use async write to persistent file to disk - part1

weed/storage/needle/async_request.go

@@ -0,0 +1,55 @@
+package needle
+
+type AsyncRequest struct {
+	N              *Needle
+	IsWriteRequest bool
+	ActualSize     int64
+	Fsync          bool
+	offset         uint64
+	size           uint64
+	doneChan       chan interface{}
+	isUnchanged    bool
+	err            error
+}
+
+func NewAsyncRequest(n *Needle, isWriteRequest bool, fsync bool) *AsyncRequest {
+	return &AsyncRequest{
+		offset:         0,
+		size:           0,
+		ActualSize:     0,
+		doneChan:       make(chan interface{}),
+		N:              n,
+		isUnchanged:    false,
+		IsWriteRequest: isWriteRequest,
+		Fsync:          fsync,
+		err:            nil,
+	}
+}
+
+func (r *AsyncRequest) WaitComplete() (uint64, uint64, bool, error) {
+	<-r.doneChan
+	return r.offset, r.size, r.isUnchanged, r.err
+}
+
+func (r *AsyncRequest) Complete(offset uint64, size uint64, isUnchanged bool, err error) {
+	r.offset = offset
+	r.size = size
+	r.isUnchanged = isUnchanged
+	r.err = err
+	close(r.doneChan)
+}
+
+func (r *AsyncRequest) UpdateResult(offset uint64, size uint64, isUnchanged bool, err error) {
+	r.offset = offset
+	r.size = size
+	r.isUnchanged = isUnchanged
+	r.err = err
+}
+
+func (r *AsyncRequest) Submit() {
+	close(r.doneChan)
+}
+
+func (r *AsyncRequest) IsSucceed() bool {
+	return r.err == nil
+}