xf.li | bdd93d5 | 2023-05-12 07:10:14 -0700 | [diff] [blame^] | 1 | /* Copyright (c) 1997-2016 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 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <stdint.h> |
| 20 | #include <rpcsvc/nis.h> |
| 21 | |
| 22 | /* This is from libc/db/hash/hash_func.c, hash3 is static there */ |
| 23 | /* |
| 24 | * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte |
| 25 | * units. On the first time through the loop we get the "leftover bytes" |
| 26 | * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle |
| 27 | * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If |
| 28 | * this routine is heavily used enough, it's worth the ugly coding. |
| 29 | * |
| 30 | * OZ's original sdbm hash |
| 31 | */ |
| 32 | uint32_t |
| 33 | __nis_hash (const void *keyarg, size_t len) |
| 34 | { |
| 35 | const u_char *key; |
| 36 | size_t loop; |
| 37 | uint32_t h; |
| 38 | |
| 39 | #define HASHC h = *key++ + 65599 * h |
| 40 | |
| 41 | h = 0; |
| 42 | key = keyarg; |
| 43 | if (len > 0) |
| 44 | { |
| 45 | loop = (len + 8 - 1) >> 3; |
| 46 | switch (len & (8 - 1)) |
| 47 | { |
| 48 | case 0: |
| 49 | do { |
| 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 | } while (--loop); |
| 73 | } |
| 74 | } |
| 75 | return h; |
| 76 | } |