std::ranges::cdata

(since C++20)
(customization point object)

(since C++20)

Let CT be

• const std::remove_reference_t <T>& if the argument is an lvalue (i.e. T is an lvalue reference type),
• const T otherwise.

A call to ranges::cdata is expression-equivalent to ranges::data (static_cast<CT&&>(t)).

The return type is equivalent to std::remove_reference_t <ranges::range_reference_t <CT>>*.

(until C++23)

If the argument is an lvalue or ranges::enable_borrowed_range <std::remove_cv_t <T>> is true, then a call to ranges::cdata is expression-equivalent to:

• as-const-pointer (ranges::data (possibly-const-range (t))).

The return type is equivalent to std::remove_reference_t <ranges::range_const_reference_t <T>>*.

In all other cases, a call to ranges::cdata is ill-formed, which can result in substitution failure when the call appears in the immediate context of a template instantiation.

(since C++23)

#include <cstring>
#include <iostream>
#include <ranges>
#include <string>
 
int main()
{
 std::string src {"hello world!\n"};
 
// std::ranges::cdata(src)[0] = 'H'; // error, src.data() is treated as read-only
 std::ranges::data (src)[0] = 'H'; // OK, src.data() is a non-const storage
 
 char dst[20]; // storage for a C-style string
 std::strcpy (dst, std::ranges::cdata(src));
 // [data(src), data(src) + size(src)] is guaranteed to be an NTBS
 
 std::cout << dst;
}

Hello world!

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

obtains the pointer to the underlying array
(function template) [edit]