nss: Add tests for the nss_hash in nss_hash.h

If we want to further optimize the function tests are needed.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

nss/Makefile

@@ -62,6 +62,7 @@ tests := \
   test-digits-dots \
   test-netdb \
   tst-nss-getpwent \
+  tst-nss-hash \
   tst-nss-test1 \
   tst-nss-test2 \
   tst-nss-test4 \

nss/nss_hash.c

@@ -75,4 +75,5 @@ __nss_hash (const void *keyarg, size_t len)
   return h;
 }
 
+
 libc_hidden_def (__nss_hash)

nss/simple-nss-hash.h

@@ -0,0 +1,42 @@
+/* __simple_nss_hash for testing nss_hash function
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SIMPLE_NSS_HASH_H
+#define _SIMPLE_NSS_HASH_H 1
+
+#include <stdint.h>
+
+/* For testing/benchmarking purposes.  Real implementation in
+   nss/nss_hash.c.  */
+static uint32_t
+__attribute__ ((unused))
+__simple_nss_hash (const void *keyarg, size_t len)
+{
+  const unsigned char *key;
+  size_t i;
+  uint32_t h = 0;
+  key = keyarg;
+
+  for (i = 0; i < len; ++i)
+    h = *key++ + 65599 * h;
+
+  return h;
+}
+
+
+#endif /* simple-nss-hash.h */

nss/tst-nss-hash.c

@@ -0,0 +1,80 @@
+/* Test __nss_hash
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+#include <support/check.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <nss.h>
+#include <simple-nss-hash.h>
+
+uint32_t __nss_hash (const void *__key, size_t __length);
+
+static int
+do_fill_tests (size_t len, int fill)
+{
+  uint32_t expec, res;
+  char buf[len];
+  memset (buf, fill, len);
+
+  expec = __simple_nss_hash (buf, len);
+  res = __nss_hash (buf, len);
+  if (expec != res)
+    FAIL_EXIT1 ("FAIL: fill(%d) (%zu), %x != %x\n", fill, len, expec, res);
+
+  return 0;
+}
+
+static int
+do_rand_tests (size_t len)
+{
+  uint32_t expec, res;
+  size_t i;
+  char buf[len];
+  for (i = 0; i < len; ++i)
+    buf[i] = random ();
+
+  expec = __simple_nss_hash (buf, len);
+  res = __nss_hash (buf, len);
+  if (expec != res)
+    FAIL_EXIT1 ("FAIL: random (%zu), %x != %x\n", len, expec, res);
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  size_t i, j;
+  for (i = 0; i < 100; ++i)
+    {
+      for (j = 0; j < 8192; ++j)
+	{
+	  if (do_rand_tests (i))
+	    return 1;
+
+	  if (do_fill_tests (i, -1) || do_fill_tests (i, 1)
+	      || do_fill_tests (i, 0x80) || do_fill_tests (i, 0x88))
+	    return 1;
+	}
+    }
+  return 0;
+}
+
+#include <support/test-driver.c>