minix/lib/ack/fphook/add_ext.fc
2009-11-09 10:26:00 +00:00

56 lines
1.3 KiB
Text

/*
(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
See the copyright notice in the ACK home directory, in the file "Copyright".
*/
/* $Header$ */
/*
ADD TWO EXTENDED FORMAT NUMBERS
*/
#include "FP_types.h"
void
add_ext(e1,e2)
register EXTEND *e1,*e2;
{
if ((e2->m1 | e2->m2) == 0L) {
return;
}
if ((e1->m1 | e1->m2) == 0L) {
*e1 = *e2;
return;
}
sft_ext(e1, e2); /* adjust mantissas to equal powers */
if (e1->sign != e2->sign) {
/* e1 + e2 = e1 - (-e2) */
if (e2->m1 > e1->m1 ||
(e2->m1 == e1->m1 && e2->m2 > e1->m2)) {
/* abs(e2) > abs(e1) */
EXTEND x;
x = *e1;
*e1 = *e2;
if (x.m2 > e1->m2) {
e1->m1 -= 1; /* carry in */
}
e1->m1 -= x.m1;
e1->m2 -= x.m2;
}
else {
if (e2->m2 > e1->m2)
e1->m1 -= 1; /* carry in */
e1->m1 -= e2->m1;
e1->m2 -= e2->m2;
}
}
else {
if (b64_add(&e1->mantissa,&e2->mantissa)) { /* addition carry */
b64_rsft(&e1->mantissa); /* shift mantissa one bit RIGHT */
e1->m1 |= 0x80000000L; /* set max bit */
e1->exp++; /* increase the exponent */
}
}
nrm_ext(e1);
}