edu.wisc.cs.java
Class Bytecode

java.lang.Object
  |
  +--edu.wisc.cs.java.Bytecode

Direct Known Subclasses:

Branch, CodeLabel, Switch

public class Bytecode

extends java.lang.Object

This class is used to represent all bytecodes which constant lengths and is the superclass of all other classes which represent Java bytecodes.

Field Summary

protected int	opcode The opcode of this instruction.
protected byte[]	params An array containing bytes which are parameters for this instruction.
protected boolean	wide True if this instruction has the wide modifier, false otherwise.

Constructor Summary

protected	Bytecode() Constructs a genaric bytecode for sub-classes.
	Bytecode(boolean w, int op, byte[] p) Constructs a new bytecode with the given opcode and parameters.

Method Summary

int	getConstantIndex() If this bytecode references the constant pool, it returns the index.
int	getNBytes() Returns the number of bytes needed to represent this instruction.
int	getOpcode() Return the opcode for this instruction.s
int	getParamBytes() Returns the number of parameter bytes for this instruction.
boolean	isWide() Returns true if the instruction has the wide modifier, false otherwise.
java.lang.String	toString() Returns a string representation of this bytecode.
void	writeTo(java.io.DataOutputStream out) Writes a bytecode to the specified stream.

Methods inherited from class java.lang.Object

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

Field Detail

wide

protected boolean wide

True if this instruction has the wide modifier, false otherwise.

opcode

protected int opcode

The opcode of this instruction.

params

protected byte[] params

An array containing bytes which are parameters for this instruction.

Constructor Detail

Bytecode

protected Bytecode()

Constructs a genaric bytecode for sub-classes. No variable length bytecode may use the wide modifier, so this is initialized.

Bytecode

public Bytecode(boolean w,
                int op,
                byte[] p)

Constructs a new bytecode with the given opcode and parameters.

Parameters:

w - true if this is to be a wide instruction, false otherwise.

op - the opcode for the new instruction.

p - an array of parameter bytes.

Method Detail

writeTo

public void writeTo(java.io.DataOutputStream out)
             throws java.io.IOException

Writes a bytecode to the specified stream.

Parameters:

out - a stream to write the bytecode data to.

Throws:

java.io.IOException - if there is a problem writing to the stream.

getConstantIndex

public int getConstantIndex()

If this bytecode references the constant pool, it returns the index. Otherwise, it returns -1;

Returns:

an index into the constant pool, if required for this opcode.

getParamBytes

public int getParamBytes()

Returns the number of parameter bytes for this instruction.

Returns:

the number of parameter bytes for this instruction.

isWide

public boolean isWide()

Returns true if the instruction has the wide modifier, false otherwise.

Returns:

true if the instruction has the wide modifier, false otherwise.

getOpcode

public int getOpcode()

Return the opcode for this instruction.s

getNBytes

public int getNBytes()

Returns the number of bytes needed to represent this instruction.

Returns:

the number of bytes needed to represent this instruction.

toString

public java.lang.String toString()

Returns a string representation of this bytecode.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of this bytecode.