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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /lib/math/int_sqrt.c | |
parent | Initial commit. (diff) | |
download | linux-upstream/6.1.76.tar.xz linux-upstream/6.1.76.zip |
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | lib/math/int_sqrt.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/lib/math/int_sqrt.c b/lib/math/int_sqrt.c new file mode 100644 index 000000000..a8170bb91 --- /dev/null +++ b/lib/math/int_sqrt.c @@ -0,0 +1,71 @@ +// 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 |