summaryrefslogtreecommitdiffstats
path: root/libtommath/bn_mp_set_int.c
blob: 4c711809ae68c065c154098d57a4db26195f7fd6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
#include <tommath_private.h>
#ifdef BN_MP_SET_INT_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
 * additional optimizations in place.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 *
 * Tom St Denis, tstdenis82@gmail.com, http://libtom.org
 */

/* set a 32-bit const */
int mp_set_int(mp_int *a, unsigned long b)
{
   int     x, res;

   mp_zero(a);

   /* set four bits at a time */
   for (x = 0; x < 8; x++) {
      /* shift the number up four bits */
      if ((res = mp_mul_2d(a, 4, a)) != MP_OKAY) {
         return res;
      }

      /* OR in the top four bits of the source */
      a->dp[0] |= (b >> 28) & 15;

      /* shift the source up to the next four bits */
      b <<= 4;

      /* ensure that digits are not clamped off */
      a->used += 1;
   }
   mp_clamp(a);
   return MP_OKAY;
}
#endif

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