From d6e65a373533ee4b407df56e3ee9249f72561a4c Mon Sep 17 00:00:00 2001
From: Konstantin Osipov <kostja@scylladb.com>
Date: Sat, 5 Dec 2020 00:11:31 +0300
Subject: [PATCH] test: add a test case for monotonicity of timeuuid least
 significant bits

Ensure that timeuuid least significant bits are compared correctly.
---
 test/boost/UUID_test.cc | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/test/boost/UUID_test.cc b/test/boost/UUID_test.cc
index ad707ec202..a24dc677c7 100644
--- a/test/boost/UUID_test.cc
+++ b/test/boost/UUID_test.cc
@@ -96,6 +96,44 @@ BOOST_AUTO_TEST_CASE(test_get_time_uuid) {
     BOOST_CHECK(unix_timestamp == millis);
 }
 
+BOOST_AUTO_TEST_CASE(test_timeuuid_submicro_is_monotonic) {
+    const int64_t PAD6 = 0xFFFF'FFFF'FFFF;
+    using namespace std::chrono;
+    using utils::UUID, utils::UUID_gen;
+    UUID current_timeuuid = UUID_gen::get_time_UUID();
+    // Node identifier must be set to avoid collisions
+    BOOST_CHECK((current_timeuuid.get_least_significant_bits() & PAD6) != 0);
+    int64_t micros = UUID_gen::micros_timestamp(current_timeuuid);
+    int maxsubmicro = (1 << 17) - 1;
+    int step = 1 + (random() % 169);
+    auto prev = UUID_gen::get_time_UUID_bytes_from_micros_and_submicros(micros, 0);
+    auto prev_timeuuid = UUID_gen::get_UUID(prev.data());
+    // Check prev_timeuuid node identifier is set. It uses
+    // a spoof MAC address, not the same as a standard UUID.
+    BOOST_CHECK((prev_timeuuid.get_least_significant_bits() & PAD6) != 0);
+    auto check_is_valid_timeuuid = [&](UUID uuid) {
+        // UUID is version 1
+        BOOST_CHECK(uuid.is_timestamp());
+        // UUID preserves the original microsecond time
+        BOOST_CHECK(UUID_gen::micros_timestamp(uuid) == micros);
+        // UUID 100nsec time grows monotonically
+        BOOST_CHECK(uuid.timestamp() >= prev_timeuuid.timestamp());
+        // UUID node is the same for all generated UUIDs
+        BOOST_CHECK((prev_timeuuid.get_least_significant_bits() & PAD6) ==
+                    (uuid.get_least_significant_bits() & PAD6));
+    };
+    for (int i = 1; i <= maxsubmicro; i += step) {
+        auto uuid = UUID_gen::get_time_UUID_bytes_from_micros_and_submicros(
+                micros, i);
+        check_is_valid_timeuuid(UUID_gen::get_UUID(uuid.data()));
+        // UUID submicro part grows monotonically
+        BOOST_CHECK(utils::timeuuid_tri_compare({uuid.data(), 16}, {prev.data(), 16}) > 0);
+        prev = uuid;
+    }
+    BOOST_CHECK_EXCEPTION(UUID_gen::get_time_UUID_bytes_from_micros_and_submicros(micros, 2 * maxsubmicro),
+        utils::timeuuid_submicro_out_of_range, [](auto& x) -> bool { return true; });
+}
+
 BOOST_AUTO_TEST_CASE(test_min_time_uuid) {
     using namespace std::chrono;