Tuple1<typename TupleTraits<A>::RefType> RefTuple;
  typedef Tuple1<typename TupleTraits<A>::ParamType> ParamTuple;

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

  A a;
};

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