68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
|
#include <tommath.h>
|
||
|
|
#ifdef BN_MP_LSHD_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, tomstdenis@gmail.com, http://libtom.org
|
||
|
|
*/
|
||
|
|
|
||
|
|
/* shift left a certain amount of digits */
|
||
|
|
int mp_lshd (mp_int * a, int b)
|
||
|
|
{
|
||
|
|
int x, res;
|
||
|
|
|
||
|
|
/* if its less than zero return */
|
||
|
|
if (b <= 0) {
|
||
|
|
return MP_OKAY;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* grow to fit the new digits */
|
||
|
|
if (a->alloc < a->used + b) {
|
||
|
|
if ((res = mp_grow (a, a->used + b)) != MP_OKAY) {
|
||
|
|
return res;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
{
|
||
|
|
register mp_digit *top, *bottom;
|
||
|
|
|
||
|
|
/* increment the used by the shift amount then copy upwards */
|
||
|
|
a->used += b;
|
||
|
|
|
||
|
|
/* top */
|
||
|
|
top = a->dp + a->used - 1;
|
||
|
|
|
||
|
|
/* base */
|
||
|
|
bottom = a->dp + a->used - 1 - b;
|
||
|
|
|
||
|
|
/* much like mp_rshd this is implemented using a sliding window
|
||
|
|
* except the window goes the otherway around. Copying from
|
||
|
|
* the bottom to the top. see bn_mp_rshd.c for more info.
|
||
|
|
*/
|
||
|
|
for (x = a->used - 1; x >= b; x--) {
|
||
|
|
*top-- = *bottom--;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* zero the lower digits */
|
||
|
|
top = a->dp;
|
||
|
|
for (x = 0; x < b; x++) {
|
||
|
|
*top++ = 0;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return MP_OKAY;
|
||
|
|
}
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/* $Source$ */
|
||
|
|
/* $Revision: 0.41 $ */
|
||
|
|
/* $Date: 2007-04-18 09:58:18 +0000 $ */
|