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1 /* LibTomMath, multiple-precision integer library -- Tom St Denis |
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2 * |
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3 * LibTomMath is a library that provides multiple-precision |
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4 * integer arithmetic as well as number theoretic functionality. |
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5 * |
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6 * The library was designed directly after the MPI library by |
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7 * Michael Fromberger but has been written from scratch with |
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8 * additional optimizations in place. |
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9 * |
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10 * The library is free for all purposes without any express |
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11 * guarantee it works. |
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12 * |
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13 * Tom St Denis, [email protected], http://math.libtomcrypt.org |
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14 */ |
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15 #include <tommath.h> |
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16 |
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17 /* computes least common multiple as |a*b|/(a, b) */ |
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18 int mp_lcm (mp_int * a, mp_int * b, mp_int * c) |
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19 { |
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20 int res; |
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21 mp_int t1, t2; |
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22 |
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23 |
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24 if ((res = mp_init_multi (&t1, &t2, NULL)) != MP_OKAY) { |
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25 return res; |
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26 } |
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27 |
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28 /* t1 = get the GCD of the two inputs */ |
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29 if ((res = mp_gcd (a, b, &t1)) != MP_OKAY) { |
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30 goto __T; |
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31 } |
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32 |
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33 /* divide the smallest by the GCD */ |
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34 if (mp_cmp_mag(a, b) == MP_LT) { |
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35 /* store quotient in t2 such that t2 * b is the LCM */ |
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36 if ((res = mp_div(a, &t1, &t2, NULL)) != MP_OKAY) { |
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37 goto __T; |
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38 } |
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39 res = mp_mul(b, &t2, c); |
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40 } else { |
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41 /* store quotient in t2 such that t2 * a is the LCM */ |
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42 if ((res = mp_div(b, &t1, &t2, NULL)) != MP_OKAY) { |
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43 goto __T; |
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44 } |
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45 res = mp_mul(a, &t2, c); |
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46 } |
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47 |
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48 /* fix the sign to positive */ |
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49 c->sign = MP_ZPOS; |
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50 |
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51 __T: |
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52 mp_clear_multi (&t1, &t2, NULL); |
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53 return res; |
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54 } |
