/*
 * Sources of the "SETS" group instructions
 */

/* $Header$ */

#include	<em_abs.h>
#include	"global.h"
#include	"log.h"
#include	"trap.h"
#include	"mem.h"
#include	"text.h"
#include	"fra.h"

PRIVATE bit_test(), create_set();

DoINN(l)
	register size l;
{
	/* INN w: Bit test on w byte set (bit number on top of stack) */

	LOG(("@Y6 DoINN(%ld)", l));
	spoilFRA();
	bit_test(arg_w(l));
}

DoSET(l)
	register size l;
{
	/* SET w: Create singleton w byte set with bit n on (n is top of stack) */

	LOG(("@Y6 DoSET(%ld)", l));
	spoilFRA();
	create_set(arg_w(l));
}

/********************************************************
 *		bit testing				*
 *							*
 *	Tests whether the bit with number to be found	*
 *	on TOS is on in 'w'-byte set.			*
 *	ON --> push 1 on stack.				*
 *	OFF -> push 0 on stack.				*
 ********************************************************/

PRIVATE bit_test(w)
	size w;
{
	register int bitno =
		(int) swpop();	/* bitno on TOS */
	register char test_byte = (char) 0;/* default value to be tested */
	register int wordoff = bitno / 8;
	register int bitoff = bitno % 8; 

	if (bitoff < 0) bitoff += 8;

	if (must_test && !(IgnMask&BIT(ESET))) {
		/* Only w*8 bits CAN be tested */
		if (wordoff >= w) {
			trap(ESET);
		}
	}
	test_byte = stack_loc(SP + wordoff);
	st_dec(w);
	wpush((long)((test_byte & BIT(bitoff)) ? 1 : 0));
}

/********************************************************
 *		set creation				*
 *							*
 *	Creates a singleton 'w'-byte set with as	*
 *	singleton member, the bit with number on	*
 *	TOS. The w bytes constituting the set are	*
 *	pushed on the stack.				*
 ********************************************************/

PRIVATE create_set(w)
	size w;
{
	register int bitno = (int) swpop();
	register size nbytes = w;
	register int wordoff = bitno / 8;
	register int bitoff = bitno % 8;

	if (bitoff < 0) bitoff += 8;

	st_inc(nbytes);
	while (--nbytes >= 0) {
		st_stn(SP + nbytes, 0L, 1L);
	}

	if (must_test && !(IgnMask&BIT(ESET))) {
		if (wordoff >= w) {
			trap(ESET);
		}
	}
	st_stn(SP + wordoff, (long)BIT(bitoff), 1L);
}

