bcda8fc696
* these double checks are not necessary * the compiler will move the early return outside of the called function, basically the functions is partially inlined * however lto/amalgamation needed for the optimization
43 lines
983 B
C
43 lines
983 B
C
#include "tommath_private.h"
|
|
#ifdef MP_LSHD_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
|
/* SPDX-License-Identifier: Unlicense */
|
|
|
|
/* shift left a certain amount of digits */
|
|
mp_err mp_lshd(mp_int *a, int b)
|
|
{
|
|
mp_err err;
|
|
int x;
|
|
|
|
/* if its less than zero return */
|
|
if (b <= 0) {
|
|
return MP_OKAY;
|
|
}
|
|
/* no need to shift 0 around */
|
|
if (mp_iszero(a)) {
|
|
return MP_OKAY;
|
|
}
|
|
|
|
/* grow to fit the new digits */
|
|
if ((err = mp_grow(a, a->used + b)) != MP_OKAY) {
|
|
return err;
|
|
}
|
|
|
|
/* increment the used by the shift amount then copy upwards */
|
|
a->used += 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 mp_rshd.c for more info.
|
|
*/
|
|
for (x = a->used; x --> b;) {
|
|
a->dp[x] = a->dp[x - b];
|
|
}
|
|
|
|
/* zero the lower digits */
|
|
s_mp_zero_digs(a->dp, b);
|
|
|
|
return MP_OKAY;
|
|
}
|
|
#endif
|