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leegao/ClassReader.java

Created November 20, 2010 04:52
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Java bytecode reader prototype
Raw
ClassReader.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package classreader;
import java.io.ByteArrayInputStream;
import java.io.DataInput;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.lang.reflect.Array;
import java.math.BigInteger;
import java.util.LinkedList;
/**
*
* @author Lee Gao: lg342@cornell.edu
*/
public class ClassReader {
public enum ClassAccess {
PUBLIC(0x0001),
FINAL(0x0010), SUPER(0x0020),
INTERFACE(0x0200), ABSTRACT(0x0400),
SYNTHETIC(0x1000), ANNOTATION(0x2000), ENUM(0x4000),
UNDEFINED(0x0000);
int flag;
private ClassAccess(int flag) {
this.flag = flag;
}
public static LinkedList<ClassAccess> get(int flag) {
LinkedList<ClassAccess> flags = new LinkedList<ClassAccess>();
if ((flag & 0x0001) > 0) {
flags.add(PUBLIC); // May be accessed from outside the package.
}
if ((flag & 0x0010) > 0) {
flags.add(FINAL); // Cannot be subclassed. mutex with INTERFACE and ABSTRACT
}
if ((flag & 0x0020) > 0) {
flags.add(SUPER); // For backward compatibility, special invocation instruction
}
if ((flag & 0x0200) > 0) {
flags.add(INTERFACE); // Interface - Must also have ABSTRACT set and mutex with FINAL, SUPER, ENUM
}
if ((flag & 0x0400) > 0) {
flags.add(ABSTRACT); // Cannot be instantiated
}
if ((flag & 0x1000) > 0) {
flags.add(SYNTHETIC); // Compiler generated, will not be included in the src
}
if ((flag & 0x2000) > 0) {
flags.add(ANNOTATION); // @Annotation must also have INTERFACE set
}
if ((flag & 0x4000) > 0) {
flags.add(ENUM); // ENUM type
}
return flags;
}
}
public enum FieldAccess {
PUBLIC(0x0001),
PRIVATE(0x0002), PROTECTED(0x0004),
STATIC(0x0008), FINAL(0x0010),
VOLATILE(0x0040), TRANSIENT(0x0080), SYNTHETIC(0x1000),
ENUM(0x4000);
int flag;
private FieldAccess(int flag) {
this.flag = flag;
}
public static LinkedList<FieldAccess> get(int flag) {
LinkedList<FieldAccess> flags = new LinkedList<FieldAccess>();
if ((flag & 0x0001) > 0) {
flags.add(PUBLIC); // May be accessed from outside the class
}
if ((flag & 0x0002) > 0) {
flags.add(PRIVATE); // Usable only within the defining class.
}
if ((flag & 0x0004) > 0) {
flags.add(PROTECTED); // May only be accessed from class and subclasses
}
if ((flag & 0x0008) > 0) {
flags.add(STATIC); // Static
}
if ((flag & 0x0010) > 0) {
flags.add(FINAL); // Cannot be changed during instantiation
}
if ((flag & 0x0040) > 0) {
flags.add(VOLATILE); // Cannot be cached
}
if ((flag & 0x0080) > 0) {
flags.add(TRANSIENT); // Not written/read by persistent object managers
}
if ((flag & 0x1000) > 0) {
flags.add(SYNTHETIC); // Compiler generated, will not be included in the src
}
if ((flag & 0x4000) > 0) {
flags.add(ENUM); // ENUM type
}
return flags;
}
}
public enum MethodAccess {
PUBLIC(0x0001),
PRIVATE(0x0002), PROTECTED(0x0004),
STATIC(0x0008), FINAL(0x0010), SYNCHRONIZED(0x0020),
BRIDGE(0x0040), VARARGS(0x0080), NATIVE(0x0100), ABSTRACT(0x0400), STRICT(0x0800), SYNTHETIC(0x1000);
int flag;
private MethodAccess(int flag) {
this.flag = flag;
}
public static LinkedList<MethodAccess> get(int flag) {
LinkedList<MethodAccess> flags = new LinkedList<MethodAccess>();
if ((flag & 0x0001) > 0) {
flags.add(PUBLIC); // May be accessed from outside the class
}
if ((flag & 0x0002) > 0) {
flags.add(PRIVATE); // Usable only within the defining class.
}
if ((flag & 0x0004) > 0) {
flags.add(PROTECTED); // May only be accessed from class and subclasses
}
if ((flag & 0x0008) > 0) {
flags.add(STATIC); // Static
}
if ((flag & 0x0010) > 0) {
flags.add(FINAL); // Cannot be changed during instantiation
}
if ((flag & 0x0020) > 0) {
flags.add(SYNCHRONIZED); // Threadsafe
}
if ((flag & 0x0040) > 0) {
flags.add(BRIDGE); // Compiler generated bridge method
}
if ((flag & 0x0080) > 0) {
flags.add(VARARGS); // Variable number of args : variadic
}
if ((flag & 0x0100) > 0) {
flags.add(NATIVE); // Not a java method
}
if ((flag & 0x0400) > 0) {
flags.add(ABSTRACT); // No implementation is provided
}
if ((flag & 0x0800) > 0) {
flags.add(STRICT); // Strict floating point manipulation
}
if ((flag & 0x1000) > 0) {
flags.add(SYNTHETIC); // Compiler generated, will not be included in the src
}
return flags;
}
}
class AttributeStruct {
class LineNumberTable {
short length;
short[][] line_number_table;
}
class LocalVariableTable {
short length;
short[][] local_variable_table;
public String[][] localStack(ClassReader reader) throws Exception {
String[][] stack = new String[length][2];
int i = 0;
for (short[] local : local_variable_table) {
stack[i++] = new String[]{(String) (reader.resolve(local[2])), (String) (reader.resolve(local[3]))};
}
return stack;
}
}
class Code {
short max_stack;
short max_locals;
int code_length;
byte[] code;
short exception_length;
short[][] exceptions;
short attributes_count;
AttributeStruct[] attributes;
public void printCode(){
int cursor = 0;
for (byte c : code){
int k = (int)((char)c%256);
cursor++;
System.out.print(((cursor-1)%20==0?(cursor/20)+" | ":"")+(k<=0x0F?"0":"")+Integer.toHexString(k).toUpperCase()+(cursor%10==0?(cursor%20!=0?" ":"\n"):" "));
}
System.out.println("\n");
}
}
short name;
int alength;
byte[] info;
Object o;
public void parseInfo(ClassReader reader) throws Exception {
String name_ = (String) reader.resolve(this.name);
if (name_.equals("ConstantValue")) {
o = reader.resolve((short) ((info[0] << 8) + info[1]));
} else if (name_.equals("Signature")) {
o = reader.resolve((short) ((info[0] << 8) + info[1]));
} else if (name_.equals("LineNumberTable")) {
DataInputStream bytes = new DataInputStream(new ByteArrayInputStream(info));
LineNumberTable table = new LineNumberTable();
table.length = bytes.readShort();
table.line_number_table = new short[table.length][2];
for (int i = 0; i < table.length; i++) {
table.line_number_table[i] = new short[]{bytes.readShort(), bytes.readShort()};
}
o = table;
} else if (name_.equals("LocalVariableTable")) {
DataInputStream bytes = new DataInputStream(new ByteArrayInputStream(info));
LocalVariableTable table = new LocalVariableTable();
table.length = bytes.readShort();
table.local_variable_table = new short[table.length][5];
for (int i = 0; i < table.length; i++) {
table.local_variable_table[i] = new short[]{bytes.readShort(), bytes.readShort(), (short) (bytes.readShort() - (short) 1), (short) (bytes.readShort() - (short) 1), bytes.readShort()};
}
o = table;
} else if (name_.equals("Code")) {
DataInputStream bytes = new DataInputStream(new ByteArrayInputStream(info));
Code code = new Code();
code.max_stack = bytes.readShort();
code.max_locals = bytes.readShort();
code.code_length = bytes.readInt();
code.code = new byte[code.code_length];
bytes.read(code.code);
code.exception_length = bytes.readShort();
code.exceptions = new short[code.exception_length][4];
for (int i = 0; i < code.exception_length; i++) {
code.exceptions[i] = new short[]{bytes.readShort(), bytes.readShort(), bytes.readShort(), bytes.readShort()};
}
code.attributes_count = bytes.readShort();
code.attributes = new AttributeStruct[code.attributes_count];
for (int i = 0; i < code.attributes_count; i++) {
AttributeStruct a = new AttributeStruct();
a.name = (short) (bytes.readShort() - (short) 1);
a.alength = bytes.readInt();
a.info = new byte[a.alength];
bytes.read(a.info);
a.parseInfo(reader);
code.attributes[i] = a;
}
o = code;
} else {
//print("Unknown Attribute " + name_);
o = info;
}
}
}
class FieldStruct {
short aflags;
short name;
short descriptor;
short attributes_count;
AttributeStruct[] attributes;
}
class MethodStruct {
short aflags;
short name;
short descriptor;
short attributes_count;
AttributeStruct[] attributes;
}
class ClassStruct {
int magic = 0xCAFEBABE;
short minor_version = 0;
short major_version = 0;
short cpool_count = 0;
Object[] cpool;
short aflags;
short self = 0;
short parent = 0;
short interfaces_count = 0;
short[] interfaces;
short fields_count = 0;
FieldStruct[] fields;
short methods_count = 0;
MethodStruct[] methods;
short attributes_count = 0;
AttributeStruct[] attributes;
}
DataInputStream source;
ClassStruct struct = new ClassStruct();
public static String parseDescriptor(String descriptor) {
if (descriptor.startsWith("(")){
int starts = descriptor.indexOf(")", 0);
String postfix = descriptor.substring(starts+1);
String prefix = descriptor.substring(1, starts);
return parseDescriptor(postfix) + " %s("+(prefix.isEmpty()?"":(parseDescriptor(prefix)+" %s"))+")";
}
String array = "";
while (descriptor.startsWith("[")){
array += "[]";
descriptor = descriptor.substring(1);
}
if (descriptor.isEmpty()) return "";
char tag = descriptor.charAt(0);
descriptor = descriptor.substring(1);
String obj = "";
switch(tag){
case 'B':
obj = "byte";break;
case 'C':
obj = "char";break;
case 'D':
obj = "double";break;
case 'F':
obj = "float";break;
case 'I':
obj = "int";break;
case 'J':
obj = "long";break;
case 'S':
obj = "short";break;
case 'Z':
obj = "boolean";break;
case 'V':
obj = "void";break;
case 'L':
int next = descriptor.indexOf(";", 0);
obj = ClassReader.parseQualifiedName(descriptor.substring(0, next));
descriptor = descriptor.substring(next+1);
break;
}
return obj + array + (descriptor.isEmpty()?"":" %s, "+parseDescriptor(descriptor));
}
public Object resolve(short index) throws Exception {
if (index >= 0 && index < struct.cpool_count) {
Object o = struct.cpool[index];
if (o.getClass().isArray()) {
short tag = (short) Array.get(o, (short) 0);
switch (tag) {
// 9,10,11
case 0x09:
case 0x0A:
case 0x0B:
Object class_ = resolve((short) Array.get(o, 1));
Object descriptor = resolve((short) Array.get(o, 2));
return new Object[]{class_, descriptor};
case 0x07:
return parseQualifiedName((String) resolve((short) Array.get(o, 1)));
case 0x08:
return resolve((short) Array.get(o, 1));
case 0x0C:
Object name = parseQualifiedName((String) resolve((short) Array.get(o, 1)));
Object type = parseDescriptor((String) resolve((short) Array.get(o, 2)));
return new String[]{(String) name, (String) type};
default:
throw new Exception("Fell through the cpool during symbol lookup. " + tag);
}
} else {
return struct.cpool[index];
}
}
return null;
}
public static void print(Object o, String end) {
if (o.getClass().isArray()) {
System.out.print("{");
for (int i = 0; i < Array.getLength(o) - 1; i++) {
print(Array.get(o, i), ", ");
}
print(Array.get(o, Array.getLength(o) - 1), "");
System.out.print("}");
} else if (o instanceof String) {
System.out.print("\"" + o + "\"");
} else {
System.out.print(o);
}
System.out.print(end);
}
public static void print(Object o) {
print(o, "\n");
}
public static void print(Object... objs) {
if (objs.length < 5) {
for (Object o : objs) {
print(o, "\t");
}
} else {
print(objs, "");
}
System.out.println();
}
public ClassReader(FileInputStream stream) throws IOException, Exception {
source = new DataInputStream(stream);
// Validate the magic number
assert source.readInt() == 0xCAFEBABE;
// Versioning
struct.minor_version = source.readShort();
struct.major_version = source.readShort();
if (struct.major_version < 49) {
throw new Exception("Java SDK not supported, only se > 5.0");
}
// Constant pool
struct.cpool_count = (short) (source.readShort() - ((short) 1));
struct.cpool = new Object[struct.cpool_count];
for (int i = 0; i < struct.cpool_count; i++) {
byte tag = source.readByte();
switch (tag) {
case 0x01:
struct.cpool[i] = source.readUTF();
break;
case 0x03:
struct.cpool[i] = source.readInt();
break;
case 0x04:
struct.cpool[i] = source.readFloat();
break;
case 0x05:
struct.cpool[i] = source.readLong();
struct.cpool[++i] = struct.cpool[i - 1];
break;
case 0x06:
struct.cpool[i] = source.readDouble();
struct.cpool[++i] = struct.cpool[i - 1];
break;
case 0x08:
case 0x07:
struct.cpool[i] = new short[]{tag, (short) (source.readShort() - (short) 1)};
break;
case 0x09:
case 0x0A:
case 0x0B:
case 0x0C:
struct.cpool[i] = new short[]{tag,
(short) (source.readShort() - (short) 1),
(short) (source.readShort() - (short) 1)};
break;
default:
throw new Exception("Fell through cpool switch with tag " + tag + " at " + i);
}
}
// Access Flags / Bitmasks
struct.aflags = source.readShort();
// This/Super
struct.self = (short) (source.readShort() - 1);
struct.parent = (short) (source.readShort() - 1);
if (struct.parent < 0) {
struct.parent = 0; // TODO: resolve to java/lang/Object
}
// Interfaces
struct.interfaces_count = source.readShort();
struct.interfaces = new short[struct.interfaces_count];
for (int i = 0; i < struct.interfaces_count; i++) {
struct.interfaces[i] = (short) (source.readShort() - (short) 1);
}
// Fields
struct.fields_count = source.readShort();
struct.fields = new FieldStruct[struct.fields_count];
for (int i = 0; i < struct.fields_count; i++) {
FieldStruct field = new FieldStruct();
field.aflags = source.readShort();
field.name = (short) (source.readShort() - (short) 1);
field.descriptor = (short) (source.readShort() - (short) 1);
field.attributes_count = source.readShort();
field.attributes = new AttributeStruct[field.attributes_count];
for (int j = 0; j < field.attributes_count; j++) {
AttributeStruct attr = new AttributeStruct();
attr.name = (short) (source.readShort() - (short) 1);
attr.alength = source.readInt();
attr.info = new byte[attr.alength];
for (int b = 0; b < attr.alength; b++) {
attr.info[b] = source.readByte();
}
attr.parseInfo(this);
field.attributes[j] = attr;
}
struct.fields[i] = field;
}
// Methods
struct.methods_count = source.readShort();
struct.methods = new MethodStruct[struct.methods_count];
for (int i = 0; i < struct.methods_count; i++) {
MethodStruct method = new MethodStruct();
method.aflags = source.readShort();
method.name = (short) (source.readShort() - (short) 1);
method.descriptor = (short) (source.readShort() - (short) 1);
method.attributes_count = source.readShort();
method.attributes = new AttributeStruct[method.attributes_count];
for (int j = 0; j < method.attributes_count; j++) {
AttributeStruct attr = new AttributeStruct();
attr.name = (short) (source.readShort() - (short) 1);
attr.alength = source.readInt();
attr.info = new byte[attr.alength];
for (int b = 0; b < attr.alength; b++) {
attr.info[b] = source.readByte();
}
attr.parseInfo(this);
method.attributes[j] = attr;
}
struct.methods[i] = method;
}
// Attributes
struct.attributes_count = source.readShort();
struct.attributes = new AttributeStruct[struct.attributes_count];
for (int i = 0; i < struct.attributes_count; i++) {
AttributeStruct attr = new AttributeStruct();
attr.name = (short) (source.readShort() - (short) 1);
attr.alength = source.readInt();
attr.info = new byte[attr.alength];
for (int b = 0; b < attr.alength; b++) {
attr.info[b] = source.readByte();
}
attr.parseInfo(this);
struct.attributes[i] = attr;
}
}
public ClassReader(String filename) throws FileNotFoundException, IOException, Exception {
this(new FileInputStream(filename));
}
public static String parseQualifiedName(String name) {
return name.replace('/', '.');
}
}
Raw
ClassReaderTest.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package classreader;
import classreader.ClassReader.ClassAccess;
import classreader.ClassReader.FieldAccess;
import classreader.ClassReader.MethodStruct;
import classreader.ClassReader.AttributeStruct;
import classreader.ClassReader.FieldStruct;
import classreader.ClassReader.MethodAccess;
import java.lang.reflect.Array;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import classreader.ClassReader.AttributeStruct.*;
/**
*
* @author Lee
*/
public class ClassReaderTest {
@Before
public void setUp() {
}
@After
public void tearDown() {
}
// <editor-fold defaultstate="collapsed" desc="Convenient Print Function">
public static void print(Object o, String end) {
if (o.getClass().isArray()) {
System.out.print("{");
for (int i = 0; i < Array.getLength(o) - 1; i++) {
print(Array.get(o, i), ", ");
}
print(Array.get(o, Array.getLength(o) - 1), "");
System.out.print("}");
} else if (o instanceof String) {
System.out.print("\"" + o + "\"");
} else {
System.out.print(o);
}
System.out.print(end);
}
public static void print(Object o) {
print(o, "\n");
}
public static void print(Object... objs) {
if (objs.length < 5) {
for (Object o : objs) {
print(o, "\t");
}
} else {
print(objs, "");
}
System.out.println();
}// </editor-fold>
/**
* Test of print method, of class ClassReader.
*/
@Test
public void testConstructor() throws Exception{
ClassReader c = new ClassReader("build/classes/dummy/Dummy.class");
for (short i = 0; i<c.struct.cpool.length; i++){
//print(i, c.struct.cpool[i], c.resolve(i));
}
for (FieldStruct f : c.struct.fields){
//print(FieldAccess.get(f.aflags), c.resolve(f.name), c.resolve(f.descriptor));
if (f.attributes_count>0){
for (int i=0; i<f.attributes_count;i++){
AttributeStruct a = f.attributes[i];
//print(i ,c.resolve(a.name));
}
}
}
for (MethodStruct m : c.struct.methods){
print(MethodAccess.get(m.aflags), c.resolve(m.name), c.resolve(m.descriptor));
if (m.attributes_count>0){
for (int i=0; i<m.attributes_count;i++){
AttributeStruct a = m.attributes[i];
if (a.o instanceof Code){
Code code = (Code) a.o;
code.printCode();
}
}
}
}
}
@Test
public void testDescriptor(){
String descriptor = "([Ljava/lang/Object;IBS)Ldummy/Dummy;";
print(ClassReader.parseDescriptor(descriptor));
}
}
Raw
Opcode.java
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package classreader;
import java.util.HashMap;
/**
*
* @author Lee
*/
public class Opcode {
byte op;
String[] params;
String comment;
String name;
public Opcode(byte op, String name, String comment, String... parameters){
this.op = op;
this.params = parameters;
this.comment = comment;
this.name = name;
}
}
class Opcodes{
static{
HashMap<Byte, Opcode> ops = new HashMap<Byte, Opcode>();
ops.put((byte)0x032, new Opcode((byte)0x32, "aaload", ":oads onto the stack a reference from an array"));
}
}
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