std::data - cppreference.com (original) (raw)

Defined in header
Defined in header
Defined in header <flat_map>
Defined in header <flat_set>
Defined in header <forward_list>
Defined in header <inplace_vector>
Defined in header
Defined in header
Defined in header
Defined in header
Defined in header
Defined in header
Defined in header
Defined in header <string_view>
Defined in header <unordered_map>
Defined in header <unordered_set>
Defined in header
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().

  1. Returns array.

  2. 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()

  1. array

  2. 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 #include #include   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:

[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] |