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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 char-like objects with the first el- ement of the sequence at position zero. 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 - basic_string, Traits::char_type must name the same type as CharT or the program is ill-formed. Member types Member 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 , ConstexprIterator (since C++20) and const_iterator LegacyContiguousIterator (until C++20) 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 (C++17) (public member function) operator= assigns a view (C++17) (public member function) Iterators begin returns an iterator to the beginning cbegin (public member function) (C++17) end returns an iterator to the end cend (public member function) (C++17) rbegin returns a reverse iterator to the beginning crbegin (public member function) (C++17) rend returns a reverse iterator to the end crend (public member function) (C++17) Element access operator[] accesses the specified character (C++17) (public member function) at accesses the specified character with bounds checking (C++17) (public member function) front accesses the first character (C++17) (public member function) back accesses the last character (C++17) (public member function) data returns a pointer to the first character of a view (C++17) (public member function) Capacity size returns the number of characters length (public member function) (C++17) max_size returns the maximum number of characters (C++17) (public member function) empty checks whether the view is empty (C++17) (public member function) Modifiers remove_prefix shrinks the view by moving its start forward (C++17) (public member function) remove_suffix shrinks the view by moving its end backward (C++17) (public member function) swap swaps the contents (C++17) (public member function) Operations copy copies characters (C++17) (public member function) substr returns a substring (C++17) (public member function) compare compares two views (C++17) (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 (C++17) (public member function) rfind find the last occurrence of a substring (C++17) (public member function) find_first_of find first occurrence of characters (C++17) (public member function) find_last_of find last occurrence of characters (C++17) (public member function) find_first_not_of find first absence of characters (C++17) (public member function) find_last_not_of find last absence of characters (C++17) (public member function) Constants npos special value. The exact meaning depends on the context [static] (C++17) (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 ranges::enable_borrowed_range<std::basic_string_view<CharT, Traits>> = C++20) 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 usually // reside in persistent data segments. 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: __cpp_lib_string_view 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'; } } Possible output: 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 2022.07.31 std::basic_string_view(3)
NAME | Synopsis | Template parameters | Member types | Member functions | Iterators | Element access | Capacity | Modifiers | Operations | Constants | Non-member functions | Input/output | Literals | Helper classes | Notes | Example | Possible output: | See also
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