enter_o16_Iw_Ib.java

/*
    JPC: An x86 PC Hardware Emulator for a pure Java Virtual Machine

    Copyright (C) 2012-2013 Ian Preston

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 2 as published by
    the Free Software Foundation.

    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, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
    Details (including contact information) can be found at: 

    jpc.sourceforge.net
    or the developer website
    sourceforge.net/projects/jpc/

    End of licence header
*/

package org.jpc.emulator.execution.opcodes.rm;

import org.jpc.emulator.execution.*;
import org.jpc.emulator.execution.decoder.*;
import org.jpc.emulator.processor.*;
import org.jpc.emulator.processor.fpu64.*;
import static org.jpc.emulator.processor.Processor.*;

public class enter_o16_Iw_Ib extends Executable
{
    final int immw;
    final int immb;

    public enter_o16_Iw_Ib(int blockStart, int eip, int prefices, PeekableInputStream input)
    {
        super(blockStart, eip);
        immw = Modrm.Iw(input);
        immb = Modrm.Ib(input);
    }

    public Branch execute(Processor cpu)
    {
            int frameSize = 0xffff & immw;
        int nestingLevel = immb;
        nestingLevel &= 0x1f;

        cpu.push16((short)cpu.r_bp.get16());
        int frame_ptr16 = 0xffff & cpu.r_esp.get16();

	if (cpu.ss.getDefaultSizeFlag())
        {
            int tmpebp = cpu.r_ebp.get32();
            if (nestingLevel != 0) {
	        while (--nestingLevel != 0) {
                    tmpebp -= 2;
                    cpu.push16(cpu.ss.getWord(tmpebp));
                }
                cpu.push16((short)frame_ptr16);
            }
        } else
        {
            int tmpbp = 0xffff & cpu.r_ebp.get16();
            if (nestingLevel != 0) {
	        while (--nestingLevel != 0) {
                    tmpbp -= 2;
                    cpu.push16(cpu.ss.getWord(tmpbp));
                }
                cpu.push16((short)frame_ptr16);
            }
        }

        cpu.r_sp.set16((short)(cpu.r_sp.get16()-frameSize)); // TODO: do a write permission check here
        cpu.r_bp.set16((short)frame_ptr16);
        return Branch.None;
    }

    public boolean isBranch()
    {
        return false;
    }

    public String toString()
    {
        return this.getClass().getName();
    }
}