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base / tuple.h [blame]
// Copyright 2011 The Chromium Authors
// 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 <utility>
#include "build/build_config.h"
namespace base {
// 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,
std::index_sequence<Ns...>) {
(obj->*method)(std::get<Ns>(std::forward<Tuple>(args))...);
}
template <typename ObjT, typename Method, typename Tuple>
inline void DispatchToMethod(const ObjT& obj,
Method method,
Tuple&& args) {
constexpr size_t size = std::tuple_size_v<std::decay_t<Tuple>>;
DispatchToMethodImpl(obj, method, std::forward<Tuple>(args),
std::make_index_sequence<size>());
}
// Static Dispatchers with no out params.
template <typename Function, typename Tuple, size_t... Ns>
inline void DispatchToFunctionImpl(Function function,
Tuple&& args,
std::index_sequence<Ns...>) {
(*function)(std::get<Ns>(std::forward<Tuple>(args))...);
}
template <typename Function, typename Tuple>
inline void DispatchToFunction(Function function, Tuple&& args) {
constexpr size_t size = std::tuple_size_v<std::decay_t<Tuple>>;
DispatchToFunctionImpl(function, std::forward<Tuple>(args),
std::make_index_sequence<size>());
}
// 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,
std::index_sequence<InNs...>,
std::index_sequence<OutNs...>) {
(obj->*method)(std::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) {
constexpr size_t in_size = std::tuple_size_v<std::decay_t<InTuple>>;
constexpr size_t out_size = std::tuple_size_v<OutTuple>;
DispatchToMethodImpl(obj, method, std::forward<InTuple>(in), out,
std::make_index_sequence<in_size>(),
std::make_index_sequence<out_size>());
}
} // namespace base
#endif // BASE_TUPLE_H_