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std::basic_string_view(3) C++ Standard Libary std::basic_string_view(3) NAME std::basic_string_view - std::basic_string_view Synopsis Defined in header <string_view> template< class CharT, (since C++17) class Traits = std::char_traits<CharT> > class basic_string_view; The class template basic_string_view describes an object that can refer to a constant contiguous sequence of CharT with the first element of the sequence at position zero. For a basic_string_view str, pointers, iterators, and references to elements of str are invalidated when an operation invalidates a pointer in the range [str.data(), str.data() + str.size()). Every specialization of std::basic_string_view is a TriviallyCopy- able (since C++23) type. A typical implementation holds only two members: a pointer to con- stant CharT and a size. Several typedefs for common character types are provided: Defined in header <string_view> Type Definition std::string_view (C++17) std::basic_string_view<char> std::wstring_view (C++17) std::basic_string_view<wchar_t> std::u8string_view (C++20) std::basic_string_view<char8_t> std::u16string_view (C++17) std::basic_string_view<char16_t> std::u32string_view (C++17) std::basic_string_view<char32_t> Template parameters CharT - character type CharTraits class specifying the operations on the character type. Like for Traits - std::basic_string, Traits::char_type must name the same type as CharT or the program is ill-formed. Nested types Nested type Definition traits_type Traits value_type CharT pointer CharT* const_pointer const CharT* reference CharT& const_reference const CharT& implementation-defined constant LegacyRando- mAccessIterator, const_iterator and LegacyContiguousIterator (until C++20) ConstexprIterator, and contiguous_iterator (since C++20) whose value_type is CharT iterator const_iterator const_reverse_iterator std::reverse_iterator<const_iterator> reverse_iterator const_reverse_iterator size_type std::size_t difference_type std::ptrdiff_t Note: iterator and const_iterator are the same type because string views are views into constant character sequences. All requirements on the iterator types of a Container applies to the iterator and const_iterator types of basic_string_view as well. Member functions Constructors and assignment constructor constructs a basic_string_view (public member function) operator= assigns a view (public member function) Iterators begin returns an iterator to the beginning cbegin (public member function) end returns an iterator to the end cend (public member function) rbegin returns a reverse iterator to the beginning crbegin (public member function) rend returns a reverse iterator to the end crend (public member function) Element access operator[] accesses the specified character (public member function) at accesses the specified character with bounds checking (public member function) front accesses the first character (public member function) back accesses the last character (public member function) data returns a pointer to the first character of a view (public member function) Capacity size returns the number of characters length (public member function) max_size returns the maximum number of characters (public member function) empty checks whether the view is empty (public member function) Modifiers remove_prefix shrinks the view by moving its start forward (public member function) remove_suffix shrinks the view by moving its end backward (public member function) swap swaps the contents (public member function) Operations copy copies characters (public member function) substr returns a substring (public member function) compare compares two views (public member function) starts_with checks if the string view starts with the given prefix (C++20) (public member function) ends_with checks if the string view ends with the given suf- fix (C++20) (public member function) contains checks if the string view contains the given sub- string or (C++23) character (public member function) find find characters in the view (public member function) rfind find the last occurrence of a substring (public member function) find_first_of find first occurrence of characters (public member function) find_last_of find last occurrence of characters (public member function) find_first_not_of find first absence of characters (public member function) find_last_not_of find last absence of characters (public member function) Constants npos special value. The exact meaning depends on the context [static] (public static member constant) Non-member functions operator== operator!= operator< operator> operator<= operator>= operator<=> lexicographically compares two string views (C++17) (function template) (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (C++20) Input/output operator<< performs stream output on string views (C++17) (function template) Literals Defined in inline namespace std::literals::string_view_literals operator""sv creates a string view of a character array literal (C++17) (function) Helper classes std::hash<std::string_view> std::hash<std::wstring_view> std::hash<std::u8string_view> std::hash<std::u16string_view> std::hash<std::u32string_view> hash support for string views (C++17) (class template specialization) (C++17) (C++20) (C++17) (C++17) Helper templates template< class CharT, class Traits > inline constexpr bool (since C++20) ranges::enable_borrowed_range<std::basic_string_view<CharT, Traits>> = true; This specialization of ranges::enable_borrowed_range makes ba- sic_string_view satisfy borrowed_range. template< class CharT, class Traits > inline constexpr bool (since C++20) ranges::enable_view<std::basic_string_view<CharT, Traits>> = true; This specialization of ranges::enable_view makes basic_string_view satisfy view. Deduction guides (since C++20) Notes It is the programmer's responsibility to ensure that std::string_view does not outlive the pointed-to character array: std::string_view good{"a string literal"}; // "Good" case: `good` points to a static array. // String literals reside in persistent data storage. std::string_view bad{"a temporary string"s}; // "Bad" case: `bad` holds a dangling pointer since the std::string temporary, // created by std::operator""s, will be destroyed at the end of the statement. Specializations of std::basic_string_view are already trivially copyable types in all existing implementations, even before the formal requirement in- troduced in C++23. Feature-test macro Value Std Feature __cpp_lib_string_view 201606L (C++17) std::string_view 201803L (C++20) ConstexprIterator __cpp_lib_string_contains 202011L (C++23) contains Example // Run this code #include <iostream> #include <string_view> int main() { constexpr std::string_view unicode[]{"", "", "", ""}; for (int y{}, p{}; y != 6; ++y, p = ((p + 1) % 4)) { for (int x{}; x != 16; ++x) std::cout << unicode[p]; std::cout << '\n'; } } Output: Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior only pointers, iterators, and all point- ers, iterators, and references references LWG 3203 C++17 returned from the member functions to elements of of ba- sic_string_view basic_string_view might be may be in- validated invalidated See also basic_string stores and manipulates sequences of characters (class template) span a non-owning view over a contiguous sequence of ob- jects (C++20) (class template) initializer_list creates a temporary array in list-initialization and then (C++11) references it (class template) http://cppreference.com 2024.06.10 std::basic_string_view(3)
NAME | Synopsis | Template parameters | Member functions | Iterators | Element access | Capacity | Modifiers | Operations | Constants | Non-member functions | Input/output | Literals | Helper classes | Notes | Example | Output: | See also
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