1 files changed, 43 insertions, 0 deletions
diff --git a/lib/isc/win32/once.c b/lib/isc/win32/once.c
new file mode 100644
index 0000000..23966cb
--- /dev/null
+++ b/lib/isc/win32/once.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0.  If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+#include <windows.h>
+
+#include <isc/assertions.h>
+#include <isc/once.h>
+#include <isc/util.h>
+
+isc_result_t
+isc_once_do(isc_once_t *controller, void (*function)(void)) {
+	REQUIRE(controller != NULL && function != NULL);
+
+	if (controller->status == ISC_ONCE_INIT_NEEDED) {
+		if (InterlockedDecrement(&controller->counter) == 0) {
+			if (controller->status == ISC_ONCE_INIT_NEEDED) {
+				function();
+				controller->status = ISC_ONCE_INIT_DONE;
+			}
+		} else {
+			while (controller->status == ISC_ONCE_INIT_NEEDED) {
+				/*
+				 * Sleep(0) indicates that this thread
+				 * should be suspended to allow other
+				 * waiting threads to execute.
+				 */
+				Sleep(0);
+			}
+		}
+	}
+
+	return (ISC_R_SUCCESS);
+}