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
|
//
// Copyright 2019 The Abseil Authors.
//
// 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
//
// https://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.
//
#ifndef ABSL_TYPES_INTERNAL_SPAN_H_
#define ABSL_TYPES_INTERNAL_SPAN_H_
#include <algorithm>
#include <cstddef>
#include <string>
#include <type_traits>
#include "absl/algorithm/algorithm.h"
#include "absl/base/internal/throw_delegate.h"
#include "absl/meta/type_traits.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
template <typename T>
class Span;
namespace span_internal {
// Wrappers for access to container data pointers.
template <typename C>
constexpr auto GetDataImpl(C& c, char) noexcept // NOLINT(runtime/references)
-> decltype(c.data()) {
return c.data();
}
// Before C++17, std::string::data returns a const char* in all cases.
inline char* GetDataImpl(std::string& s, // NOLINT(runtime/references)
int) noexcept {
return &s[0];
}
template <typename C>
constexpr auto GetData(C& c) noexcept // NOLINT(runtime/references)
-> decltype(GetDataImpl(c, 0)) {
return GetDataImpl(c, 0);
}
// Detection idioms for size() and data().
template <typename C>
using HasSize =
std::is_integral<absl::decay_t<decltype(std::declval<C&>().size())>>;
// We want to enable conversion from vector<T*> to Span<const T* const> but
// disable conversion from vector<Derived> to Span<Base>. Here we use
// the fact that U** is convertible to Q* const* if and only if Q is the same
// type or a more cv-qualified version of U. We also decay the result type of
// data() to avoid problems with classes which have a member function data()
// which returns a reference.
template <typename T, typename C>
using HasData =
std::is_convertible<absl::decay_t<decltype(GetData(std::declval<C&>()))>*,
T* const*>;
// Extracts value type from a Container
template <typename C>
struct ElementType {
using type = typename absl::remove_reference_t<C>::value_type;
};
template <typename T, size_t N>
struct ElementType<T (&)[N]> {
using type = T;
};
template <typename C>
using ElementT = typename ElementType<C>::type;
template <typename T>
using EnableIfMutable =
typename std::enable_if<!std::is_const<T>::value, int>::type;
template <template <typename> class SpanT, typename T>
bool EqualImpl(SpanT<T> a, SpanT<T> b) {
static_assert(std::is_const<T>::value, "");
return std::equal(a.begin(), a.end(), b.begin(), b.end());
}
template <template <typename> class SpanT, typename T>
bool LessThanImpl(SpanT<T> a, SpanT<T> b) {
// We can't use value_type since that is remove_cv_t<T>, so we go the long way
// around.
static_assert(std::is_const<T>::value, "");
return std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end());
}
template <typename From, typename To>
using EnableIfConvertibleTo =
typename std::enable_if<std::is_convertible<From, To>::value>::type;
// IsView is true for types where the return type of .data() is the same for
// mutable and const instances. This isn't foolproof, but it's only used to
// enable a compiler warning.
template <typename T, typename = void, typename = void>
struct IsView {
static constexpr bool value = false;
};
template <typename T>
struct IsView<
T, absl::void_t<decltype(span_internal::GetData(std::declval<const T&>()))>,
absl::void_t<decltype(span_internal::GetData(std::declval<T&>()))>> {
private:
using Container = std::remove_const_t<T>;
using ConstData =
decltype(span_internal::GetData(std::declval<const Container&>()));
using MutData = decltype(span_internal::GetData(std::declval<Container&>()));
public:
static constexpr bool value = std::is_same<ConstData, MutData>::value;
};
// These enablers result in 'int' so they can be used as typenames or defaults
// in template parameters lists.
template <typename T>
using EnableIfIsView = std::enable_if_t<IsView<T>::value, int>;
template <typename T>
using EnableIfNotIsView = std::enable_if_t<!IsView<T>::value, int>;
} // namespace span_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_TYPES_INTERNAL_SPAN_H_
|
