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comparison tomsfastmath/src/mul/fp_mul_2d.c @ 643:a362b62d38b2 dropbear-tfm

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Add tomsfastmath from git rev bfa4582842bc3bab42e4be4aed5703437049502a with Makefile.in renamed
author Matt Johnston <matt@ucc.asn.au>
date Wed, 23 Nov 2011 18:10:20 +0700
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642:33fd2f3499d2 643:a362b62d38b2
1 /* TomsFastMath, a fast ISO C bignum library.
2 *
3 * This project is meant to fill in where LibTomMath
4 * falls short. That is speed ;-)
5 *
6 * This project is public domain and free for all purposes.
7 *
8 * Tom St Denis, [email protected]
9 */
10 #include <tfm.h>
11
12 /* c = a * 2**d */
13 void fp_mul_2d(fp_int *a, int b, fp_int *c)
14 {
15 fp_digit carry, carrytmp, shift;
16 int x;
17
18 /* copy it */
19 fp_copy(a, c);
20
21 /* handle whole digits */
22 if (b >= DIGIT_BIT) {
23 fp_lshd(c, b/DIGIT_BIT);
24 }
25 b %= DIGIT_BIT;
26
27 /* shift the digits */
28 if (b != 0) {
29 carry = 0;
30 shift = DIGIT_BIT - b;
31 for (x = 0; x < c->used; x++) {
32 carrytmp = c->dp[x] >> shift;
33 c->dp[x] = (c->dp[x] << b) + carry;
34 carry = carrytmp;
35 }
36 /* store last carry if room */
37 if (carry && x < FP_SIZE) {
38 c->dp[c->used++] = carry;
39 }
40 }
41 fp_clamp(c);
42 }
43
44
45 /* $Source$ */
46 /* $Revision$ */
47 /* $Date$ */