搜索引擎在进行索引和检索的时候,需要对一些词语的各种形式转换为原型。

在 Lucene 中,提供了这样的一个java文件。特此进行备份。

以后,可以用C/C++进行移植。

注意:稍微进行了一下修改,这个里面用到了 StringUtil

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import StringUtil;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed 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.
 */

/*

 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.  ]

 */

/**
 * 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 INC = 50; /* unit of size whereby b is increased */

    private static final int EXTRA = 1;

    public PorterStemmer()
    {
        b = new char[INC];
        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 + EXTRA)
        {
            char[] new_b = new char[b.length + INC];
            for (int c = 0; c < b.length; c++)
                new_b[c] = b[c];
            b = new_b;
        }
        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.)
     */
    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)
        {
            char[] new_b = new char[wordLen + EXTRA];
            b = new_b;
        }
        for (int j = 0; j < wordLen; j++)
            b[j] = wordBuffer[offset + j];
        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
     * @throws IOException
     */
    public static void main(String[] args) throws IOException
    {
        PorterStemmer s = new PorterStemmer();
        String[] str = new String[] { "d://stop.txt" };
        for (String key : str)
        {
            InputStream in = new FileInputStream(key);
            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 (StringUtil.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();
        }
    }
}