tests: add printflags function to libtests

* tests/printflags.c: New file.
* tests/tests.h (printflags): New prototype.
* tests/Makefile.am (libtests_a_SOURCES): Add it.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index d23d0d8..bd170fd 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -49,6 +49,7 @@
 	inode_of_sockfd.c \
 	overflowuid.c \
 	print_quoted_string.c \
+	printflags.c \
 	tail_alloc.c \
 	tests.h \
 	tprintf.c \
diff --git a/tests/printflags.c b/tests/printflags.c
new file mode 100644
index 0000000..badc85d
--- /dev/null
+++ b/tests/printflags.c
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 1991, 1992 Paul Kranenburg <pk@cs.few.eur.nl>
+ * Copyright (c) 1993 Branko Lankester <branko@hacktic.nl>
+ * Copyright (c) 1993, 1994, 1995, 1996 Rick Sladkey <jrs@world.std.com>
+ * Copyright (c) 1996-1999 Wichert Akkerman <wichert@cistron.nl>
+ * Copyright (c) 2005-2016 Dmitry V. Levin <ldv@altlinux.org>
+ * 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 ``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 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 "tests.h"
+#include "xlat.h"
+#include <stdio.h>
+
+int
+printflags(const struct xlat *xlat, unsigned long long flags,
+	   const char *const dflt)
+{
+	if (flags == 0 && xlat->val == 0 && xlat->str) {
+		fputs(xlat->str, stdout);
+		return 1;
+	}
+
+	int n;
+	char sep = 0;
+	for (n = 0; xlat->str; xlat++) {
+		if (xlat->val && (flags & xlat->val) == xlat->val) {
+			if (sep)
+				putc(sep, stdout);
+			else
+				sep = '|';
+			fputs(xlat->str, stdout);
+			flags &= ~xlat->val;
+			n++;
+		}
+	}
+
+	if (n) {
+		if (flags) {
+			if (sep)
+				putc(sep, stdout);
+			printf("%#llx", flags);
+			n++;
+		}
+	} else {
+		if (flags) {
+			printf("%#llx", flags);
+			if (dflt)
+				printf(" /* %s */", dflt);
+		} else {
+			if (dflt)
+				putc('0', stdout);
+		}
+	}
+
+	return n;
+}
diff --git a/tests/tests.h b/tests/tests.h
index 1d14f43..5604efc 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -87,9 +87,13 @@
 /* Check whether given gid matches kernel overflowgid. */
 void check_overflowgid(const int);
 
-/* Translate errno to its name */
+/* Translate errno to its name. */
 const char *errno2name(void);
 
+/* Print flags in symbolic form according to xlat table. */
+struct xlat;
+int printflags(const struct xlat *, const unsigned long long, const char *);
+
 # define ARRAY_SIZE(arg) ((unsigned int) (sizeof(arg) / sizeof((arg)[0])))
 # define LENGTH_OF(arg) ((unsigned int) sizeof(arg) - 1)