Better explain what 1<<22-24 means for packet length

rpc.go

@@ -364,7 +364,8 @@ func (l *Libvirt) requestStream(proc uint32, program uint32, payload []byte, out
 }
 
 func (l *Libvirt) sendStream(serial uint32, proc uint32, program uint32, stream io.Reader, abort chan bool) error {
-	buf := make([]byte, 1<<22-24)
+	// Keep total packet length under 4 MiB to follow possible limitation in libvirt server code
+	buf := make([]byte, 4*MiB-constants.HeaderSize)
 	for {
 		select {
 		case <-abort:

units.go

@@ -0,0 +1,24 @@
+// Copyright 2016 The go-libvirt Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This module provides different units of measurement to make other
+// code more readable.
+
+package libvirt
+
+const (
+	B   = 1
+	KiB = 1024 * B
+	MiB = 1024 * KiB
+)