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sync: remove RwLockWriteGuard::map and RwLockWriteGuard::try_map #3345

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Dec 25, 2020
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sync: remove RwLockWriteGuard::map and RwLockWriteGuard::try_map #3345

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108 changes: 0 additions & 108 deletions tokio/src/sync/rwlock.rs
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Expand Up @@ -237,114 +237,6 @@ pub struct RwLockWriteGuard<'a, T: ?Sized> {
}

impl<'a, T: ?Sized> RwLockWriteGuard<'a, T> {
/// Make a new `RwLockWriteGuard` for a component of the locked data.
///
/// This operation cannot fail as the `RwLockWriteGuard` passed in already
/// locked the data.
///
/// This is an associated function that needs to be used as
/// `RwLockWriteGuard::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].
///
/// [`RwLockWriteGuard::map`]: https://docs.rs/lock_api/latest/lock_api/struct.RwLockWriteGuard.html#method.map
/// [`parking_lot` crate]: https://crates.io/crates/parking_lot
///
/// # Examples
///
/// ```
/// use tokio::sync::{RwLock, RwLockWriteGuard};
///
/// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
/// struct Foo(u32);
///
/// # #[tokio::main]
/// # async fn main() {
/// 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);
/// # }
/// ```
#[inline]
pub fn map<F, U: ?Sized>(mut this: Self, f: F) -> RwLockWriteGuard<'a, U>
where
F: FnOnce(&mut T) -> &mut U,
{
let data = f(&mut *this) as *mut U;
let s = this.s;
// NB: Forget to avoid drop impl from being called.
mem::forget(this);
RwLockWriteGuard {
s,
data,
marker: marker::PhantomData,
}
}

/// Attempts to make a new [`RwLockWriteGuard`] for a component of
/// the locked data. The original guard is returned if the closure returns
/// `None`.
///
/// This operation cannot fail as the `RwLockWriteGuard` passed in already
/// locked the data.
///
/// This is an associated function that needs to be
/// used as `RwLockWriteGuard::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].
///
/// [`RwLockWriteGuard::try_map`]: https://docs.rs/lock_api/latest/lock_api/struct.RwLockWriteGuard.html#method.try_map
/// [`parking_lot` crate]: https://crates.io/crates/parking_lot
///
/// # Examples
///
/// ```
/// use tokio::sync::{RwLock, RwLockWriteGuard};
///
/// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
/// struct Foo(u32);
///
/// # #[tokio::main]
/// # async fn main() {
/// 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);
/// # }
/// ```
#[inline]
pub fn try_map<F, U: ?Sized>(mut this: Self, f: F) -> Result<RwLockWriteGuard<'a, U>, Self>
where
F: FnOnce(&mut T) -> Option<&mut U>,
{
let data = match f(&mut *this) {
Some(data) => data as *mut U,
None => return Err(this),
};
let s = this.s;
// NB: Forget to avoid drop impl from being called.
mem::forget(this);
Ok(RwLockWriteGuard {
s,
data,
marker: marker::PhantomData,
})
}

/// Atomically downgrades a write lock into a read lock without allowing
/// any writers to take exclusive access of the lock in the meantime.
///
Expand Down