89 lines
1.7 KiB
Go
89 lines
1.7 KiB
Go
package queue
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import (
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"sync"
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"codeberg.org/gruf/go-list"
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)
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// SimpleQueue provides a simple concurrency safe
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// queue using generics and a memory pool of list
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// elements to reduce overall memory usage.
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type SimpleQueue[T any] struct {
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l list.List[T]
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p []*list.Elem[T]
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w chan struct{}
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m sync.Mutex
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}
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// Push will push given value to the queue.
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func (q *SimpleQueue[T]) Push(value T) {
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q.m.Lock()
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elem := q.alloc()
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elem.Value = value
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q.l.PushElemFront(elem)
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q.broadcast()
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q.m.Unlock()
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}
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// Pop will attempt to pop value from the queue.
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func (q *SimpleQueue[T]) Pop() (value T, ok bool) {
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q.m.Lock()
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if ok = (q.l.Tail != nil); ok {
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tail := q.l.Tail
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value = tail.Value
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q.l.Remove(tail)
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q.free(tail)
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}
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q.m.Unlock()
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return
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}
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// Len returns the current length of the queue.
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func (q *SimpleQueue[T]) Len() int {
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q.m.Lock()
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l := q.l.Len()
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q.m.Unlock()
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return l
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}
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// Wait returns current wait channel, which may be
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// blocked on to awaken when new value pushed to queue.
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func (q *SimpleQueue[T]) Wait() (ch <-chan struct{}) {
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q.m.Lock()
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if q.w == nil {
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q.w = make(chan struct{})
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}
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ch = q.w
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q.m.Unlock()
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return
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}
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// alloc will allocate new list element (relying on memory pool).
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func (q *SimpleQueue[T]) alloc() *list.Elem[T] {
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if len(q.p) > 0 {
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elem := q.p[len(q.p)-1]
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q.p = q.p[:len(q.p)-1]
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return elem
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}
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return new(list.Elem[T])
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}
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// free will free list element and release to pool.
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func (q *SimpleQueue[T]) free(elem *list.Elem[T]) {
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var zero T
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elem.Next = nil
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elem.Prev = nil
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elem.Value = zero
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q.p = append(q.p, elem)
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}
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// broadcast safely closes wait channel if
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// currently set, releasing waiting goroutines.
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func (q *SimpleQueue[T]) broadcast() {
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if q.w != nil {
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close(q.w)
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q.w = nil
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}
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}
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