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