/
queue.go
69 lines (58 loc) · 1.27 KB
/
queue.go
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package prefixmap
// little queue implementation
const q_PAGE_SIZE = 4096 // common page size
type queue struct {
q []*Node
pages [][]*Node
h, t, page_index int
}
func (q *queue) enqueue(node *Node) {
if q.t == cap(q.q) {
// moving to the next page
q.page_index += 1
// incrementing pages slice
// if no empty pages are available
if q.page_index == len(q.pages) {
page := make([]*Node, q_PAGE_SIZE)
q.pages = append(q.pages, page)
}
q.q = q.pages[q.page_index]
// resetting indexes
q.t = 0
q.h = 0
}
q.q[q.t] = node
q.t += 1
}
func (q *queue) isEmpty() bool {
return q.h == q.t
}
func (q *queue) dequeue() (node *Node) {
if q.h == q.t {
if q.page_index > 0 {
q.page_index -= 1
q.q = q.pages[q.page_index]
q.h = 0
q.t = len(q.q)
} else {
node = nil
return
}
}
node = q.q[q.h]
q.h += 1
return
}
func (q *queue) clear() {
q.h = 0
q.t = 0
}
func newQueue() *queue {
q := new(queue)
q.q = make([]*Node, q_PAGE_SIZE)
q.pages = [][]*Node{q.q}
q.h = 0
q.t = 0
q.page_index = 0
return q
}