std::ranges::cdata

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

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)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range primitives
iterator_tsentinel_t	range_size_trange_difference_t	range_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
views::all_tviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

Defined in header <ranges>
inline namespace /*unspecified*/ {     inline constexpr /*unspecified*/ cdata = /*unspecified*/; }		(since C++20) (customization point object)
Call signature
template< class T >     requires /* see below */ constexpr std::remove_reference_t<ranges::range_reference_t</*CT*/>>* cdata(T&& t);

Returns a pointer to the first element of a contiguous range denoted by a const-qualified argument.

Let CT be

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

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

If ranges::cdata(t) is valid, then it returns a pointer to a object.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

Customization point objects

The name ranges::cdata denotes a customization point object, which is a const function object of a literal semiregular class type (denoted, for exposition purposes, as cdata_ftor). All instances of cdata_ftor are equal. Thus, ranges::cdata can be copied freely and its copies can be used interchangeably.

Given a set of types Args..., if std::declval<Args>()... meet the requirements for arguments to ranges::cdata above, cdata_ftor will satisfy std::invocable<const cdata_ftor&, Args...>. Otherwise, no function call operator of cdata_ftor participates in overload resolution.

Example

Run this code

#include <cstring>
#include <iostream>
#include <ranges>
#include <string>
 
int main()
{
    std::string src {"Hello world!\n"};
 
    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;
}

Output:

Hello world!

See also

ranges::data (C++20)	obtains a pointer to the beginning of a contiguous range (customization point object)
data (C++17)	obtains the pointer to the underlying array (function template)