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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172// 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