Mercurial > dropbear

annotate libtommath/bn_mp_lcm.c @ 375:8d149b812669 channel-fix

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- Add some extra tracing. - Be clearer about errfd be used for read versus write with ERRFD_IS_READ and ERRFD_IS_WRITE macros
author Matt Johnston <matt@ucc.asn.au>
date Tue, 05 Dec 2006 14:42:03 +0000
parents eed26cff980b
children 5ff8218bcee9
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284
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1 #include <tommath.h>
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2 #ifdef BN_MP_LCM_C
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3 /* LibTomMath, multiple-precision integer library -- Tom St Denis
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4 *
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5 * LibTomMath is a library that provides multiple-precision
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6 * integer arithmetic as well as number theoretic functionality.
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7 *
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8 * The library was designed directly after the MPI library by
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9 * Michael Fromberger but has been written from scratch with
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10 * additional optimizations in place.
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11 *
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12 * The library is free for all purposes without any express
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13 * guarantee it works.
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14 *
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15 * Tom St Denis, [email protected], http://math.libtomcrypt.org
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16 */
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17
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18 /* computes least common multiple as |a*b|/(a, b) */
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19 int mp_lcm (mp_int * a, mp_int * b, mp_int * c)
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20 {
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21 int res;
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22 mp_int t1, t2;
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23
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24
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25 if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) {
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26 return res;
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27 }
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28
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29 /* t1 = get the GCD of the two inputs */
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30 if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) {
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31 goto LBL_T;
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32 }
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33
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34 /* divide the smallest by the GCD */
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35 if (mp_cmp_mag(a, b) == MP_LT) {
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36 /* store quotient in t2 such that t2 * b is the LCM */
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37 if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) {
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38 goto LBL_T;
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39 }
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40 res = mp_mul(b, &t2, c);
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41 } else {
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42 /* store quotient in t2 such that t2 * a is the LCM */
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43 if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) {
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44 goto LBL_T;
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45 }
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46 res = mp_mul(a, &t2, c);
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47 }
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48
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49 /* fix the sign to positive */
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50 c->sign = MP_ZPOS;
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51
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52 LBL_T:
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53 mp_clear_multi (&t1, &t2, NULL);
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54 return res;
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55 }
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56 #endif