nss: Export nscd hash function as __nss_hash [BZ #22459]

1 files changed, 79 insertions, 0 deletions

diff --git a/nss/nss_hash.c b/nss/nss_hash.c
new file mode 100644
index 0000000000..5fb837a381
--- /dev/null
+++ b/nss/nss_hash.c
@@ -0,0 +1,79 @@
+/* Copyright (c) 1997-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997.
+
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <nss.h>
+
+/* This is from libc/db/hash/hash_func.c, hash3 is static there */
+/*
+ * This is INCREDIBLY ugly, but fast.  We break the string up into 8 byte
+ * units.  On the first time through the loop we get the "leftover bytes"
+ * (strlen % 8).  On every other iteration, we perform 8 HASHC's so we handle
+ * all 8 bytes.  Essentially, this saves us 7 cmp & branch instructions.  If
+ * this routine is heavily used enough, it's worth the ugly coding.
+ *
+ * OZ's original sdbm hash
+ */
+uint32_t
+__nss_hash (const void *keyarg, size_t len)
+{
+  const unsigned char *key;
+  size_t loop;
+  uint32_t h;
+
+#define HASHC   h = *key++ + 65599 * h
+
+  h = 0;
+  key = keyarg;
+  if (len > 0)
+    {
+      loop = (len + 8 - 1) >> 3;
+      switch (len & (8 - 1))
+        {
+        case 0:
+          do
+            {
+              HASHC;
+              /* FALLTHROUGH */
+            case 7:
+              HASHC;
+              /* FALLTHROUGH */
+            case 6:
+              HASHC;
+              /* FALLTHROUGH */
+            case 5:
+              HASHC;
+              /* FALLTHROUGH */
+            case 4:
+              HASHC;
+              /* FALLTHROUGH */
+            case 3:
+              HASHC;
+              /* FALLTHROUGH */
+            case 2:
+              HASHC;
+              /* FALLTHROUGH */
+            case 1:
+              HASHC;
+            }
+	  while (--loop);
+        }
+    }
+  return h;
+}
+
+libc_hidden_def (__nss_hash)