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Diffstat (limited to 'third_party/abseil_cpp/absl/utility/utility.h')
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diff --git a/third_party/abseil_cpp/absl/utility/utility.h b/third_party/abseil_cpp/absl/utility/utility.h new file mode 100644 index 000000000000..e6647c7b2e61 --- /dev/null +++ b/third_party/abseil_cpp/absl/utility/utility.h @@ -0,0 +1,350 @@ +// Copyright 2017 The Abseil Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// This header file contains C++11 versions of standard <utility> header +// abstractions available within C++14 and C++17, and are designed to be drop-in +// replacement for code compliant with C++14 and C++17. +// +// The following abstractions are defined: +// +// * integer_sequence<T, Ints...> == std::integer_sequence<T, Ints...> +// * index_sequence<Ints...> == std::index_sequence<Ints...> +// * make_integer_sequence<T, N> == std::make_integer_sequence<T, N> +// * make_index_sequence<N> == std::make_index_sequence<N> +// * index_sequence_for<Ts...> == std::index_sequence_for<Ts...> +// * apply<Functor, Tuple> == std::apply<Functor, Tuple> +// * exchange<T> == std::exchange<T> +// * make_from_tuple<T> == std::make_from_tuple<T> +// +// This header file also provides the tag types `in_place_t`, `in_place_type_t`, +// and `in_place_index_t`, as well as the constant `in_place`, and +// `constexpr` `std::move()` and `std::forward()` implementations in C++11. +// +// References: +// +// https://en.cppreference.com/w/cpp/utility/integer_sequence +// https://en.cppreference.com/w/cpp/utility/apply +// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3658.html + +#ifndef ABSL_UTILITY_UTILITY_H_ +#define ABSL_UTILITY_UTILITY_H_ + +#include <cstddef> +#include <cstdlib> +#include <tuple> +#include <utility> + +#include "absl/base/config.h" +#include "absl/base/internal/inline_variable.h" +#include "absl/base/internal/invoke.h" +#include "absl/meta/type_traits.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN + +// integer_sequence +// +// Class template representing a compile-time integer sequence. An instantiation +// of `integer_sequence<T, Ints...>` has a sequence of integers encoded in its +// type through its template arguments (which is a common need when +// working with C++11 variadic templates). `absl::integer_sequence` is designed +// to be a drop-in replacement for C++14's `std::integer_sequence`. +// +// Example: +// +// template< class T, T... Ints > +// void user_function(integer_sequence<T, Ints...>); +// +// int main() +// { +// // user_function's `T` will be deduced to `int` and `Ints...` +// // will be deduced to `0, 1, 2, 3, 4`. +// user_function(make_integer_sequence<int, 5>()); +// } +template <typename T, T... Ints> +struct integer_sequence { + using value_type = T; + static constexpr size_t size() noexcept { return sizeof...(Ints); } +}; + +// index_sequence +// +// A helper template for an `integer_sequence` of `size_t`, +// `absl::index_sequence` is designed to be a drop-in replacement for C++14's +// `std::index_sequence`. +template <size_t... Ints> +using index_sequence = integer_sequence<size_t, Ints...>; + +namespace utility_internal { + +template <typename Seq, size_t SeqSize, size_t Rem> +struct Extend; + +// Note that SeqSize == sizeof...(Ints). It's passed explicitly for efficiency. +template <typename T, T... Ints, size_t SeqSize> +struct Extend<integer_sequence<T, Ints...>, SeqSize, 0> { + using type = integer_sequence<T, Ints..., (Ints + SeqSize)...>; +}; + +template <typename T, T... Ints, size_t SeqSize> +struct Extend<integer_sequence<T, Ints...>, SeqSize, 1> { + using type = integer_sequence<T, Ints..., (Ints + SeqSize)..., 2 * SeqSize>; +}; + +// Recursion helper for 'make_integer_sequence<T, N>'. +// 'Gen<T, N>::type' is an alias for 'integer_sequence<T, 0, 1, ... N-1>'. +template <typename T, size_t N> +struct Gen { + using type = + typename Extend<typename Gen<T, N / 2>::type, N / 2, N % 2>::type; +}; + +template <typename T> +struct Gen<T, 0> { + using type = integer_sequence<T>; +}; + +template <typename T> +struct InPlaceTypeTag { + explicit InPlaceTypeTag() = delete; + InPlaceTypeTag(const InPlaceTypeTag&) = delete; + InPlaceTypeTag& operator=(const InPlaceTypeTag&) = delete; +}; + +template <size_t I> +struct InPlaceIndexTag { + explicit InPlaceIndexTag() = delete; + InPlaceIndexTag(const InPlaceIndexTag&) = delete; + InPlaceIndexTag& operator=(const InPlaceIndexTag&) = delete; +}; + +} // namespace utility_internal + +// Compile-time sequences of integers + +// make_integer_sequence +// +// This template alias is equivalent to +// `integer_sequence<int, 0, 1, ..., N-1>`, and is designed to be a drop-in +// replacement for C++14's `std::make_integer_sequence`. +template <typename T, T N> +using make_integer_sequence = typename utility_internal::Gen<T, N>::type; + +// make_index_sequence +// +// This template alias is equivalent to `index_sequence<0, 1, ..., N-1>`, +// and is designed to be a drop-in replacement for C++14's +// `std::make_index_sequence`. +template <size_t N> +using make_index_sequence = make_integer_sequence<size_t, N>; + +// index_sequence_for +// +// Converts a typename pack into an index sequence of the same length, and +// is designed to be a drop-in replacement for C++14's +// `std::index_sequence_for()` +template <typename... Ts> +using index_sequence_for = make_index_sequence<sizeof...(Ts)>; + +// Tag types + +#ifdef ABSL_USES_STD_OPTIONAL + +using std::in_place_t; +using std::in_place; + +#else // ABSL_USES_STD_OPTIONAL + +// in_place_t +// +// Tag type used to specify in-place construction, such as with +// `absl::optional`, designed to be a drop-in replacement for C++17's +// `std::in_place_t`. +struct in_place_t {}; + +ABSL_INTERNAL_INLINE_CONSTEXPR(in_place_t, in_place, {}); + +#endif // ABSL_USES_STD_OPTIONAL + +#if defined(ABSL_USES_STD_ANY) || defined(ABSL_USES_STD_VARIANT) +using std::in_place_type; +using std::in_place_type_t; +#else + +// in_place_type_t +// +// Tag type used for in-place construction when the type to construct needs to +// be specified, such as with `absl::any`, designed to be a drop-in replacement +// for C++17's `std::in_place_type_t`. +template <typename T> +using in_place_type_t = void (*)(utility_internal::InPlaceTypeTag<T>); + +template <typename T> +void in_place_type(utility_internal::InPlaceTypeTag<T>) {} +#endif // ABSL_USES_STD_ANY || ABSL_USES_STD_VARIANT + +#ifdef ABSL_USES_STD_VARIANT +using std::in_place_index; +using std::in_place_index_t; +#else + +// in_place_index_t +// +// Tag type used for in-place construction when the type to construct needs to +// be specified, such as with `absl::any`, designed to be a drop-in replacement +// for C++17's `std::in_place_index_t`. +template <size_t I> +using in_place_index_t = void (*)(utility_internal::InPlaceIndexTag<I>); + +template <size_t I> +void in_place_index(utility_internal::InPlaceIndexTag<I>) {} +#endif // ABSL_USES_STD_VARIANT + +// Constexpr move and forward + +// move() +// +// A constexpr version of `std::move()`, designed to be a drop-in replacement +// for C++14's `std::move()`. +template <typename T> +constexpr absl::remove_reference_t<T>&& move(T&& t) noexcept { + return static_cast<absl::remove_reference_t<T>&&>(t); +} + +// forward() +// +// A constexpr version of `std::forward()`, designed to be a drop-in replacement +// for C++14's `std::forward()`. +template <typename T> +constexpr T&& forward( + absl::remove_reference_t<T>& t) noexcept { // NOLINT(runtime/references) + return static_cast<T&&>(t); +} + +namespace utility_internal { +// Helper method for expanding tuple into a called method. +template <typename Functor, typename Tuple, std::size_t... Indexes> +auto apply_helper(Functor&& functor, Tuple&& t, index_sequence<Indexes...>) + -> decltype(absl::base_internal::Invoke( + absl::forward<Functor>(functor), + std::get<Indexes>(absl::forward<Tuple>(t))...)) { + return absl::base_internal::Invoke( + absl::forward<Functor>(functor), + std::get<Indexes>(absl::forward<Tuple>(t))...); +} + +} // namespace utility_internal + +// apply +// +// Invokes a Callable using elements of a tuple as its arguments. +// Each element of the tuple corresponds to an argument of the call (in order). +// Both the Callable argument and the tuple argument are perfect-forwarded. +// For member-function Callables, the first tuple element acts as the `this` +// pointer. `absl::apply` is designed to be a drop-in replacement for C++17's +// `std::apply`. Unlike C++17's `std::apply`, this is not currently `constexpr`. +// +// Example: +// +// class Foo { +// public: +// void Bar(int); +// }; +// void user_function1(int, std::string); +// void user_function2(std::unique_ptr<Foo>); +// auto user_lambda = [](int, int) {}; +// +// int main() +// { +// std::tuple<int, std::string> tuple1(42, "bar"); +// // Invokes the first user function on int, std::string. +// absl::apply(&user_function1, tuple1); +// +// std::tuple<std::unique_ptr<Foo>> tuple2(absl::make_unique<Foo>()); +// // Invokes the user function that takes ownership of the unique +// // pointer. +// absl::apply(&user_function2, std::move(tuple2)); +// +// auto foo = absl::make_unique<Foo>(); +// std::tuple<Foo*, int> tuple3(foo.get(), 42); +// // Invokes the method Bar on foo with one argument, 42. +// absl::apply(&Foo::Bar, tuple3); +// +// std::tuple<int, int> tuple4(8, 9); +// // Invokes a lambda. +// absl::apply(user_lambda, tuple4); +// } +template <typename Functor, typename Tuple> +auto apply(Functor&& functor, Tuple&& t) + -> decltype(utility_internal::apply_helper( + absl::forward<Functor>(functor), absl::forward<Tuple>(t), + absl::make_index_sequence<std::tuple_size< + typename std::remove_reference<Tuple>::type>::value>{})) { + return utility_internal::apply_helper( + absl::forward<Functor>(functor), absl::forward<Tuple>(t), + absl::make_index_sequence<std::tuple_size< + typename std::remove_reference<Tuple>::type>::value>{}); +} + +// exchange +// +// Replaces the value of `obj` with `new_value` and returns the old value of +// `obj`. `absl::exchange` is designed to be a drop-in replacement for C++14's +// `std::exchange`. +// +// Example: +// +// Foo& operator=(Foo&& other) { +// ptr1_ = absl::exchange(other.ptr1_, nullptr); +// int1_ = absl::exchange(other.int1_, -1); +// return *this; +// } +template <typename T, typename U = T> +T exchange(T& obj, U&& new_value) { + T old_value = absl::move(obj); + obj = absl::forward<U>(new_value); + return old_value; +} + +namespace utility_internal { +template <typename T, typename Tuple, size_t... I> +T make_from_tuple_impl(Tuple&& tup, absl::index_sequence<I...>) { + return T(std::get<I>(std::forward<Tuple>(tup))...); +} +} // namespace utility_internal + +// make_from_tuple +// +// Given the template parameter type `T` and a tuple of arguments +// `std::tuple(arg0, arg1, ..., argN)` constructs an object of type `T` as if by +// calling `T(arg0, arg1, ..., argN)`. +// +// Example: +// +// std::tuple<const char*, size_t> args("hello world", 5); +// auto s = absl::make_from_tuple<std::string>(args); +// assert(s == "hello"); +// +template <typename T, typename Tuple> +constexpr T make_from_tuple(Tuple&& tup) { + return utility_internal::make_from_tuple_impl<T>( + std::forward<Tuple>(tup), + absl::make_index_sequence< + std::tuple_size<absl::decay_t<Tuple>>::value>{}); +} + +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_UTILITY_UTILITY_H_ |