1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
|
#ifndef AL_SPAN_H
#define AL_SPAN_H
#include <cstddef>
#include <array>
#include <type_traits>
#include <initializer_list>
namespace al {
template<typename T>
constexpr auto size(T &cont) -> decltype(cont.size())
{ return cont.size(); }
template<typename T>
constexpr auto size(const T &cont) -> decltype(cont.size())
{ return cont.size(); }
template<typename T, size_t N>
constexpr size_t size(T (&)[N]) noexcept
{ return N; }
template<typename T>
constexpr size_t size(std::initializer_list<T> list) noexcept
{ return list.size(); }
template<typename T>
constexpr auto data(T &cont) -> decltype(cont.data())
{ return cont.data(); }
template<typename T>
constexpr auto data(const T &cont) -> decltype(cont.data())
{ return cont.data(); }
template<typename T, size_t N>
constexpr T* data(T (&arr)[N]) noexcept
{ return arr; }
template<typename T>
constexpr const T* data(std::initializer_list<T> list) noexcept
{ return list.begin(); }
template<typename T>
class span {
public:
using element_type = T;
using value_type = typename std::remove_cv<T>::type;
using index_type = size_t;
using difference_type = ptrdiff_t;
using pointer = T*;
using const_pointer = const T*;
using reference = T&;
using const_reference = const T&;
using iterator = pointer;
using const_iterator = const_pointer;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
constexpr span() noexcept = default;
constexpr span(pointer ptr, index_type count) : mData{ptr}, mCount{count} { }
constexpr span(pointer first, pointer last) : mData{first}, mCount{std::distance(first, last)} { }
template<size_t N>
constexpr span(element_type (&arr)[N]) noexcept : span{al::data(arr), al::size(arr)} { }
template<size_t N>
constexpr span(std::array<value_type,N> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
template<size_t N>
constexpr span(const std::array<value_type,N> &arr) noexcept : span{al::data(arr), al::size(arr)} { }
template<typename U>
constexpr span(U &cont) : span{al::data(cont), al::size(cont)} { }
template<typename U>
constexpr span(const U &cont) : span{al::data(cont), al::size(cont)} { }
constexpr span(const span&) noexcept = default;
span& operator=(const span &rhs) noexcept = default;
constexpr reference front() const { return mData[0]; }
constexpr reference back() const { return mData[mCount-1]; }
constexpr reference operator[](index_type idx) const { return mData[idx]; }
constexpr pointer data() const noexcept { return mData; }
constexpr index_type size() const noexcept { return mCount; }
constexpr index_type size_bytes() const noexcept { return mCount * sizeof(value_type); }
constexpr bool empty() const noexcept { return mCount == 0; }
constexpr iterator begin() const noexcept { return mData; }
constexpr iterator end() const noexcept { return mData + mCount; }
constexpr const_iterator cbegin() const noexcept { return mData; }
constexpr const_iterator cend() const noexcept { return mData + mCount; }
constexpr reverse_iterator rbegin() const noexcept { return end(); }
constexpr reverse_iterator rend() const noexcept { return begin(); }
constexpr const_reverse_iterator crbegin() const noexcept { return cend(); }
constexpr const_reverse_iterator crend() const noexcept { return cbegin(); }
private:
pointer mData{nullptr};
index_type mCount{0u};
};
} // namespace al
#endif /* AL_SPAN_H */
|
