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65 lines
1.9 KiB
C++
65 lines
1.9 KiB
C++
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef DOM_CANVAS_TUPLE_UTILS_H
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#define DOM_CANVAS_TUPLE_UTILS_H
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#include <tuple>
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namespace mozilla {
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// -
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// ToTupleOfConstRefs
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template <class T>
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constexpr const auto& ToConstRef1(T& ret) {
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return ret;
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}
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template <class Tup, size_t... Ids>
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constexpr auto ToTupleOfConstRefsN(const Tup& tup,
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const std::index_sequence<Ids...>&) {
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return std::tie(ToConstRef1(std::get<Ids>(tup))...);
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}
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template <class... Args, size_t... Ids, class Tup = std::tuple<Args...>>
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constexpr auto ToTupleOfConstRefs(const Tup& tup) {
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return ToTupleOfConstRefsN(
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tup, std::make_index_sequence<std::tuple_size_v<Tup>>());
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}
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// -
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// MapTuple
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template <class Tup, class Callable, size_t... Ids>
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constexpr auto MapTupleN(Tup&& tup, Callable&& fn,
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const std::index_sequence<Ids...>&) {
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return std::make_tuple(fn(std::get<Ids>(tup))...);
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}
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/// Callable::operator()(T) cannot return void or you will get weird errors.
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template <class... Args, class Callable, class Tup = std::tuple<Args...>>
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constexpr auto MapTuple(Tup&& t, Callable&& fn) {
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using Tup2 = typename std::remove_reference<Tup>::type;
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return MapTupleN(t, fn, std::make_index_sequence<std::tuple_size_v<Tup2>>());
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}
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// -
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template <class Tup>
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struct SizeofTupleArgs;
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// c++17 fold expressions make this easy, once we pull out the Args parameter
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// pack by constraining the default template:
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template <class... Args>
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struct SizeofTupleArgs<std::tuple<Args...>>
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: std::integral_constant<size_t, (... + sizeof(Args))> {};
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static_assert(SizeofTupleArgs<std::tuple<size_t, char, char, char>>::value ==
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sizeof(size_t) + 3);
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} // namespace mozilla
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#endif // DOM_CANVAS_TUPLE_UTILS_H
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