package org.drools.util.asm;
import java.util.List;
import org.drools.asm.AnnotationVisitor;
import org.drools.asm.Attribute;
import org.drools.asm.ClassReader;
import org.drools.asm.ClassVisitor;
import org.drools.asm.FieldVisitor;
import org.drools.asm.MethodVisitor;
import org.drools.asm.util.TraceMethodVisitor;
/**
* The purpose of this utility it to check if 2 method implementations are equivalent, by comparing the bytecode.
* This essentual for node sharing where java semantics are involved.
* @author Michael Neale
*/
public class MethodComparator {
/**
* This actually does the comparing.
* Class1 and Class2 are class reader instances to the respective classes. method1 and method2 are looked up on the
* respective classes and their contents compared.
*
* This is a convenience method.
*/
public boolean equivalent(final String method1,
final ClassReader class1,
final String method2,
final ClassReader class2) {
final List list1 = getMethodBytecode( method1,
class1 );
final List list2 = getMethodBytecode( method2,
class2 );
return compareBytecode( list1,
list2 );
}
/**
* This will return a series of bytecode instructions which can be used to compare one method with another.
* debug info like local var declarations and line numbers are ignored, so the focus is on the content.
*/
public List getMethodBytecode(final String methodName,
final ClassReader classReader) {
final Tracer visit = new Tracer( methodName );
classReader.accept( visit,
true );
final TraceMethodVisitor trace = visit.getTrace();
return trace.getText();
}
/**
* This will return a series of bytecode instructions which can be used to compare one method with another.
* debug info like local var declarations and line numbers are ignored, so the focus is on the content.
*/
public static List getMethodBytecode(final String methodName,
final byte[] bytes) {
final Tracer visit = new Tracer( methodName );
final ClassReader classReader = new ClassReader( bytes );
classReader.accept( visit,
true );
final TraceMethodVisitor trace = visit.getTrace();
return trace.getText();
}
/**
* Compares 2 bytecode listings.
* Returns true if they are identical.
*/
public static boolean compareBytecode(final List b1,
final List b2) {
if ( b1.size() != b2.size() ) {
return false;
}
for ( int i = 0; i < b1.size(); i++ ) {
if ( !(b1.get( i ).equals( b2.get( i ) )) ) {
return false;
}
}
return true;
}
public static class Tracer
implements
ClassVisitor {
private TraceMethodVisitor trace;
private String methodName;
public Tracer(final String methodName) {
this.methodName = methodName;
}
public void visit(final int version,
final int access,
final String name,
final String signature,
final String superName,
final String[] interfaces) {
}
public AnnotationVisitor visitAnnotation(final String desc,
final boolean visible) {
return new DummyAnnotationVisitor();
}
public void visitAttribute(final Attribute attr) {
}
public void visitEnd() {
}
public FieldVisitor visitField(final int access,
final String name,
final String desc,
final String signature,
final Object value) {
return null;
}
public void visitInnerClass(final String name,
final String outerName,
final String innerName,
final int access) {
}
public MethodVisitor visitMethod(final int access,
final String name,
final String desc,
final String signature,
final String[] exceptions) {
if ( this.methodName.equals( name ) ) {
this.trace = new TraceMethodVisitor();
return this.trace;
}
return null;
}
public void visitOuterClass(final String owner,
final String name,
final String desc) {
}
public void visitSource(final String source,
final String debug) {
}
public TraceMethodVisitor getTrace() {
return this.trace;
}
}
static class DummyAnnotationVisitor
implements
AnnotationVisitor {
public void visit(final String name,
final Object value) {
}
public AnnotationVisitor visitAnnotation(final String name,
final String desc) {
return new DummyAnnotationVisitor();
}
public AnnotationVisitor visitArray(final String name) {
return new DummyAnnotationVisitor();
}
public void visitEnd() {
}
public void visitEnum(final String name,
final String desc,
final String value) {
}
}
}