/*
insn_rel.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
*/

/*
for handling relative mode instructions
*/

#define __insn_rel_c_seen__

#include <stdlib.h>

#include "expr.h"
#include "lwasm.h"
#include "instab.h"

OPFUNC(insn_rel8)
{
	lwasm_expr_stack_t *s;
	int v;
	
	lwasm_emitop(as, l, instab[opnum].ops[0]);
	
	s = lwasm_expr_eval(*p, NULL);
	if (!s)
	{
		register_error(as, l, 1, "Bad operand");
		lwasm_emitop(as, l, 0);
		return;
	}
	if (lwasm_expr_is_constant(s))
		register_error(as, l, 2, "Incomplete reference");
	v = lwasm_expr_get_value(s);
	v -= as -> addr + 1;
	if (v < -128 || v > 127)
		register_error(as, l, 2, "Byte overflow");
	lwasm_emit(as, l, v & 0xff);
	
	lwasm_expr_stack_free(s);
}

OPFUNC(insn_rel16)
{
	lwasm_expr_stack_t *s;
	int v;
	
	lwasm_emitop(as, l, instab[opnum].ops[0]);
	
	s = lwasm_expr_eval(*p, NULL);
	if (!s)
	{
		register_error(as, l, 1, "Bad operand");
		lwasm_emitop(as, l, 0);
		return;
	}
	if (lwasm_expr_is_constant(s))
		register_error(as, l, 2, "Incomplete reference");
	v = lwasm_expr_get_value(s);
	v -= as -> addr + 2;
	lwasm_emit(as, l, (v >> 8) & 0xff);
	lwasm_emit(as, l, v & 0xff);
	
	lwasm_expr_stack_free(s);
}