Add microbenchmark for isc_iterated_hash()

Add microbenchmark for isc_iterated_hash() to measure the speed of NSEC3
per second.

tests/bench/.gitignore

@@ -1,4 +1,5 @@
 /ascii
 /compress
+/iterated_hash
 /dns_name_fromwire
 /siphash

tests/bench/Makefile.am

@@ -12,6 +12,7 @@ LDADD +=			\
 noinst_PROGRAMS =		\
 	ascii			\
 	compress		\
+	iterated_hash		\
 	dns_name_fromwire	\
 	siphash
 

tests/bench/iterated_hash.c

@@ -0,0 +1,76 @@
+/*
+ * 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 <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <isc/iterated_hash.h>
+#include <isc/random.h>
+#include <isc/time.h>
+
+#include <dns/name.h>
+
+static void
+time_it(const int count, const int iterations, const unsigned char *salt,
+	const int saltlen, const unsigned char *in, const int inlen) {
+	uint8_t out[NSEC3_MAX_HASH_LENGTH] = { 0 };
+	isc_time_t start, finish;
+
+	printf("%d iterations, %d salt length, %d input length: ", iterations,
+	       saltlen, inlen);
+	fflush(stdout);
+
+	isc_time_now_hires(&start);
+
+	int i = 0;
+	while (i++ < count) {
+		isc_iterated_hash(out, 1, iterations, salt, saltlen, in, inlen);
+	}
+
+	isc_time_now_hires(&finish);
+
+	uint64_t microseconds = isc_time_microdiff(&finish, &start);
+	printf("%0.2f us per iterated_hash()\n", (double)microseconds / count);
+	fflush(stdout);
+}
+
+int
+main(void) {
+	uint8_t salt[DNS_NAME_MAXWIRE];
+	uint8_t in[DNS_NAME_MAXWIRE];
+	size_t saltlen = sizeof(salt);
+	size_t inlen = sizeof(in);
+
+	isc_random_buf(salt, saltlen);
+	isc_random_buf(in, inlen);
+
+	time_it(10000, 150, salt, saltlen, in, inlen);
+	time_it(10000, 15, salt, saltlen, in, inlen);
+	time_it(10000, 0, salt, saltlen, in, inlen);
+
+	saltlen = 32;
+	inlen = 32;
+
+	time_it(10000, 150, salt, 32, in, inlen);
+	time_it(10000, 15, salt, 32, in, inlen);
+	time_it(10000, 0, salt, saltlen, in, inlen);
+
+	saltlen = 0;
+	inlen = 1;
+
+	time_it(10000, 150, salt, 32, in, inlen);
+	time_it(10000, 15, salt, 32, in, inlen);
+	time_it(10000, 0, salt, saltlen, in, inlen);
+}