class CharT,
class Traits = std::char_traits<CharT>
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 TriviallyCopyable type.
Several typedefs for common character types are provided:
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> [edit] Template parameters CharT - character type Traits - CharTraits class specifying the operations on the character type. Like for std::basic_string,Traits::char_type must name the same type as CharT or the program is ill-formed. [edit] Nested types 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,
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.
const_pointer data_ a pointer to the underlying sequence
size_type size_ the number of characters
basic_string_view
This specialization of ranges::enable_borrowed_range makes basic_string_view satisfy borrowed_range.
inline constexpr bool
This specialization of ranges::enable_view makes basic_string_view satisfy view.
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 introduced in C++23.
#include <iostream>
#include <string_view>
int main()
{
#define A "â"
#define B "â"
#define C "â"
constexpr std::string_view blocks[]{A B C, B A C, A C B, B C A};
for (int y{}, p{}; y != 8; ++y, p = ((p + 1) % 4))
{
for (char x{}; x != 29; ++x)
std::cout << blocks[p];
std::cout << '\n';
}
}
Output:
âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ âââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 3203 C++17 only pointers, iterators, and referencesbasic_string_view might be invalidated all pointers, iterators, and references
basic_string_view
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