std::data
From cppreference.com
Defined in header <array>
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Defined in header <deque>
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Defined in header <flat_map>
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Defined in header <flat_set>
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Defined in header <forward_list>
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Defined in header <inplace_vector>
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Defined in header <iterator>
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Defined in header <list>
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Defined in header <map>
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Defined in header <regex>
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Defined in header <set>
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Defined in header <span>
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Defined in header <string>
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Defined in header <string_view>
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Defined in header <unordered_map>
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Defined in header <unordered_set>
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Defined in header <vector>
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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 |
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__cpp_lib_nonmember_container_access |
201411L |
(C++17) | std::size(), std::data() , and std::empty()
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[edit] Possible implementation
First version |
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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
Run this code
#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
(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) |