125 lines
2.4 KiB
C
Executable File
125 lines
2.4 KiB
C
Executable File
/* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
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/* All Rights Reserved */
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/* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */
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/* The copyright notice above does not evidence any */
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/* actual or intended publication of such source code. */
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/*
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* Copyright (c) 1980 Regents of the University of California.
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* All rights reserved. The Berkeley software License Agreement
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* specifies the terms and conditions for redistribution.
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*/
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/* Portions Copyright(c) 1988, Sun Microsystems Inc. */
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/* All Rights Reserved */
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#ident "@(#)mult.c 1.2 90/02/20 SMI" /* SVr4.0 1.1 */
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/* LINTLIBRARY */
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#include <mp.h>
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mult(a,b,c)
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register struct mint *a,*b,*c;
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{
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struct mint x,y;
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int sign;
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_mp_mcan(a);
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_mp_mcan(b);
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if (a->len == 0 || b->len == 0) {
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xfree(c);
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return;
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}
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sign = 1;
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x.len = y.len = 0;
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_mp_move(a, &x);
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_mp_move(b, &y);
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if (a->len < 0) {
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x.len = -x.len;
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sign = -sign;
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}
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if (b->len < 0) {
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y.len = -y.len;
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sign = -sign;
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}
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xfree(c);
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if (x.len < y.len) {
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m_mult(&x,&y,c);
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} else {
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m_mult(&y,&x,c);
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}
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if (sign < 0)
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c->len = -c->len;
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if (c->len == 0)
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xfree(c);
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xfree(&x);
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xfree(&y);
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}
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/*
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* Knuth 4.3.1, Algorithm M
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*/
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m_mult(a,b,c)
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struct mint *a;
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struct mint *b;
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struct mint *c;
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{
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register int i,j;
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register long sum;
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register short bcache;
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register short *aptr;
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register short *bptr;
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register short *cptr;
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register unsigned short fifteen = 15;
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register int alen;
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int blen;
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# define BASEBITS (8*sizeof(short)-1)
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# define BASE (1 << BASEBITS)
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# define LOWBITS (BASE - 1)
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alen = a->len;
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blen = b->len;
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c->len = alen + blen;
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c->val = xalloc(c->len,"m_mult");
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aptr = a->val;
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bptr = b->val;
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cptr = c->val;
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sum = 0;
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bcache = *bptr++;
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for (i = alen; i > 0; i--) {
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sum += *aptr++ * bcache;
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*cptr++ = sum & LOWBITS;
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/* sum >>= fifteen; */ /*most machines*/
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if (sum >=0) sum >>= (short) fifteen; /*3b2*/
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else sum=0xfffe0000 | (sum >> (short) fifteen); /*3b2*/
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}
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*cptr = sum;
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aptr -= alen;
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cptr -= alen;
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cptr++;
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for (j = blen - 1; j > 0; j--) {
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sum = 0;
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bcache = *bptr++;
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for (i = alen; i > 0; i--) {
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sum += *aptr++ * bcache + *cptr;
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*cptr++ = sum & LOWBITS;
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/* sum >>= fifteen; */ /*most machines*/
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if (sum >=0) sum >>= (short) fifteen; /*3b2*/
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else sum=0xfffe0000 | (sum >> (short) fifteen); /*3b2*/
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}
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*cptr = sum;
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aptr -= alen;
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cptr -= alen;
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cptr++;
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}
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if (c->val[c->len-1] == 0) {
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c->len--;
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}
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}
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