/*
* 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.
*/
/*
* $Id: Operation.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xpath.operations;
import org.apache.xpath.Expression;
import org.apache.xpath.ExpressionOwner;
import org.apache.xpath.XPathContext;
import org.apache.xpath.XPathVisitor;
import org.apache.xpath.objects.XObject;
/**
* The baseclass for a binary operation.
*/
public class Operation extends Expression implements ExpressionOwner
{
static final long serialVersionUID = -3037139537171050430L;
/** The left operand expression.
* @serial */
protected Expression m_left;
/** The right operand expression.
* @serial */
protected Expression m_right;
/**
* This function is used to fixup variables from QNames to stack frame
* indexes at stylesheet build time.
* @param vars List of QNames that correspond to variables. This list
* should be searched backwards for the first qualified name that
* corresponds to the variable reference qname. The position of the
* QName in the vector from the start of the vector will be its position
* in the stack frame (but variables above the globalsTop value will need
* to be offset to the current stack frame).
*/
public void fixupVariables(java.util.Vector vars, int globalsSize)
{
m_left.fixupVariables(vars, globalsSize);
m_right.fixupVariables(vars, globalsSize);
}
/**
* Tell if this expression or it's subexpressions can traverse outside
* the current subtree.
*
* @return true if traversal outside the context node's subtree can occur.
*/
public boolean canTraverseOutsideSubtree()
{
if (null != m_left && m_left.canTraverseOutsideSubtree())
return true;
if (null != m_right && m_right.canTraverseOutsideSubtree())
return true;
return false;
}
/**
* Set the left and right operand expressions for this operation.
*
*
* @param l The left expression operand.
* @param r The right expression operand.
*/
public void setLeftRight(Expression l, Expression r)
{
m_left = l;
m_right = r;
l.exprSetParent(this);
r.exprSetParent(this);
}
/**
* Execute a binary operation by calling execute on each of the operands,
* and then calling the operate method on the derived class.
*
*
* @param xctxt The runtime execution context.
*
* @return The XObject result of the operation.
*
* @throws javax.xml.transform.TransformerException
*/
public XObject execute(XPathContext xctxt)
throws javax.xml.transform.TransformerException
{
XObject left = m_left.execute(xctxt, true);
XObject right = m_right.execute(xctxt, true);
XObject result = operate(left, right);
left.detach();
right.detach();
return result;
}
/**
* Apply the operation to two operands, and return the result.
*
*
* @param left non-null reference to the evaluated left operand.
* @param right non-null reference to the evaluated right operand.
*
* @return non-null reference to the XObject that represents the result of the operation.
*
* @throws javax.xml.transform.TransformerException
*/
public XObject operate(XObject left, XObject right)
throws javax.xml.transform.TransformerException
{
return null; // no-op
}
/** @return the left operand of binary operation, as an Expression.
*/
public Expression getLeftOperand(){
return m_left;
}
/** @return the right operand of binary operation, as an Expression.
*/
public Expression getRightOperand(){
return m_right;
}
class LeftExprOwner implements ExpressionOwner
{
/**
* @see ExpressionOwner#getExpression()
*/
public Expression getExpression()
{
return m_left;
}
/**
* @see ExpressionOwner#setExpression(Expression)
*/
public void setExpression(Expression exp)
{
exp.exprSetParent(Operation.this);
m_left = exp;
}
}
/**
* @see org.apache.xpath.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
*/
public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
{
if(visitor.visitBinaryOperation(owner, this))
{
m_left.callVisitors(new LeftExprOwner(), visitor);
m_right.callVisitors(this, visitor);
}
}
/**
* @see ExpressionOwner#getExpression()
*/
public Expression getExpression()
{
return m_right;
}
/**
* @see ExpressionOwner#setExpression(Expression)
*/
public void setExpression(Expression exp)
{
exp.exprSetParent(this);
m_right = exp;
}
/**
* @see Expression#deepEquals(Expression)
*/
public boolean deepEquals(Expression expr)
{
if(!isSameClass(expr))
return false;
if(!m_left.deepEquals(((Operation)expr).m_left))
return false;
if(!m_right.deepEquals(((Operation)expr).m_right))
return false;
return true;
}
}