90 lines
2.1 KiB
C++
90 lines
2.1 KiB
C++
/*
|
|
* 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
|