Struct tokio::io::Registration

pub struct Registration { /* private fields */ }

Associates an I/O resource with the reactor instance that drives it.

A registration represents an I/O resource registered with a Reactor such that it will receive task notifications on readiness. This is the lowest level API for integrating with a reactor.

The association between an I/O resource is made by calling new. Once the association is established, it remains established until the registration instance is dropped.

A registration instance represents two separate readiness streams. One for the read readiness and one for write readiness. These streams are independent and can be consumed from separate tasks.

Note: while Registration is Sync, the caller must ensure that there are at most two tasks that use a registration instance concurrently. One task for poll_read_ready and one task for poll_write_ready. While violating this requirement is “safe” from a Rust memory safety point of view, it will result in unexpected behavior in the form of lost notifications and tasks hanging.

Platform-specific events

Registration also allows receiving platform-specific mio::Ready events. These events are included as part of the read readiness event stream. The write readiness event stream is only for Ready::writable() events.

Implementations

impl Registration

pub fn new<T>(io: &T) -> Result<Registration> where
    T: Evented, 

Registers the I/O resource with the default reactor.

Return

• Ok if the registration happened successfully
• Err if an error was encountered during registration

Panics

This function panics if thread-local runtime is not set.

The runtime is usually set implicitly when this function is called from a future driven by a tokio runtime, otherwise runtime can be set explicitly with Handle::enter function.

pub fn new_with_ready<T>(io: &T, ready: Ready) -> Result<Registration> where
    T: Evented, 

Registers the I/O resource with the default reactor, for a specific mio::Ready state. new_with_ready should be used over new when you need control over the readiness state, such as when a file descriptor only allows reads. This does not add hup or error so if you are interested in those states, you will need to add them to the readiness state passed to this function.

An example to listen to read only

#[cfg(unix)]
    mio::Ready::from_usize(
        mio::Ready::readable().as_usize()
        | mio::unix::UnixReady::error().as_usize()
        | mio::unix::UnixReady::hup().as_usize()
    );

Return

• Ok if the registration happened successfully
• Err if an error was encountered during registration

Panics

This function panics if thread-local runtime is not set.

The runtime is usually set implicitly when this function is called from a future driven by a tokio runtime, otherwise runtime can be set explicitly with Handle::enter function.

pub fn deregister<T>(&mut self, io: &T) -> Result<()> where
    T: Evented, 

Deregisters the I/O resource from the reactor it is associated with.

This function must be called before the I/O resource associated with the registration is dropped.

Note that deregistering does not guarantee that the I/O resource can be registered with a different reactor. Some I/O resource types can only be associated with a single reactor instance for their lifetime.

Return

If the deregistration was successful, Ok is returned. Any calls to Reactor::turn that happen after a successful call to deregister will no longer result in notifications getting sent for this registration.

Err is returned if an error is encountered.

pub fn poll_read_ready(&self, cx: &mut Context<'_>) -> Poll<Result<Ready>>

Polls for events on the I/O resource’s read readiness stream.

If the I/O resource receives a new read readiness event since the last call to poll_read_ready, it is returned. If it has not, the current task is notified once a new event is received.

All events except HUP are edge-triggered. Once HUP is returned, the function will always return Ready(HUP). This should be treated as the end of the readiness stream.

Return value

There are several possible return values:

• Poll::Ready(Ok(readiness)) means that the I/O resource has received a new readiness event. The readiness value is included.

• Poll::Pending means that no new readiness events have been received since the last call to poll_read_ready.

• Poll::Ready(Err(err)) means that the registration has encountered an error. This could represent a permanent internal error for example.

Panics

This function will panic if called from outside of a task context.

pub fn take_read_ready(&self) -> Result<Option<Ready>>

Consume any pending read readiness event.

This function is identical to poll_read_ready except that it will not notify the current task when a new event is received. As such, it is safe to call this function from outside of a task context.

pub fn poll_write_ready(&self, cx: &mut Context<'_>) -> Poll<Result<Ready>>

Polls for events on the I/O resource’s write readiness stream.

If the I/O resource receives a new write readiness event since the last call to poll_write_ready, it is returned. If it has not, the current task is notified once a new event is received.

All events except HUP are edge-triggered. Once HUP is returned, the function will always return Ready(HUP). This should be treated as the end of the readiness stream.

Return value

There are several possible return values:

• Poll::Ready(Ok(readiness)) means that the I/O resource has received a new readiness event. The readiness value is included.

• Poll::Pending means that no new readiness events have been received since the last call to poll_write_ready.

• Poll::Ready(Err(err)) means that the registration has encountered an error. This could represent a permanent internal error for example.

Panics

This function will panic if called from outside of a task context.

pub fn take_write_ready(&self) -> Result<Option<Ready>>

Consumes any pending write readiness event.

This function is identical to poll_write_ready except that it will not notify the current task when a new event is received. As such, it is safe to call this function from outside of a task context.

Trait Implementations

impl Debug for Registration

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

Formats the value using the given formatter.

impl Drop for Registration

fn drop(&mut self)

Executes the destructor for this type.

impl Send for Registration

impl Sync for Registration