nix-store --serve: Use a versioned protocol

Signed-off-by: Shea Levy <shea@shealevy.com>

src/nix-store/serve-protocol.hh

@@ -0,0 +1,24 @@
+#pragma once
+
+namespace nix {
+
+
+#define SERVE_MAGIC_1 0x390c9deb
+#define SERVE_MAGIC_2 0x5452eecb
+
+#define SERVE_PROTOCOL_VERSION 0x101
+#define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
+#define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
+
+
+typedef enum {
+    cmdQuery = 0,
+    cmdSubstitute = 1,
+} ServeCommand;
+
+typedef enum {
+    qCmdHave = 0,
+    qCmdInfo = 1,
+} QueryCommand;
+
+}