72 lines
1.7 KiB
C
72 lines
1.7 KiB
C
#include <tommath_private.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, tstdenis82@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;
|
|
}
|
|
/* no need to shift 0 around */
|
|
if (mp_iszero(a) == MP_YES) {
|
|
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;
|
|
}
|
|
}
|
|
|
|
{
|
|
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
|
|
|
|
/* ref: $Format:%D$ */
|
|
/* git commit: $Format:%H$ */
|
|
/* commit time: $Format:%ai$ */
|