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/********************************************************************
Copyright (c) 1996 Artima Software Company. All Rights Reserved.
* Permission to use, copy, modify, and distribute this software
* and its documentation for EVALUATION purposes only
* is hereby granted provided that this copyright notice
* appears in all copies. "Evaluation purposes" are any uses which
* do not constitute the sale, sharing, or redistribution of this
* software with or to any other persons in any medium.
*
* ARTIMA SOFTWARE COMPANY MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT
* THE SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING
* BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. ARTIMA SOFTWARE COMPANY
* SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
* USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
PROJECT: JavaWorld
MODULE: Under The Hood
FILE: CircleOfSquares.java
AUTHOR: Bill Venners, August 1996
DESCRIPTION:
This file contains all the code for the java virtual machine simulation
applet, named Circle Of Squares, that accompanies the Under The Hood article
titled, "Floating Point Arithmetic".
As I developed this applet I had every class in a separate file. I combined
them in one file here to make it easier to download.
*********************************************************************/
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Event;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.Label;
import java.awt.LayoutManager;
import java.awt.Panel;
public class CircleOfSquares extends java.applet.Applet {
// Vars for the three outer panels that are contained inside the Applet's
// panel.
// twoParts contains the stack and the method area. simulationController
// contains the Step and Reset buttons and the hint label.
private ThreeParts threeParts;
private RegisterPanel registers;
private ControlPanel simulationController;
// Local reference to reset button on control panel allows for easy enabling
// and
// disabling of this button.
private Button resetButton;
// Vars that implement the Java stack
private final int stackBase = 0x33330000;
private final int stackMemorySectionSize = 8;
private StackMemorySection stackMemorySection = new StackMemorySection(stackBase,
stackMemorySectionSize);
private StackMemoryView stackMemoryView;
// Vars that implement the method area of the JVM
private final int methodAreaBase = 0x44440000;
private MemorySection methodAreaMemorySection = new MemorySection(methodAreaBase,
SimData.methodAreaMemorySectionSize);
private MemoryView methodAreaMemoryView;
// Vars that implement the Java registers
private int pcRegister;
private int optopRegister;
private int frameRegister;
private int varsRegister;
public void init() {
setBackground(ColorTable.appletBackgroundColor);
setLayout(new BorderLayout(5, 5));
threeParts = new ThreeParts(SimData.methodAreaMemorySectionSize);
simulationController = new ControlPanel();
resetButton = simulationController.getResetButton();
ColoredLabel title = new ColoredLabel(StringTable.appletTitle, Label.CENTER,
ColorTable.titleColor);
title.setFont(new Font("Helvetica", Font.BOLD, 12));
add("North", title);
add("South", simulationController);
add("Center", threeParts);
// Get a reference to the UI objects that are actually manipulated by
// the handlers of the Step and Reset buttons. These aren't available
// without this explicit get() because these objects are buried several
// levels down in embedded panels.
stackMemoryView = threeParts.getStackMemoryViewReference();
methodAreaMemoryView = threeParts.getMethodAreaMemoryViewReference();
registers = threeParts.getRegisterPanel();
// Place the bytecodes into the method area
for (int i = 0; i < SimData.methodAreaMemorySectionSize; ++i) {
methodAreaMemorySection.setAtAddress(methodAreaBase + i, SimData.theProgram[i]);
methodAreaMemorySection.setLogicalValueAtAddress(methodAreaBase + i,
SimData.byteCodeMnemonics[i]);
}
ResetState();
UpdateStateDisplay();
}
public boolean action(Event evt, Object arg) {
if (evt.target instanceof Button) {
String bname = (String) arg;
if (bname.equals(StringTable.reset)) {
resetButton.disable();
ResetState();
UpdateStateDisplay();
} else if (bname.equals(StringTable.step)) {
if (!resetButton.isEnabled()) {
resetButton.enable();
}
ExecuteNextInstruction();
UpdateStateDisplay();
}
}
return true;
}
// ExecuteNextInstruction() grabs the instruction pointed to by the program
// counter, decodes it via the switch statement, and executes it by running
// the
// code under the appropriate case statement. The program counter is always
// set to the next instruction that should be executed, naturally. Only those
// bytecodes that appear in the short sequence presented in this simulation
// are interpreted here to save time (your time in downloading and my time
// in writing.)
void ExecuteNextInstruction() {
int a, b, result, i;
float fa, fb, fresult;
Float f;
int operand0, operand1;
int nextOpCode = methodAreaMemorySection.getAtAddress(pcRegister);
switch (nextOpCode) {
case OpCode.BIPUSH:
operand0 = methodAreaMemorySection.getAtAddress(pcRegister + 1);
stackMemorySection.setAtAddress(optopRegister, operand0);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
pcRegister += 2;
break;
case OpCode.FCONST_0:
stackMemorySection.setAtAddress(optopRegister, Float.floatToIntBits((float) 0));
stackMemorySection.setLogicalValueAtAddress(optopRegister, "0");
optopRegister += 4;
++pcRegister;
break;
case OpCode.FCONST_2:
stackMemorySection.setAtAddress(optopRegister, Float.floatToIntBits((float) 2));
stackMemorySection.setLogicalValueAtAddress(optopRegister, "2");
optopRegister += 4;
++pcRegister;
break;
case OpCode.FLOAD_0:
a = stackMemorySection.getAtAddress(varsRegister);
stackMemorySection.setAtAddress(optopRegister, a);
fa = Float.intBitsToFloat(a);
stackMemorySection.setLogicalValueAtAddress(optopRegister, Float.toString(fa));
optopRegister += 4;
++pcRegister;
break;
case OpCode.FMUL:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
fa = Float.intBitsToFloat(a);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
optopRegister -= 4;
b = stackMemorySection.getAtAddress(optopRegister);
fb = Float.intBitsToFloat(b);
fresult = fa * fb;
result = Float.floatToIntBits(fresult);
stackMemorySection.setAtAddress(optopRegister, result);
stackMemorySection.setLogicalValueAtAddress(optopRegister, Float.toString(fresult));
optopRegister += 4;
++pcRegister;
break;
case OpCode.FSTORE_0:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
stackMemorySection.setAtAddress(varsRegister, a);
fa = Float.intBitsToFloat(a);
stackMemorySection.setLogicalValueAtAddress(varsRegister, Float.toString(fa));
++pcRegister;
break;
case OpCode.FSUB:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
fa = Float.intBitsToFloat(a);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
optopRegister -= 4;
b = stackMemorySection.getAtAddress(optopRegister);
fb = Float.intBitsToFloat(b);
fresult = fb - fa;
result = Float.floatToIntBits(fresult);
stackMemorySection.setAtAddress(optopRegister, result);
stackMemorySection.setLogicalValueAtAddress(optopRegister, Float.toString(fresult));
optopRegister += 4;
++pcRegister;
break;
case OpCode.GOTO:
operand1 = methodAreaMemorySection.getAtAddress(pcRegister + 1);
operand0 = methodAreaMemorySection.getAtAddress(pcRegister + 2);
int offset = (operand1 << 8) | (operand0 & 0xff);
pcRegister += offset;
break;
case OpCode.IADD:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
optopRegister -= 4;
b = stackMemorySection.getAtAddress(optopRegister);
result = a + b;
stackMemorySection.setAtAddress(optopRegister, result);
optopRegister += 4;
++pcRegister;
break;
case OpCode.ICONST_M1:
stackMemorySection.setAtAddress(optopRegister, -1);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.ICONST_0:
stackMemorySection.setAtAddress(optopRegister, 0);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.ICONST_1:
stackMemorySection.setAtAddress(optopRegister, 1);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.ICONST_2:
stackMemorySection.setAtAddress(optopRegister, 2);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.IINC:
operand0 = methodAreaMemorySection.getAtAddress(pcRegister + 1);
operand1 = methodAreaMemorySection.getAtAddress(pcRegister + 2);
a = stackMemorySection.getAtAddress(varsRegister + (operand0 * 4));
a += operand1;
stackMemorySection.setAtAddress(varsRegister + (operand0 * 4), a);
pcRegister += 3;
break;
case OpCode.ILOAD_0:
a = stackMemorySection.getAtAddress(varsRegister);
stackMemorySection.setAtAddress(optopRegister, a);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.ILOAD_1:
a = stackMemorySection.getAtAddress(varsRegister + 4);
stackMemorySection.setAtAddress(optopRegister, a);
stackMemorySection.setLogicalValueAtAddress(optopRegister, StringTable.operand);
optopRegister += 4;
++pcRegister;
break;
case OpCode.IMUL:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
optopRegister -= 4;
b = stackMemorySection.getAtAddress(optopRegister);
result = a * b;
stackMemorySection.setAtAddress(optopRegister, result);
optopRegister += 4;
++pcRegister;
break;
case OpCode.INT2BYTE:
a = stackMemorySection.getAtAddress(optopRegister - 4);
a = (byte) a;
stackMemorySection.setAtAddress(optopRegister - 4, a);
stackMemorySection.setLogicalValueAtAddress(optopRegister - 4, StringTable.operand);
++pcRegister;
break;
case OpCode.ISTORE_0:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
stackMemorySection.setLogicalValueAtAddress(optopRegister, "");
stackMemorySection.setAtAddress(varsRegister, a);
++pcRegister;
break;
case OpCode.ISTORE_1:
optopRegister -= 4;
a = stackMemorySection.getAtAddress(optopRegister);
stackMemorySection.setLogicalValueAtAddress(optopRegister + 4, "");
stackMemorySection.setAtAddress(varsRegister + 4, a);
++pcRegister;
break;
}
}
// Pushing the Reset button will cause ResetState() to be executed, which will
// reset all the data to its initial values.
void ResetState() {
pcRegister = methodAreaBase;
optopRegister = stackBase + SimData.optopOffset;
frameRegister = stackBase + SimData.frameOffset;
varsRegister = stackBase;
int i;
for (i = 0; i < 7; ++i) {
stackMemorySection.setLogicalValueAtAddress(stackBase + (i * 4), "");
stackMemorySection.setAtAddress(stackBase + (i * 4), 0);
}
methodAreaMemoryView.update(methodAreaMemorySection, methodAreaBase);
}
// UpdateStateDisplay writes the current state of the JVM to the UI.
void UpdateStateDisplay() {
registers.setPcRegister(pcRegister);
registers.setOptopRegister(optopRegister);
registers.setFrameRegister(frameRegister);
registers.setVarsRegister(varsRegister);
stackMemoryView.update(stackMemorySection, stackBase);
methodAreaMemoryView.updateProgramCounter(pcRegister - methodAreaBase, methodAreaMemorySection);
stackMemoryView.clearPointers();
stackMemoryView.updatePointer((varsRegister - stackBase) / 4, StringTable.varsPointer);
stackMemoryView.updatePointer((frameRegister - stackBase) / 4, StringTable.framePointer);
stackMemoryView.updatePointer((optopRegister - stackBase) / 4, StringTable.optopPointer);
int nextOpCode = methodAreaMemorySection.getAtAddress(pcRegister);
switch (nextOpCode) {
case OpCode.BIPUSH:
simulationController.setExplanationText(StringTable.bipushText);
break;
case OpCode.FCONST_0:
simulationController.setExplanationText(StringTable.fconst_0Text);
break;
case OpCode.FCONST_2:
simulationController.setExplanationText(StringTable.fconst_2Text);
break;
case OpCode.FLOAD_0:
simulationController.setExplanationText(StringTable.fload_0Text);
break;
case OpCode.FMUL:
simulationController.setExplanationText(StringTable.fmulText);
break;
case OpCode.FSTORE_0:
simulationController.setExplanationText(StringTable.fstore_0Text);
break;
case OpCode.FSUB:
simulationController.setExplanationText(StringTable.fsubText);
break;
case OpCode.GOTO:
simulationController.setExplanationText(StringTable.gotoText);
break;
case OpCode.IADD:
simulationController.setExplanationText(StringTable.iaddText);
break;
case OpCode.ICONST_M1:
simulationController.setExplanationText(StringTable.iconst_m1Text);
break;
case OpCode.ICONST_0:
simulationController.setExplanationText(StringTable.iconst_0Text);
break;
case OpCode.ICONST_1:
simulationController.setExplanationText(StringTable.iconst_1Text);
break;
case OpCode.ICONST_2:
simulationController.setExplanationText(StringTable.iconst_2Text);
break;
case OpCode.IINC:
simulationController.setExplanationText(StringTable.iincText);
break;
case OpCode.ILOAD_0:
simulationController.setExplanationText(StringTable.iload_0Text);
break;
case OpCode.ILOAD_1:
simulationController.setExplanationText(StringTable.iload_1Text);
break;
case OpCode.IMUL:
simulationController.setExplanationText(StringTable.imulText);
break;
case OpCode.INT2BYTE:
simulationController.setExplanationText(StringTable.int2byteText);
break;
case OpCode.ISTORE_0:
simulationController.setExplanationText(StringTable.istore_0Text);
break;
case OpCode.ISTORE_1:
simulationController.setExplanationText(StringTable.istore_1Text);
break;
default:
simulationController.setExplanationText("");
break;
}
}
// Make pretty border around entire applet panel
public Insets insets() {
return new Insets(5, 5, 5, 5);
}
}
// I used this class because I can't seem to set the background color of
// a label. I only want a label, but I want the backgound to be gray.
class ColoredLabel extends Panel {
private Label theLabel;
ColoredLabel(String label, int alignment, Color color) {
setLayout(new GridLayout(1, 1));
setBackground(color);
theLabel = new Label(label, alignment);
add(theLabel);
}
public void setLabelText(String s) {
theLabel.setText(s);
}
public Insets insets() {
return new Insets(0, 0, 0, 0);
}
}
class ColorTable {
static final Color appletBackgroundColor = Color.blue;
static final Color registersAreaColor = Color.magenta;
static final Color stackAreaColor = Color.magenta;
static final Color methodAreaColor = Color.magenta;
static final Color titleColor = Color.cyan;
static final Color explanationLabel = Color.cyan;
}
class ControlPanel extends Panel {
private ColoredLabel explanationLabel;
private GrayButton resetButton = new GrayButton(StringTable.reset);
ControlPanel() {
setLayout(new BorderLayout(5, 5));
Panel leftButtonPanel = new Panel();
leftButtonPanel.setLayout(new GridLayout(2, 1, 0, 5));
leftButtonPanel.add(new GrayButton(StringTable.step));
resetButton.disable();
leftButtonPanel.add(resetButton);
explanationLabel = new ColoredLabel("This is where the explanation goes...", Label.CENTER,
Color.lightGray);
explanationLabel.setBackground(ColorTable.explanationLabel);
Font plainFont = new Font("TimesRoman", Font.ITALIC, 12);
explanationLabel.setFont(plainFont);
add("West", leftButtonPanel);
add("Center", explanationLabel);
}
public void setExplanationText(String explanation) {
explanationLabel.setLabelText(explanation);
}
public Button getResetButton() {
return resetButton;
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class GrayButton extends Button {
GrayButton(String label) {
super(label);
setBackground(Color.lightGray);
}
}
// GridSnapLayout lays out components in a grid that can have columns of
// varying width. This is not a very general purpose layout manager. It
// solves the specific problem of getting all the information I want to display
// about
// the stack and method areas in a nice grid. Because some columns of info need
// more room than others, and space is limited on a web page, I needed to be
// able to specify varying widths of columns in a grid.
class GridSnapLayout implements LayoutManager {
// rows and cols are the number of rows and columns of the grid upon
// which the components are placed. Components are always one row
// in height, but may be more than one column in width. The number
// of columns width of each component is stored in hComponentCellWidths.
// The array length of hComponentCellWidths indicates the number of
// components that will appear on each row.
private int rows;
private int cols;
private int[] hComponentCellWidths;
public GridSnapLayout(int rows, int cols, int[] hComponentCellWidths) {
this.rows = rows;
this.cols = cols;
this.hComponentCellWidths = hComponentCellWidths;
}
public void addLayoutComponent(String name, Component comp) {
}
public void removeLayoutComponent(Component comp) {
}
// Calculate preferred size as if each component were taking an equal
// share of the width of a row.
public Dimension preferredLayoutSize(Container parent) {
int rowCount = rows;
int colCount = cols;
Insets parentInsets = parent.insets();
int componentCount = parent.countComponents();
if (rowCount > 0) {
colCount = (componentCount + rowCount - 1) / rowCount;
} else {
rowCount = (componentCount + colCount - 1) / colCount;
}
// Find the maximum preferred width and the maximum preferred height
// of any component.
int w = 0;
int h = 0;
for (int i = 0; i < componentCount; i++) {
Component comp = parent.getComponent(i);
Dimension d = comp.preferredSize();
if (w < d.width) {
w = d.width;
}
if (h < d.height) {
h = d.height;
}
}
// Return the maximum preferred component width and height times the number
// of columns and rows, respectively, plus any insets in the parent.
return new Dimension(parentInsets.left + parentInsets.right + colCount * w, parentInsets.top
+ parentInsets.bottom + rowCount * h);
}
// Calculate minimum size as if each component were taking an equal
// share of the width of a row.
public Dimension minimumLayoutSize(Container parent) {
Insets parentInsets = parent.insets();
int componentCount = parent.countComponents();
int rowCount = rows;
int colCount = cols;
if (rowCount > 0) {
colCount = (componentCount + rowCount - 1) / rowCount;
} else {
rowCount = (componentCount + colCount - 1) / colCount;
}
// Find the maximum "minimum width" and the maximum "minimum height"
// of any component.
int w = 0;
int h = 0;
for (int i = 0; i < componentCount; i++) {
Component comp = parent.getComponent(i);
Dimension d = comp.minimumSize();
if (w < d.width) {
w = d.width;
}
if (h < d.height) {
h = d.height;
}
}
// Return the maximum "minimum component width and height" times the number
// of columns and rows, respectively, plus any insets in the parent.
return new Dimension(parentInsets.left + parentInsets.right + colCount * w, parentInsets.top
+ parentInsets.bottom + rowCount * h);
}
// Layout the container such that the widths of columns correspond
// to the number of columns in that components hComponentCellWidth
// array element. For example, if the
public void layoutContainer(Container parent) {
int rowCount = rows;
int colCount = hComponentCellWidths.length;
Insets parentInsets = parent.insets();
int componentCount = parent.countComponents();
if (componentCount == 0) {
return;
}
// Calculate the width and height of each grid cell. The height will
// be the height of each component, but the width may not. The width
// of a component will be some multiple of a grid cell width. The
// number of grid cells for each component is defined by the
// hComponentCellWidths array. w is width of each grid cell. h is
// height of each grid cell.
Dimension parentDim = parent.size();
int w = parentDim.width - (parentInsets.left + parentInsets.right);
int h = parentDim.height - (parentInsets.top + parentInsets.bottom);
w /= cols;
h /= rowCount;
// For each row and column of components (not grid cells) position
// the component.
for (int c = 0, x = parentInsets.left; c < colCount; c++) {
for (int r = 0, y = parentInsets.top; r < rowCount; r++) {
int i = r * colCount + c;
if (i < componentCount) {
parent.getComponent(i).reshape(x, y, w * hComponentCellWidths[c], h);
}
y += h;
}
x += (w * hComponentCellWidths[c]);
}
}
}
class HexString {
private final String hexChar = "0123456789abcdef";
private StringBuffer buf = new StringBuffer();
void Convert(int val, int maxNibblesToConvert) {
buf.setLength(0);
int v = val;
for (int i = 0; i < maxNibblesToConvert; ++i) {
if (v == 0) {
if (i == 0) {
buf.insert(0, '0');
}
break;
}
// Get lowest nibble
int remainder = v & 0xf;
// Convert nibble to a character and insert it into the beginning of the
// string
buf.insert(0, hexChar.charAt(remainder));
// Shift the int to the right four bits
v >>>= 4;
}
}
HexString(int val, int minWidth) {
Convert(val, minWidth);
int charsNeeded = minWidth - buf.length();
for (int i = 0; i < charsNeeded; ++i) {
buf.insert(0, '0');
}
}
public String getString() {
return buf.toString();
}
}
class LabeledRegister extends Panel {
private ColoredLabel registerContents;
LabeledRegister(String labelText) {
setLayout(new BorderLayout(5, 5));
registerContents = new ColoredLabel("00000000", Label.CENTER, Color.lightGray);
registerContents.setFont(new Font("TimesRoman", Font.PLAIN, 11));
Label title = new Label(labelText, Label.RIGHT);
title.setFont(new Font("Helvetica", Font.ITALIC, 11));
add("East", registerContents);
add("Center", title);
}
public void setRegister(int val) {
HexString hexString = new HexString(val, 8);
registerContents.setLabelText(hexString.getString());
}
public Insets insets() {
return new Insets(0, 0, 0, 0);
}
}
// MemorySection is just used for the method area in this applet. This
// implements
// the functionality of the method area and has nothing to do with the UI.
class MemorySection {
private int[] memory;
private int baseAddress;
private String[] logicalValueString;
MemorySection(int base, int size) {
baseAddress = base;
memory = new int[size];
logicalValueString = new String[size];
for (int i = 0; i < size; ++i) {
logicalValueString[i] = new String();
}
}
int getBaseAddress() {
return baseAddress;
}
public int getAtAddress(int address) {
return memory[address - baseAddress];
}
public String getLogicalValueAtAddress(int address) {
return logicalValueString[address - baseAddress];
}
public void setAtAddress(int address, int value) {
memory[address - baseAddress] = value;
}
public void setLogicalValueAtAddress(int address, String s) {
logicalValueString[address - baseAddress] = s;
}
int getSize() {
return memory.length;
}
}
// MemoryView is just used for the method area in this applet. It implements the
// UI of the method area.
class MemoryView extends Panel {
private final int memoryLocationsVisibleCount = SimData.methodAreaMemoryLocationsVisibleCount;
private Label[] pointer = new Label[memoryLocationsVisibleCount];
private Label[] address = new Label[memoryLocationsVisibleCount];
private Label[] byteValue = new Label[memoryLocationsVisibleCount];
private Label[] logicalValue = new Label[memoryLocationsVisibleCount];
private int firstVisibleRow;
private int currentProgramCounterRow;
MemoryView(int methodAreaMemSectionSize) {
setLayout(new GridLayout(memoryLocationsVisibleCount, 4));
setBackground(Color.lightGray);
Font plainFont = new Font("TimesRoman", Font.PLAIN, 11);
setFont(plainFont);
Font italicFont = new Font("TimesRoman", Font.ITALIC, 11);
for (int i = 0; i < memoryLocationsVisibleCount; ++i) {
pointer[i] = new Label("", Label.RIGHT);
pointer[i].setFont(italicFont);
add(pointer[i]);
address[i] = new Label("", Label.CENTER);
add(address[i]);
byteValue[i] = new Label("", Label.CENTER);
add(byteValue[i]);
logicalValue[i] = new Label("", Label.LEFT);
add(logicalValue[i]);
}
}
public void setAt(int i, int addressValue, int value, String logicalValueStr) {
HexString addressValueHexString = new HexString(addressValue, 8);
HexString byteValueHexString = new HexString(value, 2);
address[i].setText(addressValueHexString.getString());
byteValue[i].setText(byteValueHexString.getString());
logicalValue[i].setText(logicalValueStr);
}
public void update(MemorySection memorySection, int initialAddress) {
for (int i = 0; i < memoryLocationsVisibleCount; ++i) {
int theByte = memorySection.getAtAddress(initialAddress + i);
String logicalValue = memorySection.getLogicalValueAtAddress(initialAddress + i);
setAt(i, initialAddress + i, theByte, logicalValue);
}
}
public void clearPointers() {
for (int i = 0; i < memoryLocationsVisibleCount; ++i) {
pointer[i].setText("");
}
}
public void updateProgramCounter(int i, MemorySection memorySection) {
pointer[currentProgramCounterRow - firstVisibleRow].setText("");
if (i - firstVisibleRow >= memoryLocationsVisibleCount) {
firstVisibleRow += 5;
if (firstVisibleRow > memorySection.getSize() - memoryLocationsVisibleCount) {
firstVisibleRow = memorySection.getSize() - memoryLocationsVisibleCount;
}
update(memorySection, memorySection.getBaseAddress() + firstVisibleRow);
} else if (i < firstVisibleRow) {
firstVisibleRow = i;
update(memorySection, memorySection.getBaseAddress() + firstVisibleRow);
}
pointer[i - firstVisibleRow].setText("pc >");
currentProgramCounterRow = i;
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class MemoryViewTitlePanel extends Panel {
MemoryViewTitlePanel() {
setLayout(new GridLayout(1, 4));
setFont(new Font("Helvetica", Font.ITALIC, 11));
add(new Label("", Label.CENTER));
add(new Label(StringTable.address, Label.CENTER));
add(new Label(StringTable.bytecodes, Label.CENTER));
add(new Label(StringTable.mnemonics, Label.CENTER));
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class MemoryViewWithTitles extends Panel {
private MemoryView memoryView;
MemoryViewWithTitles(int methodAreaMemorySectionSize) {
memoryView = new MemoryView(methodAreaMemorySectionSize);
setLayout(new BorderLayout());
add("North", new MemoryViewTitlePanel());
add("Center", memoryView);
}
public MemoryView getMemoryViewReference() {
return memoryView;
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class MethodAreaPanel extends Panel {
private Label title;
private MemoryViewWithTitles memoryView;
MethodAreaPanel(int methodAreaMemorySectionSize) {
memoryView = new MemoryViewWithTitles(methodAreaMemorySectionSize);
setLayout(new BorderLayout());
title = new Label("Method Area", Label.CENTER);
title.setFont(new Font("Helvetica", Font.BOLD, 11));
add("North", title);
add("Center", memoryView);
}
public MemoryView getMemoryViewReference() {
return memoryView.getMemoryViewReference();
}
public Insets insets() {
return new Insets(5, 5, 5, 5);
}
}
class OpCode {
final static int NOP = 0;
final static int ACONST_NULL = 1;
final static int ICONST_M1 = 2;
final static int ICONST_0 = 3;
final static int ICONST_1 = 4;
final static int ICONST_2 = 5;
final static int ICONST_3 = 6;
final static int ICONST_4 = 7;
final static int ICONST_5 = 8;
final static int LCONST_0 = 9;
final static int LCONST_1 = 10;
final static int FCONST_0 = 11;
final static int FCONST_1 = 12;
final static int FCONST_2 = 13;
final static int DCONST_0 = 14;
final static int DCONST_1 = 15;
final static int BIPUSH = 16;
final static int SIPUSH = 17;
final static int LDC1 = 18;
final static int LDC2 = 19;
final static int LDC2W = 20;
final static int ILOAD = 21;
final static int LLOAD = 22;
final static int FLOAD = 23;
final static int DLOAD = 24;
final static int ALOAD = 25;
final static int ILOAD_0 = 26;
final static int ILOAD_1 = 27;
final static int ILOAD_2 = 28;
final static int ILOAD_3 = 29;
final static int LLOAD_0 = 30;
final static int LLOAD_1 = 31;
final static int LLOAD_2 = 32;
final static int LLOAD_3 = 33;
final static int FLOAD_0 = 34;
final static int FLOAD_1 = 35;
final static int FLOAD_2 = 36;
final static int FLOAD_3 = 37;
final static int DLOAD_0 = 38;
final static int DLOAD_1 = 39;
final static int DLOAD_2 = 40;
final static int DLOAD_3 = 41;
final static int ALOAD_0 = 42;
final static int ALOAD_1 = 43;
final static int ALOAD_2 = 44;
final static int ALOAD_3 = 45;
final static int IALOAD = 46;
final static int LALOAD = 47;
final static int FALOAD = 48;
final static int DALOAD = 49;
final static int AALOAD = 50;
final static int BALOAD = 51;
final static int CALOAD = 52;
final static int SALOAD = 53;
final static int ISTORE = 54;
final static int LSTORE = 55;
final static int FSTORE = 56;
final static int DSTORE = 57;
final static int ASTORE = 58;
final static int ISTORE_0 = 59;
final static int ISTORE_1 = 60;
final static int ISTORE_2 = 61;
final static int ISTORE_3 = 62;
final static int LSTORE_0 = 63;
final static int LSTORE_1 = 64;
final static int LSTORE_2 = 65;
final static int LSTORE_3 = 66;
final static int FSTORE_0 = 67;
final static int FSTORE_1 = 68;
final static int FSTORE_2 = 69;
final static int FSTORE_3 = 70;
final static int DSTORE_0 = 71;
final static int DSTORE_1 = 72;
final static int DSTORE_2 = 73;
final static int DSTORE_3 = 74;
final static int ASTORE_0 = 75;
final static int ASTORE_1 = 76;
final static int ASTORE_2 = 77;
final static int ASTORE_3 = 78;
final static int IASTORE = 79;
final static int LASTORE = 80;
final static int FASTORE = 81;
final static int DASTORE = 82;
final static int AASTORE = 83;
final static int BASTORE = 84;
final static int CASTORE = 85;
final static int SASTORE = 86;
final static int POP = 87;
final static int POP2 = 88;
final static int DUP = 89;
final static int DUP_X1 = 90;
final static int DUP_X2 = 91;
final static int DUP2 = 92;
final static int DUP2_X1 = 93;
final static int DUP2_X2 = 94;
final static int SWAP = 95;
final static int IADD = 96;
final static int LADD = 97;
final static int FADD = 98;
final static int DADD = 99;
final static int ISUB = 100;
final static int LSUB = 101;
final static int FSUB = 102;
final static int DSUB = 103;
final static int IMUL = 104;
final static int LMUL = 105;
final static int FMUL = 106;
final static int DMUL = 107;
final static int IDIV = 108;
final static int LDIV = 109;
final static int FDIV = 110;
final static int DDIV = 111;
final static int IREM = 112;
final static int LREM = 113;
final static int FREM = 114;
final static int DREM = 115;
final static int INEG = 116;
final static int LNEG = 117;
final static int FNEG = 118;
final static int DNEG = 119;
final static int ISHL = 120;
final static int LSHL = 121;
final static int ISHR = 122;
final static int LSHR = 123;
final static int IUSHR = 124;
final static int LUSHR = 125;
final static int IAND = 126;
final static int LAND = 127;
final static int IOR = 128;
final static int LOR = 129;
final static int IXOR = 130;
final static int LXOR = 131;
final static int IINC = 132;
final static int I2L = 133;
final static int I2F = 134;
final static int I2D = 135;
final static int L2I = 136;
final static int L2F = 137;
final static int L2D = 138;
final static int F2I = 139;
final static int F2L = 140;
final static int F2D = 141;
final static int D2I = 142;
final static int D2L = 143;
final static int D2F = 144;
final static int INT2BYTE = 145;
final static int INT2CHAR = 146;
final static int INT2SHORT = 147;
final static int LCMP = 148;
final static int FCMPL = 149;
final static int FCMPG = 150;
final static int DCMPL = 151;
final static int DCMPG = 152;
final static int IFEQ = 153;
final static int IFNE = 154;
final static int IFLT = 155;
final static int IFGE = 156;
final static int IFGT = 157;
final static int IFLE = 158;
final static int IF_ICMPEQ = 159;
final static int IF_ICMPNE = 160;
final static int IF_ICMPLT = 161;
final static int IF_ICMPGT = 163;
final static int IF_ICMPLE = 164;
final static int IF_ICMPGE = 162;
final static int IF_ACMPEQ = 165;
final static int IF_ACMPNE = 166;
final static int GOTO = 167;
final static int JSR = 168;
final static int RET = 169;
final static int TABLESWITCH = 170;
final static int LOOKUPSWITCH = 171;
final static int IRETURN = 172;
final static int LRETURN = 173;
final static int FRETURN = 174;
final static int DRETURN = 175;
final static int ARETURN = 176;
final static int RETURN = 177;
final static int INVOKEVIRTUAL = 182;
final static int INVOKENONVIRTUAL = 183;
final static int INVOKESTATIC = 184;
final static int INVOKEINTERFACE = 185;
final static int NEW = 187;
final static int NEWARRAY = 188;
final static int ANEWARRAY = 189;
final static int ARRAYLENGTH = 190;
final static int ATHROW = 191;
final static int CHECKCAST = 192;
final static int INSTANCEOF = 193;
final static int MONITORENTER = 194;
final static int MONITOREXIT = 195;
final static int WIDE = 196;
final static int MULTIANEWARRAY = 197;
final static int IFNULL = 198;
final static int IFNONNULL = 199;
final static int GOTO_W = 200;
final static int JSR_W = 201;
final static int BREAKPOINT = 202;
final static int RET_W = 209;
}
class PanelWithInsets extends Panel {
private int top;
private int left;
private int bottom;
private int right;
PanelWithInsets(int t, int l, int b, int r) {
top = t;
left = l;
bottom = b;
right = r;
}
PanelWithInsets() {
top = 5;
left = 5;
bottom = 5;
right = 5;
}
public Insets insets() {
return new Insets(top, left, bottom, right);
}
}
class RegisterPanel extends Panel {
private LabeledRegister pcRegister;
private LabeledRegister optopRegister;
private LabeledRegister frameRegister;
private LabeledRegister varsRegister;
RegisterPanel() {
setLayout(new BorderLayout(5, 5));
pcRegister = new LabeledRegister(StringTable.pc);
optopRegister = new LabeledRegister(StringTable.optop);
frameRegister = new LabeledRegister(StringTable.frame);
varsRegister = new LabeledRegister(StringTable.vars);
setBackground(ColorTable.registersAreaColor);
Panel labeledRegisterPanel = new Panel();
labeledRegisterPanel.setLayout(new GridLayout(1, 4, 5, 5));
labeledRegisterPanel.add(pcRegister);
labeledRegisterPanel.add(optopRegister);
labeledRegisterPanel.add(frameRegister);
labeledRegisterPanel.add(varsRegister);
Label title = new Label(StringTable.Registers, Label.CENTER);
title.setFont(new Font("Helvetica", Font.BOLD, 11));
add("West", title);
add("Center", labeledRegisterPanel);
}
public void setPcRegister(int val) {
pcRegister.setRegister(val);
}
public void setOptopRegister(int val) {
optopRegister.setRegister(val);
}
public void setFrameRegister(int val) {
frameRegister.setRegister(val);
}
public void setVarsRegister(int val) {
varsRegister.setRegister(val);
}
public Insets insets() {
// top, left, bottom, right
return new Insets(5, 5, 5, 5);
}
}
class RepeaterButton extends GrayButton {
RepeaterButton(String label) {
super(label);
}
}
class SimData {
static final int methodAreaMemorySectionSize = 13;
static final int methodAreaMemoryLocationsVisibleCount = 13;
static final int frameOffset = 4;
static final int optopOffset = 16;
static int[] theProgram = { OpCode.FCONST_2, OpCode.FSTORE_0, OpCode.FLOAD_0, OpCode.FLOAD_0,
OpCode.FMUL, OpCode.FSTORE_0, OpCode.FCONST_0, OpCode.FLOAD_0, OpCode.FSUB, OpCode.FSTORE_0,
OpCode.GOTO, (byte) 0xff, (byte) 0xf8 };
static String[] byteCodeMnemonics = { "fconst_2", "fstore_0", "fload_0", "fload_0", "fmul",
"fstore_0", "fconst_0", "fload_0", "fsub", "fstore_0", "goto -17", "", "" };
}
// StackMemorySection is just used for the stack in this applet. This implements
// the functionality of the stack and has nothing to do with the UI.
class StackMemorySection {
private int[] memory;
private int baseAddress;
private String[] logicalValueString;
StackMemorySection(int base, int size) {
baseAddress = base;
memory = new int[size];
logicalValueString = new String[size];
for (int i = 0; i < size; ++i) {
memory[i] = 0;
logicalValueString[i] = new String();
}
}
public int getAtAddress(int address) {
return memory[(address - baseAddress) / 4];
}
public String getLogicalValueAtAddress(int address) {
return logicalValueString[(address - baseAddress) / 4];
}
public void setAtAddress(int address, int value) {
memory[(address - baseAddress) / 4] = value;
}
public void setLogicalValueAtAddress(int address, String s) {
logicalValueString[(address - baseAddress) / 4] = s;
}
}
// StackMemoryView is just used for the stack in this applet. It implements the
// UI of the stack.
class StackMemoryView extends Panel {
private final int memoryLocationsVisibleCount = 8;
private Label[] pointer = new Label[memoryLocationsVisibleCount];
private Label[] address = new Label[memoryLocationsVisibleCount];
private Label[] wordValue = new Label[memoryLocationsVisibleCount];
private Label[] logicalValue = new Label[memoryLocationsVisibleCount];
StackMemoryView() {
int[] hComponentCellWidths = new int[4];
hComponentCellWidths[0] = 2;
hComponentCellWidths[1] = 2;
hComponentCellWidths[2] = 2;
hComponentCellWidths[3] = 3;
setLayout(new GridSnapLayout(memoryLocationsVisibleCount, 9, hComponentCellWidths));
setBackground(Color.lightGray);
Font plainFont = new Font("TimesRoman", Font.PLAIN, 11);
setFont(plainFont);
Font italicFont = new Font("TimesRoman", Font.ITALIC, 11);
for (int i = memoryLocationsVisibleCount - 1; i >= 0; --i) {
pointer[i] = new Label("", Label.RIGHT);
pointer[i].setFont(italicFont);
add(pointer[i]);
address[i] = new Label("", Label.CENTER);
add(address[i]);
wordValue[i] = new Label("", Label.CENTER);
add(wordValue[i]);
logicalValue[i] = new Label("", Label.CENTER);
add(logicalValue[i]);
}
}
public void setAt(int i, int addressValue, int value, String logicalValueString) {
HexString addressValueString = new HexString(addressValue, 8);
HexString wordValueString = new HexString(value, 8);
address[memoryLocationsVisibleCount - 1 - i].setText(addressValueString.getString());
wordValue[memoryLocationsVisibleCount - 1 - i].setText(wordValueString.getString());
logicalValue[memoryLocationsVisibleCount - 1 - i].setText(logicalValueString);
}
public void update(StackMemorySection memorySection, int initialAddress) {
for (int i = 0; i < memoryLocationsVisibleCount; ++i) {
int theWord = memorySection.getAtAddress(initialAddress + (i * 4));
String logicalValue = memorySection.getLogicalValueAtAddress(initialAddress + (i * 4));
setAt(i, initialAddress + (i * 4), theWord, logicalValue);
}
}
public void clearPointers() {
for (int i = 0; i < memoryLocationsVisibleCount; ++i) {
pointer[i].setText("");
}
}
public void updatePointer(int i, String pointerString) {
pointer[memoryLocationsVisibleCount - 1 - i].setText(pointerString);
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class StackMemoryViewTitlePanel extends Panel {
StackMemoryViewTitlePanel() {
// setLayout(new GridLayout(1, 4));
int[] hComponentCellWidths = new int[4];
hComponentCellWidths[0] = 2;
hComponentCellWidths[1] = 2;
hComponentCellWidths[2] = 2;
hComponentCellWidths[3] = 3;
setLayout(new GridSnapLayout(1, 9, hComponentCellWidths));
setFont(new Font("Helvetica", Font.ITALIC, 11));
add(new Label("", Label.CENTER));
add(new Label(StringTable.address, Label.CENTER));
add(new Label(StringTable.hexValue, Label.CENTER));
add(new Label(StringTable.value, Label.CENTER));
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class StackMemoryViewWithTitles extends Panel {
private StackMemoryView memoryView = new StackMemoryView();
StackMemoryViewWithTitles() {
setLayout(new BorderLayout());
add("North", new StackMemoryViewTitlePanel());
add("Center", memoryView);
}
public StackMemoryView getMemoryViewReference() {
return memoryView;
}
public Insets insets() {
// top, left, bottom, right
return new Insets(0, 0, 0, 0);
}
}
class StackPanel extends Panel {
private Label title;
private StackMemoryViewWithTitles memoryView = new StackMemoryViewWithTitles();
StackPanel() {
setLayout(new BorderLayout());
title = new Label("Stack", Label.CENTER);
title.setFont(new Font("Helvetica", Font.BOLD, 11));
add("North", title);
add("Center", memoryView);
}
public StackMemoryView getMemoryViewReference() {
return memoryView.getMemoryViewReference();
}
public Insets insets() {
return new Insets(5, 5, 5, 5);
}
}
class StringTable {
public final static String appletTitle = "CIRCLE OF SQUARES";
public final static String step = "Step";
public final static String reset = "Reset";
public final static String operand = "operand";
public final static String execEnv = "exec env";
public final static String localVars = "local vars";
public final static String varsPointer = "vars >";
public final static String framePointer = "frame >";
public final static String optopPointer = "optop >";
public final static String address = "address";
public final static String bytecodes = "bytecodes";
public final static String mnemonics = "mnemonics";
public final static String hexValue = "hex value";
public final static String value = "value";
public final static String Registers = "Registers";
public final static String pc = "pc";
public final static String optop = "optop";
public final static String frame = "frame";
public final static String vars = "vars";
public final static String bipushText = "bipush will expand the next byte to an int and push it onto the stack.";
public final static String fconst_0Text = "fconst_0 will push float 0.0 onto the stack.";
public final static String fconst_2Text = "fconst_2 will push float 2.0 onto the stack.";
public final static String fload_0Text = "fload_0 will push the float at local variable 0 onto the stack.";
public final static String fmulText = "fmul will pop two floats, multiply them, and push the result.";
public final static String fstore_0Text = "fstore_0 will pop the float off the top of the stack and store it in local variable 0.";
public final static String fsubText = "fsub will pop two floats, subtract them, and push the result.";
public final static String gotoText = "goto will cause a jump to the specified offset.";
public final static String iaddText = "iadd will pop the top two integers off the stack, add them, and push the result back onto the stack.";
public final static String iconst_m1Text = "iconst_m1 will push -1 onto the stack.";
public final static String iconst_0Text = "iconst_0 will push 0 onto the stack.";
public final static String iconst_1Text = "iconst_1 will push 1 onto the stack.";
public final static String iconst_2Text = "iconst_2 will push 2 onto the stack.";
public final static String iincText = "iinc will increment the specified local variable by the specified amount.";
public final static String iload_0Text = "iload_0 will push the integer at local variable 0 onto the stack.";
public final static String iload_1Text = "iload_1 will push the integer at local variable 1 onto the stack.";
public final static String imulText = "imul will pop two integers, multiply them, and push the result.";
public final static String int2byteText = "int2byte will convert the topmost int on the stack to a value valid for the byte type.";
public final static String istore_0Text = "istore_0 will pop the integer off the top of the stack and store it in local variable 0.";
public final static String istore_1Text = "istore_1 will pop the integer off the top of the stack and store it in local variable 1.";
}
class ThreeParts extends Panel {
private RegisterPanel registers;
private TwoParts twoParts;
ThreeParts(int methodAreaMemorySectionSize) {
setLayout(new BorderLayout(5, 5));
registers = new RegisterPanel();
twoParts = new TwoParts(methodAreaMemorySectionSize);
add("North", registers);
add("Center", twoParts);
}
StackMemoryView getStackMemoryViewReference() {
return twoParts.getStackMemoryViewReference();
}
MemoryView getMethodAreaMemoryViewReference() {
return twoParts.getMethodAreaMemoryViewReference();
}
RegisterPanel getRegisterPanel() {
return registers;
}
}
// TwoParts is the panel that contains the Stack and Method Area panels
class TwoParts extends Panel {
private StackPanel stack;
private MethodAreaPanel methodArea;
TwoParts(int methodAreaMemorySectionSize) {
setLayout(new GridLayout(1, 2, 5, 5));
stack = new StackPanel();
methodArea = new MethodAreaPanel(methodAreaMemorySectionSize);
stack.setBackground(ColorTable.stackAreaColor);
methodArea.setBackground(ColorTable.methodAreaColor);
add(stack);
add(methodArea);
}
public StackMemoryView getStackMemoryViewReference() {
return stack.getMemoryViewReference();
}
public MemoryView getMethodAreaMemoryViewReference() {
return methodArea.getMemoryViewReference();
}
// top, left, bottom, right
// Want a 10 pixel separation between the twoparts and the register panel
// above and the control panel below.
public Insets insets() {
return new Insets(0, 0, 0, 0);
}
}
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