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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.expression;
import com.yahoo.vespa.objects.Deserializer;
import com.yahoo.vespa.objects.Identifiable;
import com.yahoo.vespa.objects.ObjectVisitor;
import com.yahoo.vespa.objects.Serializer;
import java.io.Serializable;
/**
* This is the base class for all expression node types. There is no execution logic implemented in Java, since that all
* happens in the C++ backend. This class hierarchy is for <b>building</b> the expression tree to pass to the backend.
*
* @author baldersheim
* @author Simon Thoresen Hult
*/
public abstract class ExpressionNode extends Identifiable implements Serializable {
public static final int classId = registerClass(0x4000 + 40, ExpressionNode.class);
/**
* Prepare expression for execution.
*/
public void prepare() {
onPrepare();
}
/**
* Execute expression.
*
* @return true if successful, false if not.
*/
public boolean execute() {
return onExecute();
}
/**
* Give an argument to this expression and store the result.
*
* @param arg Argument to use for expression.
* @param result Node to contain the result.
*/
protected void executeIterative(final ResultNode arg, ResultNode result) {
onArgument(arg, result);
}
protected boolean onExecute() {
throw new RuntimeException("Class " + this.getClass().getName() + " does not implement onExecute().");
}
protected void onPrepare() {
throw new RuntimeException("Class " + this.getClass().getName() + " does not implement onPrepare().");
}
protected void onArgument(final ResultNode arg, ResultNode result) {
throw new RuntimeException("Class " + this.getClass().getName() + " does not implement onArgument().");
}
@Override
protected int onGetClassId() {
return classId;
}
@Override
protected void onSerialize(Serializer buf) {
super.onSerialize(buf);
}
@Override
protected void onDeserialize(Deserializer buf) {
super.onDeserialize(buf);
}
@Override
public void visitMembers(ObjectVisitor visitor) {
super.visitMembers(visitor);
}
@Override
public ExpressionNode clone() {
return (ExpressionNode)super.clone();
}
@Override
public final boolean equals(Object obj) {
if (!super.equals(obj)) {
return false;
}
if (!equalsExpression((ExpressionNode)obj)) {
return false;
}
return true;
}
protected abstract boolean equalsExpression(ExpressionNode obj);
/**
* Get the result of this expression.
*
* @return the result as a ResultNode.
*/
abstract public ResultNode getResult();
}
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