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 element of the
sequence at position zero.

Every specialization of std::basic_string_view is a TriviallyCopyable (since C++23)
type.

A typical implementation holds only two members: a pointer to constant 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 LegacyRandomAccessIterator
, 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 suffix
(C++20) (public member function)
contains checks if the string view contains the given substring 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 basic_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 introduced 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 objects
(C++20) (class template)
initializer_list creates a temporary array in list-initialization and then
(C++11) references it
(class template)