Substr.java

/*
 * Copyright 2013 Future Systems
 * 
 * Licensed 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.araqne.logdb.query.expr;

import java.util.List;

import org.araqne.logdb.QueryContext;
import org.araqne.logdb.Row;

public class Substr extends FunctionExpression {
	private final Expression valueExpr;
	private final Expression beginExpr;
	private Expression endExpr;

	public Substr(QueryContext ctx, List<Expression> exprs) {
		super("substr", exprs, 2);
		
		this.valueExpr = exprs.get(0);
		this.beginExpr = exprs.get(1);

		if (exprs.size() > 2)
			this.endExpr = exprs.get(2);
		
	}

	@Override
	public Object eval(Row map) {
		Object value = valueExpr.eval(map);
		if (value == null)
			return null;

		String s = value.toString();
		int len = s.length();
		int begin = Integer.parseInt(beginExpr.eval(map).toString());
		if (begin < 0)
			begin = len + begin;
		
		if (begin < 0 || len <= begin)
			return null;

		int end = len;
		if (endExpr != null)
			end = Math.min(len, Integer.parseInt(endExpr.eval(map).toString()));
		
		if (end < 0)
			end = len + end;
		
		if (end < 0 || begin > end)
			return null;

		return s.substring(begin, end);
	}

}