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queue.go
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queue.go
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package main
import (
"github.com/huandu/skiplist"
)
const MaxUint = ^uint(0)
const WrapTreshold = (MaxUint >> 1) + 1
type RAQueue struct {
l *skiplist.SkipList
cur_lsn uint
}
func NewRAQueue() *RAQueue {
return &RAQueue{
l: skiplist.New(skiplist.GreaterThanFunc(func(lhs, rhs interface{}) int {
x, y := lhs.(uint), rhs.(uint)
switch {
case x == y:
return 0
case (x < y && (y-x) <= WrapTreshold) || (x > y && (x-y) > WrapTreshold):
return -1
default:
return 1
}
})),
}
}
func (q *RAQueue) Push(e interface{}) uint {
lsn := q.cur_lsn
q.cur_lsn++
q.l.Set(lsn, e)
return lsn
}
func (q *RAQueue) Pop() interface{} {
if q.l.Len() == 0 {
return nil
}
return q.l.RemoveFront().Value
}
func (q *RAQueue) Delete(key uint) interface{} {
elem := q.l.Remove(key)
if elem == nil {
return nil
} else {
return elem.Value
}
}