1// Copyright (c) 2011 Google, Inc.
2//
3// Permission is hereby granted, free of charge, to any person obtaining a copy
4// of this software and associated documentation files (the "Software"), to deal
5// in the Software without restriction, including without limitation the rights
6// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
7// copies of the Software, and to permit persons to whom the Software is
8// furnished to do so, subject to the following conditions:
9//
10// The above copyright notice and this permission notice shall be included in
11// all copies or substantial portions of the Software.
12//
13// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
18// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
19// THE SOFTWARE.
20
21/*
22 * Copyright (c) 2017 by Delphix. All rights reserved.
23 */
24
25#include <sys/cityhash.h>
26
27#define	HASH_K1 0xb492b66fbe98f273ULL
28#define	HASH_K2 0x9ae16a3b2f90404fULL
29
30/*
31 * Bitwise right rotate.  Normally this will compile to a single
32 * instruction.
33 */
34static inline uint64_t
35rotate(uint64_t val, int shift)
36{
37	// Avoid shifting by 64: doing so yields an undefined result.
38	return (shift == 0 ? val : (val >> shift) | (val << (64 - shift)));
39}
40
41static inline uint64_t
42cityhash_helper(uint64_t u, uint64_t v, uint64_t mul)
43{
44	uint64_t a = (u ^ v) * mul;
45	a ^= (a >> 47);
46	uint64_t b = (v ^ a) * mul;
47	b ^= (b >> 47);
48	b *= mul;
49	return (b);
50}
51
52uint64_t
53cityhash4(uint64_t w1, uint64_t w2, uint64_t w3, uint64_t w4)
54{
55	uint64_t mul = HASH_K2 + 64;
56	uint64_t a = w1 * HASH_K1;
57	uint64_t b = w2;
58	uint64_t c = w4 * mul;
59	uint64_t d = w3 * HASH_K2;
60	return (cityhash_helper(rotate(a + b, 43) + rotate(c, 30) + d,
61	    a + rotate(b + HASH_K2, 18) + c, mul));
62
63}
64