116 lines
2.2 KiB
Go
116 lines
2.2 KiB
Go
/*
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* Copyright 2022 The Dragonfly Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package ring
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import (
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"math"
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"sync"
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)
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type sequence[T any] struct {
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locker sync.Locker
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enqCond *sync.Cond
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deqCond *sync.Cond
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closed bool
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queue []*T
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head, tail uint64
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cap, mask uint64
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}
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func NewSequence[T any](exponent int) Queue[T] {
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return newSequence[T](exponent)
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}
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func newSequence[T any](exponent int) *sequence[T] {
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capacity := uint64(math.Exp2(float64(exponent)))
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locker := &sync.Mutex{}
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return &sequence[T]{
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locker: locker,
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enqCond: &sync.Cond{
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L: locker,
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},
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deqCond: &sync.Cond{
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L: locker,
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},
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queue: make([]*T, capacity),
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head: uint64(0),
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tail: uint64(0),
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cap: capacity,
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mask: capacity - 1,
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}
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}
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func (seq *sequence[T]) Enqueue(value *T) {
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seq.locker.Lock()
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entry:
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if seq.closed {
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seq.locker.Unlock()
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return
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}
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if seq.isFull() {
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seq.enqCond.Wait()
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goto entry
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}
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newTail := (seq.tail + 1) & seq.mask
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seq.tail = newTail
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seq.queue[newTail] = value
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seq.deqCond.Signal()
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seq.locker.Unlock()
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}
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func (seq *sequence[T]) Dequeue() (value *T, ok bool) {
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seq.locker.Lock()
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entry:
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if seq.closed {
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seq.locker.Unlock()
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return nil, false
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}
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if seq.isEmpty() {
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seq.deqCond.Wait()
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goto entry
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}
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newHead := (seq.head + 1) & seq.mask
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seq.head = newHead
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val := seq.queue[newHead]
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seq.enqCond.Signal()
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seq.locker.Unlock()
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return val, true
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}
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func (seq *sequence[T]) Close() {
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seq.locker.Lock()
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seq.closed = true
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seq.enqCond.Broadcast()
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seq.deqCond.Broadcast()
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seq.locker.Unlock()
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}
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func (seq *sequence[T]) isEmpty() bool {
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return seq.head == seq.tail
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}
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func (seq *sequence[T]) isFull() bool {
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return seq.tail-seq.head == seq.cap-1 || seq.head-seq.tail == 1
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}
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