std::basic_string_view<CharT,Traits>::data

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C++
 
Strings library
 
std::basic_string_view
 
constexpr const_pointer data() const noexcept;
 (since C++17)

Returns a pointer to the underlying character array. The pointer is such that the range [data(), data() + size()) is valid and the values in it correspond to the values of the view.

Parameters

(none)

Return value

A pointer to the underlying character array.

Complexity

Constant.

Notes

Unlike std::basic_string::data() and string literals, std::basic_string_view::data() returns a pointer to a buffer that is not necessarily null-terminated, for example a substring view (e.g. from remove_suffix). Therefore, it is typically a mistake to pass data() to a routine that takes just a const CharT* and expects a null-terminated string.

Example

Run this code
#include <cstring>
#include <cwchar>
#include <iostream>
#include <string>
#include <string_view>
 
int main()
{
    std::wstring_view wcstr_v = L"xyzzy";
    std::cout << std::wcslen(wcstr_v.data()) << '\n';
    // OK: the underlying character array is null-terminated
 
    char array[3] = {'B', 'a', 'r'};
    std::string_view array_v(array, sizeof array);
    // std::cout << std::strlen(array_v.data()) << '\n';
    // error: the underlying character array is not null-terminated
 
    std::string str(array_v.data(), array_v.size()); // OK
    std::cout << std::strlen(str.data()) << '\n';
    // OK: the underlying character array of a std::string is always null-terminated
}

Output: 

5
3

See also

 accesses the first character
(public member function)
accesses the last character
(public member function)
returns a pointer to the first character of a string
(public member function of std::basic_string<CharT,Traits,Allocator>)
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