127 lines
3.8 KiB
C
127 lines
3.8 KiB
C
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/****************************************************************************
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* libs/libc/search/hash_func.c
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*
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <sys/types.h>
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#include <stdint.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define HASH4 h = (h << 5) + h + *key++;
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/****************************************************************************
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* Private Types
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****************************************************************************/
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static uint32_t hash4(FAR const void *, size_t);
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/****************************************************************************
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* Public Data
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****************************************************************************/
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/* Global default hash function */
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uint32_t (*g_default_hash)(FAR const void *, size_t) = hash4;
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/* Hash function from Chris Torek. */
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static uint32_t hash4(FAR const void *keyarg, size_t len)
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{
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FAR const u_char *key = keyarg;
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uint32_t h = 0;
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size_t loop;
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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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HASH4;
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/* FALLTHROUGH */
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case 7:
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HASH4;
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/* FALLTHROUGH */
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case 6:
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HASH4;
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/* FALLTHROUGH */
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case 5:
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HASH4;
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/* FALLTHROUGH */
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case 4:
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HASH4;
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/* FALLTHROUGH */
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case 3:
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HASH4;
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/* FALLTHROUGH */
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case 2:
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HASH4;
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/* FALLTHROUGH */
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case 1:
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HASH4;
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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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