/*
* 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 org.apache.bcel.Const;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.JavaClass;
Super class for object and array types.
/**
* Super class for object and array types.
*
*/
public abstract class ReferenceType extends Type {
protected ReferenceType(final byte t, final String s) {
super(t, s);
}
Class is non-abstract but not instantiable from the outside
/** Class is non-abstract but not instantiable from the outside
*/
ReferenceType() {
super(Const.T_OBJECT, "<null object>");
}
Return true iff this type is castable to another type t as defined in
the JVM specification. The case where this is Type.NULL is not
defined (see the CHECKCAST definition in the JVM specification).
However, because e.g. CHECKCAST doesn't throw a
ClassCastException when casting a null reference to any Object,
true is returned in this case.
Throws: - ClassNotFoundException – if any classes or interfaces required
to determine assignment compatibility can't be found
/**
* Return true iff this type is castable to another type t as defined in
* the JVM specification. The case where this is Type.NULL is not
* defined (see the CHECKCAST definition in the JVM specification).
* However, because e.g. CHECKCAST doesn't throw a
* ClassCastException when casting a null reference to any Object,
* true is returned in this case.
*
* @throws ClassNotFoundException if any classes or interfaces required
* to determine assignment compatibility can't be found
*/
public boolean isCastableTo( final Type t ) throws ClassNotFoundException {
if (this.equals(Type.NULL)) {
return t instanceof ReferenceType; // If this is ever changed in isAssignmentCompatible()
}
return isAssignmentCompatibleWith(t);
/* Yes, it's true: It's the same definition.
* See vmspec2 AASTORE / CHECKCAST definitions.
*/
}
Return true iff this is assignment compatible with another type t
as defined in the JVM specification; see the AASTORE definition
there.
Throws: - ClassNotFoundException – if any classes or interfaces required
to determine assignment compatibility can't be found
/**
* Return true iff this is assignment compatible with another type t
* as defined in the JVM specification; see the AASTORE definition
* there.
* @throws ClassNotFoundException if any classes or interfaces required
* to determine assignment compatibility can't be found
*/
public boolean isAssignmentCompatibleWith( final Type t ) throws ClassNotFoundException {
if (!(t instanceof ReferenceType)) {
return false;
}
final ReferenceType T = (ReferenceType) t;
if (this.equals(Type.NULL)) {
return true; // This is not explicitely stated, but clear. Isn't it?
}
/* If this is a class type then
*/
if ((this instanceof ObjectType) && (((ObjectType) this).referencesClassExact())) {
/* If T is a class type, then this must be the same class as T,
or this must be a subclass of T;
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClassExact())) {
if (this.equals(T)) {
return true;
}
if (Repository.instanceOf(((ObjectType) this).getClassName(), ((ObjectType) T)
.getClassName())) {
return true;
}
}
/* If T is an interface type, this must implement interface T.
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterfaceExact())) {
if (Repository.implementationOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName())) {
return true;
}
}
}
/* If this is an interface type, then:
*/
if ((this instanceof ObjectType) && (((ObjectType) this).referencesInterfaceExact())) {
/* If T is a class type, then T must be Object (�2.4.7).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClassExact())) {
if (T.equals(Type.OBJECT)) {
return true;
}
}
/* If T is an interface type, then T must be the same interface
* as this or a superinterface of this (�2.13.2).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterfaceExact())) {
if (this.equals(T)) {
return true;
}
if (Repository.implementationOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName())) {
return true;
}
}
}
/* If this is an array type, namely, the type SC[], that is, an
* array of components of type SC, then:
*/
if (this instanceof ArrayType) {
/* If T is a class type, then T must be Object (�2.4.7).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClassExact())) {
if (T.equals(Type.OBJECT)) {
return true;
}
}
/* If T is an array type TC[], that is, an array of components
* of type TC, then one of the following must be true:
*/
if (T instanceof ArrayType) {
/* TC and SC are the same primitive type (�2.4.1).
*/
final Type sc = ((ArrayType) this).getElementType();
final Type tc = ((ArrayType) T).getElementType();
if (sc instanceof BasicType && tc instanceof BasicType && sc.equals(tc)) {
return true;
}
/* TC and SC are reference types (�2.4.6), and type SC is
* assignable to TC by these runtime rules.
*/
if (tc instanceof ReferenceType && sc instanceof ReferenceType
&& ((ReferenceType) sc).isAssignmentCompatibleWith(tc)) {
return true;
}
}
/* If T is an interface type, T must be one of the interfaces implemented by arrays (�2.15). */
// TODO: Check if this is still valid or find a way to dynamically find out which
// interfaces arrays implement. However, as of the JVM specification edition 2, there
// are at least two different pages where assignment compatibility is defined and
// on one of them "interfaces implemented by arrays" is exchanged with "'Cloneable' or
// 'java.io.Serializable'"
if ((T instanceof ObjectType) && (((ObjectType) T).referencesInterfaceExact())) {
for (final String element : Const.getInterfacesImplementedByArrays()) {
if (T.equals(ObjectType.getInstance(element))) {
return true;
}
}
}
}
return false; // default.
}
This commutative operation returns the first common superclass (narrowest ReferenceType
referencing a class, not an interface).
If one of the types is a superclass of the other, the former is returned.
If "this" is Type.NULL, then t is returned.
If t is Type.NULL, then "this" is returned.
If "this" equals t ['this.equals(t)'] "this" is returned.
If "this" or t is an ArrayType, then Type.OBJECT is returned;
unless their dimensions match. Then an ArrayType of the same
number of dimensions is returned, with its basic type being the
first common super class of the basic types of "this" and t.
If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
If not all of the two classes' superclasses cannot be found, "null" is returned.
See the JVM specification edition 2, "�4.9.2 The Bytecode Verifier".
Throws: - ClassNotFoundException – on failure to find superclasses of this
type, or the type passed as a parameter
/**
* This commutative operation returns the first common superclass (narrowest ReferenceType
* referencing a class, not an interface).
* If one of the types is a superclass of the other, the former is returned.
* If "this" is Type.NULL, then t is returned.
* If t is Type.NULL, then "this" is returned.
* If "this" equals t ['this.equals(t)'] "this" is returned.
* If "this" or t is an ArrayType, then Type.OBJECT is returned;
* unless their dimensions match. Then an ArrayType of the same
* number of dimensions is returned, with its basic type being the
* first common super class of the basic types of "this" and t.
* If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
* If not all of the two classes' superclasses cannot be found, "null" is returned.
* See the JVM specification edition 2, "�4.9.2 The Bytecode Verifier".
*
* @throws ClassNotFoundException on failure to find superclasses of this
* type, or the type passed as a parameter
*/
public ReferenceType getFirstCommonSuperclass( final ReferenceType t ) throws ClassNotFoundException {
if (this.equals(Type.NULL)) {
return t;
}
if (t.equals(Type.NULL)) {
return this;
}
if (this.equals(t)) {
return this;
/*
* TODO: Above sounds a little arbitrary. On the other hand, there is
* no object referenced by Type.NULL so we can also say all the objects
* referenced by Type.NULL were derived from java.lang.Object.
* However, the Java Language's "instanceof" operator proves us wrong:
* "null" is not referring to an instance of java.lang.Object :)
*/
}
/* This code is from a bug report by Konstantin Shagin <konst@cs.technion.ac.il> */
if ((this instanceof ArrayType) && (t instanceof ArrayType)) {
final ArrayType arrType1 = (ArrayType) this;
final ArrayType arrType2 = (ArrayType) t;
if ((arrType1.getDimensions() == arrType2.getDimensions())
&& arrType1.getBasicType() instanceof ObjectType
&& arrType2.getBasicType() instanceof ObjectType) {
return new ArrayType(((ObjectType) arrType1.getBasicType())
.getFirstCommonSuperclass((ObjectType) arrType2.getBasicType()), arrType1
.getDimensions());
}
}
if ((this instanceof ArrayType) || (t instanceof ArrayType)) {
return Type.OBJECT;
// TODO: Is there a proof of OBJECT being the direct ancestor of every ArrayType?
}
if (((this instanceof ObjectType) && ((ObjectType) this).referencesInterfaceExact())
|| ((t instanceof ObjectType) && ((ObjectType) t).referencesInterfaceExact())) {
return Type.OBJECT;
// TODO: The above line is correct comparing to the vmspec2. But one could
// make class file verification a bit stronger here by using the notion of
// superinterfaces or even castability or assignment compatibility.
}
// this and t are ObjectTypes, see above.
final ObjectType thiz = (ObjectType) this;
final ObjectType other = (ObjectType) t;
final JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
final JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
final JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
final JavaClass[] t_sups = new JavaClass[other_sups.length + 1];
System.arraycopy(thiz_sups, 0, this_sups, 1, thiz_sups.length);
System.arraycopy(other_sups, 0, t_sups, 1, other_sups.length);
this_sups[0] = Repository.lookupClass(thiz.getClassName());
t_sups[0] = Repository.lookupClass(other.getClassName());
for (final JavaClass t_sup : t_sups) {
for (final JavaClass this_sup : this_sups) {
if (this_sup.equals(t_sup)) {
return ObjectType.getInstance(this_sup.getClassName());
}
}
}
// Huh? Did you ask for Type.OBJECT's superclass??
return null;
}
This commutative operation returns the first common superclass (narrowest ReferenceType
referencing a class, not an interface).
If one of the types is a superclass of the other, the former is returned.
If "this" is Type.NULL, then t is returned.
If t is Type.NULL, then "this" is returned.
If "this" equals t ['this.equals(t)'] "this" is returned.
If "this" or t is an ArrayType, then Type.OBJECT is returned.
If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
If not all of the two classes' superclasses cannot be found, "null" is returned.
See the JVM specification edition 2, "�4.9.2 The Bytecode Verifier".
Throws: - ClassNotFoundException – on failure to find superclasses of this
type, or the type passed as a parameter
Deprecated: use getFirstCommonSuperclass(ReferenceType t) which has
slightly changed semantics.
/**
* This commutative operation returns the first common superclass (narrowest ReferenceType
* referencing a class, not an interface).
* If one of the types is a superclass of the other, the former is returned.
* If "this" is Type.NULL, then t is returned.
* If t is Type.NULL, then "this" is returned.
* If "this" equals t ['this.equals(t)'] "this" is returned.
* If "this" or t is an ArrayType, then Type.OBJECT is returned.
* If "this" or t is a ReferenceType referencing an interface, then Type.OBJECT is returned.
* If not all of the two classes' superclasses cannot be found, "null" is returned.
* See the JVM specification edition 2, "�4.9.2 The Bytecode Verifier".
*
* @deprecated use getFirstCommonSuperclass(ReferenceType t) which has
* slightly changed semantics.
* @throws ClassNotFoundException on failure to find superclasses of this
* type, or the type passed as a parameter
*/
@Deprecated
public ReferenceType firstCommonSuperclass( final ReferenceType t ) throws ClassNotFoundException {
if (this.equals(Type.NULL)) {
return t;
}
if (t.equals(Type.NULL)) {
return this;
}
if (this.equals(t)) {
return this;
/*
* TODO: Above sounds a little arbitrary. On the other hand, there is
* no object referenced by Type.NULL so we can also say all the objects
* referenced by Type.NULL were derived from java.lang.Object.
* However, the Java Language's "instanceof" operator proves us wrong:
* "null" is not referring to an instance of java.lang.Object :)
*/
}
if ((this instanceof ArrayType) || (t instanceof ArrayType)) {
return Type.OBJECT;
// TODO: Is there a proof of OBJECT being the direct ancestor of every ArrayType?
}
if (((this instanceof ObjectType) && ((ObjectType) this).referencesInterface())
|| ((t instanceof ObjectType) && ((ObjectType) t).referencesInterface())) {
return Type.OBJECT;
// TODO: The above line is correct comparing to the vmspec2. But one could
// make class file verification a bit stronger here by using the notion of
// superinterfaces or even castability or assignment compatibility.
}
// this and t are ObjectTypes, see above.
final ObjectType thiz = (ObjectType) this;
final ObjectType other = (ObjectType) t;
final JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
final JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
final JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
final JavaClass[] t_sups = new JavaClass[other_sups.length + 1];
System.arraycopy(thiz_sups, 0, this_sups, 1, thiz_sups.length);
System.arraycopy(other_sups, 0, t_sups, 1, other_sups.length);
this_sups[0] = Repository.lookupClass(thiz.getClassName());
t_sups[0] = Repository.lookupClass(other.getClassName());
for (final JavaClass t_sup : t_sups) {
for (final JavaClass this_sup : this_sups) {
if (this_sup.equals(t_sup)) {
return ObjectType.getInstance(this_sup.getClassName());
}
}
}
// Huh? Did you ask for Type.OBJECT's superclass??
return null;
}
}