1 files changed, 93 insertions, 0 deletions
diff --git a/bin/tests/optional/lfsr_test.c b/bin/tests/optional/lfsr_test.c
new file mode 100644
index 0000000..c1c99f0
--- /dev/null
+++ b/bin/tests/optional/lfsr_test.c
@@ -0,0 +1,93 @@
+/*
+ * 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.
+ */
+
+/*! \file */
+
+#include <inttypes.h>
+#include <stdio.h>
+
+#include <isc/lfsr.h>
+#include <isc/print.h>
+#include <isc/util.h>
+
+uint32_t state[1024 * 64];
+
+int
+main(int argc, char **argv) {
+	isc_lfsr_t lfsr1, lfsr2;
+	int i;
+	uint32_t temp;
+
+	UNUSED(argc);
+	UNUSED(argv);
+
+	/*
+	 * Verify that returned values are reproducible.
+	 */
+	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr1, &state[i], 4);
+		printf("lfsr1:  state[%2d] = %08x\n", i, state[i]);
+	}
+	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr1, &temp, 4);
+		if (state[i] != temp) {
+			printf("lfsr1:  state[%2d] = %08x, "
+			       "but new state is %08x\n",
+			       i, state[i], temp);
+		}
+	}
+
+	/*
+	 * Now do the same with skipping.
+	 */
+	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr1, &state[i], 4);
+		isc_lfsr_skip(&lfsr1, 32);
+		printf("lfsr1:  state[%2d] = %08x\n", i, state[i]);
+	}
+	isc_lfsr_init(&lfsr1, 0, 32, 0x80000057U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr1, &temp, 4);
+		isc_lfsr_skip(&lfsr1, 32);
+		if (state[i] != temp) {
+			printf("lfsr1:  state[%2d] = %08x, "
+			       "but new state is %08x\n",
+			       i, state[i], temp);
+		}
+	}
+
+	/*
+	 * Try to find the period of the LFSR.
+	 *
+	 *	x^16 + x^5 + x^3 + x^2 + 1
+	 */
+	isc_lfsr_init(&lfsr2, 0, 16, 0x00008016U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr2, &state[i], 4);
+		printf("lfsr2:  state[%2d] = %08x\n", i, state[i]);
+	}
+	isc_lfsr_init(&lfsr2, 0, 16, 0x00008016U, 0, NULL, NULL);
+	for (i = 0; i < 32; i++) {
+		isc_lfsr_generate(&lfsr2, &temp, 4);
+		if (state[i] != temp) {
+			printf("lfsr2:  state[%2d] = %08x, "
+			       "but new state is %08x\n",
+			       i, state[i], temp);
+		}
+	}
+
+	return (0);
+}