1 b3f61791 2004-03-21 devnull #include "os.h"
 2 b3f61791 2004-03-21 devnull #include <mp.h>
 3 b3f61791 2004-03-21 devnull #include "dat.h"
 4 b3f61791 2004-03-21 devnull 
 5 cbeb0b26 2006-04-01 devnull /* res = b << shift */
 6 b3f61791 2004-03-21 devnull void
 7 b3f61791 2004-03-21 devnull mpleft(mpint *b, int shift, mpint *res)
 8 b3f61791 2004-03-21 devnull {
 9 b3f61791 2004-03-21 devnull 	int d, l, r, i, otop;
10 b3f61791 2004-03-21 devnull 	mpdigit this, last;
11 b3f61791 2004-03-21 devnull 
12 b3f61791 2004-03-21 devnull 	res->sign = b->sign;
13 b3f61791 2004-03-21 devnull 	if(b->top==0){
14 b3f61791 2004-03-21 devnull 		res->top = 0;
15 b3f61791 2004-03-21 devnull 		return;
16 b3f61791 2004-03-21 devnull 	}
17 b3f61791 2004-03-21 devnull 
18 cbeb0b26 2006-04-01 devnull 	/* a negative left shift is a right shift */
19 b3f61791 2004-03-21 devnull 	if(shift < 0){
20 b3f61791 2004-03-21 devnull 		mpright(b, -shift, res);
21 b3f61791 2004-03-21 devnull 		return;
22 b3f61791 2004-03-21 devnull 	}
23 b3f61791 2004-03-21 devnull 
24 cbeb0b26 2006-04-01 devnull 	/* b and res may be the same so remember the old top */
25 b3f61791 2004-03-21 devnull 	otop = b->top;
26 b3f61791 2004-03-21 devnull 
27 cbeb0b26 2006-04-01 devnull 	/* shift */
28 cbeb0b26 2006-04-01 devnull 	mpbits(res, otop*Dbits + shift);	/* overkill */
29 b3f61791 2004-03-21 devnull 	res->top = DIGITS(otop*Dbits + shift);
30 b3f61791 2004-03-21 devnull 	d = shift/Dbits;
31 b3f61791 2004-03-21 devnull 	l = shift - d*Dbits;
32 b3f61791 2004-03-21 devnull 	r = Dbits - l;
33 b3f61791 2004-03-21 devnull 
34 b3f61791 2004-03-21 devnull 	if(l == 0){
35 b3f61791 2004-03-21 devnull 		for(i = otop-1; i >= 0; i--)
36 b3f61791 2004-03-21 devnull 			res->p[i+d] = b->p[i];
37 b3f61791 2004-03-21 devnull 	} else {
38 b3f61791 2004-03-21 devnull 		last = 0;
39 b3f61791 2004-03-21 devnull 		for(i = otop-1; i >= 0; i--) {
40 b3f61791 2004-03-21 devnull 			this = b->p[i];
41 b3f61791 2004-03-21 devnull 			res->p[i+d+1] = (last<<l) | (this>>r);
42 b3f61791 2004-03-21 devnull 			last = this;
43 b3f61791 2004-03-21 devnull 		}
44 b3f61791 2004-03-21 devnull 		res->p[d] = last<<l;
45 b3f61791 2004-03-21 devnull 	}
46 b3f61791 2004-03-21 devnull 	for(i = 0; i < d; i++)
47 b3f61791 2004-03-21 devnull 		res->p[i] = 0;
48 b3f61791 2004-03-21 devnull 
49 cbeb0b26 2006-04-01 devnull 	/* normalize */
50 b3f61791 2004-03-21 devnull 	while(res->top > 0 && res->p[res->top-1] == 0)
51 b3f61791 2004-03-21 devnull 		res->top--;
52 b3f61791 2004-03-21 devnull }