/*
* JBoss, Home of Professional Open Source
* Copyright 2008-10 Red Hat and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*
* @authors Andrew Dinn
*/
package org.jboss.byteman.rule.expression;
import org.jboss.byteman.rule.compiler.CompileContext;
import org.jboss.byteman.rule.type.Type;
import org.jboss.byteman.rule.exception.TypeException;
import org.jboss.byteman.rule.exception.ExecuteException;
import org.jboss.byteman.rule.exception.CompileException;
import org.jboss.byteman.rule.Rule;
import org.jboss.byteman.rule.helper.HelperAdapter;
import org.jboss.byteman.rule.grammar.ParseNode;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.Opcodes;
/**
* A binary logical operator expression
*/
public class LogicalExpression extends BooleanExpression
{
public LogicalExpression(Rule rule, int oper, ParseNode token, Expression left, Expression right)
{
super(rule, oper, token, left, right);
}
public Type typeCheck(Type expected) throws TypeException {
Type type1 = getOperand(0).typeCheck(Type.Z);
Type type2 = getOperand(1).typeCheck(Type.Z);
type = Type.Z;
if (Type.dereference(expected).isDefined() && !expected.isAssignableFrom(type)) {
throw new TypeException("LogicalExpression.typeCheck : invalid expected result type " + expected.getName() + getPos());
}
return type;
}
public Object interpret(HelperAdapter helper) throws ExecuteException {
Boolean value = (Boolean)getOperand(0).interpret(helper);
if (oper == AND) {
return (value && (Boolean)getOperand(1).interpret(helper));
} else { // oper == OR
return (value || (Boolean)getOperand(1).interpret(helper));
}
}
public void compile(MethodVisitor mv, CompileContext compileContext) throws CompileException
{
Expression oper0 = getOperand(0);
Expression oper1 = getOperand(1);
int currentStack = compileContext.getStackCount();
// compile the first expression and make sure it is a boolean -- adds 1 to stack height
oper0.compile(mv, compileContext);
if (oper0.getType() == Type.BOOLEAN) {
compileBooleanConversion(Type.BOOLEAN, type.Z, mv, compileContext);
}
// plant a test and branch
Label nextLabel = new Label();
Label endLabel = new Label();
if (oper == AND) {
// only try next if we got true here
mv.visitJumpInsn(Opcodes.IFNE, nextLabel);
// ok, the first branch was false so stack a false for the result and skip to the end
mv.visitLdcInsn(false);
mv.visitJumpInsn(Opcodes.GOTO, endLabel);
} else {
// only try next if we got false here
mv.visitJumpInsn(Opcodes.IFEQ, nextLabel);
// ok, the first branch was true so stack a true for the result and skip to the end
mv.visitLdcInsn(true);
mv.visitJumpInsn(Opcodes.GOTO, endLabel);
}
// in either case if we get here the if test removed 1 from the stack
compileContext.addStackCount(-1);
// the else branch -- adds 1 to stack height
mv.visitLabel(nextLabel);
oper1.compile(mv, compileContext);
if (oper0.getType() == Type.BOOLEAN) {
compileBooleanConversion(Type.BOOLEAN, type.Z, mv, compileContext);
}
// the final result is the result of the second oper which is on the stack already
// This is the end, my beau-tiful friend
mv.visitLabel(endLabel);
// in either case if we get here we should have one extra value on the stack
// check stack height
if (compileContext.getStackCount() != currentStack + 1) {
throw new CompileException("LogicalExpression.compile : invalid stack height " + compileContext.getStackCount() + " expecting " + (currentStack + 1));
}
}
}