std::data

< cpp‎ | iterator
Defined in header <array>
Defined in header <deque>
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>
(since C++20)
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>
constexpr auto data(C& c) -> decltype(c.data());
 (1) (since C++17)
template <class C>
constexpr auto data(const C& c) -> decltype(c.data());
 (2) (since C++17)
template <class T, std::size_t N>
constexpr T* data(T (&array)[N]) noexcept;
 (3) (since C++17)
template <class E>
constexpr const E* data(std::initializer_list<E> il) noexcept;
 (4) (since C++17)

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 initializer list

Return value

A pointer to the block of memory containing the elements of the range.

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.

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

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

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