// 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/kernel.h> | |
#include <linux/export.h> | |
#include <linux/bitops.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); |