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 /* prereq: a >= b, alen >= blen, diff has at least alen digits */
 6 b3f61791 2004-03-21 devnull void
 7 b3f61791 2004-03-21 devnull mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff)
 8 b3f61791 2004-03-21 devnull {
 9 b3f61791 2004-03-21 devnull 	int i, borrow;
10 b3f61791 2004-03-21 devnull 	mpdigit x, y;
11 b3f61791 2004-03-21 devnull 
12 b3f61791 2004-03-21 devnull 	borrow = 0;
13 b3f61791 2004-03-21 devnull 	for(i = 0; i < blen; i++){
14 b3f61791 2004-03-21 devnull 		x = *a++;
15 b3f61791 2004-03-21 devnull 		y = *b++;
16 b3f61791 2004-03-21 devnull 		y += borrow;
17 b3f61791 2004-03-21 devnull 		if(y < borrow)
18 b3f61791 2004-03-21 devnull 			borrow = 1;
19 b3f61791 2004-03-21 devnull 		else
20 b3f61791 2004-03-21 devnull 			borrow = 0;
21 b3f61791 2004-03-21 devnull 		if(x < y)
22 b3f61791 2004-03-21 devnull 			borrow++;
23 b3f61791 2004-03-21 devnull 		*diff++ = x - y;
24 b3f61791 2004-03-21 devnull 	}
25 b3f61791 2004-03-21 devnull 	for(; i < alen; i++){
26 b3f61791 2004-03-21 devnull 		x = *a++;
27 b3f61791 2004-03-21 devnull 		y = x - borrow;
28 b3f61791 2004-03-21 devnull 		if(y > x)
29 b3f61791 2004-03-21 devnull 			borrow = 1;
30 b3f61791 2004-03-21 devnull 		else
31 b3f61791 2004-03-21 devnull 			borrow = 0;
32 b3f61791 2004-03-21 devnull 		*diff++ = y;
33 b3f61791 2004-03-21 devnull 	}
34 b3f61791 2004-03-21 devnull }