1/*	$NetBSD$	*/
2
3#include <tommath.h>
4#ifdef BN_MP_MUL_D_C
5/* LibTomMath, multiple-precision integer library -- Tom St Denis
6 *
7 * LibTomMath is a library that provides multiple-precision
8 * integer arithmetic as well as number theoretic functionality.
9 *
10 * The library was designed directly after the MPI library by
11 * Michael Fromberger but has been written from scratch with
12 * additional optimizations in place.
13 *
14 * The library is free for all purposes without any express
15 * guarantee it works.
16 *
17 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
18 */
19
20/* multiply by a digit */
21int
22mp_mul_d (mp_int * a, mp_digit b, mp_int * c)
23{
24  mp_digit u, *tmpa, *tmpc;
25  mp_word  r;
26  int      ix, res, olduse;
27
28  /* make sure c is big enough to hold a*b */
29  if (c->alloc < a->used + 1) {
30    if ((res = mp_grow (c, a->used + 1)) != MP_OKAY) {
31      return res;
32    }
33  }
34
35  /* get the original destinations used count */
36  olduse = c->used;
37
38  /* set the sign */
39  c->sign = a->sign;
40
41  /* alias for a->dp [source] */
42  tmpa = a->dp;
43
44  /* alias for c->dp [dest] */
45  tmpc = c->dp;
46
47  /* zero carry */
48  u = 0;
49
50  /* compute columns */
51  for (ix = 0; ix < a->used; ix++) {
52    /* compute product and carry sum for this term */
53    r       = ((mp_word) u) + ((mp_word)*tmpa++) * ((mp_word)b);
54
55    /* mask off higher bits to get a single digit */
56    *tmpc++ = (mp_digit) (r & ((mp_word) MP_MASK));
57
58    /* send carry into next iteration */
59    u       = (mp_digit) (r >> ((mp_word) DIGIT_BIT));
60  }
61
62  /* store final carry [if any] and increment ix offset  */
63  *tmpc++ = u;
64  ++ix;
65
66  /* now zero digits above the top */
67  while (ix++ < olduse) {
68     *tmpc++ = 0;
69  }
70
71  /* set used count */
72  c->used = a->used + 1;
73  mp_clamp(c);
74
75  return MP_OKAY;
76}
77#endif
78
79/* Source: /cvs/libtom/libtommath/bn_mp_mul_d.c,v */
80/* Revision: 1.4 */
81/* Date: 2006/12/28 01:25:13 */
82