[#149] client: Do not finish on empty ID list in ObjectListReader

In previous implementation `ObjectListReader.Read` returned `false` on
server responded with empty ID list. This could cause premature end of
reading since the protocol does not forbid intermediate empty lists.

Do not stop if ID list from response body is empty.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

client/object_search.go

@@ -136,34 +136,42 @@ func (x *ObjectListReader) Read(buf []oid.ID) (int, bool) {
 		return read, true
 	}
 
+	var ok bool
+	var ids []*v2refs.ObjectID
+	var i, ln, rem int
+
+	for {
 		// receive next message
-	ok := x.ctxCall.readResponse()
+		ok = x.ctxCall.readResponse()
 		if !ok {
 			return read, false
 		}
 
 		// read new chunk of objects
-	ids := x.bodyResp.GetIDList()
-	ln := len(ids)
+		ids = x.bodyResp.GetIDList()
+
+		ln = len(ids)
 		if ln == 0 {
-		x.ctxCall.err = io.EOF
-		return read, false
+			// just skip empty lists since they are not prohibited by protocol
+			continue
 		}
 
-	buf = buf[read:]
-	if ln > len(buf) {
-		ln = len(buf)
+		if rem = len(buf) - read; ln > rem {
+			ln = rem
 		}
 
-	for i := 0; i < ln; i++ {
-		buf[i] = *oid.NewIDFromV2(ids[i]) // need smth better
+		for i = 0; i < ln; i++ {
+			buf[read+i] = *oid.NewIDFromV2(ids[i]) // need smth better
 		}
 
 		read += ln
 
-	// save the tail
+		// save the tail and break
 		x.tail = append(x.tail, ids[ln:]...)
 
+		break
+	}
+
 	return read, true
 }