src/org/apache/pig/builtin/ROUND.java

/*
 * 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.pig.builtin;

import java.io.IOException;
import java.util.List;
import java.util.ArrayList;

import org.apache.pig.EvalFunc;
import org.apache.pig.FuncSpec;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.data.DataType;
import org.apache.pig.impl.logicalLayer.FrontendException;

/**
 * ROUND implements a binding to the Java function
 * {@link java.lang.Math#round(double) Math.round(double)}. 
 * Given a single data atom it Returns the closest long to the argument.
 * 
 */
public class ROUND extends EvalFunc<Long>{
	/**
	 * java level API
	 * @param input expects a single numeric value
	 * @return output returns a single numeric value, 
	 * the closest long to the argument
	 */
	@Override
	public Long exec(Tuple input) throws IOException {
        if (input == null || input.size() == 0 || input.get(0) == null)
            return null;

        try{
            Double d =  DataType.toDouble(input.get(0));
		    return Math.round(d);
        } catch (NumberFormatException nfe){
            System.err.println("Failed to process input; error - " + nfe.getMessage());
            return null;
        } catch (Exception e){
            throw new IOException("Caught exception processing input row ", e);
        }
	}
	
	@Override
	public Schema outputSchema(Schema input) {
        return new Schema(new Schema.FieldSchema(getSchemaName(this.getClass().getName().toLowerCase(), input), DataType.LONG));
	}

    /* (non-Javadoc)
     * @see org.apache.pig.EvalFunc#getArgToFuncMapping()
     */
    @Override
    public List<FuncSpec> getArgToFuncMapping() throws FrontendException {
        List<FuncSpec> funcList = new ArrayList<FuncSpec>();
        funcList.add(new FuncSpec(this.getClass().getName(), new Schema(new Schema.FieldSchema(null, DataType.BYTEARRAY))));
        funcList.add(new FuncSpec(DoubleRound.class.getName(),  new Schema(new Schema.FieldSchema(null, DataType.DOUBLE))));
        funcList.add(new FuncSpec(FloatRound.class.getName(),   new Schema(new Schema.FieldSchema(null, DataType.FLOAT))));
        return funcList;
    }

    @Override
    public boolean allowCompileTimeCalculation() {
        return true;
    }
}