## Event

# Struct Event

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    pub struct Event { /* private fields */ }

Expand description

A readiness event.

`Event` is a readiness state paired with a `Token`. It is returned by `Poll::poll`.

For more documentation on polling and events, see `Poll`.

## Implementations§

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### impl Event

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#### pub fn token(&self) -> Token

Returns the event’s token.

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#### pub fn is_readable(&self) -> bool

Returns true if the event contains readable readiness.

##### §Notes

Out-of-band (OOB) data also triggers readable events. But most applications don’t actually read OOB data, this could leave an application open to a Denial-of-Service (Dos) attack, see https://github.com/sandstorm-io/sandstorm-website/blob/58f93346028c0576e8147627667328eaaf4be9fa/_posts/2015-04-08-osx-security-bug.md. However because Mio uses edge-triggers it will not result in an infinite loop as described in the article above.

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#### pub fn is_writable(&self) -> bool

Returns true if the event contains writable readiness.

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#### pub fn is_error(&self) -> bool

Returns true if the event contains error readiness.

Error events occur when the socket enters an error state. In this case, the socket will also receive a readable or writable event. Reading or writing to the socket will result in an error.

##### §Notes

Method is available on all platforms, but not all platforms trigger the error event.

The table below shows what flags are checked on what OS.

OS selector | Flag(s) checked
--- | ---
epoll | `EPOLLERR`
kqueue | `EV_ERROR` and `EV_EOF` with `fflags` set to `0`.

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#### pub fn is_read_closed(&self) -> bool

Returns true if the event contains read closed readiness.

##### §Notes

Read closed readiness can be expected after any of the following have occurred:

- The local stream has shutdown the read half of its socket
- The local stream has shutdown both the read half and the write half of its socket
- The peer stream has shutdown the write half its socket; this sends a `FIN` packet that has been received by the local stream

Method is a best effort implementation. While some platforms may not return readiness when read half is closed, it is guaranteed that false-positives will not occur.

The table below shows what flags are checked on what OS.

OS selector | Flag(s) checked
--- | ---
epoll | `EPOLLHUP`, or
| `EPOLLIN` and `EPOLLRDHUP`
kqueue | `EV_EOF`

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#### pub fn is_write_closed(&self) -> bool

Returns true if the event contains write closed readiness.

##### §Notes

On epoll this is essentially a check for `EPOLLHUP` flag as the local stream shutting down its write half does not trigger this event.

On kqueue the local stream shutting down the write half of its socket will trigger this event.

Method is a best effort implementation. While some platforms may not return readiness when write half is closed, it is guaranteed that false-positives will not occur.

The table below shows what flags are checked on what OS.

OS selector | Flag(s) checked
--- | ---
epoll | `EPOLLHUP`, or
| only `EPOLLERR`, or
| `EPOLLOUT` and `EPOLLERR`
kqueue | `EV_EOF`

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#### pub fn is_priority(&self) -> bool

Returns true if the event contains priority readiness.

##### §Notes

Method is available on all platforms, but not all platforms trigger the priority event.

The table below shows what flags are checked on what OS.

OS selector | Flag(s) checked
--- | ---
epoll | `EPOLLPRI`
kqueue | Not supported

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#### pub fn is_aio(&self) -> bool

Returns true if the event contains AIO readiness.

##### §Notes

Method is available on all platforms, but not all platforms support AIO.

The table below shows what flags are checked on what OS.

OS selector | Flag(s) checked
--- | ---
epoll | Not supported
kqueue1 | `EVFILT_AIO`

1: Only supported on DragonFly BSD, FreeBSD, iOS and macOS.

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#### pub fn is_lio(&self) -> bool

Returns true if the event contains LIO readiness.

##### §Notes

Method is available on all platforms, but only FreeBSD supports LIO. On FreeBSD this method checks the `EVFILT_LIO` flag.

## Trait Implementations§

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### impl Clone for Event

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#### fn clone(&self) -> Event

Returns a duplicate of the value. Read more
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#### fn clone_from(&mut self, source: &Self)

Performs copy-assignment from `source`. Read more
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### impl Debug for Event

When the alternate flag is enabled this will print platform specific details, for example the fields of the `kevent` structure on platforms that use `kqueue(2)`. Note however that the output of this implementation is not consider a part of the stable API.

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl Freeze for Event

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### impl RefUnwindSafe for Event

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### impl Send for Event

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### impl Sync for Event

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### impl Unpin for Event

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### impl UnwindSafe for Event

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> CloneToUninit for T
where T: Clone,

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#### unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (`clone_to_uninit`)
Performs copy-assignment from `self` to `dest`. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T> ToOwned for T
where T: Clone,

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#### type Owned = T

The resulting type after obtaining ownership.
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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.