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## org.apache.bcel.generic
Class InstructionHandle

    java.lang.Object
      |
      +--org.apache.bcel.generic.InstructionHandle

All Implemented Interfaces:
  java.io.Serializable

Direct Known Subclasses:
  BranchHandle

public class InstructionHandle
extends java.lang.Object
implements java.io.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,v 1.1.1.1 2001/10/29 20:00:19 jvanzyl Exp $
Author:
  M. Dahm
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(java.lang.Object key, java.lang.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.
`java.lang.Object` | `getAttribute(java.lang.Object key)` Get attribute of an instruction handle.
`java.util.Collection` | `getAttributes()`
`Instruction` | `getInstruction()`
`InstructionHandle` | `getNext()`
`int` | `getPosition()`
`InstructionHandle` | `getPrev()`
`InstructionTargeter[]` | `getTargeters()`
`boolean` | `hasTargeters()`
`void` | `removeAllTargeters()` Remove all targeters, if any.
`void` | `removeAttribute(java.lang.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.
`java.lang.String` | `toString()`
`java.lang.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 java.lang.String toString(boolean verbose)

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

### toString

    public java.lang.String toString()

  Overrides:
    `toString` in class `java.lang.Object`
  Returns:
    a string representation of the contained instruction.

### addAttribute

    public void addAttribute(java.lang.Object key,
                             java.lang.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(java.lang.Object key)

  Delete an attribute of an instruction handle.

  Parameters:
    `key` - the key object to retrieve the attribute

### getAttribute

    public java.lang.Object getAttribute(java.lang.Object key)

  Get attribute of an instruction handle.

  Parameters:
    `key` - the key object to store/retrieve the attribute

### getAttributes

    public java.util.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

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