1/* Copyright (c) 1997-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <nss.h>
20
21/* This is from libc/db/hash/hash_func.c, hash3 is static there */
22/*
23 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
24 * units. On the first time through the loop we get the "leftover bytes"
25 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
26 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
27 * this routine is heavily used enough, it's worth the ugly coding.
28 *
29 * OZ's original sdbm hash
30 */
31uint32_t
32__nss_hash (const void *keyarg, size_t len)
33{
34 const unsigned char *key;
35 size_t loop;
36 uint32_t h;
37
38#define HASHC h = *key++ + 65599 * h
39
40 h = 0;
41 key = keyarg;
42 if (len > 0)
43 {
44 loop = (len + 8 - 1) >> 3;
45 switch (len & (8 - 1))
46 {
47 case 0:
48 do
49 {
50 HASHC;
51 /* FALLTHROUGH */
52 case 7:
53 HASHC;
54 /* FALLTHROUGH */
55 case 6:
56 HASHC;
57 /* FALLTHROUGH */
58 case 5:
59 HASHC;
60 /* FALLTHROUGH */
61 case 4:
62 HASHC;
63 /* FALLTHROUGH */
64 case 3:
65 HASHC;
66 /* FALLTHROUGH */
67 case 2:
68 HASHC;
69 /* FALLTHROUGH */
70 case 1:
71 HASHC;
72 }
73 while (--loop);
74 }
75 }
76 return h;
77}
78
79libc_hidden_def (__nss_hash)
80