1/*
2 * Copyright 2017-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#pragma once
18
19#include <initializer_list>
20#include <iterator>
21
22/**
23 * include or backport:
24 * * std::size
25 * * std::empty
26 * * std::data
27 */
28
29#if __cpp_lib_nonmember_container_access >= 201411 || _MSC_VER
30
31namespace folly {
32
33/* using override */ using std::data;
34/* using override */ using std::empty;
35/* using override */ using std::size;
36
37} // namespace folly
38
39#else
40
41namespace folly {
42
43// mimic: std::size, C++17
44template <typename C>
45constexpr auto size(C const& c) -> decltype(c.size()) {
46 return c.size();
47}
48template <typename T, std::size_t N>
49constexpr std::size_t size(T const (&)[N]) noexcept {
50 return N;
51}
52
53// mimic: std::empty, C++17
54template <typename C>
55constexpr auto empty(C const& c) -> decltype(c.empty()) {
56 return c.empty();
57}
58template <typename T, std::size_t N>
59constexpr bool empty(T const (&)[N]) noexcept {
60 // while zero-length arrays are not allowed in the language, some compilers
61 // may permit them in some cases
62 return N == 0;
63}
64template <typename E>
65constexpr bool empty(std::initializer_list<E> il) noexcept {
66 return il.size() == 0;
67}
68
69// mimic: std::data, C++17
70template <typename C>
71constexpr auto data(C& c) -> decltype(c.data()) {
72 return c.data();
73}
74template <typename C>
75constexpr auto data(C const& c) -> decltype(c.data()) {
76 return c.data();
77}
78template <typename T, std::size_t N>
79constexpr T* data(T (&a)[N]) noexcept {
80 return a;
81}
82template <typename E>
83constexpr E const* data(std::initializer_list<E> il) noexcept {
84 return il.begin();
85}
86
87} // namespace folly
88
89#endif
90