89 lines
1.8 KiB
Go
89 lines
1.8 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/rand"
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"time"
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)
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type random[T any] struct {
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*sequence[T]
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seed *rand.Rand
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}
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func NewRandom[T any](exponent int) Queue[T] {
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return &random[T]{
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sequence: newSequence[T](exponent),
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seed: rand.New(rand.NewSource(time.Now().UnixNano())),
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}
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}
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func (r *random[T]) Enqueue(value *T) {
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r.sequence.Enqueue(value)
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}
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func (r *random[T]) Dequeue() (value *T, ok bool) {
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r.locker.Lock()
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entry:
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if r.closed {
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r.locker.Unlock()
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return nil, false
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}
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if r.isEmpty() {
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r.deqCond.Wait()
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goto entry
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}
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var (
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count uint64
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newHead = (r.head + 1) & r.mask
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)
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if r.head < r.tail {
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count = r.tail - r.head
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} else {
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count = r.mask - (r.head - r.tail) + 1
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}
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if count > 1 {
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// generate a random index
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idx := r.seed.Int63n(int64(count))
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randomHead := (newHead + uint64(idx)) & r.mask
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// skip same idx with newHeader
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if idx > 0 {
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// swap the new idx and newHead
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var tmp *T
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tmp = r.queue[randomHead]
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r.queue[randomHead] = r.queue[newHead]
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r.queue[newHead] = tmp
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}
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}
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r.head = newHead
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val := r.queue[newHead]
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r.enqCond.Signal()
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r.locker.Unlock()
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return val, true
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}
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func (r *random[T]) Close() {
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r.sequence.Close()
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}
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