/*
* reserved comment block
* DO NOT REMOVE OR ALTER!
*/
package com.sun.org.apache.bcel.internal.generic;
/* ====================================================================
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* individuals on behalf of the Apache Software Foundation. For more
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import com.sun.org.apache.bcel.internal.classfile.Utility;
import java.util.HashSet;
import java.util.Collection;
import java.util.HashMap;
/**
* 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 1.1.2.1 2005/07/31 23:45:01 jeffsuttor Exp $
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
* @see Instruction
* @see BranchHandle
* @see InstructionList
*/
public class InstructionHandle implements java.io.Serializable {
InstructionHandle next, prev; // Will be set from the outside
Instruction instruction;
protected int i_position = -1; // byte code offset of instruction
private HashSet targeters;
private HashMap attributes;
public final InstructionHandle getNext() { return next; }
public final InstructionHandle getPrev() { return prev; }
public final Instruction getInstruction() { return instruction; }
/**
* Replace current instruction contained in this handle.
* Old instruction is disposed using Instruction.dispose().
*/
public void setInstruction(Instruction i) { // Overridden in BranchHandle
if(i == null)
throw new ClassGenException("Assigning null to handle");
if((this.getClass() != BranchHandle.class) && (i instanceof BranchInstruction))
throw new ClassGenException("Assigning branch instruction " + i + " to plain handle");
if(instruction != null)
instruction.dispose();
instruction = i;
}
/**
* Temporarily swap the current instruction, without disturbing
* anything. Meant to be used by a debugger, implementing
* breakpoints. Current instruction is returned.
*/
public Instruction swapInstruction(Instruction i) {
Instruction oldInstruction = instruction;
instruction = i;
return oldInstruction;
}
/*private*/ protected InstructionHandle(Instruction i) {
setInstruction(i);
}
private static InstructionHandle ih_list = null; // List of reusable handles
/** Factory method.
*/
static final InstructionHandle getInstructionHandle(Instruction i) {
if(ih_list == null)
return new InstructionHandle(i);
else {
InstructionHandle ih = ih_list;
ih_list = ih.next;
ih.setInstruction(i);
return ih;
}
}
/**
* 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.
*
* @param offset additional offset caused by preceding (variable length) instructions
* @param max_offset the maximum offset that may be caused by these instructions
* @return additional offset caused by possible change of this instruction's length
*/
protected int updatePosition(int offset, int max_offset) {
i_position += offset;
return 0;
}
/** @return the position, i.e., the byte code offset of the contained
* instruction. This is accurate only after
* InstructionList.setPositions() has been called.
*/
public int getPosition() { return i_position; }
/** Set the position, i.e., the byte code offset of the contained
* instruction.
*/
void setPosition(int pos) { i_position = pos; }
/** Overridden in BranchHandle
*/
protected void addHandle() {
next = ih_list;
ih_list = this;
}
/**
* Delete contents, i.e., remove user access and make handle reusable.
*/
void dispose() {
next = prev = null;
instruction.dispose();
instruction = null;
i_position = -1;
attributes = null;
removeAllTargeters();
addHandle();
}
/** Remove all targeters, if any.
*/
public void removeAllTargeters() {
if(targeters != null)
targeters.clear();
}
/**
* Denote this handle isn't referenced anymore by t.
*/
public void removeTargeter(InstructionTargeter t) {
targeters.remove(t);
}
/**
* Denote this handle is being referenced by t.
*/
public void addTargeter(InstructionTargeter t) {
if(targeters == null)
targeters = new HashSet();
//if(!targeters.contains(t))
targeters.add(t);
}
public boolean hasTargeters() {
return (targeters != null) && (targeters.size() > 0);
}
/**
* @return null, if there are no targeters
*/
public InstructionTargeter[] getTargeters() {
if(!hasTargeters())
return null;
InstructionTargeter[] t = new InstructionTargeter[targeters.size()];
targeters.toArray(t);
return t;
}
/** @return a (verbose) string representation of the contained instruction.
*/
public String toString(boolean verbose) {
return Utility.format(i_position, 4, false, ' ') + ": " + instruction.toString(verbose);
}
/** @return a string representation of the contained instruction.
*/
public String toString() {
return toString(true);
}
/** Add an attribute to an instruction handle.
*
* @param key the key object to store/retrieve the attribute
* @param attr the attribute to associate with this handle
*/
public void addAttribute(Object key, Object attr) {
if(attributes == null)
attributes = new HashMap(3);
attributes.put(key, attr);
}
/** Delete an attribute of an instruction handle.
*
* @param key the key object to retrieve the attribute
*/
public void removeAttribute(Object key) {
if(attributes != null)
attributes.remove(key);
}
/** Get attribute of an instruction handle.
*
* @param key the key object to store/retrieve the attribute
*/
public Object getAttribute(Object key) {
if(attributes != null)
return attributes.get(key);
return null;
}
/** @return all attributes associated with this handle
*/
public Collection getAttributes() {
return attributes.values();
}
/** Convenience method, simply calls accept() on the contained instruction.
*
* @param v Visitor object
*/
public void accept(Visitor v) {
instruction.accept(v);
}
}