36 lines
790 B
C
36 lines
790 B
C
#include "tommath_private.h"
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#ifdef MP_2EXPT_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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/* computes a = 2**b
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*
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* Simple algorithm which zeroes the int, grows it then just sets one bit
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* as required.
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*/
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mp_err mp_2expt(mp_int *a, int b)
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{
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mp_err err;
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if (b < 0) {
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return MP_VAL;
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}
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/* zero a as per default */
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mp_zero(a);
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/* grow a to accommodate the single bit */
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if ((err = mp_grow(a, (b / MP_DIGIT_BIT) + 1)) != MP_OKAY) {
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return err;
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}
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/* set the used count of where the bit will go */
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a->used = (b / MP_DIGIT_BIT) + 1;
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/* put the single bit in its place */
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a->dp[b / MP_DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % MP_DIGIT_BIT);
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return MP_OKAY;
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}
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#endif
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