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- /*
- * Copyright 2017-present Facebook, Inc.
- *
- * 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
- *
- * http://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.
- */
- #pragma once
- #include <initializer_list>
- #include <iterator>
- /**
- * include or backport:
- * * std::size
- * * std::empty
- * * std::data
- */
- #if __cpp_lib_nonmember_container_access >= 201411 || _MSC_VER
- namespace folly {
- /* using override */ using std::data;
- /* using override */ using std::empty;
- /* using override */ using std::size;
- } // namespace folly
- #else
- namespace folly {
- // mimic: std::size, C++17
- template <typename C>
- constexpr auto size(C const& c) -> decltype(c.size()) {
- return c.size();
- }
- template <typename T, std::size_t N>
- constexpr std::size_t size(T const (&)[N]) noexcept {
- return N;
- }
- // mimic: std::empty, C++17
- template <typename C>
- constexpr auto empty(C const& c) -> decltype(c.empty()) {
- return c.empty();
- }
- template <typename T, std::size_t N>
- constexpr bool empty(T const (&)[N]) noexcept {
- // while zero-length arrays are not allowed in the language, some compilers
- // may permit them in some cases
- return N == 0;
- }
- template <typename E>
- constexpr bool empty(std::initializer_list<E> il) noexcept {
- return il.size() == 0;
- }
- // mimic: std::data, C++17
- template <typename C>
- constexpr auto data(C& c) -> decltype(c.data()) {
- return c.data();
- }
- template <typename C>
- constexpr auto data(C const& c) -> decltype(c.data()) {
- return c.data();
- }
- template <typename T, std::size_t N>
- constexpr T* data(T (&a)[N]) noexcept {
- return a;
- }
- template <typename E>
- constexpr E const* data(std::initializer_list<E> il) noexcept {
- return il.begin();
- }
- } // namespace folly
- #endif
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