utils: add make_random_uuid()

configure.py

@@ -228,6 +228,7 @@ deps = {
                  'thrift/handler.cc',
                  'thrift/server.cc',
                  'utils/murmur_hash.cc',
+                 'utils/uuid.cc',
 		 'db/db.cc',
 		 'io/io.cc',
                  'utils/utils.cc',

utils/UUID.hh

@@ -42,4 +42,6 @@ public:
     }
 };
 
+UUID make_random_uuid();
+
 }

utils/uuid.cc

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2015 Cloudius Systems, Ltd.
+ */
+
+
+#include "UUID.hh"
+#include "net/byteorder.hh"
+#include <random>
+#include <boost/iterator/function_input_iterator.hpp>
+
+namespace utils {
+
+UUID
+make_random_uuid() {
+    // FIXME: keep in userspace
+    static thread_local std::random_device urandom;
+    static thread_local std::uniform_int_distribution<uint8_t> dist(0, 255);
+    union {
+        uint8_t b[16];
+        struct {
+            uint64_t msb, lsb;
+        } w;
+    } v;
+    for (auto& b : v.b) {
+        b = dist(urandom);
+    }
+    v.b[6] &= 0x0f;
+    v.b[6] |= 0x40; // version 4
+    v.b[8] &= 0x3f;
+    v.b[8] |= 0x80; // IETF variant
+    return UUID(net::hton(v.w.msb), net::hton(v.w.lsb));
+}
+
+}