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std::data

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.

Feature-test macro
`__cpp_lib_nonmember_container_access`

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!

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