Struct evmap::ReadGuard

pub struct ReadGuard<'rh, T> where
    T: ?Sized,  { /* fields omitted */ }

A guard wrapping a live reference into a left-right protected T.

As long as this guard lives, the T being read cannot change. If a writer attempts to call WriteHandle::publish, that call will block until this guard is dropped.

To scope the guard to a subset of the data in T, use map and try_map.

Implementations

impl<'rh, T> ReadGuard<'rh, T> where
    T: ?Sized, 

pub fn map<F, U>(orig: ReadGuard<'rh, T>, f: F) -> ReadGuard<'rh, U> where
    F: for<'a> FnOnce(&'a T) -> &'a U,
    U: ?Sized, 

Makes a new ReadGuard for a component of the borrowed data.

This is an associated function that needs to be used as ReadGuard::map(...), since a method would interfere with methods of the same name on the contents of a Readguard used through Deref.

Examples

use left_right::{ReadGuard, ReadHandle};

fn get_str(handle: &ReadHandle<Vec<(String, i32)>>, i: usize) -> Option<ReadGuard<'_, str>> {
    handle.enter().map(|guard| {
        ReadGuard::map(guard, |t| {
            &*t[i].0
        })
    })
}

pub fn try_map<F, U>(orig: ReadGuard<'rh, T>, f: F) -> Option<ReadGuard<'rh, U>> where
    F: for<'a> FnOnce(&'a T) -> Option<&'a U>,
    U: ?Sized, 

Makes a new ReadGuard for a component of the borrowed data that may not exist.

This method differs from map in that it drops the guard if the closure maps to None. This allows you to "lift" a ReadGuard<Option<T>> into an Option<ReadGuard<T>>.

This is an associated function that needs to be used as ReadGuard::try_map(...), since a method would interfere with methods of the same name on the contents of a Readguard used through Deref.

Examples

use left_right::{ReadGuard, ReadHandle};

fn try_get_str(handle: &ReadHandle<Vec<(String, i32)>>, i: usize) -> Option<ReadGuard<'_, str>> {
    handle.enter().and_then(|guard| {
        ReadGuard::try_map(guard, |t| {
            t.get(i).map(|v| &*v.0)
        })
    })
}

Trait Implementations

impl<'rh, T> AsRef<T> for ReadGuard<'rh, T> where
    T: ?Sized, 

pub fn as_ref(&self) -> &T

Performs the conversion.

impl<'rh, T> Debug for ReadGuard<'rh, T> where
    T: Debug + ?Sized, 

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

Formats the value using the given formatter.

impl<'rh, T> Deref for ReadGuard<'rh, T> where
    T: ?Sized, 

type Target = T

The resulting type after dereferencing.

pub fn deref(&self) -> &<ReadGuard<'rh, T> as Deref>::Target

Dereferences the value.

impl<'rh, T> Drop for ReadGuard<'rh, T> where
    T: ?Sized, 

pub fn drop(&mut self)

Executes the destructor for this type.