forked from ibphoenix/tomsfastmath
32 lines
705 B
C
32 lines
705 B
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@iahu.ca
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*/
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#include <tfm.h>
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/* unsigned subtraction ||a|| >= ||b|| ALWAYS! */
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void s_fp_sub(fp_int *a, fp_int *b, fp_int *c)
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{
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int x, oldused;
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fp_word t;
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oldused = c->used;
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c->used = a->used;
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t = 0;
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for (x = 0; x < a->used; x++) {
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t = ((fp_word)a->dp[x]) - (((fp_word)b->dp[x]) + t);
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c->dp[x] = (fp_digit)t;
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t = (t >> DIGIT_BIT) & 1;
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}
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for (; x < oldused; x++) {
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c->dp[x] = 0;
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}
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fp_clamp(c);
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}
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