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- /*
- * This file is part of the UCB release of Plan 9. It is subject to the license
- * terms in the LICENSE file found in the top-level directory of this
- * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No
- * part of the UCB release of Plan 9, including this file, may be copied,
- * modified, propagated, or distributed except according to the terms contained
- * in the LICENSE file.
- */
- #include "os.h"
- #include <mp.h>
- #include "dat.h"
- // prereq: a >= b, alen >= blen, diff has at least alen digits
- void
- mpvecsub(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *diff)
- {
- int i, borrow;
- mpdigit x, y;
- borrow = 0;
- for(i = 0; i < blen; i++){
- x = *a++;
- y = *b++;
- y += borrow;
- if(y < borrow)
- borrow = 1;
- else
- borrow = 0;
- if(x < y)
- borrow++;
- *diff++ = x - y;
- }
- for(; i < alen; i++){
- x = *a++;
- y = x - borrow;
- if(y > x)
- borrow = 1;
- else
- borrow = 0;
- *diff++ = y;
- }
- }
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