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// Copyright 2024 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package queue
import (
"container/heap"
)
type priority []int64
func (p priority) greaterThan(other priority) bool {
for i := range p {
if i >= len(other) || p[i] > other[i] {
return true
}
if p[i] < other[i] {
return false
}
}
for i := len(p); i < len(other); i++ {
if other[i] < 0 {
return true
}
if other[i] > 0 {
return false
}
}
return false
}
func (p priority) next() priority {
if len(p) == 0 {
return p
}
newPrio := append([]int64{}, p...)
newPrio[len(newPrio)-1]--
return newPrio
}
type priorityQueueOps[T any] struct {
impl priorityQueueImpl[T]
}
func (pq *priorityQueueOps[T]) Len() int {
return pq.impl.Len()
}
func (pq *priorityQueueOps[T]) Push(item T, prio priority) {
heap.Push(&pq.impl, &priorityQueueItem[T]{item, prio})
}
func (pq *priorityQueueOps[T]) Pop() T {
if len(pq.impl) == 0 {
var def T
return def
}
return heap.Pop(&pq.impl).(*priorityQueueItem[T]).value
}
// The implementation below is based on the example provided
// by https://pkg.go.dev/container/heap.
type priorityQueueItem[T any] struct {
value T
prio priority
}
type priorityQueueImpl[T any] []*priorityQueueItem[T]
func (pq priorityQueueImpl[T]) Len() int { return len(pq) }
func (pq priorityQueueImpl[T]) Less(i, j int) bool {
// We want Pop to give us the highest, not lowest,
// priority so we use greater than here.
return pq[i].prio.greaterThan(pq[j].prio)
}
func (pq priorityQueueImpl[T]) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
}
func (pq *priorityQueueImpl[T]) Push(x any) {
*pq = append(*pq, x.(*priorityQueueItem[T]))
}
func (pq *priorityQueueImpl[T]) Pop() any {
n := len(*pq)
item := (*pq)[n-1]
(*pq)[n-1] = nil
*pq = (*pq)[:n-1]
return item
}
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