Fix handling of integer wraparound in megolm.c

1 files changed, 16 insertions, 0 deletions

diff --git a/tests/test_megolm.cpp b/tests/test_megolm.cpp
index 871de36..bf53346 100644
--- a/tests/test_megolm.cpp
+++ b/tests/test_megolm.cpp
@@ -82,4 +82,20 @@ std::uint8_t random_bytes[] =
     assert_equals(expected3, megolm_get_data(&mr), MEGOLM_RATCHET_LENGTH);
 }
 
+{
+    TestCase test_case("Megolm::advance wraparound");
+
+    Megolm mr1, mr2;
+
+    megolm_init(&mr1, random_bytes, 0xffffffffUL);
+    megolm_advance_to(&mr1, 0x1000000);
+    assert_equals(0x1000000U, mr1.counter);
+
+    megolm_init(&mr2, random_bytes, 0);
+    megolm_advance_to(&mr2, 0x2000000);
+    assert_equals(0x2000000U, mr2.counter);
+
+    assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
+}
+
 }