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Commit | Line | Data |
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1 | /* | |
2 | * Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com> | |
3 | * | |
4 | * Based on the shift-and-subtract algorithm for computing integer | |
5 | * square root from Guy L. Steele. | |
6 | */ | |
7 | ||
8 | #include <linux/kernel.h> | |
9 | #include <linux/export.h> | |
10 | ||
11 | /** | |
12 | * int_sqrt - rough approximation to sqrt | |
13 | * @x: integer of which to calculate the sqrt | |
14 | * | |
15 | * A very rough approximation to the sqrt() function. | |
16 | */ | |
17 | unsigned long int_sqrt(unsigned long x) | |
18 | { | |
19 | unsigned long b, m, y = 0; | |
20 | ||
21 | if (x <= 1) | |
22 | return x; | |
23 | ||
24 | m = 1UL << (BITS_PER_LONG - 2); | |
25 | while (m != 0) { | |
26 | b = y + m; | |
27 | y >>= 1; | |
28 | ||
29 | if (x >= b) { | |
30 | x -= b; | |
31 | y += m; | |
32 | } | |
33 | m >>= 2; | |
34 | } | |
35 | ||
36 | return y; | |
37 | } | |
38 | EXPORT_SYMBOL(int_sqrt); |