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From cppreference.com
< cpp‎ | iterator
 
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Range access
(C++11)(C++14)
(C++14)(C++14)  
(C++11)(C++14)
(C++14)(C++14)  
(C++17)(C++20)
(C++17)
data
(C++17)
 
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 >
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().

Contents

[edit] Parameters

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

[edit] Return value

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

[edit] Exceptions

1) May throw implementation-defined exceptions.

[edit] 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()

[edit] 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();
}

[edit] Example

#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!

[edit] See also

obtains a pointer to the beginning of a contiguous range
(customization point object)[edit]
obtains a pointer to the beginning of a read-only contiguous range
(customization point object)[edit]