NAME¶

std::data - std::data

Synopsis¶

Defined in header <array>
Defined in header <deque>
Defined in header <flat_map>
Defined in header <flat_set>
Defined in header <forward_list>
Defined in header <iterator>
Defined in header <list>
Defined in header <map>
Defined in header <regex>
Defined in header <set>
Defined in header <span>
Defined in header <string>
Defined in header <string_view>
Defined in header <unordered_map>
Defined in header <unordered_set>
Defined in header <vector>
template< class C > (1) (since C++17)
constexpr auto data( C& c ) -> decltype(c.data());
template< class C > (2) (since C++17)
constexpr auto data( const C& c ) -> decltype(c.data());
template< class T, std::size_t N > (3) (since C++17)
constexpr T* data( T (&array)[N] ) noexcept;
template< class E > (4) (since C++17)
constexpr const E* data( std::initializer_list<E> il ) noexcept;

Returns a pointer to the block of memory containing the elements of the range.

1,2) Returns c.data().
3) Returns array.
4) Returns il.begin().

Parameters¶

c - a container or view with a data() member function
array - an array of arbitrary type
il - an std::initializer_list

Return value¶

1,2) c.data()
3) array
4) il.begin()

Exceptions¶

1) May throw implementation-defined exceptions.

Notes¶

The overload for std::initializer_list is necessary because it does not have a
member function data.

Feature-test macro Value Std Feature
__cpp_lib_nonmember_container_access 201411L (C++17) std::size(), std::data(), and
std::empty()

Possible implementation¶

First version¶

template<class C>
constexpr auto data(C& c) -> decltype(c.data())
{
return c.data();
}

Second version¶

template<class C>
constexpr auto data(const C& c) -> decltype(c.data())
{
return c.data();
}
Third version
template<class T, std::size_t N>
constexpr T* data(T (&array)[N]) noexcept
{
return array;
}
Fourth version
template<class E>
constexpr const E* data(std::initializer_list<E> il) noexcept
{
return il.begin();
}

Example¶

// Run this code

#include <cstring>
#include <iostream>
#include <string>

int main()
{
std::string s{"Hello world!\n"};

char a[20]; // storage for a C-style string
std::strcpy(a, std::data(s));
// [s.data(), s.data() + s.size()] is guaranteed to be an NTBS since C++11

std::cout << a;
}

Output:¶

Hello world!

See also¶

ranges::data obtains a pointer to the beginning of a contiguous range
(C++20) (customization point object)
ranges::cdata obtains a pointer to the beginning of a read-only contiguous range
(C++20) (customization point object)