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random.go
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random.go
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/*
* Copyright 2022 The Dragonfly Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package ring
import (
"math/rand"
"time"
)
type random[T any] struct {
*sequence[T]
seed *rand.Rand
}
func NewRandom[T any](exponent int) Queue[T] {
return &random[T]{
sequence: newSequence[T](exponent),
seed: rand.New(rand.NewSource(time.Now().UnixNano())),
}
}
func (r *random[T]) Enqueue(value *T) {
r.sequence.Enqueue(value)
}
func (r *random[T]) Dequeue() (value *T, ok bool) {
r.locker.Lock()
entry:
if r.closed {
r.locker.Unlock()
return nil, false
}
if r.isEmpty() {
r.deqCond.Wait()
goto entry
}
var (
count uint64
newHead = (r.head + 1) & r.mask
)
if r.head < r.tail {
count = r.tail - r.head
} else {
count = r.mask - (r.head - r.tail) + 1
}
if count > 1 {
// generate a random index
idx := r.seed.Int63n(int64(count))
randomHead := (newHead + uint64(idx)) & r.mask
// skip same idx with newHeader
if idx > 0 {
// swap the new idx and newHead
var tmp *T
tmp = r.queue[randomHead]
r.queue[randomHead] = r.queue[newHead]
r.queue[newHead] = tmp
}
}
r.head = newHead
val := r.queue[newHead]
r.enqCond.Signal()
r.locker.Unlock()
return val, true
}
func (r *random[T]) Close() {
r.sequence.Close()
}