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annotate tomsfastmath/src/mul/fp_mul_2d.c @ 643:a362b62d38b2 dropbear-tfm

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Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a with Makefile.in renamed
author Matt Johnston <matt@ucc.asn.au>
date Wed, 23 Nov 2011 18:10:20 +0700
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a362b62d38b2 Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a
Matt Johnston <matt@ucc.asn.au>
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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 * 2**d */
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13 void fp_mul_2d(fp_int *a, int b, fp_int *c)
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14 {
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15 fp_digit carry, carrytmp, shift;
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16 int x;
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18 /* copy it */
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19 fp_copy(a, c);
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21 /* handle whole digits */
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22 if (b >= DIGIT_BIT) {
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23 fp_lshd(c, b/DIGIT_BIT);
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24 }
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25 b %= DIGIT_BIT;
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27 /* shift the digits */
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28 if (b != 0) {
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29 carry = 0;
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30 shift = DIGIT_BIT - b;
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31 for (x = 0; x < c->used; x++) {
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32 carrytmp = c->dp[x] >> shift;
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33 c->dp[x] = (c->dp[x] << b) + carry;
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34 carry = carrytmp;
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35 }
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36 /* store last carry if room */
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37 if (carry && x < FP_SIZE) {
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38 c->dp[c->used++] = carry;
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39 }
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40 }
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41 fp_clamp(c);
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42 }
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45 /* $Source$ */
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46 /* $Revision$ */
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47 /* $Date$ */