90 lines
2.1 KiB
C
90 lines
2.1 KiB
C
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/*
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* Copyright 2017-present Facebook, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <initializer_list>
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#include <iterator>
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/**
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* include or backport:
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* * std::size
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* * std::empty
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* * std::data
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*/
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#if __cpp_lib_nonmember_container_access >= 201411 || _MSC_VER
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namespace folly {
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/* using override */ using std::data;
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/* using override */ using std::empty;
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/* using override */ using std::size;
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} // namespace folly
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#else
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namespace folly {
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// mimic: std::size, C++17
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template <typename C>
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constexpr auto size(C const& c) -> decltype(c.size()) {
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return c.size();
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}
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template <typename T, std::size_t N>
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constexpr std::size_t size(T const (&)[N]) noexcept {
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return N;
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}
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// mimic: std::empty, C++17
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template <typename C>
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constexpr auto empty(C const& c) -> decltype(c.empty()) {
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return c.empty();
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}
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template <typename T, std::size_t N>
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constexpr bool empty(T const (&)[N]) noexcept {
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// while zero-length arrays are not allowed in the language, some compilers
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// may permit them in some cases
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return N == 0;
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}
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template <typename E>
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constexpr bool empty(std::initializer_list<E> il) noexcept {
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return il.size() == 0;
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}
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// mimic: std::data, C++17
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template <typename C>
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constexpr auto data(C& c) -> decltype(c.data()) {
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return c.data();
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}
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template <typename C>
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constexpr auto data(C const& c) -> decltype(c.data()) {
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return c.data();
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}
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template <typename T, std::size_t N>
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constexpr T* data(T (&a)[N]) noexcept {
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return a;
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}
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template <typename E>
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constexpr E const* data(std::initializer_list<E> il) noexcept {
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return il.begin();
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}
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} // namespace folly
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#endif
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