std::experimental::make_unique_resource_checked
| Defined in header <experimental/scope>
|
||
template< class R, class D, class S = std::decay_t<R> >
std::experimental::unique_resource<std::decay_t<R>, std::decay_t<D>>
make_unique_resource_checked( R&& r, const S& invalid, D&& d )
noexcept(/*see below*/);
|
(library fundamentals TS v3) | |
Creates a unique_resource, initializes its stored resource handle with std::forward<R>(r) and its deleter with std::forward<D>(d). The created unique_resource owns the resource if and only if bool(r == invalid) is false.
The program is ill-formed if the expression r == invalid cannot be contextually converted to bool, and the behavior is undefined if the conversion results in undefined behavior or throws an exception.
Paramaters
| r | - | a resource handle |
| d | - | a deleter to use to dispose the resource |
| invalid | - | a value indicating the resource handle is invalid |
Reture value
A unique_resource described above.
Exceptions
Any exception thrown in initialization of the stored resource handle and the deleter.
noexcept( std::is_nothrow_constructible_v<std::decay_t<R>, R> && std::is_nothrow_constructible_v<std::decay_t<D>, D> )
Notes
make_unique_resource_checked exists to avoid calling a deleter function with an invalid argument.
Resource handle r is either copied or moved into the return value, and the created unique_resource always holds an underlying resource handle with object type.
Example
#include <cstdio>
#include <experimental/scope>
int main()
{
// avoid calling fclose when fopen fails
auto file = std::experimental::make_unique_resource_checked(
std::fopen("potentially_nonexistent_file.txt", "r"),
nullptr,
[](std::FILE *fptr) { std::fclose(fptr); }
);
if (file.get())
std::puts("The file exists.");
else
std::puts("The file does not exist.");
}
Possible output:
The file does not exist.