Struct tokio::sync::RwLockMappedWriteGuard
source · pub struct RwLockMappedWriteGuard<'a, T: ?Sized> { /* private fields */ }
Expand description
RAII structure used to release the exclusive write access of a lock when dropped.
This structure is created by mapping an RwLockWriteGuard
. It is a
separate type from RwLockWriteGuard
to disallow downgrading a mapped
guard, since doing so can cause undefined behavior.
Implementations§
source§impl<'a, T: ?Sized> RwLockMappedWriteGuard<'a, T>
impl<'a, T: ?Sized> RwLockMappedWriteGuard<'a, T>
sourcepub fn map<F, U: ?Sized>(this: Self, f: F) -> RwLockMappedWriteGuard<'a, U>
pub fn map<F, U: ?Sized>(this: Self, f: F) -> RwLockMappedWriteGuard<'a, U>
Makes a new RwLockMappedWriteGuard
for a component of the locked data.
This operation cannot fail as the RwLockMappedWriteGuard
passed in already
locked the data.
This is an associated function that needs to be used as
RwLockMappedWriteGuard::map(..)
. A method would interfere with methods
of the same name on the contents of the locked data.
This is an asynchronous version of RwLockWriteGuard::map
from the
parking_lot
crate.
§Examples
use tokio::sync::{RwLock, RwLockWriteGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let lock = RwLock::new(Foo(1));
{
let mut mapped = RwLockWriteGuard::map(lock.write().await, |f| &mut f.0);
*mapped = 2;
}
assert_eq!(Foo(2), *lock.read().await);
sourcepub fn try_map<F, U: ?Sized>(
this: Self,
f: F,
) -> Result<RwLockMappedWriteGuard<'a, U>, Self>
pub fn try_map<F, U: ?Sized>( this: Self, f: F, ) -> Result<RwLockMappedWriteGuard<'a, U>, Self>
Attempts to make a new RwLockMappedWriteGuard
for a component of
the locked data. The original guard is returned if the closure returns
None
.
This operation cannot fail as the RwLockMappedWriteGuard
passed in already
locked the data.
This is an associated function that needs to be
used as RwLockMappedWriteGuard::try_map(...)
. A method would interfere
with methods of the same name on the contents of the locked data.
This is an asynchronous version of RwLockWriteGuard::try_map
from
the parking_lot
crate.
§Examples
use tokio::sync::{RwLock, RwLockWriteGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let lock = RwLock::new(Foo(1));
{
let guard = lock.write().await;
let mut guard = RwLockWriteGuard::try_map(guard, |f| Some(&mut f.0)).expect("should not fail");
*guard = 2;
}
assert_eq!(Foo(2), *lock.read().await);