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150
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1 // -*- C++ -*-
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2 //===------------------------------ span ---------------------------------===//
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3 //
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4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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5 // See https://llvm.org/LICENSE.txt for license information.
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6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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7 //
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8 //===---------------------------------------------------------------------===//
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9
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10 #ifndef _LIBCPP_SPAN
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11 #define _LIBCPP_SPAN
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12
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13 /*
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14 span synopsis
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15
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16 namespace std {
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17
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18 // constants
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19 inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
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20
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21 // [views.span], class template span
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22 template <class ElementType, size_t Extent = dynamic_extent>
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23 class span;
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24
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25 // [span.objectrep], views of object representation
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26 template <class ElementType, size_t Extent>
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27 span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
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28 (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
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29
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30 template <class ElementType, size_t Extent>
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31 span< byte, ((Extent == dynamic_extent) ? dynamic_extent :
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32 (sizeof(ElementType) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
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33
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34
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35 namespace std {
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36 template <class ElementType, size_t Extent = dynamic_extent>
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37 class span {
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38 public:
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39 // constants and types
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40 using element_type = ElementType;
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41 using value_type = remove_cv_t<ElementType>;
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42 using size_type = size_t;
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43 using difference_type = ptrdiff_t;
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44 using pointer = element_type*;
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45 using const_pointer = const element_type*;
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46 using reference = element_type&;
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47 using const_reference = const element_type&;
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48 using iterator = implementation-defined;
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49 using reverse_iterator = std::reverse_iterator<iterator>;
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50 static constexpr size_type extent = Extent;
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51
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52 // [span.cons], span constructors, copy, assignment, and destructor
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53 constexpr span() noexcept;
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173
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54 constexpr explicit(Extent != dynamic_extent) span(pointer ptr, size_type count);
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55 constexpr explicit(Extent != dynamic_extent) span(pointer firstElem, pointer lastElem);
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150
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56 template <size_t N>
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57 constexpr span(element_type (&arr)[N]) noexcept;
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58 template <size_t N>
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59 constexpr span(array<value_type, N>& arr) noexcept;
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60 template <size_t N>
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61 constexpr span(const array<value_type, N>& arr) noexcept;
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62 template <class Container>
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173
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63 constexpr explicit(Extent != dynamic_extent) span(Container& cont);
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150
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64 template <class Container>
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173
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65 constexpr explicit(Extent != dynamic_extent) span(const Container& cont);
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150
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66 constexpr span(const span& other) noexcept = default;
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67 template <class OtherElementType, size_t OtherExtent>
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173
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68 constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept;
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150
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69 ~span() noexcept = default;
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70 constexpr span& operator=(const span& other) noexcept = default;
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71
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72 // [span.sub], span subviews
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73 template <size_t Count>
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74 constexpr span<element_type, Count> first() const;
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75 template <size_t Count>
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76 constexpr span<element_type, Count> last() const;
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77 template <size_t Offset, size_t Count = dynamic_extent>
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78 constexpr span<element_type, see below> subspan() const;
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79
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80 constexpr span<element_type, dynamic_extent> first(size_type count) const;
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81 constexpr span<element_type, dynamic_extent> last(size_type count) const;
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82 constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
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83
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84 // [span.obs], span observers
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85 constexpr size_type size() const noexcept;
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86 constexpr size_type size_bytes() const noexcept;
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87 constexpr bool empty() const noexcept;
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88
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89 // [span.elem], span element access
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90 constexpr reference operator[](size_type idx) const;
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91 constexpr reference front() const;
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92 constexpr reference back() const;
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93 constexpr pointer data() const noexcept;
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94
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95 // [span.iterators], span iterator support
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96 constexpr iterator begin() const noexcept;
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97 constexpr iterator end() const noexcept;
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98 constexpr reverse_iterator rbegin() const noexcept;
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99 constexpr reverse_iterator rend() const noexcept;
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100
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101 private:
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102 pointer data_; // exposition only
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103 size_type size_; // exposition only
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104 };
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105
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106 template<class T, size_t N>
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107 span(T (&)[N]) -> span<T, N>;
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108
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109 template<class T, size_t N>
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110 span(array<T, N>&) -> span<T, N>;
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111
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112 template<class T, size_t N>
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113 span(const array<T, N>&) -> span<const T, N>;
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114
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115 template<class Container>
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116 span(Container&) -> span<typename Container::value_type>;
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117
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118 template<class Container>
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119 span(const Container&) -> span<const typename Container::value_type>;
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120
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121 } // namespace std
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122
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123 */
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124
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125 #include <__config>
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126 #include <array> // for array
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127 #include <cstddef> // for byte
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128 #include <iterator> // for iterators
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129 #include <type_traits> // for remove_cv, etc
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130
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131 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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132 #pragma GCC system_header
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133 #endif
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134
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135 _LIBCPP_BEGIN_NAMESPACE_STD
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136
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137 #if _LIBCPP_STD_VER > 17
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138
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139 inline constexpr size_t dynamic_extent = (numeric_limits<size_t>::max)();
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140 template <typename _Tp, size_t _Extent = dynamic_extent> class span;
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141
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142
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143 template <class _Tp>
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144 struct __is_span_impl : public false_type {};
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145
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146 template <class _Tp, size_t _Extent>
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147 struct __is_span_impl<span<_Tp, _Extent>> : public true_type {};
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148
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149 template <class _Tp>
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150 struct __is_span : public __is_span_impl<remove_cv_t<_Tp>> {};
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151
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152 template <class _Tp>
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153 struct __is_std_array_impl : public false_type {};
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154
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155 template <class _Tp, size_t _Sz>
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156 struct __is_std_array_impl<array<_Tp, _Sz>> : public true_type {};
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157
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158 template <class _Tp>
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159 struct __is_std_array : public __is_std_array_impl<remove_cv_t<_Tp>> {};
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160
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161 template <class _Tp, class _ElementType, class = void>
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162 struct __is_span_compatible_container : public false_type {};
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163
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164 template <class _Tp, class _ElementType>
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165 struct __is_span_compatible_container<_Tp, _ElementType,
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166 void_t<
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167 // is not a specialization of span
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168 typename enable_if<!__is_span<_Tp>::value, nullptr_t>::type,
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169 // is not a specialization of array
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170 typename enable_if<!__is_std_array<_Tp>::value, nullptr_t>::type,
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171 // is_array_v<Container> is false,
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172 typename enable_if<!is_array_v<_Tp>, nullptr_t>::type,
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173 // data(cont) and size(cont) are well formed
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174 decltype(data(declval<_Tp>())),
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175 decltype(size(declval<_Tp>())),
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176 // remove_pointer_t<decltype(data(cont))>(*)[] is convertible to ElementType(*)[]
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177 typename enable_if<
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178 is_convertible_v<remove_pointer_t<decltype(data(declval<_Tp &>()))>(*)[],
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179 _ElementType(*)[]>,
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180 nullptr_t>::type
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181 >>
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182 : public true_type {};
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183
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184
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185 template <typename _Tp, size_t _Extent>
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186 class _LIBCPP_TEMPLATE_VIS span {
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187 public:
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188 // constants and types
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189 using element_type = _Tp;
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190 using value_type = remove_cv_t<_Tp>;
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191 using size_type = size_t;
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192 using difference_type = ptrdiff_t;
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193 using pointer = _Tp *;
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194 using const_pointer = const _Tp *;
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195 using reference = _Tp &;
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196 using const_reference = const _Tp &;
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197 using iterator = __wrap_iter<pointer>;
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198 using reverse_iterator = _VSTD::reverse_iterator<iterator>;
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199
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200 static constexpr size_type extent = _Extent;
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201
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202 // [span.cons], span constructors, copy, assignment, and destructor
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173
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203 template <size_t _Sz = _Extent, enable_if_t<_Sz == 0, nullptr_t> = nullptr>
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204 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr} {}
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150
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205
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206 constexpr span (const span&) noexcept = default;
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207 constexpr span& operator=(const span&) noexcept = default;
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208
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173
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209 _LIBCPP_INLINE_VISIBILITY constexpr explicit span(pointer __ptr, size_type __count) : __data{__ptr}
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150
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210 { (void)__count; _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (ptr, len)"); }
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173
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211 _LIBCPP_INLINE_VISIBILITY constexpr explicit span(pointer __f, pointer __l) : __data{__f}
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150
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212 { (void)__l; _LIBCPP_ASSERT(_Extent == distance(__f, __l), "size mismatch in span's constructor (ptr, ptr)"); }
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213
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214 _LIBCPP_INLINE_VISIBILITY constexpr span(element_type (&__arr)[_Extent]) noexcept : __data{__arr} {}
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173
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215
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216 template <class _OtherElementType,
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217 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
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218 _LIBCPP_INLINE_VISIBILITY
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219 constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {}
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220
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221 template <class _OtherElementType,
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222 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
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223 _LIBCPP_INLINE_VISIBILITY
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224 constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {}
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225
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226 template <class _Container>
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227 _LIBCPP_INLINE_VISIBILITY
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228 constexpr explicit span( _Container& __c,
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229 enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
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230 : __data{_VSTD::data(__c)} {
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231 _LIBCPP_ASSERT(_Extent == _VSTD::size(__c), "size mismatch in span's constructor (range)");
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232 }
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233
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234 template <class _Container>
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235 _LIBCPP_INLINE_VISIBILITY
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236 constexpr explicit span(const _Container& __c,
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237 enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
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238 : __data{_VSTD::data(__c)} {
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239 _LIBCPP_ASSERT(_Extent == _VSTD::size(__c), "size mismatch in span's constructor (range)");
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240 }
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150
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241
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242 template <class _OtherElementType>
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243 _LIBCPP_INLINE_VISIBILITY
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244 constexpr span(const span<_OtherElementType, _Extent>& __other,
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245 enable_if_t<
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246 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
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247 nullptr_t> = nullptr)
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248 : __data{__other.data()} {}
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249
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250 template <class _OtherElementType>
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251 _LIBCPP_INLINE_VISIBILITY
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173
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252 constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other,
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150
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253 enable_if_t<
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254 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
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255 nullptr_t> = nullptr) noexcept
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256 : __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); }
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257
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258
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259 // ~span() noexcept = default;
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260
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261 template <size_t _Count>
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262 _LIBCPP_INLINE_VISIBILITY
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263 constexpr span<element_type, _Count> first() const noexcept
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264 {
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265 static_assert(_Count <= _Extent, "Count out of range in span::first()");
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173
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266 return span<element_type, _Count>{data(), _Count};
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150
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267 }
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268
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269 template <size_t _Count>
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270 _LIBCPP_INLINE_VISIBILITY
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271 constexpr span<element_type, _Count> last() const noexcept
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272 {
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273 static_assert(_Count <= _Extent, "Count out of range in span::last()");
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173
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274 return span<element_type, _Count>{data() + size() - _Count, _Count};
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150
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275 }
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276
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277 _LIBCPP_INLINE_VISIBILITY
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278 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
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279 {
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280 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
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281 return {data(), __count};
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282 }
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283
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284 _LIBCPP_INLINE_VISIBILITY
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285 constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept
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286 {
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287 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
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288 return {data() + size() - __count, __count};
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289 }
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290
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291 template <size_t _Offset, size_t _Count = dynamic_extent>
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292 _LIBCPP_INLINE_VISIBILITY
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293 constexpr auto subspan() const noexcept
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294 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>
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295 {
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296 static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()");
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297 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, "Offset + count out of range in span::subspan()");
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173
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298
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299 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
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300 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
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150
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301 }
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302
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303
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304 _LIBCPP_INLINE_VISIBILITY
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305 constexpr span<element_type, dynamic_extent>
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306 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
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307 {
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308 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
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309 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)");
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310 if (__count == dynamic_extent)
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311 return {data() + __offset, size() - __offset};
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312 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)");
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313 return {data() + __offset, __count};
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314 }
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315
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316 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; }
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317 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
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318 _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; }
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319
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320 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
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321 {
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322 _LIBCPP_ASSERT(__idx < size(), "span<T,N>[] index out of bounds");
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323 return __data[__idx];
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324 }
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325
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326 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
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327 {
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173
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328 _LIBCPP_ASSERT(!empty(), "span<T, N>::front() on empty span");
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150
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329 return __data[0];
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330 }
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331
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332 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
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333 {
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173
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334 _LIBCPP_ASSERT(!empty(), "span<T, N>::back() on empty span");
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150
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335 return __data[size()-1];
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336 }
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337
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338 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
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339
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340 // [span.iter], span iterator support
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341 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
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342 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
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343 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
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344 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
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345
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346 _LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept
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173
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347 { return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte *>(data()), size_bytes()}; }
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150
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348
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349 _LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept
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173
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350 { return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte *>(data()), size_bytes()}; }
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150
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351
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352 private:
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353 pointer __data;
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354
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355 };
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356
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357
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358 template <typename _Tp>
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359 class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> {
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360 private:
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361
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362 public:
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363 // constants and types
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364 using element_type = _Tp;
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365 using value_type = remove_cv_t<_Tp>;
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366 using size_type = size_t;
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367 using difference_type = ptrdiff_t;
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368 using pointer = _Tp *;
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369 using const_pointer = const _Tp *;
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370 using reference = _Tp &;
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371 using const_reference = const _Tp &;
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372 using iterator = __wrap_iter<pointer>;
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373 using reverse_iterator = _VSTD::reverse_iterator<iterator>;
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374
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375 static constexpr size_type extent = dynamic_extent;
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376
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377 // [span.cons], span constructors, copy, assignment, and destructor
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378 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {}
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379
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380 constexpr span (const span&) noexcept = default;
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381 constexpr span& operator=(const span&) noexcept = default;
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382
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383 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}, __size{__count} {}
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384 _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}, __size{static_cast<size_t>(distance(__f, __l))} {}
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385
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386 template <size_t _Sz>
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387 _LIBCPP_INLINE_VISIBILITY
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388 constexpr span(element_type (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {}
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389
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173
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390 template <class _OtherElementType, size_t _Sz,
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391 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
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150
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392 _LIBCPP_INLINE_VISIBILITY
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173
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393 constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
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150
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394
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173
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395 template <class _OtherElementType, size_t _Sz,
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396 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr>
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150
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397 _LIBCPP_INLINE_VISIBILITY
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173
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398 constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {}
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150
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399
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400 template <class _Container>
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401 _LIBCPP_INLINE_VISIBILITY
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402 constexpr span( _Container& __c,
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403 enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
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404 : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
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405
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406 template <class _Container>
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407 _LIBCPP_INLINE_VISIBILITY
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408 constexpr span(const _Container& __c,
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409 enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
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410 : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
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411
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412
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413 template <class _OtherElementType, size_t _OtherExtent>
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414 _LIBCPP_INLINE_VISIBILITY
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415 constexpr span(const span<_OtherElementType, _OtherExtent>& __other,
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416 enable_if_t<
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417 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>,
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418 nullptr_t> = nullptr) noexcept
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419 : __data{__other.data()}, __size{__other.size()} {}
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420
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421 // ~span() noexcept = default;
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422
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423 template <size_t _Count>
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424 _LIBCPP_INLINE_VISIBILITY
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425 constexpr span<element_type, _Count> first() const noexcept
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426 {
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427 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()");
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173
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428 return span<element_type, _Count>{data(), _Count};
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150
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429 }
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430
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431 template <size_t _Count>
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432 _LIBCPP_INLINE_VISIBILITY
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433 constexpr span<element_type, _Count> last() const noexcept
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434 {
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435 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()");
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173
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436 return span<element_type, _Count>{data() + size() - _Count, _Count};
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150
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437 }
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438
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439 _LIBCPP_INLINE_VISIBILITY
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440 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
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441 {
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442 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
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443 return {data(), __count};
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444 }
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445
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446 _LIBCPP_INLINE_VISIBILITY
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447 constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept
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448 {
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449 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
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450 return {data() + size() - __count, __count};
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451 }
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452
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453 template <size_t _Offset, size_t _Count = dynamic_extent>
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454 _LIBCPP_INLINE_VISIBILITY
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455 constexpr span<element_type, _Count> subspan() const noexcept
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456 {
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457 _LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()");
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458 _LIBCPP_ASSERT(_Count == dynamic_extent || _Count <= size() - _Offset, "Offset + count out of range in span::subspan()");
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173
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459 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
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150
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460 }
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461
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462 constexpr span<element_type, dynamic_extent>
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463 _LIBCPP_INLINE_VISIBILITY
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464 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
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465 {
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466 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
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467 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)");
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468 if (__count == dynamic_extent)
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469 return {data() + __offset, size() - __offset};
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470 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)");
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471 return {data() + __offset, __count};
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472 }
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473
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474 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; }
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475 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); }
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476 _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; }
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477
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478 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
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479 {
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480 _LIBCPP_ASSERT(__idx < size(), "span<T>[] index out of bounds");
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481 return __data[__idx];
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482 }
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483
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484 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept
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485 {
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486 _LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span");
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487 return __data[0];
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488 }
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489
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490 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept
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491 {
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492 _LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span");
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493 return __data[size()-1];
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494 }
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495
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496
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497 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; }
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498
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499 // [span.iter], span iterator support
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500 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); }
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501 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); }
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502 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
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503 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
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504
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505 _LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept
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506 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; }
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507
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508 _LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept
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509 { return {reinterpret_cast<byte *>(data()), size_bytes()}; }
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510
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511 private:
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512 pointer __data;
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513 size_type __size;
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514 };
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515
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516 // as_bytes & as_writable_bytes
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517 template <class _Tp, size_t _Extent>
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518 _LIBCPP_INLINE_VISIBILITY
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519 auto as_bytes(span<_Tp, _Extent> __s) noexcept
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520 -> decltype(__s.__as_bytes())
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521 { return __s.__as_bytes(); }
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522
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523 template <class _Tp, size_t _Extent>
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524 _LIBCPP_INLINE_VISIBILITY
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525 auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept
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526 -> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())>
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527 { return __s.__as_writable_bytes(); }
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528
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529 // Deduction guides
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530 template<class _Tp, size_t _Sz>
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531 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
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532
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533 template<class _Tp, size_t _Sz>
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534 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
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535
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536 template<class _Tp, size_t _Sz>
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537 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
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538
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539 template<class _Container>
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540 span(_Container&) -> span<typename _Container::value_type>;
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541
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542 template<class _Container>
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543 span(const _Container&) -> span<const typename _Container::value_type>;
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544
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545 #endif // _LIBCPP_STD_VER > 17
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546
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547 _LIBCPP_END_NAMESPACE_STD
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548
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549 #endif // _LIBCPP_SPAN
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