math_func.cpp

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/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */
 
#include "../stdafx.h"
#include "math_func.hpp"
 
#include "../safeguards.h"
 
int DivideApprox(int a, int b)
{
  int random_like = ((a + b) * (a - b)) % b;
 
  int remainder = a % b;
 
  int ret = a / b;
  if (abs(random_like) < abs(remainder)) {
    ret += ((a < 0) ^ (b < 0)) ? -1 : 1;
  }
 
  return ret;
}
 
uint32_t IntSqrt(uint32_t num)
{
  uint32_t res = 0;
  uint32_t bit = 1UL << 30; // Second to top bit number.
 
  /* 'bit' starts at the highest power of four <= the argument. */
  while (bit > num) bit >>= 2;
 
  while (bit != 0) {
    if (num >= res + bit) {
      num -= res + bit;
      res = (res >> 1) + bit;
    } else {
      res >>= 1;
    }
    bit >>= 2;
  }
 
  /* Arithmetic rounding to nearest integer. */
  if (num > res) res++;
 
  return res;
}