Fix our ffs() / fls() and add unit tests.

include/cryb/bitwise.h

@@ -79,9 +79,12 @@ static inline int cryb_ffs(int n) {
 #elif HAVE___BUILTIN_CTZ
 	return (n ? __builtin_ctz(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = m = 1; i <= sizeof n * 8; ++i, m <<= 1)
+		if ((unsigned int)n & m)
 			break;
 	return (i);
 #endif
@@ -93,9 +96,12 @@ static inline int cryb_ffsl(long int n) {
 #elif HAVE___BUILTIN_CLZ
 	return (n ? __builtin_ctz(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned long int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = m = 1; i <= sizeof n * 8; ++i, m <<= 1)
+		if ((unsigned long int)n & m)
 			break;
 	return (i);
 #endif
@@ -107,9 +113,12 @@ static inline int cryb_ffsll(long long int n) {
 #elif HAVE___BUILTIN_CLZ
 	return (n ? __builtin_ctz(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned long long int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = m = 1; i <= sizeof n * 8; ++i, m <<= 1)
+		if ((unsigned long long int)n & m)
 			break;
 	return (i);
 #endif
@@ -121,9 +130,12 @@ static inline int cryb_fls(int n) {
 #elif HAVE___BUILTIN_CLZ
 	return (n ? (8 * sizeof n) - __builtin_clz(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = sizeof n * 8, m = 1U << (i - 1); i > 0; --i, m >>= 1)
+		if ((unsigned int)n & m)
 			break;
 	return (i);
 #endif
@@ -135,9 +147,12 @@ static inline int cryb_flsl(long int n) {
 #elif HAVE___BUILTIN_CLZ
 	return (n ? (8 * sizeof n) - __builtin_clzl(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned long int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = sizeof n * 8, m = 1UL << (i - 1); i > 0; --i, m >>= 1)
+		if ((unsigned long int)n & m)
 			break;
 	return (i);
 #endif
@@ -149,9 +164,12 @@ static inline int cryb_flsll(long long int n) {
 #elif HAVE___BUILTIN_CLZ
 	return (n ? (8 * sizeof n) - __builtin_clzll(n) : 0);
 #else
-	int i = 8 * sizeof n - 1;
+	unsigned long long int m;
-	for (i > 0)
+	unsigned int i;
-		if (n & (1 << --i))
+	if (n == 0)
+		return (0);
+	for (i = sizeof n * 8, m = 1ULL << (i - 1); i > 0; --i, m >>= 1)
+		if ((unsigned long long int)n & m)
 			break;
 	return (i);
 #endif

t/.gitignore

@@ -10,6 +10,7 @@
 /t_digest
 /t_enc
 /t_endian
+/t_ffs_fls
 /t_fletcher
 /t_hash
 /t_hmac_sha1

t/Makefile.am

@@ -105,7 +105,8 @@ t_strchrnul_LDADD = $(libt) $(libcore)
 t_strlcat_LDADD = $(libt) $(libcore)
 t_strlcmp_LDADD = $(libt) $(libcore)
 t_strlcpy_LDADD = $(libt) $(libcore)
-TESTS += t_rol_ror
+TESTS += t_ffs_fls t_rol_ror
+t_ffs_fls_LDADD = $(libt) $(libcore)
 t_rol_ror_LDADD = $(libt) $(libcore)
 TESTS += t_string t_wstring
 EXTRA_DIST += t__string.c

t/t_ffs_fls.c

@@ -0,0 +1,153 @@
+/*-
+ * Copyright (c) 2014-2018 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stddef.h>
+#include <stdint.h>
+#include <unistd.h>
+
+/* test our own code, not the compiler's */
+#undef HAVE___BUILTIN_CLZ
+#undef HAVE___BUILTIN_CTZ
+#undef HAVE___BUILTIN_FFS
+#undef HAVE___BUILTIN_FFSL
+#undef HAVE___BUILTIN_FFSLL
+#undef HAVE___BUILTIN_FLS
+#undef HAVE___BUILTIN_FLSL
+#undef HAVE___BUILTIN_FLSLL
+
+#include <cryb/bitwise.h>
+
+#include <cryb/test.h>
+
+static int
+t_ffs(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_ffs(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++) {
+		t_printv("ffs(0x%08x) == %d\n", u, cryb_ffs(u));
+		ret &= t_compare_i(n, cryb_ffs(u));
+	}
+	return (ret);
+}
+
+static int
+t_ffsl(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	long int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_ffs(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++)
+		ret &= t_compare_i(n, cryb_ffsl(u));
+	return (ret);
+}
+
+static int
+t_ffsll(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	long long int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_ffs(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++)
+		ret &= t_compare_i(n, cryb_ffsll(u));
+	return (ret);
+}
+
+static int
+t_fls(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	unsigned int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_fls(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++) {
+		t_printv("fls(0x%08x) == %d\n", u, cryb_fls(u));
+		ret &= t_compare_i(n, cryb_fls(u));
+	}
+	return (ret);
+}
+
+static int
+t_flsl(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	unsigned long int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_flsl(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++) {
+		t_printv("flsl(0x%08lx) == %d\n", u, cryb_flsl(u));
+		ret &= t_compare_i(n, cryb_flsl(u));
+	}
+	return (ret);
+}
+
+static int
+t_flsll(char **desc CRYB_UNUSED, void *arg CRYB_UNUSED)
+{
+	unsigned long long int u;
+	int n, ret;
+
+	ret = t_compare_i(0, cryb_flsll(0));
+	for (u = 1, n = 1; u != 0; u <<= 1, n++) {
+		t_printv("flsll(0x%016llx) == %d\n", u, cryb_flsll(u));
+		ret &= t_compare_i(n, cryb_flsll(u));
+	}
+	return (ret);
+}
+
+
+/***************************************************************************
+ * Boilerplate
+ */
+
+static int
+t_prepare(int argc CRYB_UNUSED, char *argv[] CRYB_UNUSED)
+{
+
+	t_add_test(t_ffs, 0, "ffs");
+	t_add_test(t_ffsl, 0, "ffsl");
+	t_add_test(t_ffsll, 0, "ffsll");
+	t_add_test(t_fls, 0, "fls");
+	t_add_test(t_flsl, 0, "flsl");
+	t_add_test(t_flsll, 0, "flsll");
+	return (0);
+}
+
+int
+main(int argc, char *argv[])
+{
+
+	t_main(t_prepare, NULL, argc, argv);
+}