std::data

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Iterator library

Iterator concepts
indirectly_readable (C++20) indirectly_writable (C++20) weakly_incrementable (C++20) incrementable (C++20) input_or_output_iterator (C++20) sentinel_for (C++20) sized_sentinel_for (C++20)	input_iterator (C++20) output_iterator (C++20) forward_iterator (C++20) bidirectional_iterator (C++20) random_access_iterator (C++20) contiguous_iterator (C++20)
Iterator primitives
iterator_traits input_iterator_tagoutput_iterator_tagforward_iterator_tagbidirectional_iterator_tagrandom_access_iterator_tagcontiguous_iterator_tag (C++20) iterator (deprecated in C++17)	incrementable_traits (C++20) indirectly_readable_traits (C++20) iter_value_titer_difference_titer_reference_titer_const_reference_titer_rvalue_reference_titer_common_reference_t (C++20)(C++20)(C++20)(C++23)(C++20)(C++20)
Algorithm concepts and utilities
Indirect callable concepts
indirectly_unary_invocableindirectly_regular_unary_invocable (C++20)(C++20)   indirect_unary_predicate (C++20)	indirect_binary_predicate (C++20) indirect_equivalence_relation (C++20) indirect_strict_weak_order (C++20)
Common algorithm requirements
indirectly_movable (C++20) indirectly_movable_storable (C++20) indirectly_copyable (C++20) indirectly_copyable_storable (C++20)	indirectly_swappable (C++20) indirectly_comparable (C++20) permutable (C++20) mergeable (C++20) sortable (C++20)
Utilities
indirect_result_t (C++20)	projected (C++20)
Iterator adaptors
reverse_iterator move_iterator (C++11) move_sentinel (C++20) common_iterator (C++20) counted_iterator (C++20) basic_const_iterator (C++23) const_iterator (C++23) const_sentinel (C++23) back_insert_iterator front_insert_iterator insert_iterator	make_reverse_iterator (C++14) make_move_iterator (C++11) default_sentinel_tdefault_sentinel (C++20)(C++20) unreachable_sentinel_tunreachable_sentinel (C++20)(C++20) make_const_iterator (C++23) make_const_sentinel (C++23) back_inserter front_inserter inserter
Stream iterators
istream_iterator ostream_iterator	istreambuf_iterator ostreambuf_iterator
Iterator customization points
ranges::iter_move (C++20)
ranges::iter_swap (C++20)
Iterator operations
advance distance prev (C++11) next (C++11)	ranges::advance (C++20) ranges::distance (C++20) ranges::prev (C++20) ranges::next (C++20)
Range access
begincbegin (C++11)(C++14) endcend (C++11)(C++14) sizessize (C++17)(C++20)	rbegincrbegin (C++14)(C++14) rendcrend (C++14)(C++14) empty (C++17) data (C++17)

 

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

Run this code

#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

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)