// 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