fp_mul_d.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 /* c = a * b */
00013 void fp_mul_d(fp_int *a, fp_digit b, fp_int *c)
00014 {
00015    fp_word  w;
00016    int      x, oldused;
00017 
00018    oldused = c->used;
00019    c->used = a->used;
00020    c->sign = a->sign;
00021    w       = 0;
00022    for (x = 0; x < a->used; x++) {
00023        w         = ((fp_word)a->dp[x]) * ((fp_word)b) + w;
00024        c->dp[x]  = (fp_digit)w;
00025        w         = w >> DIGIT_BIT;
00026    }
00027    if (w != 0 && (a->used != FP_SIZE)) {
00028       c->dp[c->used++] = w;
00029       ++x;
00030    }
00031    for (; x < oldused; x++) {
00032       c->dp[x] = 0;
00033    }
00034    fp_clamp(c);
00035 }
00036 
00037 
00038 /* $Source: /cvs/libtom/tomsfastmath/src/mul/fp_mul_d.c,v $ */
00039 /* $Revision: 1.1 $ */
00040 /* $Date: 2006/12/31 21:25:53 $ */