88 lines
1.8 KiB
C
88 lines
1.8 KiB
C
/*
|
|
(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
|
|
See the copyright notice in the ACK home directory, in the file "Copyright".
|
|
*/
|
|
|
|
/* $Header$ */
|
|
|
|
/*
|
|
* these are the routines the routines to do 32 and 64-bit addition
|
|
*/
|
|
|
|
# ifdef DEBUG
|
|
# include <stdio.h>
|
|
# endif
|
|
|
|
# include "adder.h"
|
|
# define UNKNOWN -1
|
|
# define TRUE 1
|
|
# define FALSE 0
|
|
# define MAXBIT 0x80000000L
|
|
|
|
/*
|
|
* add 64 bits
|
|
*/
|
|
b64_add(e1,e2)
|
|
/*
|
|
* pointers to 64 bit 'registers'
|
|
*/
|
|
register B64 *e1,*e2;
|
|
{
|
|
register short overflow;
|
|
short carry;
|
|
|
|
/* add higher pair of 32 bits */
|
|
overflow = b32_add(&e1->h_32,&e2->h_32);
|
|
|
|
/* add lower pair of 32 bits */
|
|
carry = b32_add(&e1->l_32,&e2->l_32);
|
|
# ifdef DEBUG
|
|
printf("\t\t\t\t\tb64_add: overflow (%d); internal carry(%d)\n",
|
|
overflow,carry);
|
|
fflush(stdout);
|
|
# endif
|
|
if ((carry) && (++e1->h_32 == 0))
|
|
return(TRUE); /* had a 64 bit overflow */
|
|
else
|
|
return(overflow); /* return status from higher add */
|
|
}
|
|
|
|
/*
|
|
* add 32 bits (unsigned longs)
|
|
* and return the carry status
|
|
*/
|
|
|
|
b32_add(e1,e2)
|
|
register unsigned long *e1,*e2;
|
|
{
|
|
register short carry;
|
|
|
|
if (*e1 & *e2 & MAXBIT) /* both max_bits are set */
|
|
carry = TRUE; /* so there is a carry */
|
|
else
|
|
carry = ((*e1 | *e2) & MAXBIT)
|
|
/* only one is set - might be a carry */
|
|
? UNKNOWN
|
|
/* both are clear - no carry */
|
|
: FALSE;
|
|
# ifdef DEBUG
|
|
fflush(stdout);
|
|
printf("\t\t\t\t\tb32_add: overflow before add(%d) test(%d)\n",
|
|
carry,(*e1&MAXBIT)?FALSE:TRUE);
|
|
printf("%08X\n%08X\n",*e1,*e2);
|
|
# endif
|
|
|
|
*e1 += *e2;
|
|
# ifdef DEBUG
|
|
printf("%08X\n",*e1);
|
|
fflush(stdout);
|
|
# endif
|
|
if (carry != UNKNOWN)
|
|
return(carry);
|
|
else
|
|
/*
|
|
* if maxbit in answer is set there is no carry
|
|
* return the NAND of this bit
|
|
*/
|
|
return((*e1&MAXBIT)?FALSE:TRUE);
|
|
}
|