Fix header in protocol spec (fixes #360)

protocol/protocol_test.go

@@ -25,6 +25,31 @@ func TestHeaderFunctions(t *testing.T) {
 	}
 }
 
+func TestHeaderLayout(t *testing.T) {
+	var e, a uint32
+
+	// Version are the first four bits
+	e = 0xf0000000
+	a = encodeHeader(header{0xf, 0, 0})
+	if a != e {
+		t.Errorf("Header layout incorrect; %08x != %08x", a, e)
+	}
+
+	// Message ID are the following 12 bits
+	e = 0x0fff0000
+	a = encodeHeader(header{0, 0xfff, 0})
+	if a != e {
+		t.Errorf("Header layout incorrect; %08x != %08x", a, e)
+	}
+
+	// Type are the last 8 bits before reserved
+	e = 0x0000ff00
+	a = encodeHeader(header{0, 0, 0xff})
+	if a != e {
+		t.Errorf("Header layout incorrect; %08x != %08x", a, e)
+	}
+}
+
 func TestPing(t *testing.T) {
 	ar, aw := io.Pipe()
 	br, bw := io.Pipe()