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annotate tomsfastmath/src/numtheory/fp_gcd.c @ 647:939cd3e22c87 dropbear-tfm

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- Fix constraints so we don't get warned about uninitialised variable (it isn't used as input by the asm)
author Matt Johnston <matt@ucc.asn.au>
date Wed, 30 Nov 2011 23:15:21 +0800
parents a362b62d38b2
children
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1 /* TomsFastMath, a fast ISO C bignum library.
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2 *
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3 * This project is meant to fill in where LibTomMath
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4 * falls short. That is speed ;-)
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5 *
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6 * This project is public domain and free for all purposes.
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7 *
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8 * Tom St Denis, [email protected]
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9 */
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10 #include <tfm.h>
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12 /* c = (a, b) */
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13 void fp_gcd(fp_int *a, fp_int *b, fp_int *c)
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14 {
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15 fp_int u, v, r;
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17 /* either zero than gcd is the largest */
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18 if (fp_iszero (a) == 1 && fp_iszero (b) == 0) {
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19 fp_abs (b, c);
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20 return;
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21 }
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22 if (fp_iszero (a) == 0 && fp_iszero (b) == 1) {
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23 fp_abs (a, c);
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24 return;
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25 }
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27 /* optimized. At this point if a == 0 then
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28 * b must equal zero too
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29 */
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30 if (fp_iszero (a) == 1) {
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31 fp_zero(c);
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32 return;
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33 }
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35 /* sort inputs */
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36 if (fp_cmp_mag(a, b) != FP_LT) {
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37 fp_init_copy(&u, a);
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38 fp_init_copy(&v, b);
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39 } else {
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40 fp_init_copy(&u, b);
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41 fp_init_copy(&v, a);
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42 }
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44 fp_zero(&r);
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45 while (fp_iszero(&v) == FP_NO) {
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46 fp_mod(&u, &v, &r);
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47 fp_copy(&v, &u);
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48 fp_copy(&r, &v);
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49 }
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50 fp_copy(&u, c);
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51 }
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53 /* $Source$ */
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54 /* $Revision$ */
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55 /* $Date$ */