1 files changed, 37 insertions, 0 deletions
diff --git a/lib/isc/include/isc/magic.h b/lib/isc/include/isc/magic.h
new file mode 100644
index 0000000..1dc9fc2
--- /dev/null
+++ b/lib/isc/include/isc/magic.h
@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+
+#ifndef ISC_MAGIC_H
+#define ISC_MAGIC_H 1
+
+#include <isc/likely.h>
+
+/*! \file isc/magic.h */
+
+typedef struct {
+	unsigned int magic;
+} isc__magic_t;
+
+/*%
+ * To use this macro the magic number MUST be the first thing in the
+ * structure, and MUST be of type "unsigned int".
+ * The intent of this is to allow magic numbers to be checked even though
+ * the object is otherwise opaque.
+ */
+#define ISC_MAGIC_VALID(a, b)       \
+	(ISC_LIKELY((a) != NULL) && \
+	 ISC_LIKELY(((const isc__magic_t *)(a))->magic == (b)))
+
+#define ISC_MAGIC(a, b, c, d) ((a) << 24 | (b) << 16 | (c) << 8 | (d))
+
+#endif /* ISC_MAGIC_H */