uk.co.javagear
Class Memory

java.lang.Object
  uk.co.javagear.Memory

public final class Memory
extends java.lang.Object

Emulates SMS/GG Memory and Paging Hardware. Also Handles Reading ROMs and configuring the memory appropriately.

Version:

18th January 2003

Author:

Copyright (C) 2002-2003 Chris White, Jesús Adolfo García Pasquel

See Also:

"JavaGear Final Project Report"

Field Summary

private int	cartRamPage Stores which page of cartridge RAM to use.
private byte[][]	cartRamPages Array of cartridge RAM pages.
private byte[][]	frames Array of memory frames.
private boolean	frameTwoRom Stores whether frame 2 contains cartridge ROM or cartridge RAM.
private int	numberOfPages Stores number of pages.
private byte[][]	pages Array of memory pages.
private Setup	setup Pointer to general parameters.

Constructor Summary

Memory(Setup set)
Memory constructor.

Method Summary

private static java.lang.String	getExtension(java.lang.String filename) Strip an extension from a file.
private static java.util.zip.ZipEntry	getRomEntry(java.util.zip.ZipInputStream zis) Returns the first entry in the ZipInputStream that contains an SMS or GG ROM or null if none is found.
private void	page(int address, int value) Write to a paging register.
int	read(int address) Read from a memory location.
private void	readCart(java.io.InputStream is, int size) Read a cartridge's data from an InputStream.
void	readCart(java.net.URL url) Read a cartridge into memory from the specified URL.
int	readSigned(int address) Read a signed value from a memory location.
int	readWord(int address) Read a word (two bytes) from a memory location.
void	reset() Reset memory to default values.
private int	unsigned(int b) Unsign an integer.
void	write(int address, int value) Write to a memory location.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

frames

private byte[][] frames

Array of memory frames.

pages

private byte[][] pages

Array of memory pages.

cartRamPages

private byte[][] cartRamPages

Array of cartridge RAM pages.

frameTwoRom

private boolean frameTwoRom

Stores whether frame 2 contains cartridge ROM or cartridge RAM.

cartRamPage

private int cartRamPage

Stores which page of cartridge RAM to use.

numberOfPages

private int numberOfPages

Stores number of pages.

setup

private Setup setup

Pointer to general parameters.

Constructor Detail

Memory

public Memory(Setup set)

Memory constructor.

Parameters:

set - pointer to general parameters.

Method Detail

reset

public void reset()

Reset memory to default values.

write

public void write(int address,
                  int value)

Write to a memory location.

Parameters:

address - memory address

value - value to write

read

public int read(int address)

Read from a memory location.

Parameters:

address - memory location.

Returns:

value from memory location.

readSigned

public int readSigned(int address)

Read a signed value from a memory location.

Parameters:

address - Memory address

Returns:

Value from memory location

readWord

public int readWord(int address)

Read a word (two bytes) from a memory location.

Parameters:

address - memory address.

Returns:

value from memory location

unsigned

private int unsigned(int b)

Unsign an integer.

Parameters:

b - value to unsign.

Returns:

unsigned value.

page

private void page(int address,
                  int value)

Write to a paging register.

Parameters:

address - memory location.

value - value to write.

readCart

public void readCart(java.net.URL url)
              throws java.io.IOException,
                     java.lang.IllegalArgumentException

Read a cartridge into memory from the specified URL. The file it points to must be a ROM for the SMS or GG, or a zip file containing one.

Parameters:

url - URL of cartridge image.

Throws:

java.io.IOException - if an error occurs while reading the file.

java.lang.IllegalArgumentException - if the file is neither a ROM, nor a Zip file containing one.

getRomEntry

private static java.util.zip.ZipEntry getRomEntry(java.util.zip.ZipInputStream zis)
                                           throws java.io.IOException

Returns the first entry in the ZipInputStream that contains an SMS or GG ROM or null if none is found. If the stream does not include a ROM or an IOException occurs while looking for a valid entry, the stream will be closed. Otherwise it is left open, pointing at the ROM's contents.

Parameters:

zis - an instance of ZipInputStream, may be null.

Returns:

an SMS or GG ROM in the form of a ZipEntry or null if none were found.

Throws:

java.io.IOException - if an error occurs while reading from the stream.

readCart

private void readCart(java.io.InputStream is,
                      int size)
               throws java.io.IOException,
                      java.lang.IllegalArgumentException

Read a cartridge's data from an InputStream. The method does not close when it finishes reading.

Parameters:

is - the stream to read the ROM's data from.

size - the size of the stream's content.

Throws:

java.lang.IllegalArgumentException - if is is null or size.

java.io.IOException - if an error occurs while reading the file.

getExtension

private static java.lang.String getExtension(java.lang.String filename)

Strip an extension from a file.

Parameters:

filename - filename to strip.

Returns:

extension of file in lowercase characters.