1#include <tommath.h>
2#ifdef BN_MP_LSHD_C
3/* LibTomMath, multiple-precision integer library -- Tom St Denis
4 *
5 * LibTomMath is a library that provides multiple-precision
6 * integer arithmetic as well as number theoretic functionality.
7 *
8 * The library was designed directly after the MPI library by
9 * Michael Fromberger but has been written from scratch with
10 * additional optimizations in place.
11 *
12 * The library is free for all purposes without any express
13 * guarantee it works.
14 *
15 * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
16 */
17
18/* shift left a certain amount of digits */
19int mp_lshd (mp_int * a, int b)
20{
21  int     x, res;
22
23  /* if its less than zero return */
24  if (b <= 0) {
25    return MP_OKAY;
26  }
27
28  /* grow to fit the new digits */
29  if (a->alloc < a->used + b) {
30     if ((res = mp_grow (a, a->used + b)) != MP_OKAY) {
31       return res;
32     }
33  }
34
35  {
36    register mp_digit *top, *bottom;
37
38    /* increment the used by the shift amount then copy upwards */
39    a->used += b;
40
41    /* top */
42    top = a->dp + a->used - 1;
43
44    /* base */
45    bottom = a->dp + a->used - 1 - b;
46
47    /* much like mp_rshd this is implemented using a sliding window
48     * except the window goes the otherway around.  Copying from
49     * the bottom to the top.  see bn_mp_rshd.c for more info.
50     */
51    for (x = a->used - 1; x >= b; x--) {
52      *top-- = *bottom--;
53    }
54
55    /* zero the lower digits */
56    top = a->dp;
57    for (x = 0; x < b; x++) {
58      *top++ = 0;
59    }
60  }
61  return MP_OKAY;
62}
63#endif
64
65/* $Source$ */
66/* $Revision$ */
67/* $Date$ */
68