46 lines
1.1 KiB
C
46 lines
1.1 KiB
C
#include "tommath_private.h"
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#ifdef BN_MP_2EXPT_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
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*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
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*
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* The library was designed directly after the MPI library by
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* Michael Fromberger but has been written from scratch with
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*/
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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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int mp_2expt(mp_int *a, int b)
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{
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int res;
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/* zero a as per default */
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mp_zero(a);
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/* grow a to accomodate the single bit */
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if ((res = mp_grow(a, (b / DIGIT_BIT) + 1)) != MP_OKAY) {
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return res;
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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 / DIGIT_BIT) + 1;
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/* put the single bit in its place */
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a->dp[b / DIGIT_BIT] = (mp_digit)1 << (mp_digit)(b % DIGIT_BIT);
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return MP_OKAY;
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}
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#endif
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/* ref: $Format:%D$ */
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/* git commit: $Format:%H$ */
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/* commit time: $Format:%ai$ */
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