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sync: add examples for SemaphorePermit, OwnedSemaphorePermit #6477

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merged 5 commits into from
Apr 12, 2024
Merged

sync: add examples for SemaphorePermit, OwnedSemaphorePermit #6477

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b1faf5c
sync: add examples for `SemaphorePermit`, `OwnedSemaphorePermit`
mox692 Apr 8, 2024
1f67fbe
delete unnecessary wrapper comments
mox692 Apr 11, 2024
9ce0e07
mention Drop in forget's doc comment
mox692 Apr 11, 2024
45954ac
fix comment
mox692 Apr 11, 2024
c5fd809
Merge remote-tracking branch 'origin' into add_semaphore_permit_examples
mox692 Apr 11, 2024
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122 changes: 122 additions & 0 deletions tokio/src/sync/semaphore.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -968,6 +968,25 @@ impl<'a> SemaphorePermit<'a> {
/// Forgets the permit **without** releasing it back to the semaphore.
/// This can be used to reduce the amount of permits available from a
/// semaphore.
///
/// # Examples
///
/// ```
/// # fn main() {
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/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(10));
/// {
/// let permit = sem.try_acquire_many(5).unwrap();
/// assert_eq!(sem.available_permits(), 5);
/// permit.forget();
/// }
///
/// // Since we forgot the permit, available permits won't go back to its initial value.
/// assert_eq!(sem.available_permits(), 5);
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/// # }
/// ```
pub fn forget(mut self) {
self.permits = 0;
}
Expand All @@ -981,6 +1000,31 @@ impl<'a> SemaphorePermit<'a> {
///
/// This function panics if permits from different [`Semaphore`] instances
/// are merged.
///
/// # Examples
///
/// ```
/// # fn main() {
/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(10));
/// let mut permit = sem.try_acquire().unwrap();
///
/// for _ in 0..9 {
/// let _permit = sem.try_acquire().unwrap();
/// // Merge individual permits into a single one.
/// permit.merge(_permit)
/// }
///
/// assert_eq!(sem.available_permits(), 0);
///
/// // Release all permits in a single batch.
/// drop(permit);
///
/// assert_eq!(sem.available_permits(), 10);
/// # }
/// ```
#[track_caller]
pub fn merge(&mut self, mut other: Self) {
assert!(
Expand All @@ -994,6 +1038,23 @@ impl<'a> SemaphorePermit<'a> {
/// Splits `n` permits from `self` and returns a new [`SemaphorePermit`] instance that holds `n` permits.
///
/// If there are insufficient permits and it's not possible to reduce by `n`, returns `None`.
///
/// # Examples
///
/// ```
/// # fn main() {
/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(3));
///
/// let mut p1 = sem.try_acquire_many(3).unwrap();
/// let p2 = p1.split(1).unwrap();
///
/// assert_eq!(p1.num_permits(), 2);
/// assert_eq!(p2.num_permits(), 1);
/// # }
/// ```
pub fn split(&mut self, n: u32) -> Option<Self> {
if n > self.permits {
return None;
Expand All @@ -1017,6 +1078,25 @@ impl OwnedSemaphorePermit {
/// Forgets the permit **without** releasing it back to the semaphore.
/// This can be used to reduce the amount of permits available from a
/// semaphore.
///
/// # Examples
///
/// ```
/// # fn main() {
/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(10));
/// {
/// let permit = sem.clone().try_acquire_many_owned(5).unwrap();
/// assert_eq!(sem.available_permits(), 5);
/// permit.forget();
/// }
///
/// // Since we forgot the permit, available permits won't go back to its initial value.
/// assert_eq!(sem.available_permits(), 5);
/// # }
/// ```
pub fn forget(mut self) {
self.permits = 0;
}
Expand All @@ -1030,6 +1110,31 @@ impl OwnedSemaphorePermit {
///
/// This function panics if permits from different [`Semaphore`] instances
/// are merged.
///
/// # Examples
///
/// ```
/// # fn main() {
/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(10));
/// let mut permit = sem.clone().try_acquire_owned().unwrap();
///
/// for _ in 0..9 {
/// let _permit = sem.clone().try_acquire_owned().unwrap();
/// // Merge individual permits into a single one.
/// permit.merge(_permit)
/// }
///
/// assert_eq!(sem.available_permits(), 0);
///
/// // Release all permits in a single batch.
/// drop(permit);
///
/// assert_eq!(sem.available_permits(), 10);
/// # }
/// ```
#[track_caller]
pub fn merge(&mut self, mut other: Self) {
assert!(
Expand All @@ -1047,6 +1152,23 @@ impl OwnedSemaphorePermit {
/// # Note
///
/// It will clone the owned `Arc<Semaphore>` to construct the new instance.
///
/// # Examples
///
/// ```
/// # fn main() {
/// use std::sync::Arc;
/// use tokio::sync::Semaphore;
///
/// let sem = Arc::new(Semaphore::new(3));
///
/// let mut p1 = sem.try_acquire_many_owned(3).unwrap();
/// let p2 = p1.split(1).unwrap();
///
/// assert_eq!(p1.num_permits(), 2);
/// assert_eq!(p2.num_permits(), 1);
/// # }
/// ```
pub fn split(&mut self, n: u32) -> Option<Self> {
if n > self.permits {
return None;
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