fp_2expt.c

00001 /* TomsFastMath, a fast ISO C bignum library.
00002  * 
00003  * This project is meant to fill in where LibTomMath
00004  * falls short.  That is speed ;-)
00005  *
00006  * This project is public domain and free for all purposes.
00007  * 
00008  * Tom St Denis, tomstdenis@gmail.com
00009  */
00010 #include <tfm.h>
00011 
00012 /* computes a = 2**b */
00013 void fp_2expt(fp_int *a, int b)
00014 {
00015    int     z;
00016 
00017    /* zero a as per default */
00018    fp_zero (a);
00019 
00020    if (b < 0) { 
00021       return;
00022    }
00023 
00024    z = b / DIGIT_BIT;
00025    if (z >= FP_SIZE) {
00026       return; 
00027    }
00028 
00029   /* set the used count of where the bit will go */
00030   a->used = z + 1;
00031 
00032   /* put the single bit in its place */
00033   a->dp[z] = ((fp_digit)1) << (b % DIGIT_BIT);
00034 }
00035 
00036 
00037 /* $Source: /cvs/libtom/tomsfastmath/src/exptmod/fp_2expt.c,v $ */
00038 /* $Revision: 1.1 $ */
00039 /* $Date: 2006/12/31 21:25:53 $ */