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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/* ====================================================================
   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.poi.ss.formula.udf;

import org.apache.poi.ss.formula.atp.AnalysisToolPak;
import org.apache.poi.ss.formula.functions.FreeRefFunction;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;

/**
 * Collects add-in libraries and VB macro functions together into one UDF finder
 *
 * @author PUdalau
 */
public class AggregatingUDFFinder implements UDFFinder {
    
    /**
     * Default UDFFinder implementation
     */ 
    public static final UDFFinder DEFAULT = new AggregatingUDFFinder(AnalysisToolPak.instance);

    private final Collection _usedToolPacks;

    public AggregatingUDFFinder(UDFFinder ... usedToolPacks) {
        _usedToolPacks = new ArrayList<>(usedToolPacks.length);
        _usedToolPacks.addAll(Arrays.asList(usedToolPacks));
    }

    /**
     * Returns executor by specified name. Returns null if
     * function isn't contained by any registered tool pack.
     *
     * @param name Name of function.
     * @return Function executor. null if not found
     */
    @Override
    public FreeRefFunction findFunction(String name) {
        FreeRefFunction evaluatorForFunction;
        for (UDFFinder pack : _usedToolPacks) {
            evaluatorForFunction = pack.findFunction(name);
            if (evaluatorForFunction != null) {
                return evaluatorForFunction;
            }
        }
        return null;
    }

    /**
     * Add a new toolpack
     *
     * @param toolPack the UDF toolpack to add
     */
    public void add(UDFFinder toolPack){
        _usedToolPacks.add(toolPack);
    }
}