1*8ccd4a63SDavid du Colombier #include "os.h"
2*8ccd4a63SDavid du Colombier #include <mp.h>
3*8ccd4a63SDavid du Colombier #include "dat.h"
4*8ccd4a63SDavid du Colombier
5*8ccd4a63SDavid du Colombier // res = b << shift
6*8ccd4a63SDavid du Colombier void
mpleft(mpint * b,int shift,mpint * res)7*8ccd4a63SDavid du Colombier mpleft(mpint *b, int shift, mpint *res)
8*8ccd4a63SDavid du Colombier {
9*8ccd4a63SDavid du Colombier int d, l, r, i, otop;
10*8ccd4a63SDavid du Colombier mpdigit this, last;
11*8ccd4a63SDavid du Colombier
12*8ccd4a63SDavid du Colombier // a negative left shift is a right shift
13*8ccd4a63SDavid du Colombier if(shift < 0){
14*8ccd4a63SDavid du Colombier mpright(b, -shift, res);
15*8ccd4a63SDavid du Colombier return;
16*8ccd4a63SDavid du Colombier }
17*8ccd4a63SDavid du Colombier
18*8ccd4a63SDavid du Colombier // b and res may be the same so remember the old top
19*8ccd4a63SDavid du Colombier otop = b->top;
20*8ccd4a63SDavid du Colombier
21*8ccd4a63SDavid du Colombier // shift
22*8ccd4a63SDavid du Colombier mpbits(res, otop*Dbits + shift); // overkill
23*8ccd4a63SDavid du Colombier res->top = DIGITS(otop*Dbits + shift);
24*8ccd4a63SDavid du Colombier d = shift/Dbits;
25*8ccd4a63SDavid du Colombier l = shift - d*Dbits;
26*8ccd4a63SDavid du Colombier r = Dbits - l;
27*8ccd4a63SDavid du Colombier
28*8ccd4a63SDavid du Colombier if(l == 0){
29*8ccd4a63SDavid du Colombier for(i = otop-1; i >= 0; i--)
30*8ccd4a63SDavid du Colombier res->p[i+d] = b->p[i];
31*8ccd4a63SDavid du Colombier } else {
32*8ccd4a63SDavid du Colombier last = 0;
33*8ccd4a63SDavid du Colombier for(i = otop-1; i >= 0; i--) {
34*8ccd4a63SDavid du Colombier this = b->p[i];
35*8ccd4a63SDavid du Colombier res->p[i+d+1] = (last<<l) | (this>>r);
36*8ccd4a63SDavid du Colombier last = this;
37*8ccd4a63SDavid du Colombier }
38*8ccd4a63SDavid du Colombier res->p[d] = last<<l;
39*8ccd4a63SDavid du Colombier }
40*8ccd4a63SDavid du Colombier for(i = 0; i < d; i++)
41*8ccd4a63SDavid du Colombier res->p[i] = 0;
42*8ccd4a63SDavid du Colombier
43*8ccd4a63SDavid du Colombier // normalize
44*8ccd4a63SDavid du Colombier while(res->top > 0 && res->p[res->top-1] == 0)
45*8ccd4a63SDavid du Colombier res->top--;
46*8ccd4a63SDavid du Colombier }
47