java/engine/org/apache/derby/impl/sql/compile/NotNode.java

/*

   Derby - Class org.apache.derby.impl.sql.compile.NotNode

   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.derby.impl.sql.compile;

import java.lang.reflect.Modifier;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.reference.ClassName;
import org.apache.derby.iapi.services.classfile.VMOpcode;
import org.apache.derby.iapi.services.compiler.LocalField;
import org.apache.derby.iapi.services.compiler.MethodBuilder;
import org.apache.derby.iapi.services.context.ContextManager;

/**
 * A NotNode represents a NOT operator. Preprocessing will eliminate the 
 * NotNodes which exist above comparison operators so that the optimizer
 * will see a query tree in CNF.
 *
 */

public final class NotNode extends UnaryLogicalOperatorNode
{
    /**
     * @param operand The operand of the NOT
     * @param cm context manager
     * @throws StandardException
     */
    NotNode(ValueNode operand, ContextManager cm)
            throws StandardException {
        super(operand, "not", cm);
    }

    /**
	 * Eliminate NotNodes in the current query block.  We traverse the tree, 
	 * inverting ANDs and ORs and eliminating NOTs as we go.  We stop at 
	 * ComparisonOperators and boolean expressions.  We invert 
	 * ComparisonOperators and replace boolean expressions with 
	 * boolean expression = false.
	 *
	 * @param	underNotNode		Whether or not we are under a NotNode.
	 *							
	 *
	 * @return		The modified expression
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
	ValueNode eliminateNots(boolean underNotNode) 
					throws StandardException
	{
		return operand.eliminateNots(! underNotNode);
	}

	/**
	 * Do code generation for the NOT operator.
	 *
	 * @param acb	The ExpressionClassBuilder for the class we're generating
	 * @param mb	The method the expression will go into
	 *
	 * @exception StandardException		Thrown on error
	 */
    @Override
    void generateExpression(ExpressionClassBuilder acb, MethodBuilder mb)
									throws StandardException
	{
		/*
		** This generates the following code:
		**
		** <boolean field> = <operand>.equals(<operand>,
		**					 					<false truth value>);
		*/

		/*
		** Generate the code for a Boolean false constant value.
		*/
		String interfaceName = getTypeCompiler().interfaceName();
		LocalField field = acb.newFieldDeclaration(Modifier.PRIVATE, interfaceName);
		/*
		** Generate the call to the equals method.
		** equals is only on Orderable, not any subinterfaces.
		*/

		/* Generate the code for operand */
		operand.generateExpression(acb, mb);
		mb.upCast(ClassName.DataValueDescriptor);

		mb.dup(); // arg 1 is instance

		// arg 2
		mb.push(false);
		acb.generateDataValue(mb, getTypeCompiler(), 
				getTypeServices().getCollationType(), field);
		mb.upCast(ClassName.DataValueDescriptor);

		mb.callMethod(VMOpcode.INVOKEINTERFACE, (String) null, "equals", interfaceName, 2);
	}
}