48 lines
967 B
C
48 lines
967 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@gmail.com
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*/
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#include <tfm_private.h>
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/* c = a * 2**d */
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void fp_mul_2d(fp_int *a, int b, fp_int *c)
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{
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fp_digit carry, carrytmp, shift;
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int x;
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/* copy it */
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fp_copy(a, c);
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/* handle whole digits */
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if (b >= DIGIT_BIT) {
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fp_lshd(c, b/DIGIT_BIT);
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}
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b %= DIGIT_BIT;
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/* shift the digits */
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if (b != 0) {
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carry = 0;
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shift = DIGIT_BIT - b;
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for (x = 0; x < c->used; x++) {
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carrytmp = c->dp[x] >> shift;
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c->dp[x] = (c->dp[x] << b) + carry;
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carry = carrytmp;
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}
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/* store last carry if room */
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if (carry && x < FP_SIZE) {
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c->dp[c->used++] = carry;
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}
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}
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fp_clamp(c);
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}
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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