// https://svn.apache.org/repos/asf/lucene/lucene.net/tags/Lucene.Net_2_9_1/src/Lucene.Net/Analysis/PorterStemmer.cs
public class PorterStemmer
{
private char[] b;
private int i, j, k, k0;
private bool dirty = false;
private const int INC = 50; /* unit of size whereby b is increased */
private const int EXTRA = 1;
public PorterStemmer()
{
b = new char[INC];
i = 0;
}
/// <summary> 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.
/// </summary>
public virtual void Reset()
{
i = 0; dirty = false;
}
/// <summary> Add a character to the word being stemmed. When you are finished
/// adding characters, you can call stem(void) to process the word.
/// </summary>
public virtual void Add(char ch)
{
if (b.Length <= i + EXTRA)
{
char[] new_b = new char[b.Length + INC];
Array.Copy(b, 0, new_b, 0, b.Length);
b = new_b;
}
b[i++] = ch;
}
/// <summary> 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.)
/// </summary>
public override System.String ToString()
{
return new System.String(b, 0, i);
}
/// <summary> Returns the length of the word resulting from the stemming process.</summary>
public virtual int GetResultLength()
{
return i;
}
/// <summary> 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.
/// </summary>
public virtual char[] GetResultBuffer()
{
return b;
}
private bool 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 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 bool 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 bool 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 bool 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 bool Ends(System.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[i])
return false;
j = k - l;
return true;
}
/* setto(s) sets (j+1),...k to the characters in the string s, readjusting
k. */
internal virtual void Setto(System.String s)
{
int l = s.Length;
int o = j + 1;
for (int i = 0; i < l; i++)
b[o + i] = s[i];
k = j + l;
dirty = true;
}
/* r(s) is used further down. */
internal virtual void R(System.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 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 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 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;
}
break;
}
}
/* step4() deals with -ic-, -full, -ness etc. similar strategy to step3. */
private 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 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 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--;
}
/// <summary> Stem a word provided as a String. Returns the result as a String.</summary>
public virtual System.String Stem(System.String s)
{
if (Stem(s.ToCharArray(), s.Length))
{
return ToString();
}
else
return s;
}
/// <summary>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().
/// </summary>
public virtual bool Stem(char[] word)
{
return Stem(word, word.Length);
}
/// <summary>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().
/// </summary>
public virtual bool Stem(char[] wordBuffer, int offset, int wordLen)
{
Reset();
if (b.Length < wordLen)
{
char[] new_b = new char[wordLen + EXTRA];
b = new_b;
}
Array.Copy(wordBuffer, offset, b, 0, wordLen);
i = wordLen;
return Stem(0);
}
/// <summary>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().
/// </summary>
public virtual bool Stem(char[] word, int wordLen)
{
return Stem(word, 0, wordLen);
}
/// <summary>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().
/// </summary>
public virtual bool Stem()
{
return Stem(0);
}
public virtual bool 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;
}
/// <summary>Test program for demonstrating the Stemmer. It reads a file and
/// stems each word, writing the result to standard out.
/// Usage: Stemmer file-name
/// </summary>
[STAThread]
public static void Main(System.String[] args)
{
PorterStemmer s = new PorterStemmer();
for (int i = 0; i < args.Length; i++)
{
try
{
System.IO.Stream in_Renamed = new System.IO.FileStream(args[i], System.IO.FileMode.Open, System.IO.FileAccess.Read);
byte[] buffer = new byte[1024];
int bufferLen, offset, ch;
bufferLen = in_Renamed.Read(buffer, 0, buffer.Length);
offset = 0;
s.Reset();
while (true)
{
if (offset < bufferLen)
ch = buffer[offset++];
else
{
bufferLen = in_Renamed.Read(buffer, 0, buffer.Length);
offset = 0;
if (bufferLen < 0)
ch = -1;
else
ch = buffer[offset++];
}
if (System.Char.IsLetter((char)ch))
{
s.Add(System.Char.ToLower((char)ch));
}
else
{
s.Stem();
System.Console.Out.Write(s.ToString());
s.Reset();
if (ch < 0)
break;
else
{
System.Console.Out.Write((char)ch);
}
}
}
in_Renamed.Close();
}
catch (System.IO.IOException e)
{
System.Console.Out.WriteLine("error reading " + args[i]);
}
}
}
}
Comments