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element.go
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package skiplist
import (
"math/rand"
)
const SKIPLIST_MAXLEVEL = 32
const SKIPLIST_BRANCH = 4
type skiplistLevel struct {
forward *Element
span int
}
type Element struct {
Value Interface
backward *Element
level []*skiplistLevel
}
// Next returns the next skiplist element or nil.
func (e *Element) Next() *Element {
return e.level[0].forward
}
// Prev returns the previous skiplist element of nil.
func (e *Element) Prev() *Element {
return e.backward
}
// newElement returns an initialized element.
func newElement(level int, v Interface) *Element {
slLevels := make([]*skiplistLevel, level)
for i := 0; i < level; i++ {
slLevels[i] = new(skiplistLevel)
}
return &Element{
Value: v,
backward: nil,
level: slLevels,
}
}
// randomLevel returns a random level.
func randomLevel() int {
level := 1
for (rand.Int31()&0xFFFF)%SKIPLIST_BRANCH == 0 {
level += 1
}
if level < SKIPLIST_MAXLEVEL {
return level
} else {
return SKIPLIST_MAXLEVEL
}
}