mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 13:00:06 +00:00
85 lines
2.3 KiB
C
85 lines
2.3 KiB
C
/* Copyright (c) 1997-2023 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 <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 4 byte
|
|
* units. On the first time through the loop we get the "leftover bytes"
|
|
* (len % 4). On every other iteration, we perform a 4x unrolled version
|
|
* HASHC. Further unrolling does not appear to help.
|
|
*
|
|
* OZ's original sdbm hash
|
|
*/
|
|
uint32_t
|
|
__nss_hash (const void *keyarg, size_t len)
|
|
{
|
|
enum
|
|
{
|
|
HASH_CONST_P0 = 1, /* (uint32_t)(65599 ^ 0). */
|
|
HASH_CONST_P1 = 65599, /* (uint32_t)(65599 ^ 1). */
|
|
HASH_CONST_P2 = 8261505, /* (uint32_t)(65599 ^ 2). */
|
|
HASH_CONST_P3 = 780587199, /* (uint32_t)(65599 ^ 3). */
|
|
HASH_CONST_P4 = 1139564289 /* (uint32_t)(65599 ^ 4). */
|
|
};
|
|
|
|
const unsigned char *key;
|
|
uint32_t h;
|
|
|
|
#define HASHC h = *key++ + HASH_CONST_P1 * h
|
|
|
|
h = 0;
|
|
key = keyarg;
|
|
if (len > 0)
|
|
{
|
|
switch ((len & (4 - 1)))
|
|
{
|
|
case 0:
|
|
/* h starts out as zero so no need to include the multiply. */
|
|
h = *key++;
|
|
/* FALLTHROUGH */
|
|
case 3:
|
|
HASHC;
|
|
/* FALLTHROUGH */
|
|
case 2:
|
|
HASHC;
|
|
/* FALLTHROUGH */
|
|
case 1:
|
|
HASHC;
|
|
/* FALLTHROUGH */
|
|
}
|
|
|
|
uint32_t c0, c1, c2, c3;
|
|
for (--len; len >= 4; len -= 4)
|
|
{
|
|
c0 = (unsigned char) *(key + 0);
|
|
c1 = (unsigned char) *(key + 1);
|
|
c2 = (unsigned char) *(key + 2);
|
|
c3 = (unsigned char) *(key + 3);
|
|
h = HASH_CONST_P4 * h + HASH_CONST_P3 * c0 + HASH_CONST_P2 * c1
|
|
+ HASH_CONST_P1 * c2 + HASH_CONST_P0 * c3;
|
|
|
|
key += 4;
|
|
}
|
|
}
|
|
return h;
|
|
}
|
|
|
|
|
|
libc_hidden_def (__nss_hash)
|