/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package org.apache.bcel.generic;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.bcel.classfile.Utility;
/**
* 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 1589401 2014-04-23 12:56:36Z ebourg $
* @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
* @see Instruction
* @see BranchHandle
* @see InstructionList
*/
public class InstructionHandle implements java.io.Serializable {
private static final long serialVersionUID = -3585254135692924106L;
InstructionHandle next, prev; // Will be set from the outside
Instruction instruction;
protected int i_position = -1; // byte code offset of instruction
private Set<InstructionTargeter> targeters;
private Map<Object, Object> 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 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 ) {
if (targeters != null) {
targeters.remove(t);
}
}
/**
* Denote this handle is being referenced by t.
*/
public void addTargeter( InstructionTargeter t ) {
if (targeters == null) {
targeters = new HashSet<InstructionTargeter>();
}
//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 new InstructionTargeter[0];
}
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.
*/
@Override
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<Object, Object>(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<Object> getAttributes() {
if (attributes == null) {
attributes = new HashMap<Object, Object>(3);
}
return attributes.values();
}
/** Convenience method, simply calls accept() on the contained instruction.
*
* @param v Visitor object
*/
public void accept( Visitor v ) {
instruction.accept(v);
}
}