mfbt/MathAlgorithms.h
author Vicamo Yang <vyang@mozilla.com>
Thu, 18 Apr 2013 09:09:42 +0800
changeset 119099 1b6e432f7f8b16b3abb9922cbd043bbdad6474c8
parent 108984 b2ad6e5fc690e5fd561ef698d0bf8e0f291d9d04
permissions -rw-r--r--
Bug 849739 3/4: IPC. r=bent, a=leo+

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* mfbt maths algorithms. */

#ifndef mozilla_MathAlgorithms_h_
#define mozilla_MathAlgorithms_h_

#include "mozilla/Assertions.h"

namespace mozilla {

// Greatest Common Divisor
template<typename IntegerType>
MOZ_ALWAYS_INLINE IntegerType
EuclidGCD(IntegerType a, IntegerType b)
{
  // Euclid's algorithm; O(N) in the worst case.  (There are better
  // ways, but we don't need them for the current use of this algo.)
  MOZ_ASSERT(a > 0);
  MOZ_ASSERT(b > 0);

  while (a != b) {
    if (a > b) {
      a = a - b;
    } else {
      b = b - a;
    }
  }

  return a;
}

// Least Common Multiple
template<typename IntegerType>
MOZ_ALWAYS_INLINE IntegerType
EuclidLCM(IntegerType a, IntegerType b)
{
  // Divide first to reduce overflow risk.
  return (a / EuclidGCD(a, b)) * b;
}

} /* namespace mozilla */

#endif  /* mozilla_MathAlgorithms_h_ */