PHP 使用位运算实现四则运算的代码(2)

<?php
  require 'addition.php';

  function divide($dividend, $divisor)
  {
    // 判断符号位
    $flag = ($dividend ^ $divisor) < 0 ? false : true;
    // 取得被除数符号位
    $dividend_flag = $dividend < 0 ? false : true;
    // 取绝对值
    $dividend = $dividend < 0 ? add(~$dividend, 1) : $dividend;
    $divisor = $divisor < 0 ? add(~$divisor, 1) : $divisor;

    $quotient = 0;
    $remainder = 0;

    if ($dividend < $divisor) {
      // 被除数小于除数的情况
      $remainder = $dividend;
      return 'quotient = ' . $quotient . ' remainder = ' . $remainder;
    }

    while ($dividend >= $divisor) {
      $i = 0;
      $mul_divisor = $divisor;

      while ($dividend >= ($mul_divisor << 1)) {
        $i ++;
        $mul_divisor <<= 1;
      }

      $dividend -= $mul_divisor;
      $quotient += 1 << $i;
    }

   $remainder = $dividend;
   if (! $flag) {
     $quotient = add(~ $quotient, 1);
   }
   if (! $dividend_flag) {
     $remainder = add(~$remainder, 1);
   }

   return 'quotient = ' . $quotient . ' remainder = ' . $remainder;
  }