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 mpright(mpint *b, int shift, mpint *res)
 8 b3f61791 2004-03-21 devnull {
 9 b3f61791 2004-03-21 devnull 	int d, l, r, i;
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 right shift is a left shift */
19 b3f61791 2004-03-21 devnull 	if(shift < 0){
20 b3f61791 2004-03-21 devnull 		mpleft(b, -shift, res);
21 b3f61791 2004-03-21 devnull 		return;
22 b3f61791 2004-03-21 devnull 	}
23 b3f61791 2004-03-21 devnull 
24 b3f61791 2004-03-21 devnull 	if(res != b)
25 b3f61791 2004-03-21 devnull 		mpbits(res, b->top*Dbits - shift);
26 b3f61791 2004-03-21 devnull 	d = shift/Dbits;
27 b3f61791 2004-03-21 devnull 	r = shift - d*Dbits;
28 b3f61791 2004-03-21 devnull 	l = Dbits - r;
29 b3f61791 2004-03-21 devnull 
30 cbeb0b26 2006-04-01 devnull 	/*  shift all the bits out == zero */
31 b3f61791 2004-03-21 devnull 	if(d>=b->top){
32 b3f61791 2004-03-21 devnull 		res->top = 0;
33 b3f61791 2004-03-21 devnull 		return;
34 b3f61791 2004-03-21 devnull 	}
35 b3f61791 2004-03-21 devnull 
36 cbeb0b26 2006-04-01 devnull 	/* special case digit shifts */
37 b3f61791 2004-03-21 devnull 	if(r == 0){
38 b3f61791 2004-03-21 devnull 		for(i = 0; i < b->top-d; i++)
39 b3f61791 2004-03-21 devnull 			res->p[i] = b->p[i+d];
40 b3f61791 2004-03-21 devnull 	} else {
41 b3f61791 2004-03-21 devnull 		last = b->p[d];
42 b3f61791 2004-03-21 devnull 		for(i = 0; i < b->top-d-1; i++){
43 b3f61791 2004-03-21 devnull 			this = b->p[i+d+1];
44 b3f61791 2004-03-21 devnull 			res->p[i] = (this<<l) | (last>>r);
45 b3f61791 2004-03-21 devnull 			last = this;
46 b3f61791 2004-03-21 devnull 		}
47 b3f61791 2004-03-21 devnull 		res->p[i++] = last>>r;
48 b3f61791 2004-03-21 devnull 	}
49 b3f61791 2004-03-21 devnull 	while(i > 0 && res->p[i-1] == 0)
50 b3f61791 2004-03-21 devnull 		i--;
51 b3f61791 2004-03-21 devnull 	res->top = i;
52 b3f61791 2004-03-21 devnull 	if(i==0)
53 b3f61791 2004-03-21 devnull 		res->sign = 1;
54 b3f61791 2004-03-21 devnull }