int_sqrt.c

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#include <linux/kernel.h>
#include <linux/export.h>

unsigned long int_sqrt(unsigned long x)
{
    unsigned long op, res, one;

    op = x;
    res = 0;

    one = 1UL << (BITS_PER_LONG - 2);
    while (one > op)
        one >>= 2;

    while (one != 0) {
        if (op >= res + one) {
            op = op - (res + one);
            res = res +  2 * one;
        }
        res /= 2;
        one /= 4;
    }
    return res;
}
EXPORT_SYMBOL(int_sqrt);