DefaultMemory.java

/*
 * $Id: DefaultMemoryAccess.java 520 2007-11-13 19:14:51Z weiju $
 * 
 * Created on 2005/09/23
 * Copyright 2005-2008 by Wei-ju Wu
 * This file is part of The Z-machine Preservation Project (ZMPP).
 *
 * ZMPP 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.
 *
 * ZMPP 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 ZMPP.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.zmpp.base;

/**
 * This class is the default implementation for MemoryAccess.
 *
 * @author Wei-ju Wu
 * @version 1.0
 */
public class DefaultMemory implements Memory {

    /**
     * The data array containing the story file.
     */
    private byte[] data;

    /**
     * Constructor.
     *
     * @param data the story file data
     */
    public DefaultMemory(final byte[] data) {

        super();
        this.data = data;
    }

    /**
     * {@inheritDoc}
     */
    public long readUnsigned32(final int address) {

        return (data[address] & 0xff) << 24 | (data[address + 1] & 0xff) << 16
                | (data[address + 2] & 0xff) << 8 | (data[address + 3] & 0xff);
    }

    /**
     * {@inheritDoc}
     */
    public long readUnsigned48(final int address) {
        long a0 = data[address + 0] & 0xff;
        a0 <<= 40;
        long a1 = data[address + 1] & 0xff;
        a1 <<= 32;
        return a0 | a1
                | (data[address + 2] & 0xff) << 24
                | (data[address + 3] & 0xff) << 16
                | (data[address + 4] & 0xff) << 8
                | (data[address + 5] & 0xff);
    }

    /**
     * {@inheritDoc}
     */
    public void writeUnsigned48(final int address, final long value) {

        data[address + 0] = (byte) ((value & 0xff0000000000l) >> 40);
        data[address + 1] = (byte) ((value & 0x00ff00000000l) >> 32);
        data[address + 2] = (byte) ((value & 0x0000ff000000l) >> 24);
        data[address + 3] = (byte) ((value & 0x000000ff0000l) >> 16);
        data[address + 4] = (byte) ((value & 0x00000000ff00l) >> 8);
        data[address + 5] = (byte) (value & 0x0000000000ffl);
    }

    /**
     * {@inheritDoc}
     */
    public int readUnsignedShort(final int address) {

        return (data[address] & 0xff) << 8 | (data[address + 1] & 0xff);
    }

    /**
     * {@inheritDoc}
     */
    public short readShort(final int address) {

        return (short) (data[address] << 8 | (data[address + 1] & 0xff));
    }

    /**
     * {@inheritDoc}
     */
    public short readUnsignedByte(final int address) {

        return (short) (data[address] & 0xff);
    }

    /**
     * {@inheritDoc}
     */
    public byte readByte(final int address) {

        return data[address];
    }

    /**
     * Writes an unsigned 16 bit value to the specified address.
     *
     * @param address the address to write to
     * @param value the value to write
     */
    public void writeUnsignedShort(final int address, final int value) {

        data[address] = (byte) ((value & 0xff00) >> 8);
        data[address + 1] = (byte) (value & 0xff);
    }

    /**
     * Writes a short value to the memory.
     *
     * @param address the address
     * @param value the value
     */
    public void writeShort(final int address, final short value) {

        data[address] = (byte) ((value & 0xff00) >>> 8);
        data[address + 1] = (byte) (value & 0xff);
    }

    /**
     * Writes an unsigned byte value to the specified address.
     *
     * @param address the address to write to
     * @param value the value to write
     */
    public void writeUnsignedByte(final int address, final short value) {

        data[address] = (byte) (value & 0xff);
    }

    /**
     * Writes a byte value to the specified address.
     *
     * @param address the address
     * @param value the value
     */
    public void writeByte(final int address, final byte value) {

        data[address] = value;
    }

    /**
     * Writes an unsigned 32 bit value to the specified address.
     *
     * @param address the address to write to
     * @param value the value to write
     */
    public void writeUnsigned32(final int address, final long value) {

        data[address] = (byte) ((value & 0xff000000) >> 24);
        data[address + 1] = (byte) ((value & 0x00ff0000) >> 16);
        data[address + 2] = (byte) ((value & 0x0000ff00) >> 8);
        data[address + 3] = (byte) (value & 0x000000ff);
    }
}