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37fb3e43 PD |
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 | */ | |
34 | static inline uint64_t | |
35 | rotate(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 | ||
41 | static inline uint64_t | |
42 | cityhash_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 | ||
52 | uint64_t | |
53 | cityhash4(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 | } |