47 lines
1.1 KiB
C
47 lines
1.1 KiB
C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is library that provides for multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library is designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtommath.iahu.ca
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*/
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#include <tommath.h>
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/* multiply by a digit */
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int
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mp_mul_d (mp_int * a, mp_digit b, mp_int * c)
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{
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int res, pa, ix;
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mp_word r;
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mp_digit u;
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mp_int t;
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pa = a->used;
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if ((res = mp_init_size (&t, pa + 2)) != MP_OKAY) {
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return res;
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}
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t.used = pa + 2;
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u = 0;
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for (ix = 0; ix < pa; ix++) {
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r = ((mp_word) u) + ((mp_word) a->dp[ix]) * ((mp_word) b);
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t.dp[ix] = (mp_digit) (r & ((mp_word) MP_MASK));
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u = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
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}
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t.dp[ix] = u;
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t.sign = a->sign;
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mp_clamp (&t);
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mp_exch (&t, c);
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mp_clear (&t);
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return MP_OKAY;
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}
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