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package ttlcache
import (
"container/heap"
)
func newPriorityQueue() *priorityQueue {
queue := &priorityQueue{}
heap.Init(queue)
return queue
}
type priorityQueue struct {
items []*item
}
func (pq *priorityQueue) update(item *item) {
heap.Fix(pq, item.queueIndex)
}
func (pq *priorityQueue) push(item *item) {
heap.Push(pq, item)
}
func (pq *priorityQueue) pop() *item {
if pq.Len() == 0 {
return nil
}
return heap.Pop(pq).(*item)
}
func (pq *priorityQueue) remove(item *item) {
heap.Remove(pq, item.queueIndex)
}
func (pq priorityQueue) Len() int {
length := len(pq.items)
return length
}
// Less will consider items with time.Time default value (epoch start) as more than set items.
func (pq priorityQueue) Less(i, j int) bool {
if pq.items[i].expireAt.IsZero() {
return false
}
if pq.items[j].expireAt.IsZero() {
return true
}
return pq.items[i].expireAt.Before(pq.items[j].expireAt)
}
func (pq priorityQueue) Swap(i, j int) {
pq.items[i], pq.items[j] = pq.items[j], pq.items[i]
pq.items[i].queueIndex = i
pq.items[j].queueIndex = j
}
func (pq *priorityQueue) Push(x interface{}) {
item := x.(*item)
item.queueIndex = len(pq.items)
pq.items = append(pq.items, item)
}
func (pq *priorityQueue) Pop() interface{} {
old := pq.items
n := len(old)
item := old[n-1]
item.queueIndex = -1
pq.items = old[0 : n-1]
return item
}
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