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71 lines
1.2 KiB
71 lines
1.2 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (C) 2013 Davidlohr Bueso <[email protected]> |
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* |
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* Based on the shift-and-subtract algorithm for computing integer |
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* square root from Guy L. Steele. |
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*/ |
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#include <linux/export.h> |
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#include <linux/bitops.h> |
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#include <linux/limits.h> |
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#include <linux/math.h> |
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/** |
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* int_sqrt - computes the integer square root |
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* @x: integer of which to calculate the sqrt |
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* |
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* Computes: floor(sqrt(x)) |
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*/ |
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unsigned long int_sqrt(unsigned long x) |
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{ |
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unsigned long b, m, y = 0; |
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if (x <= 1) |
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return x; |
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m = 1UL << (__fls(x) & ~1UL); |
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while (m != 0) { |
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b = y + m; |
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y >>= 1; |
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if (x >= b) { |
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x -= b; |
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y += m; |
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} |
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m >>= 2; |
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} |
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return y; |
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} |
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EXPORT_SYMBOL(int_sqrt); |
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#if BITS_PER_LONG < 64 |
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/** |
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* int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input |
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* is expected. |
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* @x: 64bit integer of which to calculate the sqrt |
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*/ |
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u32 int_sqrt64(u64 x) |
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{ |
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u64 b, m, y = 0; |
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if (x <= ULONG_MAX) |
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return int_sqrt((unsigned long) x); |
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m = 1ULL << ((fls64(x) - 1) & ~1ULL); |
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while (m != 0) { |
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b = y + m; |
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y >>= 1; |
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if (x >= b) { |
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x -= b; |
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y += m; |
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} |
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m >>= 2; |
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} |
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return y; |
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} |
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EXPORT_SYMBOL(int_sqrt64); |
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#endif
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