source: mainline/common/include/adt/gcdlcm.h@ 283bb9f

Last change on this file since 283bb9f was 283bb9f, checked in by Martin Decky <martin@…>, 2 weeks ago

Improve the GCD/LCM implementations

Use a faster variant of the Euclid's algorithm to compute the greatest
common divisor.

Use a better variant of the least common multiple computation that
implicitly avoids overflows.

  • Property mode set to 100644
File size: 2.1 KB
Line 
1/*
2 * Copyright (c) 2009 Martin Decky
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 *
9 * - Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * - 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 * - The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/** @addtogroup libc
30 * @{
31 */
32/** @file
33 */
34
35#ifndef _LIBC_GCDLCM_H_
36#define _LIBC_GCDLCM_H_
37
38#include <stddef.h>
39#include <stdint.h>
40
41#define DECLARE_GCD(type, name) \
42 static inline type name(type a, type b) \
43 { \
44 while (b != 0) { \
45 type remainder = a % b; \
46 a = b; \
47 b = remainder; \
48 } \
49 \
50 return a; \
51 }
52
53#define DECLARE_LCM(type, name, gcd) \
54 static inline type name(type a, type b) \
55 { \
56 return (a / gcd(a, b)) * b; \
57 }
58
59DECLARE_GCD(uint32_t, gcd32);
60DECLARE_GCD(uint64_t, gcd64);
61DECLARE_GCD(size_t, gcd);
62
63DECLARE_LCM(uint32_t, lcm32, gcd32);
64DECLARE_LCM(uint64_t, lcm64, gcd64);
65DECLARE_LCM(size_t, lcm, gcd);
66
67#endif
68
69/** @}
70 */
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