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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.
// A Tuple is a generic templatized container, similar in concept to std::pair
// and std::tuple. The convenient MakeTuple() function takes any number of
// 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.
// Tuple<int, const char*> tuple_a(1, "wee");
// Tuple<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);
#ifndef BASE_TUPLE_H_
#define BASE_TUPLE_H_
#include <stddef.h>
#include <tuple>
#include "base/bind_helpers.h"
#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;
#if defined(_PREFAST_) && defined(OS_WIN)
// Work around VC++ 2013 /analyze internal compiler error:
template <> struct MakeIndexSequenceImpl<0> {
using Type = IndexSequence<>;
template <> struct MakeIndexSequenceImpl<1> {
using Type = IndexSequence<0>;
template <> struct MakeIndexSequenceImpl<2> {
using Type = IndexSequence<0,1>;
template <> struct MakeIndexSequenceImpl<3> {
using Type = IndexSequence<0,1,2>;
template <> struct MakeIndexSequenceImpl<4> {
using Type = IndexSequence<0,1,2,3>;
template <> struct MakeIndexSequenceImpl<5> {
using Type = IndexSequence<0,1,2,3,4>;
template <> struct MakeIndexSequenceImpl<6> {
using Type = IndexSequence<0,1,2,3,4,5>;
template <> struct MakeIndexSequenceImpl<7> {
using Type = IndexSequence<0,1,2,3,4,5,6>;
template <> struct MakeIndexSequenceImpl<8> {
using Type = IndexSequence<0,1,2,3,4,5,6,7>;
template <> struct MakeIndexSequenceImpl<9> {
using Type = IndexSequence<0,1,2,3,4,5,6,7,8>;
template <> struct MakeIndexSequenceImpl<10> {
using Type = IndexSequence<0,1,2,3,4,5,6,7,8,9>;
template <> struct MakeIndexSequenceImpl<11> {
using Type = IndexSequence<0,1,2,3,4,5,6,7,8,9,10>;
template <> struct MakeIndexSequenceImpl<12> {
using Type = IndexSequence<0,1,2,3,4,5,6,7,8,9,10,11>;
template <> struct MakeIndexSequenceImpl<13> {
using Type = IndexSequence<0,1,2,3,4,5,6,7,8,9,10,11,12>;
#else // defined(WIN) && defined(_PREFAST_)
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...> {};
#endif // defined(WIN) && defined(_PREFAST_)
template <size_t N>
using MakeIndexSequence = typename MakeIndexSequenceImpl<N>::Type;
// 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;
// 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.
// Tuple<> 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).
// Tuple<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.
template <typename... Ts>
using Tuple = std::tuple<Ts...>;
using std::get;
// Tuple types ----------------------------------------------------------------
// Allows for selection of ValueTuple/RefTuple/ParamTuple without needing the
// definitions of class types the tuple takes as parameters.
template <typename T>
struct TupleTypes;
template <typename... Ts>
struct TupleTypes<Tuple<Ts...>> {
using ValueTuple = Tuple<typename TupleTraits<Ts>::ValueType...>;
using RefTuple = Tuple<typename TupleTraits<Ts>::RefType...>;
using ParamTuple = Tuple<typename TupleTraits<Ts>::ParamType...>;
// Tuple creators -------------------------------------------------------------
// Helper functions for constructing tuples while inferring the template
// argument types.
template <typename... Ts>
inline Tuple<Ts...> MakeTuple(const Ts&... arg) {
return Tuple<Ts...>(arg...);
// The following set of helpers make what Boost refers to as "Tiers" - a tuple
// of references.
template <typename... Ts>
inline Tuple<Ts&...> MakeRefTuple(Ts&... arg) {
return Tuple<Ts&...>(arg...);
// 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... Ts, size_t... Ns>
inline void DispatchToMethodImpl(ObjT* obj,
Method method,
const Tuple<Ts...>& arg,
IndexSequence<Ns...>) {
template <typename ObjT, typename Method, typename... Ts>
inline void DispatchToMethod(ObjT* obj,
Method method,
const Tuple<Ts...>& arg) {
DispatchToMethodImpl(obj, method, arg, MakeIndexSequence<sizeof...(Ts)>());
// Static Dispatchers with no out params.
template <typename Function, typename... Ts, size_t... Ns>
inline void DispatchToFunctionImpl(Function function,
const Tuple<Ts...>& arg,
IndexSequence<Ns...>) {
template <typename Function, typename... Ts>
inline void DispatchToFunction(Function function, const Tuple<Ts...>& arg) {
DispatchToFunctionImpl(function, arg, MakeIndexSequence<sizeof...(Ts)>());
// Dispatchers with out parameters.
template <typename ObjT,
typename Method,
typename... InTs,
typename... OutTs,
size_t... InNs,
size_t... OutNs>
inline void DispatchToMethodImpl(ObjT* obj,
Method method,
const Tuple<InTs...>& in,
Tuple<OutTs...>* out,
IndexSequence<OutNs...>) {
template <typename ObjT, typename Method, typename... InTs, typename... OutTs>
inline void DispatchToMethod(ObjT* obj,
Method method,
const Tuple<InTs...>& in,
Tuple<OutTs...>* out) {
DispatchToMethodImpl(obj, method, in, out,
} // namespace base
#endif // BASE_TUPLE_H_