// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com>
 *
 *  Based on the shift-and-subtract algorithm for computing integer
 *  square root from Guy L. Steele.
 */

#include <linux/export.h>
#include <linux/bitops.h>
#include <linux/limits.h>
#include <linux/math.h>

/**
 * int_sqrt - computes the integer square root
 * @x: integer of which to calculate the sqrt
 *
 * Computes: floor(sqrt(x))
 */
unsigned long int_sqrt(unsigned long x)
{
        unsigned long b, m, y = 0;

        if (x <= 1)
                return x;

        m = 1UL << (__fls(x) & ~1UL);
        while (m != 0) {
                b = y + m;
                y >>= 1;

                if (x >= b) {
                        x -= b;
                        y += m;
                }
                m >>= 2;
        }

        return y;
}
EXPORT_SYMBOL(int_sqrt);

#if BITS_PER_LONG < 64
/**
 * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
 * is expected.
 * @x: 64bit integer of which to calculate the sqrt
 */
u32 int_sqrt64(u64 x)
{
        u64 b, m, y = 0;

        if (x <= ULONG_MAX)
                return int_sqrt((unsigned long) x);

        m = 1ULL << ((fls64(x) - 1) & ~1ULL);
        while (m != 0) {
                b = y + m;
                y >>= 1;

                if (x >= b) {
                        x -= b;
                        y += m;
                }
                m >>= 2;
        }

        return y;
}
EXPORT_SYMBOL(int_sqrt64);
#endif