Arch.SM213.Machine.Student
Class MainMemory

java.lang.Object
  java.util.Observable
      Util.AbstractDataModel
          Machine.AbstractMainMemory
              Arch.SM213.Machine.Student.MainMemory

All Implemented Interfaces:

DataModel

public class MainMemory
extends AbstractMainMemory

Main Memory of Simple CPU Provides an abstraction of main memory (DRAM).

Nested Class Summary

Nested classes/interfaces inherited from class Machine.AbstractMainMemory

AbstractMainMemory.InvalidAddressException

Constructor Summary

MainMemory(int byteCapacity)
Allocate memory.

Method Summary

int	bytesToInteger(UnsignedByte byteAtAddrPlus0, UnsignedByte byteAtAddrPlus1, UnsignedByte byteAtAddrPlus2, UnsignedByte byteAtAddrPlus3) Convert an sequence of four bytes into a Big Endian integer.
protected UnsignedByte[]	get(int address, int length) Fetch a sequence of bytes from memory.
UnsignedByte[]	integerToBytes(int i) Convert a Big Endian integer into an array of 4 bytes organized by memory address.
protected boolean	isAccessAligned(int address, int length) Determine whether an address is aligned to specified length.
int	length() Determine the size of memory.
protected void	set(int address, UnsignedByte[] value) Store a sequence of bytes into memory.

Methods inherited from class Machine.AbstractMainMemory

getColumnClass, getColumnCount, getColumnName, getRowCount, getValueAt, isCellEditable, read, readInteger, readIntegerUnaligned, readUnaligned, setValueAt, setValueAt, setValueAtByUser, setValueAtByUser, write, writeInteger, writeIntegerUnaligned, writeUnaligned

Methods inherited from class Util.AbstractDataModel

addUndoableEditListener, canDeleteRow, canInsertRow, deleteRow, insertRow, tellObservers, tellObservers

Methods inherited from class java.util.Observable

addObserver, clearChanged, countObservers, deleteObserver, deleteObservers, hasChanged, notifyObservers, notifyObservers, setChanged

Methods inherited from class java.lang.Object

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

Methods inherited from interface Util.DataModel

addObserver

Constructor Detail

MainMemory

public MainMemory(int byteCapacity)

Allocate memory.

Parameters:

byteCapacity - size of memory in bytes

Method Detail

isAccessAligned

protected boolean isAccessAligned(int address,
                                  int length)

Determine whether an address is aligned to specified length.

Specified by:

isAccessAligned in class AbstractMainMemory

Parameters:

address - memory address

length - byte length

Returns:

true iff address is aligned to length

bytesToInteger

public int bytesToInteger(UnsignedByte byteAtAddrPlus0,
                          UnsignedByte byteAtAddrPlus1,
                          UnsignedByte byteAtAddrPlus2,
                          UnsignedByte byteAtAddrPlus3)

Convert an sequence of four bytes into a Big Endian integer.

Specified by:

bytesToInteger in class AbstractMainMemory

Parameters:

byteAtAddrPlus0 - value of byte with lowest memory address (base address)

byteAtAddrPlus1 - value of byte at base address plus 1

byteAtAddrPlus2 - value of byte at base address plus 2

byteAtAddrPlus3 - value of byte at base address plus 3 (highest memory address)

Returns:

Big Endian integer formed by these four bytes

integerToBytes

public UnsignedByte[] integerToBytes(int i)

Convert a Big Endian integer into an array of 4 bytes organized by memory address.

Specified by:

integerToBytes in class AbstractMainMemory

Parameters:

i - an Big Endian integer

Returns:

an array of UnsignedByte where [0] is value of low-address byte of the number etc.

get

protected UnsignedByte[] get(int address,
                             int length)
                      throws AbstractMainMemory.InvalidAddressException

Fetch a sequence of bytes from memory.

Specified by:

get in class AbstractMainMemory

Parameters:

address - address of the first byte to fetch

length - number of bytes to fetch

Returns:

an array of UnsignedByte where [0] is memory value at address, [1] is memory value at address+1 etc.

Throws:

AbstractMainMemory.InvalidAddressException - if address is out of range.

set

protected void set(int address,
                   UnsignedByte[] value)
            throws AbstractMainMemory.InvalidAddressException

Store a sequence of bytes into memory.

Specified by:

set in class AbstractMainMemory

Parameters:

address - address of the first byte in memory to receive the specified value

value - an array of UnsignedByte values to store in memory at the specified address

Throws:

InvalidAddressException - if any address in the range address to address+value.length-1 is invalid

AbstractMainMemory.InvalidAddressException

length

public int length()

Determine the size of memory.

Specified by:

length in class AbstractMainMemory

Returns:

the number of bytes allocated to this memory.