47 lines
1002 B
C
47 lines
1002 B
C
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/* TomsFastMath, a fast ISO C bignum library.
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*
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* This project is meant to fill in where LibTomMath
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* falls short. That is speed ;-)
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*
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* This project is public domain and free for all purposes.
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*
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* Tom St Denis, tomstdenis@gmail.com
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*/
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#include "bignum_fast.h"
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static const int lnz[16] = {
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4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0
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};
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/* Counts the number of lsbs which are zero before the first zero bit */
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int fp_cnt_lsb(fp_int *a)
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{
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int x;
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fp_digit q, qq;
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/* easy out */
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if (fp_iszero(a) == 1) {
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return 0;
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}
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/* scan lower digits until non-zero */
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for (x = 0; x < a->used && a->dp[x] == 0; x++);
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q = a->dp[x];
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x *= DIGIT_BIT;
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/* now scan this digit until a 1 is found */
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if ((q & 1) == 0) {
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do {
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qq = q & 15;
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x += lnz[qq];
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q >>= 4;
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} while (qq == 0);
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}
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return x;
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}
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/* $Source: /cvs/libtom/tomsfastmath/src/bit/fp_cnt_lsb.c,v $ */
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/* $Revision: 1.1 $ */
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/* $Date: 2006/12/31 21:25:53 $ */
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