| /* | |
| * 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 opennlp.tools.stemmer; | |
| import java.io.IOException; | |
| import java.io.InputStream; | |
| import java.io.FileInputStream; | |
| import static org.apache.lucene.util.RamUsageEstimator.NUM_BYTES_CHAR; | |
| 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. | |
| */ | |
| public 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. | |
| */ | |
| 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. | |
| */ | |
| 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.) | |
| */ | |
| @Override | |
| public String toString() { return new String(b,0,i); } | |
| /** | |
| * 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. | |
| */ | |
| 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. | |
| */ | |
| 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(). | |
| */ | |
| 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(). | |
| */ | |
| public boolean stem(char[] wordBuffer, int offset, int wordLen) { | |
| reset(); | |
| if (b.length < wordLen) { | |
| b = new char[ArrayUtil.oversize(wordLen, NUM_BYTES_CHAR)]; | |
| } | |
| 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(). | |
| */ | |
| 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(). | |
| */ | |
| 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]); | |
| } | |
| } | |
| } | |
| } | |