lib/int_sqrt.c

   1
   2 #include <linux/kernel.h>
   3 #include <linux/module.h>
   4
   5 /**
   6  * int_sqrt - rough approximation to sqrt
   7  * @x: integer of which to calculate the sqrt
   8  *
   9  * A very rough approximation to the sqrt() function.
  10  */
  11 unsigned long int_sqrt(unsigned long x)
  12 {
  13         unsigned long op, res, one;
  14
  15         op = x;
  16         res = 0;
  17
  18         one = 1UL << (BITS_PER_LONG - 2);
  19         while (one > op)
  20                 one >>= 2;
  21
  22         while (one != 0) {
  23                 if (op >= res + one) {
  24                         op = op - (res + one);
  25                         res = res +  2 * one;
  26                 }
  27                 res /= 2;
  28                 one /= 4;
  29         }
  30         return res;
  31 }
  32 EXPORT_SYMBOL(int_sqrt);