1 files changed, 95 insertions, 0 deletions
diff --git a/tests/helpers/c/prng.c b/tests/helpers/c/prng.c
new file mode 100644
index 0000000..612c433
--- /dev/null
+++ b/tests/helpers/c/prng.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Very simple prng to allow for randomized tests with reproducable
+ * results.
+ *
+ * Copyright (C) 2012 by Open Source Routing.
+ * Copyright (C) 2012 by Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (C) 2017 Christian Franke
+ *
+ * This file is part of Quagga
+ */
+
+#include <zebra.h>
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "prng.h"
+
+struct prng {
+	uint64_t state;
+};
+
+struct prng *prng_new(unsigned long long seed)
+{
+	struct prng *rv = calloc(sizeof(*rv), 1);
+	assert(rv);
+
+	rv->state = seed;
+
+	return rv;
+}
+
+/*
+ * This implementation has originally been provided to musl libc by
+ * Szabolcs Nagy <nsz at port70 dot net> in 2013 under the terms of
+ * the MIT license.
+ * It is a simple LCG which D.E. Knuth attributes to C.E. Haynes in
+ * TAOCP Vol2 3.3.4
+ */
+int prng_rand(struct prng *prng)
+{
+	prng->state = 6364136223846793005ULL * prng->state + 1;
+	return prng->state >> 33;
+}
+
+const char *prng_fuzz(struct prng *prng, const char *string,
+		      const char *charset, unsigned int operations)
+{
+	static char buf[256];
+	unsigned int charset_len;
+	unsigned int i;
+	unsigned int offset;
+	unsigned int op;
+	unsigned int character;
+
+	assert(strlen(string) < sizeof(buf));
+
+	strncpy(buf, string, sizeof(buf));
+	charset_len = strlen(charset);
+
+	for (i = 0; i < operations; i++) {
+		offset = prng_rand(prng) % strlen(buf);
+		op = prng_rand(prng) % 3;
+
+		switch (op) {
+		case 0:
+			/* replace */
+			character = prng_rand(prng) % charset_len;
+			buf[offset] = charset[character];
+			break;
+		case 1:
+			/* remove */
+			memmove(buf + offset, buf + offset + 1,
+				strlen(buf) - offset);
+			break;
+		case 2:
+			/* insert */
+			assert(strlen(buf) + 1 < sizeof(buf));
+
+			memmove(buf + offset + 1, buf + offset,
+				strlen(buf) + 1 - offset);
+			character = prng_rand(prng) % charset_len;
+			buf[offset] = charset[character];
+			break;
+		}
+	}
+	return buf;
+}
+
+void prng_free(struct prng *prng)
+{
+	free(prng);
+}