Mercurial > dropbear
comparison tomsfastmath/src/exptmod/fp_2expt.c @ 643:a362b62d38b2 dropbear-tfm
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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| children |
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| 642:33fd2f3499d2 | 643:a362b62d38b2 |
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| 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 /* computes a = 2**b */ | |
| 13 void fp_2expt(fp_int *a, int b) | |
| 14 { | |
| 15 int z; | |
| 16 | |
| 17 /* zero a as per default */ | |
| 18 fp_zero (a); | |
| 19 | |
| 20 if (b < 0) { | |
| 21 return; | |
| 22 } | |
| 23 | |
| 24 z = b / DIGIT_BIT; | |
| 25 if (z >= FP_SIZE) { | |
| 26 return; | |
| 27 } | |
| 28 | |
| 29 /* set the used count of where the bit will go */ | |
| 30 a->used = z + 1; | |
| 31 | |
| 32 /* put the single bit in its place */ | |
| 33 a->dp[z] = ((fp_digit)1) << (b % DIGIT_BIT); | |
| 34 } | |
| 35 | |
| 36 | |
| 37 /* $Source$ */ | |
| 38 /* $Revision$ */ | |
| 39 /* $Date$ */ |