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80 lines
2.2 KiB
C
80 lines
2.2 KiB
C
/* Copyright (c) 1997-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <nss.h>
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/* This is from libc/db/hash/hash_func.c, hash3 is static there */
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/*
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* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
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* units. On the first time through the loop we get the "leftover bytes"
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* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
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* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
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* this routine is heavily used enough, it's worth the ugly coding.
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*
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* OZ's original sdbm hash
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*/
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uint32_t
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__nss_hash (const void *keyarg, size_t len)
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{
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const unsigned char *key;
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size_t loop;
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uint32_t h;
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#define HASHC h = *key++ + 65599 * h
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h = 0;
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key = keyarg;
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if (len > 0)
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{
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loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1))
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{
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case 0:
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do
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{
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HASHC;
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/* FALLTHROUGH */
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case 7:
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HASHC;
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/* FALLTHROUGH */
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case 6:
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HASHC;
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/* FALLTHROUGH */
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case 5:
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HASHC;
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/* FALLTHROUGH */
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case 4:
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HASHC;
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/* FALLTHROUGH */
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case 3:
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HASHC;
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/* FALLTHROUGH */
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case 2:
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HASHC;
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/* FALLTHROUGH */
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case 1:
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HASHC;
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}
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while (--loop);
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}
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}
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return h;
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}
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libc_hidden_def (__nss_hash)
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