1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
|
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef DOM_CANVAS_TUPLE_UTILS_H
#define DOM_CANVAS_TUPLE_UTILS_H
#include <tuple>
namespace mozilla {
// -
// ToTupleOfConstRefs
template <class T>
constexpr const auto& ToConstRef1(T& ret) {
return ret;
}
template <class Tup, size_t... Ids>
constexpr auto ToTupleOfConstRefsN(const Tup& tup,
const std::index_sequence<Ids...>&) {
return std::tie(ToConstRef1(std::get<Ids>(tup))...);
}
template <class... Args, size_t... Ids, class Tup = std::tuple<Args...>>
constexpr auto ToTupleOfConstRefs(const Tup& tup) {
return ToTupleOfConstRefsN(
tup, std::make_index_sequence<std::tuple_size_v<Tup>>());
}
// -
// MapTuple
template <class Tup, class Callable, size_t... Ids>
constexpr auto MapTupleN(Tup&& tup, Callable&& fn,
const std::index_sequence<Ids...>&) {
return std::make_tuple(fn(std::get<Ids>(tup))...);
}
/// Callable::operator()(T) cannot return void or you will get weird errors.
template <class... Args, class Callable, class Tup = std::tuple<Args...>>
constexpr auto MapTuple(Tup&& t, Callable&& fn) {
using Tup2 = typename std::remove_reference<Tup>::type;
return MapTupleN(t, fn, std::make_index_sequence<std::tuple_size_v<Tup2>>());
}
// -
template <class Tup>
struct SizeofTupleArgs;
// c++17 fold expressions make this easy, once we pull out the Args parameter
// pack by constraining the default template:
template <class... Args>
struct SizeofTupleArgs<std::tuple<Args...>>
: std::integral_constant<size_t, (... + sizeof(Args))> {};
static_assert(SizeofTupleArgs<std::tuple<size_t, char, char, char>>::value ==
sizeof(size_t) + 3);
} // namespace mozilla
#endif // DOM_CANVAS_TUPLE_UTILS_H
|
