Struct calloop::generic::NoIoDrop

pub struct NoIoDrop<T>(/* private fields */);

A wrapper around a type that doesn’t expose it mutably safely.

The EventSource trait’s Metadata type demands mutable access to the inner I/O source. However, the inner polling source used by calloop keeps the handle-based equivalent of an immutable pointer to the underlying object’s I/O handle. Therefore, if the inner source is dropped, this leaves behind a dangling pointer which immediately invokes undefined behavior on the next poll of the event loop.

In order to prevent this from happening, the Generic I/O source must not directly expose a mutable reference to the underlying handle. This type wraps around the underlying handle and easily allows users to take immutable (&) references to the type, but makes mutable (&mut) references unsafe to get. Therefore, it prevents the source from being moved out and dropped while it is still registered in the event loop.

Implementations

impl<T> NoIoDrop<T>

pub unsafe fn get_mut(&mut self) -> &mut T

Get a mutable reference.

Safety

The inner type’s I/O source must not be dropped.

Trait Implementations

impl<T: AsFd> AsFd for NoIoDrop<T>

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl<T> AsRef<T> for NoIoDrop<T>

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> Borrow<T> for NoIoDrop<T>

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T: Debug> Debug for NoIoDrop<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Deref for NoIoDrop<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.