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/*
* Javassist, a Java-bytecode translator toolkit.
* Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. Alternatively, the contents of this file may be used under
* the terms of the GNU Lesser General Public License Version 2.1 or later,
* or the Apache License Version 2.0.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*/
package javassist.bytecode.analysis;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javassist.CtClass;
/**
* MultiType represents an unresolved type. Whenever two {@code Type}
* instances are merged, if they share more than one super type (either an
* interface or a superclass), then a {@code MultiType} is used to
* represent the possible super types. The goal of a {@code MultiType}
* is to reduce the set of possible types down to a single resolved type. This
* is done by eliminating non-assignable types from the typeset when the
* {@code MultiType} is passed as an argument to
* {@link Type#isAssignableFrom(Type)}, as well as removing non-intersecting
* types during a merge.
*
* Note: Currently the {@code MultiType} instance is reused as much
* as possible so that updates are visible from all frames. In addition, all
* {@code MultiType} merge paths are also updated. This is somewhat
* hackish, but it appears to handle most scenarios.
*
* @author Jason T. Greene
*/
/* TODO - A better, but more involved, approach would be to track the instruction
* offset that resulted in the creation of this type, and
* whenever the typeset changes, to force a merge on that position. This
* would require creating a new MultiType instance every time the typeset
* changes, and somehow communicating assignment changes to the Analyzer
*/
public class MultiType extends Type {
private Map interfaces;
private Type resolved;
private Type potentialClass;
private MultiType mergeSource;
private boolean changed = false;
public MultiType(Map interfaces) {
this(interfaces, null);
}
public MultiType(Map interfaces, Type potentialClass) {
super(null);
this.interfaces = interfaces;
this.potentialClass = potentialClass;
}
/**
* Gets the class that corresponds with this type. If this information
* is not yet known, java.lang.Object will be returned.
*/
public CtClass getCtClass() {
if (resolved != null)
return resolved.getCtClass();
return Type.OBJECT.getCtClass();
}
/**
* Always returns null since this type is never used for an array.
*/
public Type getComponent() {
return null;
}
/**
* Always returns 1, since this type is a reference.
*/
public int getSize() {
return 1;
}
/**
* Always reutnrs false since this type is never used for an array
*/
public boolean isArray() {
return false;
}
/**
* Returns true if the internal state has changed.
*/
boolean popChanged() {
boolean changed = this.changed;
this.changed = false;
return changed;
}
public boolean isAssignableFrom(Type type) {
throw new UnsupportedOperationException("Not implemented");
}
public boolean isAssignableTo(Type type) {
if (resolved != null)
return type.isAssignableFrom(resolved);
if (Type.OBJECT.equals(type))
return true;
if (potentialClass != null && !type.isAssignableFrom(potentialClass))
potentialClass = null;
Map map = mergeMultiAndSingle(this, type);
if (map.size() == 1 && potentialClass == null) {
// Update previous merge paths to the same resolved type
resolved = Type.get((CtClass)map.values().iterator().next());
propogateResolved();
return true;
}
// Keep all previous merge paths up to date
if (map.size() >= 1) {
interfaces = map;
propogateState();
return true;
}
if (potentialClass != null) {
resolved = potentialClass;
propogateResolved();
return true;
}
return false;
}
private void propogateState() {
MultiType source = mergeSource;
while (source != null) {
source.interfaces = interfaces;
source.potentialClass = potentialClass;
source = source.mergeSource;
}
}
private void propogateResolved() {
MultiType source = mergeSource;
while (source != null) {
source.resolved = resolved;
source = source.mergeSource;
}
}
/**
* Always returns true, since this type is always a reference.
*
* @return true
*/
public boolean isReference() {
return true;
}
private Map getAllMultiInterfaces(MultiType type) {
Map map = new HashMap();
Iterator iter = type.interfaces.values().iterator();
while (iter.hasNext()) {
CtClass intf = (CtClass)iter.next();
map.put(intf.getName(), intf);
getAllInterfaces(intf, map);
}
return map;
}
private Map mergeMultiInterfaces(MultiType type1, MultiType type2) {
Map map1 = getAllMultiInterfaces(type1);
Map map2 = getAllMultiInterfaces(type2);
return findCommonInterfaces(map1, map2);
}
private Map mergeMultiAndSingle(MultiType multi, Type single) {
Map map1 = getAllMultiInterfaces(multi);
Map map2 = getAllInterfaces(single.getCtClass(), null);
return findCommonInterfaces(map1, map2);
}
private boolean inMergeSource(MultiType source) {
while (source != null) {
if (source == this)
return true;
source = source.mergeSource;
}
return false;
}
public Type merge(Type type) {
if (this == type)
return this;
if (type == UNINIT)
return this;
if (type == BOGUS)
return BOGUS;
if (type == null)
return this;
if (resolved != null)
return resolved.merge(type);
if (potentialClass != null) {
Type mergePotential = potentialClass.merge(type);
if (! mergePotential.equals(potentialClass) || mergePotential.popChanged()) {
potentialClass = Type.OBJECT.equals(mergePotential) ? null : mergePotential;
changed = true;
}
}
Map merged;
if (type instanceof MultiType) {
MultiType multi = (MultiType)type;
if (multi.resolved != null) {
merged = mergeMultiAndSingle(this, multi.resolved);
} else {
merged = mergeMultiInterfaces(multi, this);
if (! inMergeSource(multi))
mergeSource = multi;
}
} else {
merged = mergeMultiAndSingle(this, type);
}
// Keep all previous merge paths up to date
if (merged.size() > 1 || (merged.size() == 1 && potentialClass != null)) {
// Check for changes
if (merged.size() != interfaces.size()) {
changed = true;
} else if (changed == false){
Iterator iter = merged.keySet().iterator();
while (iter.hasNext())
if (! interfaces.containsKey(iter.next()))
changed = true;
}
interfaces = merged;
propogateState();
return this;
}
if (merged.size() == 1) {
resolved = Type.get((CtClass) merged.values().iterator().next());
} else if (potentialClass != null){
resolved = potentialClass;
} else {
resolved = OBJECT;
}
propogateResolved();
return resolved;
}
public boolean equals(Object o) {
if (! (o instanceof MultiType))
return false;
MultiType multi = (MultiType) o;
if (resolved != null)
return resolved.equals(multi.resolved);
else if (multi.resolved != null)
return false;
return interfaces.keySet().equals(multi.interfaces.keySet());
}
public String toString() {
if (resolved != null)
return resolved.toString();
StringBuffer buffer = new StringBuffer("{");
Iterator iter = interfaces.keySet().iterator();
while (iter.hasNext()) {
buffer.append(iter.next());
buffer.append(", ");
}
buffer.setLength(buffer.length() - 2);
if (potentialClass != null)
buffer.append(", *").append(potentialClass.toString());
buffer.append("}");
return buffer.toString();
}
}
