Difference between revisions of "cpp/container/vector/data"

Latest revision as of 12:45, 4 December 2020

Returns a pointer to the underlying array serving as element storage. The pointer is such that range [data(), data() + size()) is always a valid range, even if the container is empty (data() is not dereferenceable in that case).

[edit] Parameters

(none)

[edit] Return value

Pointer to the underlying element storage. For non-empty containers, the returned pointer compares equal to the address of the first element.

[edit] Complexity

Constant.

[edit] Notes

If size() is ​0​, data() may or may not return a null pointer.

[edit] Example

#include <cstddef>
#include <iostream>
#include <span>
#include <vector>
 
void pointer_func(const int* p, std::size_t size)
{
    std::cout << "data = ";
    for (std::size_t i = 0; i < size; ++i)
        std::cout << p[i] << ' ';
    std::cout << '\n';
}
 
void span_func(std::span<const int> data) // since C++20
{
    std::cout << "data = ";
    for (const int e : data)
        std::cout << e << ' ';
    std::cout << '\n';
}
 
int main()
{
    std::vector<int> container{1, 2, 3, 4};
 
    // Prefer container.data() over &container[0]
    pointer_func(container.data(), container.size());
 
    // std::span is a safer alternative to separated pointer/size.
    span_func({container.data(), container.size()});
}

data = 1 2 3 4
data = 1 2 3 4

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also