1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // Use std::tuple as tuple type. This file contains helper functions for
6 // working with std::tuples.
7 // The functions DispatchToMethod and DispatchToFunction take a function pointer
8 // or instance and method pointer, and unpack a tuple into arguments to the
9 // call.
10 //
11 // Example usage:
12 // // These two methods of creating a Tuple are identical.
13 // std::tuple<int, const char*> tuple_a(1, "wee");
14 // std::tuple<int, const char*> tuple_b = std::make_tuple(1, "wee");
15 //
16 // void SomeFunc(int a, const char* b) { }
17 // DispatchToFunction(&SomeFunc, tuple_a); // SomeFunc(1, "wee")
18 // DispatchToFunction(
19 // &SomeFunc, std::make_tuple(10, "foo")); // SomeFunc(10, "foo")
20 //
21 // struct { void SomeMeth(int a, int b, int c) { } } foo;
22 // DispatchToMethod(&foo, &Foo::SomeMeth, std::make_tuple(1, 2, 3));
23 // // foo->SomeMeth(1, 2, 3);
24
25 #ifndef BASE_TUPLE_H_
26 #define BASE_TUPLE_H_
27
28 #include <stddef.h>
29 #include <tuple>
30 #include <utility>
31
32 #include "build/build_config.h"
33
34 namespace base {
35
36 // Dispatchers ----------------------------------------------------------------
37 //
38 // Helper functions that call the given method on an object, with the unpacked
39 // tuple arguments. Notice that they all have the same number of arguments,
40 // so you need only write:
41 // DispatchToMethod(object, &Object::method, args);
42 // This is very useful for templated dispatchers, since they don't need to know
43 // what type |args| is.
44
45 // Non-Static Dispatchers with no out params.
46
47 template <typename ObjT, typename Method, typename Tuple, size_t... Ns>
DispatchToMethodImpl(const ObjT & obj,Method method,Tuple && args,std::index_sequence<Ns...>)48 inline void DispatchToMethodImpl(const ObjT& obj,
49 Method method,
50 Tuple&& args,
51 std::index_sequence<Ns...>) {
52 (obj->*method)(std::get<Ns>(std::forward<Tuple>(args))...);
53 }
54
55 template <typename ObjT, typename Method, typename Tuple>
DispatchToMethod(const ObjT & obj,Method method,Tuple && args)56 inline void DispatchToMethod(const ObjT& obj,
57 Method method,
58 Tuple&& args) {
59 constexpr size_t size = std::tuple_size<std::decay_t<Tuple>>::value;
60 DispatchToMethodImpl(obj, method, std::forward<Tuple>(args),
61 std::make_index_sequence<size>());
62 }
63
64 // Static Dispatchers with no out params.
65
66 template <typename Function, typename Tuple, size_t... Ns>
DispatchToFunctionImpl(Function function,Tuple && args,std::index_sequence<Ns...>)67 inline void DispatchToFunctionImpl(Function function,
68 Tuple&& args,
69 std::index_sequence<Ns...>) {
70 (*function)(std::get<Ns>(std::forward<Tuple>(args))...);
71 }
72
73 template <typename Function, typename Tuple>
DispatchToFunction(Function function,Tuple && args)74 inline void DispatchToFunction(Function function, Tuple&& args) {
75 constexpr size_t size = std::tuple_size<std::decay_t<Tuple>>::value;
76 DispatchToFunctionImpl(function, std::forward<Tuple>(args),
77 std::make_index_sequence<size>());
78 }
79
80 // Dispatchers with out parameters.
81
82 template <typename ObjT,
83 typename Method,
84 typename InTuple,
85 typename OutTuple,
86 size_t... InNs,
87 size_t... OutNs>
DispatchToMethodImpl(const ObjT & obj,Method method,InTuple && in,OutTuple * out,std::index_sequence<InNs...>,std::index_sequence<OutNs...>)88 inline void DispatchToMethodImpl(const ObjT& obj,
89 Method method,
90 InTuple&& in,
91 OutTuple* out,
92 std::index_sequence<InNs...>,
93 std::index_sequence<OutNs...>) {
94 (obj->*method)(std::get<InNs>(std::forward<InTuple>(in))...,
95 &std::get<OutNs>(*out)...);
96 }
97
98 template <typename ObjT, typename Method, typename InTuple, typename OutTuple>
DispatchToMethod(const ObjT & obj,Method method,InTuple && in,OutTuple * out)99 inline void DispatchToMethod(const ObjT& obj,
100 Method method,
101 InTuple&& in,
102 OutTuple* out) {
103 constexpr size_t in_size = std::tuple_size<std::decay_t<InTuple>>::value;
104 constexpr size_t out_size = std::tuple_size<OutTuple>::value;
105 DispatchToMethodImpl(obj, method, std::forward<InTuple>(in), out,
106 std::make_index_sequence<in_size>(),
107 std::make_index_sequence<out_size>());
108 }
109
110 } // namespace base
111
112 #endif // BASE_TUPLE_H_
113