syncs

Documentation

Overview

Package syncs contains additional sync types and functionality.

Index

• func AssertLocked(m *sync.Mutex)
• func AssertRLocked(rw *sync.RWMutex)
• func AssertWLocked(rw *sync.RWMutex)
• func ClosedChan() <-chan struct{}
• func Watch(ctx context.Context, mu sync.Locker, tick, max time.Duration) chan time.Duration
• type AtomicValue
  • func (v *AtomicValue[T]) CompareAndSwap(oldV, newV T) (swapped bool)
  • func (v *AtomicValue[T]) Load() T
  • func (v *AtomicValue[T]) LoadOk() (_ T, ok bool)
  • func (v *AtomicValue[T]) Store(x T)
  • func (v *AtomicValue[T]) Swap(x T) (old T)
• type Map
  • func (m *Map[K, V]) Delete(key K)
  • func (m *Map[K, V]) Len() int
  • func (m *Map[K, V]) Load(key K) (value V, ok bool)
  • func (m *Map[K, V]) LoadAndDelete(key K) (value V, loaded bool)
  • func (m *Map[K, V]) LoadOrStore(key K, value V) (actual V, loaded bool)
  • func (m *Map[K, V]) Range(f func(key K, value V) bool)
  • func (m *Map[K, V]) Store(key K, value V)
• type Semaphore
  • func NewSemaphore(n int) Semaphore
  • func (s Semaphore) Acquire()
  • func (s Semaphore) AcquireContext(ctx context.Context) bool
  • func (s Semaphore) Release()
  • func (s Semaphore) TryAcquire() bool
• type ShardedMap
  • func NewShardedMap[K comparable, V any](shards int, shard func(K) int) *ShardedMap[K, V]
  • func (m *ShardedMap[K, V]) Contains(key K) bool
  • func (m *ShardedMap[K, V]) Delete(key K) (shrunk bool)
  • func (m *ShardedMap[K, V]) Get(key K) (value V)
  • func (m *ShardedMap[K, V]) GetOk(key K) (value V, ok bool)
  • func (m *ShardedMap[K, V]) Len() int
  • func (m *ShardedMap[K, V]) Mutate(key K, mutator func(oldValue V, oldValueExisted bool) (newValue V, keep bool)) (sizeDelta int)
  • func (m *ShardedMap[K, V]) Set(key K, value V) (grew bool)
• type WaitGroup
  • func (wg *WaitGroup) Go(f func())
• type WaitGroupChan
  • func NewWaitGroupChan() *WaitGroupChan
  • func (wg *WaitGroupChan) Add(delta int)
  • func (wg *WaitGroupChan) Decr()
  • func (wg *WaitGroupChan) DoneChan() <-chan struct{}
  • func (wg *WaitGroupChan) Wait()

Functions

func AssertLocked

func AssertLocked(m *sync.Mutex)

AssertLocked panics if m is not locked.

func AssertRLocked

func AssertRLocked(rw *sync.RWMutex)

AssertRLocked panics if rw is not locked for reading or writing.

func AssertWLocked

func AssertWLocked(rw *sync.RWMutex)

AssertWLocked panics if rw is not locked for writing.

func ClosedChan

func ClosedChan() <-chan struct{}

ClosedChan returns a channel that's already closed.

func Watch

func Watch(ctx context.Context, mu sync.Locker, tick, max time.Duration) chan time.Duration

Watch monitors mu for contention. On first call, and at every tick, Watch locks and unlocks mu. (Tick should be large to avoid adding contention to mu.) Max is the maximum length of time Watch will wait to acquire the lock. The time required to lock mu is sent on the returned channel. Watch exits when ctx is done, and closes the returned channel.

Types

type AtomicValue

type AtomicValue[T any] struct {
	// contains filtered or unexported fields
}

AtomicValue is the generic version of atomic.Value.

func (*AtomicValue[T]) CompareAndSwap

func (v *AtomicValue[T]) CompareAndSwap(oldV, newV T) (swapped bool)

CompareAndSwap executes the compare-and-swap operation for the Value.

func (*AtomicValue[T]) Load

func (v *AtomicValue[T]) Load() T

Load returns the value set by the most recent Store. It returns the zero value for T if the value is empty.

func (*AtomicValue[T]) LoadOk

func (v *AtomicValue[T]) LoadOk() (_ T, ok bool)

LoadOk is like Load but returns a boolean indicating whether the value was loaded.

func (*AtomicValue[T]) Store

func (v *AtomicValue[T]) Store(x T)

Store sets the value of the Value to x.

func (*AtomicValue[T]) Swap

func (v *AtomicValue[T]) Swap(x T) (old T)

Swap stores new into Value and returns the previous value. It returns the zero value for T if the value is empty.

type Map

type Map[K comparable, V any] struct {
	// contains filtered or unexported fields
}

Map is a Go map protected by a sync.RWMutex. It is preferred over sync.Map for maps with entries that change at a relatively high frequency. This must not be shallow copied.

func (*Map[K, V]) Delete

func (m *Map[K, V]) Delete(key K)

func (*Map[K, V]) Len

func (m *Map[K, V]) Len() int

Len returns the length of the map.

func (*Map[K, V]) Load

func (m *Map[K, V]) Load(key K) (value V, ok bool)

func (*Map[K, V]) LoadAndDelete

func (m *Map[K, V]) LoadAndDelete(key K) (value V, loaded bool)

func (*Map[K, V]) LoadOrStore

func (m *Map[K, V]) LoadOrStore(key K, value V) (actual V, loaded bool)

func (*Map[K, V]) Range

func (m *Map[K, V]) Range(f func(key K, value V) bool)

Range iterates over the map in undefined order calling f for each entry. Iteration stops if f returns false. Map changes are blocked during iteration.

func (*Map[K, V]) Store

func (m *Map[K, V]) Store(key K, value V)

type Semaphore

type Semaphore struct {
	// contains filtered or unexported fields
}

Semaphore is a counting semaphore.

Use NewSemaphore to create one.

func NewSemaphore

func NewSemaphore(n int) Semaphore

NewSemaphore returns a semaphore with resource count n.

func (Semaphore) Acquire

func (s Semaphore) Acquire()

Acquire blocks until a resource is acquired.

func (Semaphore) AcquireContext

func (s Semaphore) AcquireContext(ctx context.Context) bool

AcquireContext reports whether the resource was acquired before the ctx was done.

func (Semaphore) Release

func (s Semaphore) Release()

Release releases a resource.

func (Semaphore) TryAcquire

func (s Semaphore) TryAcquire() bool

TryAcquire reports, without blocking, whether the resource was acquired.

type ShardedMap

type ShardedMap[K comparable, V any] struct {
	// contains filtered or unexported fields
}

ShardedMap is a synchronized map[K]V, internally sharded by a user-defined K-sharding function.

The zero value is not safe for use; use NewShardedMap.

func NewShardedMap

func NewShardedMap[K comparable, V any](shards int, shard func(K) int) *ShardedMap[K, V]

NewShardedMap returns a new ShardedMap with the given number of shards and sharding function.

The shard func must return a integer in the range [0, shards) purely deterministically based on the provided K.

func (*ShardedMap[K, V]) Contains

func (m *ShardedMap[K, V]) Contains(key K) bool

Contains reports whether m contains key.

func (*ShardedMap[K, V]) Delete

func (m *ShardedMap[K, V]) Delete(key K) (shrunk bool)

Delete removes key from m.

It reports whether the map size shrunk (that is, whether key was present in the map).

func (*ShardedMap[K, V]) Get

func (m *ShardedMap[K, V]) Get(key K) (value V)

Get returns m[key] or the zero value of V if key is not present.

func (*ShardedMap[K, V]) GetOk

func (m *ShardedMap[K, V]) GetOk(key K) (value V, ok bool)

GetOk returns m[key] and whether it was present.

func (*ShardedMap[K, V]) Len

func (m *ShardedMap[K, V]) Len() int

Len returns the number of elements in m.

It does so by locking shards one at a time, so it's not particularly cheap, nor does it give a consistent snapshot of the map. It's mostly intended for metrics or testing.

func (*ShardedMap[K, V]) Mutate

func (m *ShardedMap[K, V]) Mutate(key K, mutator func(oldValue V, oldValueExisted bool) (newValue V, keep bool)) (sizeDelta int)

Mutate atomically mutates m[k] by calling mutator.

The mutator function is called with the old value (or its zero value) and whether it existed in the map and it returns the new value and whether it should be set in the map (true) or deleted from the map (false).

It returns the change in size of the map as a result of the mutation, one of -1 (delete), 0 (change), or 1 (addition).

func (*ShardedMap[K, V]) Set

func (m *ShardedMap[K, V]) Set(key K, value V) (grew bool)

Set sets m[key] = value.

present in m).

type WaitGroup

type WaitGroup struct{ sync.WaitGroup }

WaitGroup is identical to sync.WaitGroup, but provides a Go method to start a goroutine.

func (*WaitGroup) Go

func (wg *WaitGroup) Go(f func())

Go calls the given function in a new goroutine. It automatically increments the counter before execution and automatically decrements the counter after execution. It must not be called concurrently with Wait.

type WaitGroupChan

type WaitGroupChan struct {
	// contains filtered or unexported fields
}

WaitGroupChan is like a sync.WaitGroup, but has a chan that closes on completion that you can wait on. (This, you can only use the value once) Also, its zero value is not usable. Use the constructor.

func NewWaitGroupChan

func NewWaitGroupChan() *WaitGroupChan

NewWaitGroupChan returns a new single-use WaitGroupChan.

func (*WaitGroupChan) Add

func (wg *WaitGroupChan) Add(delta int)

Add adds delta, which may be negative, to the WaitGroupChan counter. If the counter becomes zero, all goroutines blocked on Wait or the Done chan are released. If the counter goes negative, Add panics.

Note that calls with a positive delta that occur when the counter is zero must happen before a Wait. Calls with a negative delta, or calls with a positive delta that start when the counter is greater than zero, may happen at any time. Typically this means the calls to Add should execute before the statement creating the goroutine or other event to be waited for.

func (*WaitGroupChan) Decr

func (wg *WaitGroupChan) Decr()

Decr decrements the WaitGroup counter by one.

(It is like sync.WaitGroup's Done method, but we don't use Done in this type, because it's ambiguous between Context.Done and WaitGroup.Done. So we use DoneChan and Decr instead.)

func (*WaitGroupChan) DoneChan

func (wg *WaitGroupChan) DoneChan() <-chan struct{}

DoneChan returns a channel that's closed on completion.

func (*WaitGroupChan) Wait

func (wg *WaitGroupChan) Wait()

Wait blocks until the WaitGroupChan counter is zero.