fix #782 (bring vendor into the main tree)

vendor/github.com/tidwall/tinyqueue/tinyqueue.go

@@ -0,0 +1,86 @@
+package tinyqueue
+
+type Queue struct {
+	length int
+	data   []Item
+}
+
+type Item interface {
+	Less(Item) bool
+}
+
+func New(data []Item) *Queue {
+	q := &Queue{}
+	q.data = data
+	q.length = len(data)
+	if q.length > 0 {
+		i := q.length >> 1
+		for ; i >= 0; i-- {
+			q.down(i)
+		}
+	}
+	return q
+}
+
+func (q *Queue) Push(item Item) {
+	q.data = append(q.data, item)
+	q.length++
+	q.up(q.length - 1)
+}
+func (q *Queue) Pop() Item {
+	if q.length == 0 {
+		return nil
+	}
+	top := q.data[0]
+	q.length--
+	if q.length > 0 {
+		q.data[0] = q.data[q.length]
+		q.down(0)
+	}
+	q.data = q.data[:len(q.data)-1]
+	return top
+}
+func (q *Queue) Peek() Item {
+	if q.length == 0 {
+		return nil
+	}
+	return q.data[0]
+}
+func (q *Queue) Len() int {
+	return q.length
+}
+func (q *Queue) down(pos int) {
+	data := q.data
+	halfLength := q.length >> 1
+	item := data[pos]
+	for pos < halfLength {
+		left := (pos << 1) + 1
+		right := left + 1
+		best := data[left]
+		if right < q.length && data[right].Less(best) {
+			left = right
+			best = data[right]
+		}
+		if !best.Less(item) {
+			break
+		}
+		data[pos] = best
+		pos = left
+	}
+	data[pos] = item
+}
+
+func (q *Queue) up(pos int) {
+	data := q.data
+	item := data[pos]
+	for pos > 0 {
+		parent := (pos - 1) >> 1
+		current := data[parent]
+		if !item.Less(current) {
+			break
+		}
+		data[pos] = current
+		pos = parent
+	}
+	data[pos] = item
+}