1d2baefc13
this showed a conservative 3% incrase in PPS. Differential Revision: https://reviews.freebsd.org/D461 Submitted by: des Reviewed by: emaste MFC after: 1 month
75 lines
2.3 KiB
C
75 lines
2.3 KiB
C
/*-
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* Copyright (c) 2014 Dag-Erling Smørgrav
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* All rights reserved.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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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#include <sys/hash.h>
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#include <sys/endian.h>
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#include <sys/stdint.h>
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#include <sys/types.h>
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#define rol32(i32, n) ((i32) << (n) | (i32) >> (32 - (n)))
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/*
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* $FreeBSD$
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* Simple implementation of the Murmur3-32 hash function optimized for
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* aligned sequences of 32-bit words. If len is not a multiple of 4, it
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* will be rounded down, droping trailer bytes.
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*/
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uint32_t
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murmur3_aligned_32(const void *data, size_t len, uint32_t seed)
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{
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const uint32_t *data32;
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uint32_t hash, k;
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size_t res;
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/* initialize */
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len -= len % sizeof(*data32);
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res = len;
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data32 = data;
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hash = seed;
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/* iterate */
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for (res = 0; res < len; res += sizeof(*data32), data32++) {
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k = le32toh(*data32);
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k *= 0xcc9e2d51;
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k = rol32(k, 15);
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k *= 0x1b873593;
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hash ^= k;
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hash = rol32(hash, 13);
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hash *= 5;
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hash += 0xe6546b64;
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}
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/* finalize */
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hash ^= (uint32_t)len;
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hash ^= hash >> 16;
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hash *= 0x85ebca6b;
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hash ^= hash >> 13;
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hash *= 0xc2b2ae35;
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hash ^= hash >> 16;
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return (hash);
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}
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