filer: speed up filer.meta.save by parallelizing

weed/util/queue.go

@@ -0,0 +1,61 @@
+package util
+
+import "sync"
+
+type node struct {
+	data interface{}
+	next *node
+}
+
+type Queue struct {
+	head  *node
+	tail  *node
+	count int
+	sync.RWMutex
+}
+
+func NewQueue() *Queue {
+	q := &Queue{}
+	return q
+}
+
+func (q *Queue) Len() int {
+	q.RLock()
+	defer q.RUnlock()
+	return q.count
+}
+
+func (q *Queue) Enqueue(item interface{}) {
+	q.Lock()
+	defer q.Unlock()
+
+	n := &node{data: item}
+
+	if q.tail == nil {
+		q.tail = n
+		q.head = n
+	} else {
+		q.tail.next = n
+		q.tail = n
+	}
+	q.count++
+}
+
+func (q *Queue) Dequeue() interface{} {
+	q.Lock()
+	defer q.Unlock()
+
+	if q.head == nil {
+		return nil
+	}
+
+	n := q.head
+	q.head = n.next
+
+	if q.head == nil {
+		q.tail = nil
+	}
+	q.count--
+
+	return n.data
+}