43 lines
984 B
C
43 lines
984 B
C
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#include "tommath_private.h"
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#ifdef MP_LSHD_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis */
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/* SPDX-License-Identifier: Unlicense */
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/* shift left a certain amount of digits */
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mp_err mp_lshd(mp_int *a, int b)
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{
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mp_err err;
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int x;
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/* if its less than zero return */
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if (b <= 0) {
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return MP_OKAY;
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}
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/* no need to shift 0 around */
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if (mp_iszero(a)) {
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return MP_OKAY;
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}
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/* grow to fit the new digits */
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if ((err = mp_grow(a, a->used + b)) != MP_OKAY) {
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return err;
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}
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/* increment the used by the shift amount then copy upwards */
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a->used += b;
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/* much like mp_rshd this is implemented using a sliding window
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* except the window goes the other way around. Copying from
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* the bottom to the top. see mp_rshd.c for more info.
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*/
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for (x = a->used; x --> b;) {
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a->dp[x] = a->dp[x - b];
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}
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/* zero the lower digits */
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s_mp_zero_digs(a->dp, b);
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return MP_OKAY;
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}
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#endif
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