std::string_view data() method

od C++17

// Const version only
constexpr const_pointer data() const noexcept;

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 storage.

Complexity

Constant - O(1).

Notes

uwaga

Unlike std::string::data() and string literals, std::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

Main.cpp

#include <iostream>
#include <cstring>
#include <cwchar>
#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