### view libtommath/bn_mp_lshd.c @ 1549:5212630893ab

only clean libtom when using bundled libraries
author Matt Johnston Mon, 26 Feb 2018 23:13:54 +0800 8bba51a55704 f52919ffd3b1
line wrap: on
line source
```#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
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, [email protected], 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;
}
}

{
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
*/
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\$ */
```