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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.commons.codec.language;

import java.util.Locale;

import org.apache.commons.codec.EncoderException;
import org.apache.commons.codec.StringEncoder;

/**
 * Encodes a string into a Cologne Phonetic value.
 * 

* Implements the Kölner Phonetik (Cologne * Phonetic) algorithm issued by Hans Joachim Postel in 1969. *

*

* The Kölner Phonetik is a phonetic algorithm which is optimized for the German language. It is related to * the well-known soundex algorithm. *

* *

Algorithm

* *
    * *
  • *

    Step 1:

    * After preprocessing (conversion to upper case, transcription of germanic umlauts, removal of non alphabetical characters) the * letters of the supplied text are replaced by their phonetic code according to the following table. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
    (Source: Wikipedia (de): Kölner Phonetik -- * Buchstabencodes)
    LetterContextCode
    A, E, I, J, O, U, Y0
    H-
    B1
    Pnot before H
    D, Tnot before C, S, Z2
    F, V, W3
    Pbefore H
    G, K, Q4
    Cat onset before A, H, K, L, O, Q, R, U, X
    before A, H, K, O, Q, U, X except after S, Z
    Xnot after C, K, Q48
    L5
    M, N6
    R7
    S, Z8
    Cafter S, Z
    at onset except before A, H, K, L, O, Q, R, U, X
    not before A, H, K, O, Q, U, X
    D, Tbefore C, S, Z
    Xafter C, K, Q
    * *

    Example:

    * * "Müller-Lü * denscheidt" => "MULLERLUDENSCHEIDT" => "6005507500206880022" * *
  • * *
  • *

    Step 2:

    * Collapse of all multiple consecutive code digits. *

    Example:

    * "6005507500206880022" => "6050750206802"
  • * *
  • *

    Step 3:

    * Removal of all codes "0" except at the beginning. This means that two or more identical consecutive digits can occur * if they occur after removing the "0" digits. * *

    Example:

    * "6050750206802" => "65752682"
  • * *
* *

* This class is thread-safe. *

* * @see Wikipedia (de): Kölner Phonetik (in German) * @since 1.5 */ public class ColognePhonetic implements StringEncoder { // Predefined char arrays for better performance and less GC load private static final char[] AEIJOUY = new char[] { 'A', 'E', 'I', 'J', 'O', 'U', 'Y' }; private static final char[] SCZ = new char[] { 'S', 'C', 'Z' }; private static final char[] WFPV = new char[] { 'W', 'F', 'P', 'V' }; private static final char[] GKQ = new char[] { 'G', 'K', 'Q' }; private static final char[] CKQ = new char[] { 'C', 'K', 'Q' }; private static final char[] AHKLOQRUX = new char[] { 'A', 'H', 'K', 'L', 'O', 'Q', 'R', 'U', 'X' }; private static final char[] SZ = new char[] { 'S', 'Z' }; private static final char[] AHOUKQX = new char[] { 'A', 'H', 'O', 'U', 'K', 'Q', 'X' }; private static final char[] TDX = new char[] { 'T', 'D', 'X' }; /** * This class is not thread-safe; the field {@link #length} is mutable. * However, it is not shared between threads, as it is constructed on demand * by the method {@link ColognePhonetic#colognePhonetic(String)} */ private abstract class CologneBuffer { protected final char[] data; protected int length = 0; public CologneBuffer(final char[] data) { this.data = data; this.length = data.length; } public CologneBuffer(final int buffSize) { this.data = new char[buffSize]; this.length = 0; } protected abstract char[] copyData(int start, final int length); public int length() { return length; } @Override public String toString() { return new String(copyData(0, length)); } } private class CologneOutputBuffer extends CologneBuffer { public CologneOutputBuffer(final int buffSize) { super(buffSize); } public void addRight(final char chr) { data[length] = chr; length++; } @Override protected char[] copyData(final int start, final int length) { final char[] newData = new char[length]; System.arraycopy(data, start, newData, 0, length); return newData; } } private class CologneInputBuffer extends CologneBuffer { public CologneInputBuffer(final char[] data) { super(data); } public void addLeft(final char ch) { length++; data[getNextPos()] = ch; } @Override protected char[] copyData(final int start, final int length) { final char[] newData = new char[length]; System.arraycopy(data, data.length - this.length + start, newData, 0, length); return newData; } public char getNextChar() { return data[getNextPos()]; } protected int getNextPos() { return data.length - length; } public char removeNext() { final char ch = getNextChar(); length--; return ch; } } /** * Maps some Germanic characters to plain for internal processing. The following characters are mapped: *
    *
  • capital a, umlaut mark
  • *
  • capital u, umlaut mark
  • *
  • capital o, umlaut mark
  • *
  • small sharp s, German
  • *
*/ private static final char[][] PREPROCESS_MAP = new char[][]{ {'\u00C4', 'A'}, // capital a, umlaut mark {'\u00DC', 'U'}, // capital u, umlaut mark {'\u00D6', 'O'}, // capital o, umlaut mark {'\u00DF', 'S'} // small sharp s, German }; /* * Returns whether the array contains the key, or not. */ private static boolean arrayContains(final char[] arr, final char key) { for (final char element : arr) { if (element == key) { return true; } } return false; } /** *

* Implements the Kölner Phonetik algorithm. *

*

* In contrast to the initial description of the algorithm, this implementation does the encoding in one pass. *

* * @param text The source text to encode * @return the corresponding encoding according to the Kölner Phonetik algorithm */ public String colognePhonetic(String text) { if (text == null) { return null; } text = preprocess(text); final CologneOutputBuffer output = new CologneOutputBuffer(text.length() * 2); final CologneInputBuffer input = new CologneInputBuffer(text.toCharArray()); char nextChar; char lastChar = '-'; char lastCode = '/'; char code; char chr; int rightLength = input.length(); while (rightLength > 0) { chr = input.removeNext(); if ((rightLength = input.length()) > 0) { nextChar = input.getNextChar(); } else { nextChar = '-'; } if (arrayContains(AEIJOUY, chr)) { code = '0'; } else if (chr == 'H' || chr < 'A' || chr > 'Z') { if (lastCode == '/') { continue; } code = '-'; } else if (chr == 'B' || (chr == 'P' && nextChar != 'H')) { code = '1'; } else if ((chr == 'D' || chr == 'T') && !arrayContains(SCZ, nextChar)) { code = '2'; } else if (arrayContains(WFPV, chr)) { code = '3'; } else if (arrayContains(GKQ, chr)) { code = '4'; } else if (chr == 'X' && !arrayContains(CKQ, lastChar)) { code = '4'; input.addLeft('S'); rightLength++; } else if (chr == 'S' || chr == 'Z') { code = '8'; } else if (chr == 'C') { if (lastCode == '/') { if (arrayContains(AHKLOQRUX, nextChar)) { code = '4'; } else { code = '8'; } } else { if (arrayContains(SZ, lastChar) || !arrayContains(AHOUKQX, nextChar)) { code = '8'; } else { code = '4'; } } } else if (arrayContains(TDX, chr)) { code = '8'; } else if (chr == 'R') { code = '7'; } else if (chr == 'L') { code = '5'; } else if (chr == 'M' || chr == 'N') { code = '6'; } else { code = chr; } if (code != '-' && (lastCode != code && (code != '0' || lastCode == '/') || code < '0' || code > '8')) { output.addRight(code); } lastChar = chr; lastCode = code; } return output.toString(); } @Override public Object encode(final Object object) throws EncoderException { if (!(object instanceof String)) { throw new EncoderException("This method's parameter was expected to be of the type " + String.class.getName() + ". But actually it was of the type " + object.getClass().getName() + "."); } return encode((String) object); } @Override public String encode(final String text) { return colognePhonetic(text); } public boolean isEncodeEqual(final String text1, final String text2) { return colognePhonetic(text1).equals(colognePhonetic(text2)); } /** * Converts the string to upper case and replaces germanic characters as defined in {@link #PREPROCESS_MAP}. */ private String preprocess(String text) { text = text.toUpperCase(Locale.GERMAN); final char[] chrs = text.toCharArray(); for (int index = 0; index < chrs.length; index++) { if (chrs[index] > 'Z') { for (final char[] element : PREPROCESS_MAP) { if (chrs[index] == element[0]) { chrs[index] = element[1]; break; } } } } return new String(chrs); } }




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