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Showing content from https://en.cppreference.com/w/cpp/language/../string/basic_string_view/basic_string_view.html below:

std::basic_string_view<CharT,Traits>::basic_string_view - cppreference.com

constexpr basic_string_view() noexcept;

(1) (since C++17)

constexpr basic_string_view( const basic_string_view& other ) noexcept = default;

(2) (since C++17)

constexpr basic_string_view( const CharT* s, size_type count );

(3) (since C++17)

constexpr basic_string_view( const CharT* s );

(4) (since C++17)

template< class It, class End > constexpr basic_string_view( It first, End last );

(5) (since C++20)

template< class R > constexpr explicit basic_string_view( R&& r );

(6) (since C++23) (7) (since C++23) 1)

Default constructor. Constructs an empty

std::basic_string_view

. After construction,

data()

is equal to

nullptr

, and

size()

is equal to

â0â

2)

Copy constructor. Constructs a view of the same content as

other

. After construction,

data()

is equal to

other.data()

, and

size()

is equal to

other.size()

3)

Constructs a view of the first

count

characters of the character array starting with the element pointed by

s

can contain null characters. The behavior is undefined if

[s, s + count)

is not a valid range (even though the constructor may not access any of the elements of this range). After construction,

data()

is equal to

s

, and

size()

is equal to

count

4)

Constructs a view of the null-terminated character string pointed to by

s

, not including the terminating null character. The length of the view is determined as if by

Traits::length(s)

. The behavior is undefined if

[s, s + Traits::length(s))

is not a valid range. After construction,

data()

is equal to

s

, and

size()

is equal to

Traits::length(s)

7) std::basic_string_view cannot be constructed from nullptr.

[edit] Parameters other - another view to initialize the view with s - pointer to a character array or a C string to initialize the view with count - number of characters to include in the view first - iterator to the first character of the sequence last - iterator past the last character of the sequence or another sentinel r - a contiguous range that contains the sequence [edit] Complexity

1-3,5,6) Constant.

4) Linear in length of s.

[edit] Example

#include <array>
#include <iomanip>
#include <iostream>
#include <string>
#include <string_view>
 
int main()
{
    std::string cppstr = "Foo";
    std::string_view cppstr_v(cppstr); // overload (2), after
                                       // std::string::operator string_view
    std::cout << "1) cppstr_v: " << std::quoted(cppstr_v) << '\n';
 
    char array[3] = {'B', 'a', 'r'};
    std::string_view array_v(array, std::size(array)); // overload (3)
    std::cout << "2) array_v: " << std::quoted(array_v) << '\n';
 
    const char* one_0_two = "One\0Two";
 
    std::string_view one_two_v{one_0_two, 7}; // overload (3)
    std::cout << "3) one_two_v: \"";
    for (char c : one_two_v)
        std::cout << (c != '\0' ? c : '?');
    std::cout << "\", one_two_v.size(): " << one_two_v.size() << '\n';
 
    std::string_view one_v{one_0_two}; // overload (4)
    std::cout << "4) one_v: " << std::quoted(one_v) << ", one_v.size(): " 
              << one_v.size() << '\n';
 
    constexpr std::wstring_view wcstr_v = L"xyzzy"; // overload (4)
    std::cout << "5) wcstr_v.size(): " << wcstr_v.size() << '\n';
 
    std::array ar = {'P', 'u', 'b'};
    std::string_view ar_v(ar.begin(), ar.end()); // overload (5), C++20
    std::cout << "6) ar_v: " << std::quoted(ar_v) << '\n';
 
//  std::string_view ar_v2{ar}; // overload (6), OK in C++23
//  std::cout << "ar_v2: " << std::quoted(ar_v2) << '\n'; // ar_v2: "Pub"
 
    [[maybe_unused]] auto zero = [] { /* ... */ return nullptr; };
//  std::string_view s{zero()}; // overload (7), won't compile since C++23
}

Output:

1) cppstr_v: "Foo"
2) array_v: "Bar"
3) one_two_v: "One?Two", one_two_v.size(): 7
4) one_v: "One", one_v.size(): 3
5) wcstr_v.size(): 5
6) ar_v: "Pub"

[edit] See also assigns a view
(public member function) [edit] constructs a basic_string
(public member function of std::basic_string<CharT,Traits,Allocator>) [edit]

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