org.apache.bcel.generic
Class InstructionHandle

java.lang.Object
  org.apache.bcel.generic.InstructionHandle

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

BranchHandle

public class InstructionHandle
extends Object
implements Serializable

Instances of this class give users a handle to the instructions contained in an InstructionList. Instruction objects may be used more than once within a list, this is useful because it saves memory and may be much faster. Within an InstructionList an InstructionHandle object is wrapped around all instructions, i.e., it implements a cell in a doubly-linked list. From the outside only the next and the previous instruction (handle) are accessible. One can traverse the list via an Enumeration returned by InstructionList.elements().

Version:

$Id: InstructionHandle.java 386056 2006-03-15 11:31:56Z tcurdt $

See Also:

Instruction, BranchHandle, InstructionList, Serialized Form

Field Summary

protected int

i_position

Constructor Summary

protected

InstructionHandle(Instruction i)

Method Summary

void	accept(Visitor v) Convenience method, simply calls accept() on the contained instruction.
void	addAttribute(Object key, Object attr) Add an attribute to an instruction handle.
protected void	addHandle() Overridden in BranchHandle
void	addTargeter(InstructionTargeter t) Denote this handle is being referenced by t.
Object	getAttribute(Object key) Get attribute of an instruction handle.
Collection	getAttributes()
Instruction	getInstruction()
InstructionHandle	getNext()
int	getPosition()
InstructionHandle	getPrev()
InstructionTargeter[]	getTargeters()
boolean	hasTargeters()
void	removeAllTargeters() Remove all targeters, if any.
void	removeAttribute(Object key) Delete an attribute of an instruction handle.
void	removeTargeter(InstructionTargeter t) Denote this handle isn't referenced anymore by t.
void	setInstruction(Instruction i) Replace current instruction contained in this handle.
Instruction	swapInstruction(Instruction i) Temporarily swap the current instruction, without disturbing anything.
String	toString()
String	toString(boolean verbose)
protected int	updatePosition(int offset, int max_offset) Called by InstructionList.setPositions when setting the position for every instruction.

Methods inherited from class java.lang.Object

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

Field Detail

i_position

protected int i_position

Constructor Detail

InstructionHandle

protected InstructionHandle(Instruction i)

Method Detail

getNext

public final InstructionHandle getNext()

getPrev

public final InstructionHandle getPrev()

getInstruction

public final Instruction getInstruction()

setInstruction

public void setInstruction(Instruction i)

Replace current instruction contained in this handle. Old instruction is disposed using Instruction.dispose().

swapInstruction

public Instruction swapInstruction(Instruction i)

Temporarily swap the current instruction, without disturbing anything. Meant to be used by a debugger, implementing breakpoints. Current instruction is returned.

updatePosition

protected int updatePosition(int offset,
                             int max_offset)

Called by InstructionList.setPositions when setting the position for every instruction. In the presence of variable length instructions `setPositions()' performs multiple passes over the instruction list to calculate the correct (byte) positions and offsets by calling this function.

Parameters:

offset - additional offset caused by preceding (variable length) instructions

max_offset - the maximum offset that may be caused by these instructions

Returns:

additional offset caused by possible change of this instruction's length

getPosition

public int getPosition()

Returns:

the position, i.e., the byte code offset of the contained instruction. This is accurate only after InstructionList.setPositions() has been called.

addHandle

protected void addHandle()

Overridden in BranchHandle

removeAllTargeters

public void removeAllTargeters()

Remove all targeters, if any.

removeTargeter

public void removeTargeter(InstructionTargeter t)

Denote this handle isn't referenced anymore by t.

addTargeter

public void addTargeter(InstructionTargeter t)

Denote this handle is being referenced by t.

hasTargeters

public boolean hasTargeters()

getTargeters

public InstructionTargeter[] getTargeters()

Returns:

null, if there are no targeters

toString

public String toString(boolean verbose)

Returns:

a (verbose) string representation of the contained instruction.

toString

public String toString()

Overrides:

toString in class Object

Returns:

a string representation of the contained instruction.

addAttribute

public void addAttribute(Object key,
                         Object attr)

Add an attribute to an instruction handle.

Parameters:

key - the key object to store/retrieve the attribute

attr - the attribute to associate with this handle

removeAttribute

public void removeAttribute(Object key)

Delete an attribute of an instruction handle.

Parameters:

key - the key object to retrieve the attribute

getAttribute

public Object getAttribute(Object key)

Get attribute of an instruction handle.

Parameters:

key - the key object to store/retrieve the attribute

getAttributes

public Collection getAttributes()

Returns:

all attributes associated with this handle

accept

public void accept(Visitor v)

Convenience method, simply calls accept() on the contained instruction.

Parameters:

v - Visitor object