/*
* reserved comment block
* DO NOT REMOVE OR ALTER!
*/
package com.sun.org.apache.bcel.internal.generic;
/* ====================================================================
* The Apache Software License, Version 1.1
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* reserved.
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* modification, are permitted provided that the following conditions
* are met:
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* if any, must include the following acknowledgment:
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*
* This software consists of voluntary contributions made by many
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import com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.Repository;
import com.sun.org.apache.bcel.internal.classfile.JavaClass;
/**
* Super class for object and array types.
*
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
*/
public abstract class ReferenceType extends Type {
protected ReferenceType(byte t, String s) {
super(t, s);
}
/** Class is non-abstract but not instantiable from the outside
*/
ReferenceType() {
super(Constants.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.
*/
public boolean isCastableTo(Type t) {
if (this.equals(Type.NULL))
return true; // 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.
*/
public boolean isAssignmentCompatibleWith(Type t) {
if (!(t instanceof ReferenceType))
return false;
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).referencesClass())) {
/* 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).referencesClass())) {
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).referencesInterface())) {
if (Repository.implementationOf(((ObjectType) this).getClassName(),
((ObjectType) T).getClassName()))
return true;
}
}
/* If this is an interface type, then:
*/
if ((this instanceof ObjectType) && (((ObjectType) this).referencesInterface())) {
/* If T is a class type, then T must be Object (2.4.7).
*/
if ((T instanceof ObjectType) && (((ObjectType) T).referencesClass())) {
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).referencesInterface())) {
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).referencesClass())) {
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).
*/
Type sc = ((ArrayType) this).getElementType();
Type tc = ((ArrayType) this).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((ReferenceType) 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).referencesInterface())) {
for (int ii = 0; ii < Constants.INTERFACES_IMPLEMENTED_BY_ARRAYS.length; ii++) {
if (T.equals(new ObjectType(Constants.INTERFACES_IMPLEMENTED_BY_ARRAYS[ii]))) 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".
*/
public ReferenceType getFirstCommonSuperclass(ReferenceType t) {
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)) {
ArrayType arrType1 = (ArrayType) this;
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).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.
ObjectType thiz = (ObjectType) this;
ObjectType other = (ObjectType) t;
JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
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 (int i = 0; i < t_sups.length; i++) {
for (int j = 0; j < this_sups.length; j++) {
if (this_sups[j].equals(t_sups[i])) return new ObjectType(this_sups[j].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".
*
* @deprecated use getFirstCommonSuperclass(ReferenceType t) which has
* slightly changed semantics.
*/
public ReferenceType firstCommonSuperclass(ReferenceType t) {
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.
ObjectType thiz = (ObjectType) this;
ObjectType other = (ObjectType) t;
JavaClass[] thiz_sups = Repository.getSuperClasses(thiz.getClassName());
JavaClass[] other_sups = Repository.getSuperClasses(other.getClassName());
if ((thiz_sups == null) || (other_sups == null)) {
return null;
}
// Waaahh...
JavaClass[] this_sups = new JavaClass[thiz_sups.length + 1];
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 (int i = 0; i < t_sups.length; i++) {
for (int j = 0; j < this_sups.length; j++) {
if (this_sups[j].equals(t_sups[i])) return new ObjectType(this_sups[j].getClassName());
}
}
// Huh? Did you ask for Type.OBJECT's superclass??
return null;
}
}