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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"
- #define LO(x) ((x) & ((1<<(Dbits/2))-1))
- #define HI(x) ((x) >> (Dbits/2))
- static void
- mpdigmul(mpdigit a, mpdigit b, mpdigit *p)
- {
- mpdigit x, ah, al, bh, bl, p1, p2, p3, p4;
- int carry;
- // half digits
- ah = HI(a);
- al = LO(a);
- bh = HI(b);
- bl = LO(b);
- // partial products
- p1 = ah*bl;
- p2 = bh*al;
- p3 = bl*al;
- p4 = ah*bh;
- // p = ((p1+p2)<<(Dbits/2)) + (p4<<Dbits) + p3
- carry = 0;
- x = p1<<(Dbits/2);
- p3 += x;
- if(p3 < x)
- carry++;
- x = p2<<(Dbits/2);
- p3 += x;
- if(p3 < x)
- carry++;
- p4 += carry + HI(p1) + HI(p2); // can't carry out of the high digit
- p[0] = p3;
- p[1] = p4;
- }
- // prereq: p must have room for n+1 digits
- void
- mpvecdigmuladd(mpdigit *b, int n, mpdigit m, mpdigit *p)
- {
- int i;
- mpdigit carry, x, y, part[2];
- carry = 0;
- part[1] = 0;
- for(i = 0; i < n; i++){
- x = part[1] + carry;
- if(x < carry)
- carry = 1;
- else
- carry = 0;
- y = *p;
- mpdigmul(*b++, m, part);
- x += part[0];
- if(x < part[0])
- carry++;
- x += y;
- if(x < y)
- carry++;
- *p++ = x;
- }
- *p = part[1] + carry;
- }
- // prereq: p must have room for n+1 digits
- int
- mpvecdigmulsub(mpdigit *b, int n, mpdigit m, mpdigit *p)
- {
- int i;
- mpdigit x, y, part[2], borrow;
- borrow = 0;
- part[1] = 0;
- for(i = 0; i < n; i++){
- x = *p;
- y = x - borrow;
- if(y > x)
- borrow = 1;
- else
- borrow = 0;
- x = part[1];
- mpdigmul(*b++, m, part);
- x += part[0];
- if(x < part[0])
- borrow++;
- x = y - x;
- if(x > y)
- borrow++;
- *p++ = x;
- }
- x = *p;
- y = x - borrow - part[1];
- *p = y;
- if(y > x)
- return -1;
- else
- return 1;
- }
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