1 files changed, 78 insertions, 0 deletions
diff --git a/source/blender/blenlib/intern/session_uuid.c b/source/blender/blenlib/intern/session_uuid.c
new file mode 100644
index 00000000000..8ed96f02149
--- /dev/null
+++ b/source/blender/blenlib/intern/session_uuid.c
@@ -0,0 +1,78 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/** \file
+ * \ingroup bli
+ */
+
+#include "BLI_session_uuid.h"
+
+#include "BLI_utildefines.h"
+
+#include "atomic_ops.h"
+
+/* Special value which indicates the UUID has not been assigned yet. */
+#define BLI_SESSION_UUID_NONE 0
+
+static const SessionUUID global_session_uuid_none = {BLI_SESSION_UUID_NONE};
+
+/* Denotes last used UUID.
+ * It might eventually overflow, and easiest is to add more bits to it. */
+static SessionUUID global_session_uuid = {BLI_SESSION_UUID_NONE};
+
+SessionUUID BLI_session_uuid_generate(void)
+{
+  SessionUUID result;
+  result.uuid_ = atomic_add_and_fetch_uint64(&global_session_uuid.uuid_, 1);
+  if (!BLI_session_uuid_is_generated(&result)) {
+    /* Happens when the UUID overflows.
+     *
+     * Just request the UUID once again, hoping that there are not a lot of high-priority threads
+     * which will overflow the counter once again between the previous call and this one.
+     *
+     * NOTE: It is possible to have collisions after such overflow. */
+    result.uuid_ = atomic_add_and_fetch_uint64(&global_session_uuid.uuid_, 1);
+  }
+  return result;
+}
+
+bool BLI_session_uuid_is_generated(const SessionUUID *uuid)
+{
+  return !BLI_session_uuid_is_equal(uuid, &global_session_uuid_none);
+}
+
+bool BLI_session_uuid_is_equal(const SessionUUID *lhs, const SessionUUID *rhs)
+{
+  return lhs->uuid_ == rhs->uuid_;
+}
+
+uint64_t BLI_session_uuid_hash_uint64(const SessionUUID *uuid)
+{
+  return uuid->uuid_;
+}
+
+uint BLI_session_uuid_ghash_hash(const void *uuid_v)
+{
+  const SessionUUID *uuid = (const SessionUUID *)uuid_v;
+  return uuid->uuid_ & 0xffffffff;
+}
+
+bool BLI_session_uuid_ghash_compare(const void *lhs_v, const void *rhs_v)
+{
+  const SessionUUID *lhs = (const SessionUUID *)lhs_v;
+  const SessionUUID *rhs = (const SessionUUID *)rhs_v;
+  return BLI_session_uuid_is_equal(lhs, rhs);
+}