### view libtommath/bn_mp_mul_d.c @ 1470:8bba51a55704

Update to libtommath v1.0.1
author Matt Johnston Thu, 08 Feb 2018 23:11:40 +0800 60fc6476e044 f52919ffd3b1
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```#include <tommath_private.h>
#ifdef BN_MP_MUL_D_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], http://libtom.org
*/

/* multiply by a digit */
int
mp_mul_d (mp_int * a, mp_digit b, mp_int * c)
{
mp_digit u, *tmpa, *tmpc;
mp_word  r;
int      ix, res, olduse;

/* make sure c is big enough to hold a*b */
if (c->alloc < (a->used + 1)) {
if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) {
return res;
}
}

/* get the original destinations used count */
olduse = c->used;

/* set the sign */
c->sign = a->sign;

/* alias for a->dp [source] */
tmpa = a->dp;

/* alias for c->dp [dest] */
tmpc = c->dp;

/* zero carry */
u = 0;

/* compute columns */
for (ix = 0; ix < a->used; ix++) {
/* compute product and carry sum for this term */
r       = (mp_word)u + ((mp_word)*tmpa++ * (mp_word)b);

/* mask off higher bits to get a single digit */
*tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK));

/* send carry into next iteration */
u       = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
}

/* store final carry [if any] and increment ix offset  */
*tmpc++ = u;
++ix;

/* now zero digits above the top */
while (ix++ < olduse) {
*tmpc++ = 0;
}

/* set used count */
c->used = a->used + 1;
mp_clamp(c);

return MP_OKAY;
}
#endif

/* ref:         \$Format:%D\$ */
/* git commit:  \$Format:%H\$ */
/* commit time: \$Format:%ai\$ */
```