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142
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1 #include <tommath.h> |
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2 #ifdef BN_MP_LCM_C |
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2
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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 __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 __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 __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 __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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142
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56 #endif |
