org.apache.bcel.generic

Class InstructionHandle

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 $

Author: M. Dahm

Field Summary
Map	attributes
static InstructionHandle	ih_list
Instruction	instruction
protected int	i_position
InstructionHandle	next
InstructionHandle	prev
Set	targeters

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.
void	dispose() Delete contents, i.e., remove user access and make handle reusable.
Object	getAttribute(Object key) Get attribute of an instruction handle.
Collection	getAttributes()
Instruction	getInstruction()
static InstructionHandle	getInstructionHandle(Instruction i) Factory method.
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.
void	setPosition(int pos) Set the position, i.e., the byte code offset of the contained instruction.
Instruction	swapInstruction(Instruction i) Temporarily swap the current instruction, without disturbing anything.
String	toString(boolean verbose)
String	toString()
protected int	updatePosition(int offset, int max_offset) Called by InstructionList.setPositions when setting the position for every instruction.

Field Detail

attributes

private Map attributes

ih_list

private static InstructionHandle ih_list

instruction

Instruction instruction

i_position

protected int i_position

InstructionHandle next

InstructionHandle prev

targeters

private Set targeters

Constructor Detail

InstructionHandle

protected InstructionHandle(Instruction i)

Method Detail

accept

public void accept(Visitor v)

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

Parameters: v Visitor object

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

addHandle

protected void addHandle()

Overridden in BranchHandle

addTargeter

public void addTargeter(InstructionTargeter t)

Denote this handle is being referenced by t.

dispose

void dispose()

Delete contents, i.e., remove user access and make handle reusable.

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

getInstruction

public final Instruction getInstruction()

getInstructionHandle

static final InstructionHandle getInstructionHandle(Instruction i)

Factory method.

getNext

public final InstructionHandle getNext()

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.

getPrev

public final InstructionHandle getPrev()

getTargeters

public InstructionTargeter[] getTargeters()

Returns: null, if there are no targeters

hasTargeters

public boolean hasTargeters()

removeAllTargeters

public void removeAllTargeters()

Remove all targeters, if any.

removeAttribute

public void removeAttribute(Object key)

Delete an attribute of an instruction handle.

Parameters: key the key object to retrieve the attribute

removeTargeter

public void removeTargeter(InstructionTargeter t)

Denote this handle isn't referenced anymore by t.

setInstruction

public void setInstruction(Instruction i)

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

setPosition

void setPosition(int pos)

Set the position, i.e., the byte code offset of the contained instruction.

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.

toString

public String toString(boolean verbose)

Returns: a (verbose) string representation of the contained instruction.

toString

public String toString()

Returns: a string representation of the contained instruction.

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