54 lines
1.1 KiB
C
54 lines
1.1 KiB
C
/* TomsFastMath, a fast ISO C bignum library.
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*
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* This project is meant to fill in where LibTomMath
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* falls short. That is speed ;-)
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*
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* This project is public domain and free for all purposes.
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*
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* Tom St Denis, tomstdenis@gmail.com
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*/
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#include <tfm_private.h>
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/* b = a/2 */
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void fp_div_2(fp_int * a, fp_int * b)
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{
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int x, oldused;
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oldused = b->used;
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b->used = a->used;
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{
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register fp_digit r, rr, *tmpa, *tmpb;
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/* source alias */
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tmpa = a->dp + b->used - 1;
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/* dest alias */
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tmpb = b->dp + b->used - 1;
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/* carry */
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r = 0;
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for (x = b->used - 1; x >= 0; x--) {
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/* get the carry for the next iteration */
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rr = *tmpa & 1;
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/* shift the current digit, add in carry and store */
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*tmpb-- = (*tmpa-- >> 1) | (r << (DIGIT_BIT - 1));
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/* forward carry to next iteration */
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r = rr;
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}
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/* zero excess digits */
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tmpb = b->dp + b->used;
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for (x = b->used; x < oldused; x++) {
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*tmpb++ = 0;
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}
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}
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b->sign = a->sign;
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fp_clamp (b);
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}
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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