std::basic_string_view
Defined in header <string_view> |
||
---|---|---|
template< class CharT, class Traits = std::char_traits<CharT> > class basic_string_view; |
(since C++17) |
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 |
(since C++23) |
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 |
Traits | - | CharTraits class specifying the operations on the character type. Like for 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& |
const_iterator |
implementation-defined constant LegacyRandomAccessIterator, ConstexprIterator (since C++20) and 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 |
|
(C++17)
|
constructs a basic_string_view (public member function) |
(C++17)
|
assigns a view (public member function) |
Iterators |
|
(C++17)
|
returns an iterator to the beginning (public member function) |
(C++17)
|
returns an iterator to the end (public member function) |
(C++17)
|
returns a reverse iterator to the beginning (public member function) |
(C++17)
|
returns a reverse iterator to the end (public member function) |
Element access |
|
(C++17)
|
accesses the specified character (public member function) |
(C++17)
|
accesses the specified character with bounds checking (public member function) |
(C++17)
|
accesses the first character (public member function) |
(C++17)
|
accesses the last character (public member function) |
(C++17)
|
returns a pointer to the first character of a view (public member function) |
Capacity |
|
(C++17)
|
returns the number of characters (public member function) |
(C++17)
|
returns the maximum number of characters (public member function) |
(C++17)
|
checks whether the view is empty (public member function) |
Modifiers |
|
(C++17)
|
shrinks the view by moving its start forward (public member function) |
(C++17)
|
shrinks the view by moving its end backward (public member function) |
(C++17)
|
swaps the contents (public member function) |
Operations |
|
(C++17)
|
copies characters (public member function) |
(C++17)
|
returns a substring (public member function) |
(C++17)
|
compares two views (public member function) |
(C++20)
|
checks if the string view starts with the given prefix (public member function) |
(C++20)
|
checks if the string view ends with the given suffix (public member function) |
(C++23)
|
checks if the string view contains the given substring or character (public member function) |
(C++17)
|
find characters in the view (public member function) |
(C++17)
|
find the last occurrence of a substring (public member function) |
(C++17)
|
find first occurrence of characters (public member function) |
(C++17)
|
find last occurrence of characters (public member function) |
(C++17)
|
find first absence of characters (public member function) |
(C++17)
|
find last absence of characters (public member function) |
Constants |
|
[static] (C++17)
|
special value. The exact meaning depends on the context (public static member constant) |
Non-member functions
(C++17)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)
|
lexicographically compares two string views (function template) |
Input/output |
|
(C++17)
|
performs stream output on string views (function template) |
Literals
Defined in inline namespace std::literals::string_view_literals |
|
---|---|
(C++17)
|
Creates a string view of a character array literal (function) |
Helper classes
(C++17)(C++17)(C++20)(C++17)(C++17)
|
hash support for string views (class template specialization) |
Helper templates
template<class CharT, class Traits> inline constexpr bool ranges::enable_borrowed_range<std::basic_string_view<CharT, Traits>> = true; |
(since C++20) |
This specialization of ranges::enable_borrowed_range
makes basic_string_view
satisfy borrowed_range
.
template<class CharT, class Traits> inline constexpr bool ranges::enable_view<std::basic_string_view<CharT, Traits>> = true; |
(since C++20) |
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 testing macro: __cpp_lib_string_view
.
Example
#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
stores and manipulates sequences of characters (class template) |
|
(C++20)
|
a non-owning view over a contiguous sequence of objects (class template) |
(C++11)
|
creates a temporary array in list-initialization and then references it (class template) |
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