/*
 * 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
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package org.apache.lucene.analysis.en;


/*

   Porter stemmer in Java. The original paper is in

       Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
       no. 3, pp 130-137,

   See also http://www.tartarus.org/~martin/PorterStemmer/index.html

   Bug 1 (reported by Gonzalo Parra 16/10/99) fixed as marked below.
   Tthe words 'aed', 'eed', 'oed' leave k at 'a' for step 3, and b[k-1]
   is then out outside the bounds of b.

   Similarly,

   Bug 2 (reported by Steve Dyrdahl 22/2/00) fixed as marked below.
   'ion' by itself leaves j = -1 in the test for 'ion' in step 5, and
   b[j] is then outside the bounds of b.

   Release 3.

   [ This version is derived from Release 3, modified by Brian Goetz to
     optimize for fewer object creations.  ]

*/


import org.apache.lucene.util.ArrayUtil;

Stemmer, implementing the Porter Stemming Algorithm The Stemmer class transforms a word into its root form. The input word can be provided a character at time (by calling add()), or at once by calling one of the various stem(something) methods.
/** * * Stemmer, implementing the Porter Stemming Algorithm * * The Stemmer class transforms a word into its root form. The input * word can be provided a character at time (by calling add()), or at once * by calling one of the various stem(something) methods. */
class PorterStemmer { private char[] b; private int i, /* offset into b */ j, k, k0; private boolean dirty = false; private static final int INITIAL_SIZE = 50; public PorterStemmer() { b = new char[INITIAL_SIZE]; i = 0; }
reset() resets the stemmer so it can stem another word. If you invoke the stemmer by calling add(char) and then stem(), you must call reset() before starting another word.
/** * reset() resets the stemmer so it can stem another word. If you invoke * the stemmer by calling add(char) and then stem(), you must call reset() * before starting another word. */
public void reset() { i = 0; dirty = false; }
Add a character to the word being stemmed. When you are finished adding characters, you can call stem(void) to process the word.
/** * Add a character to the word being stemmed. When you are finished * adding characters, you can call stem(void) to process the word. */
public void add(char ch) { if (b.length <= i) { b = ArrayUtil.grow(b, i+1); } b[i++] = ch; }
After a word has been stemmed, it can be retrieved by toString(), or a reference to the internal buffer can be retrieved by getResultBuffer and getResultLength (which is generally more efficient.)
/** * After a word has been stemmed, it can be retrieved by toString(), * or a reference to the internal buffer can be retrieved by getResultBuffer * and getResultLength (which is generally more efficient.) */
@Override public String toString() { return new String(b,0,i); }
Returns the length of the word resulting from the stemming process.
/** * Returns the length of the word resulting from the stemming process. */
public int getResultLength() { return i; }
Returns a reference to a character buffer containing the results of the stemming process. You also need to consult getResultLength() to determine the length of the result.
/** * Returns a reference to a character buffer containing the results of * the stemming process. You also need to consult getResultLength() * to determine the length of the result. */
public char[] getResultBuffer() { return b; } /* cons(i) is true <=> b[i] is a consonant. */ private final boolean cons(int i) { switch (b[i]) { case 'a': case 'e': case 'i': case 'o': case 'u': return false; case 'y': return (i==k0) ? true : !cons(i-1); default: return true; } } /* m() measures the number of consonant sequences between k0 and j. if c is a consonant sequence and v a vowel sequence, and <..> indicates arbitrary presence, <c><v> gives 0 <c>vc<v> gives 1 <c>vcvc<v> gives 2 <c>vcvcvc<v> gives 3 .... */ private final int m() { int n = 0; int i = k0; while(true) { if (i > j) return n; if (! cons(i)) break; i++; } i++; while(true) { while(true) { if (i > j) return n; if (cons(i)) break; i++; } i++; n++; while(true) { if (i > j) return n; if (! cons(i)) break; i++; } i++; } } /* vowelinstem() is true <=> k0,...j contains a vowel */ private final boolean vowelinstem() { int i; for (i = k0; i <= j; i++) if (! cons(i)) return true; return false; } /* doublec(j) is true <=> j,(j-1) contain a double consonant. */ private final boolean doublec(int j) { if (j < k0+1) return false; if (b[j] != b[j-1]) return false; return cons(j); } /* cvc(i) is true <=> i-2,i-1,i has the form consonant - vowel - consonant and also if the second c is not w,x or y. this is used when trying to restore an e at the end of a short word. e.g. cav(e), lov(e), hop(e), crim(e), but snow, box, tray. */ private final boolean cvc(int i) { if (i < k0+2 || !cons(i) || cons(i-1) || !cons(i-2)) return false; else { int ch = b[i]; if (ch == 'w' || ch == 'x' || ch == 'y') return false; } return true; } private final boolean ends(String s) { int l = s.length(); int o = k-l+1; if (o < k0) return false; for (int i = 0; i < l; i++) if (b[o+i] != s.charAt(i)) return false; j = k-l; return true; } /* setto(s) sets (j+1),...k to the characters in the string s, readjusting k. */ void setto(String s) { int l = s.length(); int o = j+1; for (int i = 0; i < l; i++) b[o+i] = s.charAt(i); k = j+l; dirty = true; } /* r(s) is used further down. */ void r(String s) { if (m() > 0) setto(s); } /* step1() gets rid of plurals and -ed or -ing. e.g. caresses -> caress ponies -> poni ties -> ti caress -> caress cats -> cat feed -> feed agreed -> agree disabled -> disable matting -> mat mating -> mate meeting -> meet milling -> mill messing -> mess meetings -> meet */ private final void step1() { if (b[k] == 's') { if (ends("sses")) k -= 2; else if (ends("ies")) setto("i"); else if (b[k-1] != 's') k--; } if (ends("eed")) { if (m() > 0) k--; } else if ((ends("ed") || ends("ing")) && vowelinstem()) { k = j; if (ends("at")) setto("ate"); else if (ends("bl")) setto("ble"); else if (ends("iz")) setto("ize"); else if (doublec(k)) { int ch = b[k--]; if (ch == 'l' || ch == 's' || ch == 'z') k++; } else if (m() == 1 && cvc(k)) setto("e"); } } /* step2() turns terminal y to i when there is another vowel in the stem. */ private final void step2() { if (ends("y") && vowelinstem()) { b[k] = 'i'; dirty = true; } } /* step3() maps double suffices to single ones. so -ization ( = -ize plus -ation) maps to -ize etc. note that the string before the suffix must give m() > 0. */ private final void step3() { if (k == k0) return; /* For Bug 1 */ switch (b[k-1]) { case 'a': if (ends("ational")) { r("ate"); break; } if (ends("tional")) { r("tion"); break; } break; case 'c': if (ends("enci")) { r("ence"); break; } if (ends("anci")) { r("ance"); break; } break; case 'e': if (ends("izer")) { r("ize"); break; } break; case 'l': if (ends("bli")) { r("ble"); break; } if (ends("alli")) { r("al"); break; } if (ends("entli")) { r("ent"); break; } if (ends("eli")) { r("e"); break; } if (ends("ousli")) { r("ous"); break; } break; case 'o': if (ends("ization")) { r("ize"); break; } if (ends("ation")) { r("ate"); break; } if (ends("ator")) { r("ate"); break; } break; case 's': if (ends("alism")) { r("al"); break; } if (ends("iveness")) { r("ive"); break; } if (ends("fulness")) { r("ful"); break; } if (ends("ousness")) { r("ous"); break; } break; case 't': if (ends("aliti")) { r("al"); break; } if (ends("iviti")) { r("ive"); break; } if (ends("biliti")) { r("ble"); break; } break; case 'g': if (ends("logi")) { r("log"); break; } } } /* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */ private final void step4() { switch (b[k]) { case 'e': if (ends("icate")) { r("ic"); break; } if (ends("ative")) { r(""); break; } if (ends("alize")) { r("al"); break; } break; case 'i': if (ends("iciti")) { r("ic"); break; } break; case 'l': if (ends("ical")) { r("ic"); break; } if (ends("ful")) { r(""); break; } break; case 's': if (ends("ness")) { r(""); break; } break; } } /* step5() takes off -ant, -ence etc., in context <c>vcvc<v>. */ private final void step5() { if (k == k0) return; /* for Bug 1 */ switch (b[k-1]) { case 'a': if (ends("al")) break; return; case 'c': if (ends("ance")) break; if (ends("ence")) break; return; case 'e': if (ends("er")) break; return; case 'i': if (ends("ic")) break; return; case 'l': if (ends("able")) break; if (ends("ible")) break; return; case 'n': if (ends("ant")) break; if (ends("ement")) break; if (ends("ment")) break; /* element etc. not stripped before the m */ if (ends("ent")) break; return; case 'o': if (ends("ion") && j >= 0 && (b[j] == 's' || b[j] == 't')) break; /* j >= 0 fixes Bug 2 */ if (ends("ou")) break; return; /* takes care of -ous */ case 's': if (ends("ism")) break; return; case 't': if (ends("ate")) break; if (ends("iti")) break; return; case 'u': if (ends("ous")) break; return; case 'v': if (ends("ive")) break; return; case 'z': if (ends("ize")) break; return; default: return; } if (m() > 1) k = j; } /* step6() removes a final -e if m() > 1. */ private final void step6() { j = k; if (b[k] == 'e') { int a = m(); if (a > 1 || a == 1 && !cvc(k-1)) k--; } if (b[k] == 'l' && doublec(k) && m() > 1) k--; }
Stem a word provided as a String. Returns the result as a String.
/** * Stem a word provided as a String. Returns the result as a String. */
public String stem(String s) { if (stem(s.toCharArray(), s.length())) return toString(); else return s; }
Stem a word contained in a char[]. Returns true if the stemming process resulted in a word different from the input. You can retrieve the result with getResultLength()/getResultBuffer() or toString().
/** Stem a word contained in a char[]. Returns true if the stemming process * resulted in a word different from the input. You can retrieve the * result with getResultLength()/getResultBuffer() or toString(). */
public boolean stem(char[] word) { return stem(word, word.length); }
Stem a word contained in a portion of a char[] array. Returns true if the stemming process resulted in a word different from the input. You can retrieve the result with getResultLength()/getResultBuffer() or toString().
/** Stem a word contained in a portion of a char[] array. Returns * true if the stemming process resulted in a word different from * the input. You can retrieve the result with * getResultLength()/getResultBuffer() or toString(). */
public boolean stem(char[] wordBuffer, int offset, int wordLen) { reset(); if (b.length < wordLen) { b = new char[ArrayUtil.oversize(wordLen, Character.BYTES)]; } System.arraycopy(wordBuffer, offset, b, 0, wordLen); i = wordLen; return stem(0); }
Stem a word contained in a leading portion of a char[] array. Returns true if the stemming process resulted in a word different from the input. You can retrieve the result with getResultLength()/getResultBuffer() or toString().
/** Stem a word contained in a leading portion of a char[] array. * Returns true if the stemming process resulted in a word different * from the input. You can retrieve the result with * getResultLength()/getResultBuffer() or toString(). */
public boolean stem(char[] word, int wordLen) { return stem(word, 0, wordLen); }
Stem the word placed into the Stemmer buffer through calls to add(). Returns true if the stemming process resulted in a word different from the input. You can retrieve the result with getResultLength()/getResultBuffer() or toString().
/** Stem the word placed into the Stemmer buffer through calls to add(). * Returns true if the stemming process resulted in a word different * from the input. You can retrieve the result with * getResultLength()/getResultBuffer() or toString(). */
public boolean stem() { return stem(0); } public boolean stem(int i0) { k = i - 1; k0 = i0; if (k > k0+1) { step1(); step2(); step3(); step4(); step5(); step6(); } // Also, a word is considered dirty if we lopped off letters // Thanks to Ifigenia Vairelles for pointing this out. if (i != k+1) dirty = true; i = k+1; return dirty; } /* Test program for demonstrating the Stemmer. It reads a file and * stems each word, writing the result to standard out. * Usage: Stemmer file-name public static void main(String[] args) { PorterStemmer s = new PorterStemmer(); for (int i = 0; i < args.length; i++) { try { InputStream in = new FileInputStream(args[i]); byte[] buffer = new byte[1024]; int bufferLen, offset, ch; bufferLen = in.read(buffer); offset = 0; s.reset(); while(true) { if (offset < bufferLen) ch = buffer[offset++]; else { bufferLen = in.read(buffer); offset = 0; if (bufferLen < 0) ch = -1; else ch = buffer[offset++]; } if (Character.isLetter((char) ch)) { s.add(Character.toLowerCase((char) ch)); } else { s.stem(); System.out.print(s.toString()); s.reset(); if (ch < 0) break; else { System.out.print((char) ch); } } } in.close(); } catch (IOException e) { System.out.println("error reading " + args[i]); } } }*/ }