1 /*
2 * Copyright (c) 2015 Rimvydas Jasinskas
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice unmodified, this list of conditions, and the following
10 * disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /*
28 * Standard math function to compute biggest common divisor,
29 * based on Euclids algorithm.
30 *
31 * Long implementation adapted-from:
32 * lib/libc/stdlib/getopt_long.c
33 *
34 * Uses:
35 * 64-bit values;
36 * simplified loop form [if(MIN(a,b) == 0) return MAX(a,b)];
37 * swap() arguments just in case..
38 */
39
40 #ifndef _GCD_H
41 #define _GCD_H
42
43 #include <linux/kernel.h>
44
45 static inline uint64_t gcd64(uint64_t a, uint64_t b) __pure2;
46
47 /*
48 * Compute the greatest common divisor of a and b.
49 */
50 static inline uint64_t
gcd64(uint64_t a,uint64_t b)51 gcd64(uint64_t a, uint64_t b)
52 {
53 uint64_t c;
54
55 if (a < b)
56 swap(a, b);
57
58 if (b == 0)
59 return a;
60
61 while ((c = a % b) != 0) {
62 a = b;
63 b = c;
64 }
65
66 return (b);
67 }
68
69 static inline unsigned long
gcd(unsigned long a,unsigned long b)70 gcd(unsigned long a, unsigned long b)
71 {
72 return gcd64(a, b);
73 }
74
75 #endif /* _GCD_H */
76