Mercurial > dropbear

annotate tomsfastmath/src/mul/fp_mul_2.c @ 646:f10335e5e42f dropbear-tfm

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- More asm constraint fixes. Now seems to build OK on 32-bit OS X.
author Matt Johnston <matt@ucc.asn.au>
date Wed, 30 Nov 2011 23:03:47 +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 void fp_mul_2(fp_int * a, fp_int * b)
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13 {
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14 int x, oldused;
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16 oldused = b->used;
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17 b->used = a->used;
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19 {
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20 register fp_digit r, rr, *tmpa, *tmpb;
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22 /* alias for source */
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23 tmpa = a->dp;
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25 /* alias for dest */
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26 tmpb = b->dp;
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28 /* carry */
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29 r = 0;
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30 for (x = 0; x < a->used; x++) {
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32 /* get what will be the *next* carry bit from the
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33 * MSB of the current digit
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34 */
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35 rr = *tmpa >> ((fp_digit)(DIGIT_BIT - 1));
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37 /* now shift up this digit, add in the carry [from the previous] */
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38 *tmpb++ = ((*tmpa++ << ((fp_digit)1)) | r);
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40 /* copy the carry that would be from the source
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41 * digit into the next iteration
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42 */
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43 r = rr;
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44 }
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46 /* new leading digit? */
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47 if (r != 0 && b->used != (FP_SIZE-1)) {
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48 /* add a MSB which is always 1 at this point */
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49 *tmpb = 1;
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50 ++(b->used);
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51 }
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53 /* now zero any excess digits on the destination
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54 * that we didn't write to
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55 */
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56 tmpb = b->dp + b->used;
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57 for (x = b->used; x < oldused; x++) {
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58 *tmpb++ = 0;
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59 }
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60 }
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61 b->sign = a->sign;
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62 }
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65 /* $Source$ */
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66 /* $Revision$ */
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67 /* $Date$ */