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
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
|
// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
#pragma once
// Try to use either `std::span` or `gsl::span`
#if defined(OPENTELEMETRY_STL_VERSION)
# if OPENTELEMETRY_STL_VERSION >= 2020
# include <array>
# include <cstddef>
# include <iterator>
# include <type_traits>
/**
* @brief Clang 14.0.0 with libc++ do not support implicitly construct a span
* for a range. We just use our fallback version.
*
*/
# if !defined(OPENTELEMETRY_OPTION_USE_STD_SPAN) && defined(_LIBCPP_VERSION)
# if _LIBCPP_VERSION <= 14000
# define OPENTELEMETRY_OPTION_USE_STD_SPAN 0
# endif
# endif
# ifndef OPENTELEMETRY_OPTION_USE_STD_SPAN
# define OPENTELEMETRY_OPTION_USE_STD_SPAN 1
# endif
# if OPENTELEMETRY_OPTION_USE_STD_SPAN
# include "opentelemetry/std/span.h"
# endif
# endif /* OPENTELEMETRY_STL_VERSION >= 2020 */
#endif /* OPENTELEMETRY_STL_VERSION */
// Fallback to `nostd::span` if necessary
#if !defined(OPENTELEMETRY_HAVE_SPAN)
# include <array>
# include <cassert>
# include <cstddef>
# include <exception>
# include <iterator>
# include <type_traits>
# include "opentelemetry/nostd/utility.h"
# include "opentelemetry/version.h"
OPENTELEMETRY_BEGIN_NAMESPACE
namespace nostd
{
constexpr size_t dynamic_extent = static_cast<size_t>(-1);
template <class T, size_t Extent = dynamic_extent>
class span;
namespace detail
{
/**
* Helper class to resolve overloaded constructors
*/
template <class T>
struct is_specialized_span_convertible : std::false_type
{};
template <class T, size_t N>
struct is_specialized_span_convertible<std::array<T, N>> : std::true_type
{};
template <class T, size_t N>
struct is_specialized_span_convertible<T[N]> : std::true_type
{};
template <class T, size_t Extent>
struct is_specialized_span_convertible<span<T, Extent>> : std::true_type
{};
} // namespace detail
/**
* Back port of std::span.
*
* See https://en.cppreference.com/w/cpp/container/span for interface documentation.
*
* Note: This provides a subset of the methods available on std::span.
*
* Note: The std::span API specifies error cases to have undefined behavior, so this implementation
* chooses to terminate or assert rather than throw exceptions.
*/
template <class T, size_t Extent>
class span
{
public:
static constexpr size_t extent = Extent;
// This arcane code is how we make default-construction result in an SFINAE error
// with C++11 when Extent != 0 as specified by the std::span API.
//
// See https://stackoverflow.com/a/10309720/4447365
template <bool B = Extent == 0, typename std::enable_if<B>::type * = nullptr>
span() noexcept : data_{nullptr}
{}
span(T *data, size_t count) noexcept : data_{data}
{
if (count != Extent)
{
std::terminate();
}
}
span(T *first, T *last) noexcept : data_{first}
{
if (std::distance(first, last) != Extent)
{
std::terminate();
}
}
template <size_t N, typename std::enable_if<Extent == N>::type * = nullptr>
span(T (&array)[N]) noexcept : data_{array}
{}
template <size_t N, typename std::enable_if<Extent == N>::type * = nullptr>
span(std::array<T, N> &array) noexcept : data_{array.data()}
{}
template <size_t N, typename std::enable_if<Extent == N>::type * = nullptr>
span(const std::array<T, N> &array) noexcept : data_{array.data()}
{}
template <
class C,
typename std::enable_if<!detail::is_specialized_span_convertible<C>::value &&
std::is_convertible<typename std::remove_pointer<decltype(nostd::data(
std::declval<C &>()))>::type (*)[],
T (*)[]>::value &&
std::is_convertible<decltype(nostd::size(std::declval<const C &>())),
size_t>::value>::type * = nullptr>
span(C &c) noexcept(noexcept(nostd::data(c), nostd::size(c))) : data_{nostd::data(c)}
{
if (nostd::size(c) != Extent)
{
std::terminate();
}
}
template <
class C,
typename std::enable_if<!detail::is_specialized_span_convertible<C>::value &&
std::is_convertible<typename std::remove_pointer<decltype(nostd::data(
std::declval<const C &>()))>::type (*)[],
T (*)[]>::value &&
std::is_convertible<decltype(nostd::size(std::declval<const C &>())),
size_t>::value>::type * = nullptr>
span(const C &c) noexcept(noexcept(nostd::data(c), nostd::size(c))) : data_{nostd::data(c)}
{
if (nostd::size(c) != Extent)
{
std::terminate();
}
}
template <class U,
size_t N,
typename std::enable_if<N == Extent &&
std::is_convertible<U (*)[], T (*)[]>::value>::type * = nullptr>
span(const span<U, N> &other) noexcept : data_{other.data()}
{}
span(const span &) noexcept = default;
span &operator=(const span &) noexcept = default;
bool empty() const noexcept { return Extent == 0; }
T *data() const noexcept { return data_; }
size_t size() const noexcept { return Extent; }
T &operator[](size_t index) const noexcept
{
assert(index < Extent);
return data_[index];
}
T *begin() const noexcept { return data_; }
T *end() const noexcept { return data_ + Extent; }
private:
T *data_;
};
template <class T>
class span<T, dynamic_extent>
{
public:
static constexpr size_t extent = dynamic_extent;
span() noexcept : extent_{0}, data_{nullptr} {}
span(T *data, size_t count) noexcept : extent_{count}, data_{data} {}
span(T *first, T *last) noexcept
: extent_{static_cast<size_t>(std::distance(first, last))}, data_{first}
{
assert(first <= last);
}
template <size_t N>
span(T (&array)[N]) noexcept : extent_{N}, data_{array}
{}
template <size_t N>
span(std::array<T, N> &array) noexcept : extent_{N}, data_{array.data()}
{}
template <size_t N>
span(const std::array<T, N> &array) noexcept : extent_{N}, data_{array.data()}
{}
template <
class C,
typename std::enable_if<!detail::is_specialized_span_convertible<C>::value &&
std::is_convertible<typename std::remove_pointer<decltype(nostd::data(
std::declval<C &>()))>::type (*)[],
T (*)[]>::value &&
std::is_convertible<decltype(nostd::size(std::declval<const C &>())),
size_t>::value>::type * = nullptr>
span(C &c) noexcept(noexcept(nostd::data(c), nostd::size(c)))
: extent_{nostd::size(c)}, data_{nostd::data(c)}
{}
template <
class C,
typename std::enable_if<!detail::is_specialized_span_convertible<C>::value &&
std::is_convertible<typename std::remove_pointer<decltype(nostd::data(
std::declval<const C &>()))>::type (*)[],
T (*)[]>::value &&
std::is_convertible<decltype(nostd::size(std::declval<const C &>())),
size_t>::value>::type * = nullptr>
span(const C &c) noexcept(noexcept(nostd::data(c), nostd::size(c)))
: extent_{nostd::size(c)}, data_{nostd::data(c)}
{}
template <class U,
size_t N,
typename std::enable_if<std::is_convertible<U (*)[], T (*)[]>::value>::type * = nullptr>
span(const span<U, N> &other) noexcept : extent_{other.size()}, data_{other.data()}
{}
span(const span &) noexcept = default;
span &operator=(const span &) noexcept = default;
bool empty() const noexcept { return extent_ == 0; }
T *data() const noexcept { return data_; }
size_t size() const noexcept { return extent_; }
T &operator[](size_t index) const noexcept
{
assert(index < extent_);
return data_[index];
}
T *begin() const noexcept { return data_; }
T *end() const noexcept { return data_ + extent_; }
private:
size_t extent_;
T *data_;
};
} // namespace nostd
OPENTELEMETRY_END_NAMESPACE
#endif
|
