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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Use std::tuple as tuple type. This file contains helper functions for
// working with std::tuples.
// The functions DispatchToMethod and DispatchToFunction take a function pointer
// or instance and method pointer, and unpack a tuple into arguments to the
// call.
//
// Example usage:
// // These two methods of creating a Tuple are identical.
// std::tuple<int, const char*> tuple_a(1, "wee");
// std::tuple<int, const char*> tuple_b = std::make_tuple(1, "wee");
//
// void SomeFunc(int a, const char* b) { }
// DispatchToFunction(&SomeFunc, tuple_a); // SomeFunc(1, "wee")
// DispatchToFunction(
// &SomeFunc, std::make_tuple(10, "foo")); // SomeFunc(10, "foo")
//
// struct { void SomeMeth(int a, int b, int c) { } } foo;
// DispatchToMethod(&foo, &Foo::SomeMeth, std::make_tuple(1, 2, 3));
// // foo->SomeMeth(1, 2, 3);
#ifndef BASE_TUPLE_H_
#define BASE_TUPLE_H_
#include <stddef.h>
#include <tuple>
#include "build/build_config.h"
namespace base {
// Index sequences
//
// Minimal clone of the similarly-named C++14 functionality.
template <size_t...>
struct IndexSequence {};
template <size_t... Ns>
struct MakeIndexSequenceImpl;
template <size_t... Ns>
struct MakeIndexSequenceImpl<0, Ns...> {
using Type = IndexSequence<Ns...>;
};
template <size_t N, size_t... Ns>
struct MakeIndexSequenceImpl<N, Ns...>
: MakeIndexSequenceImpl<N - 1, N - 1, Ns...> {};
// std::get() in <=libstdc++-4.6 returns an lvalue-reference for
// rvalue-reference of a tuple, where an rvalue-reference is expected.
template <size_t I, typename... Ts>
typename std::tuple_element<I, std::tuple<Ts...>>::type&& get(
std::tuple<Ts...>&& t) {
using ElemType = typename std::tuple_element<I, std::tuple<Ts...>>::type;
return std::forward<ElemType>(std::get<I>(t));
}
template <size_t I, typename T>
auto get(T& t) -> decltype(std::get<I>(t)) {
return std::get<I>(t);
}
template <size_t N>
using MakeIndexSequence = typename MakeIndexSequenceImpl<N>::Type;
template <typename T>
using MakeIndexSequenceForTuple =
MakeIndexSequence<std::tuple_size<typename std::decay<T>::type>::value>;
// 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 <typename ObjT, typename Method, typename Tuple, size_t... Ns>
inline void DispatchToMethodImpl(const ObjT& obj,
Method method,
Tuple&& args,
IndexSequence<Ns...>) {
(obj->*method)(base::get<Ns>(std::forward<Tuple>(args))...);
}
template <typename ObjT, typename Method, typename Tuple>
inline void DispatchToMethod(const ObjT& obj,
Method method,
Tuple&& args) {
DispatchToMethodImpl(obj, method, std::forward<Tuple>(args),
MakeIndexSequenceForTuple<Tuple>());
}
// Static Dispatchers with no out params.
template <typename Function, typename Tuple, size_t... Ns>
inline void DispatchToFunctionImpl(Function function,
Tuple&& args,
IndexSequence<Ns...>) {
(*function)(base::get<Ns>(std::forward<Tuple>(args))...);
}
template <typename Function, typename Tuple>
inline void DispatchToFunction(Function function, Tuple&& args) {
DispatchToFunctionImpl(function, std::forward<Tuple>(args),
MakeIndexSequenceForTuple<Tuple>());
}
// Dispatchers with out parameters.
template <typename ObjT,
typename Method,
typename InTuple,
typename OutTuple,
size_t... InNs,
size_t... OutNs>
inline void DispatchToMethodImpl(const ObjT& obj,
Method method,
InTuple&& in,
OutTuple* out,
IndexSequence<InNs...>,
IndexSequence<OutNs...>) {
(obj->*method)(base::get<InNs>(std::forward<InTuple>(in))...,
&std::get<OutNs>(*out)...);
}
template <typename ObjT, typename Method, typename InTuple, typename OutTuple>
inline void DispatchToMethod(const ObjT& obj,
Method method,
InTuple&& in,
OutTuple* out) {
DispatchToMethodImpl(obj, method, std::forward<InTuple>(in), out,
MakeIndexSequenceForTuple<InTuple>(),
MakeIndexSequenceForTuple<OutTuple>());
}
} // namespace base
#endif // BASE_TUPLE_H_
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