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38 lines
652 B
38 lines
652 B
/* |
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* Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com> |
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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/kernel.h> |
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#include <linux/export.h> |
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/** |
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* int_sqrt - rough approximation to sqrt |
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* @x: integer of which to calculate the sqrt |
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* |
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* A very rough approximation to the sqrt() function. |
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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 << (BITS_PER_LONG - 2); |
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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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