Add 'lib/protocol/' from commit 'f91191218b192ace841c878f161832d19c09145a'

git-subtree-dir: lib/protocol
git-subtree-mainline: 5ecb8bdd8a
git-subtree-split: f91191218b

lib/protocol/header.go

@@ -0,0 +1,43 @@
+// Copyright (C) 2014 The Protocol Authors.
+
+package protocol
+
+import "github.com/calmh/xdr"
+
+type header struct {
+	version     int
+	msgID       int
+	msgType     int
+	compression bool
+}
+
+func (h header) encodeXDR(xw *xdr.Writer) (int, error) {
+	u := encodeHeader(h)
+	return xw.WriteUint32(u)
+}
+
+func (h *header) decodeXDR(xr *xdr.Reader) error {
+	u := xr.ReadUint32()
+	*h = decodeHeader(u)
+	return xr.Error()
+}
+
+func encodeHeader(h header) uint32 {
+	var isComp uint32
+	if h.compression {
+		isComp = 1 << 0 // the zeroth bit is the compression bit
+	}
+	return uint32(h.version&0xf)<<28 +
+		uint32(h.msgID&0xfff)<<16 +
+		uint32(h.msgType&0xff)<<8 +
+		isComp
+}
+
+func decodeHeader(u uint32) header {
+	return header{
+		version:     int(u>>28) & 0xf,
+		msgID:       int(u>>16) & 0xfff,
+		msgType:     int(u>>8) & 0xff,
+		compression: u&1 == 1,
+	}
+}