std::string_view data() method
- since 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
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
#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
}
5
3
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