UUID: add nil value for UUIDs

Add `BLI_uuid_nil()` that returns the nil UUID (used to indicate "not
set") and `BLI_uuid_is_nil(uuid)` to do an equality test with the nil
value.

1 files changed, 13 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_uuid_test.cc b/source/blender/blenlib/tests/BLI_uuid_test.cc
index bb5eb3817af..31c69002c1c 100644
--- a/source/blender/blenlib/tests/BLI_uuid_test.cc
+++ b/source/blender/blenlib/tests/BLI_uuid_test.cc
@@ -48,6 +48,19 @@ TEST(BLI_uuid, generate_many_random)
   }
 }
 
+TEST(BLI_uuid, nil_value)
+{
+  const UUID nil_uuid = BLI_uuid_nil();
+  const UUID zeroes_uuid = {0, 0, 0, 0, 0, 0};
+
+  EXPECT_TRUE(BLI_uuid_equal(nil_uuid, zeroes_uuid));
+  EXPECT_TRUE(BLI_uuid_is_nil(nil_uuid));
+
+  std::string buffer(36, '\0');
+  BLI_uuid_format(buffer.data(), nil_uuid);
+  EXPECT_EQ("00000000-0000-0000-0000-000000000000", buffer);
+}
+
 TEST(BLI_uuid, equality)
 {
   const UUID uuid1 = BLI_uuid_generate_random();