sys/dev/drm/include/linux/gcd.h

   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
  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 #endif /* _GCD_H */