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From whosc...@apache.org
Subject svn commit: r351893 - /lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java
Date Sat, 03 Dec 2005 05:27:52 GMT
Author: whoschek
Date: Fri Dec  2 21:27:50 2005
New Revision: 351893

URL: http://svn.apache.org/viewcvs?rev=351893&view=rev
Log:
indentation fixes

Added:
    lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java

Added: lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java
URL: http://svn.apache.org/viewcvs/lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java?rev=351893&view=auto
==============================================================================
--- lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java
(added)
+++ lucene/java/trunk/contrib/memory/src/java/org/apache/lucene/index/memory/PatternAnalyzer.java
Fri Dec  2 21:27:50 2005
@@ -0,0 +1,442 @@
+package org.apache.lucene.index.memory;
+
+/**
+ * Copyright 2005 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.
+ */
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.apache.lucene.analysis.Analyzer;
+import org.apache.lucene.analysis.StopAnalyzer;
+import org.apache.lucene.analysis.StopFilter;
+import org.apache.lucene.analysis.Token;
+import org.apache.lucene.analysis.TokenStream;
+
+/**
+ * Efficient Lucene analyzer/tokenizer that preferably operates on a String rather than a
+ * {@link java.io.Reader}, that can flexibly separate text into terms via a regular expression
{@link Pattern}
+ * (with behaviour identical to {@link String#split(String)}),
+ * and that combines the functionality of
+ * {@link org.apache.lucene.analysis.LetterTokenizer},
+ * {@link org.apache.lucene.analysis.LowerCaseTokenizer},
+ * {@link org.apache.lucene.analysis.WhitespaceTokenizer},
+ * {@link org.apache.lucene.analysis.StopFilter} into a single efficient
+ * multi-purpose class.
+ * <p>
+ * If you are unsure how exactly a regular expression should look like, consider 
+ * prototyping by simply trying various expressions on some test texts via
+ * {@link String#split(String)}. Once you are satisfied, give that regex to 
+ * PatternAnalyzer. Also see <a target="_blank" 
+ * href="http://java.sun.com/docs/books/tutorial/extra/regex/">Java Regular Expression
Tutorial</a>.
+ * <p>
+ * This class can be considerably faster than the "normal" Lucene tokenizers. 
+ * It can also serve as a building block in a compound Lucene
+ * {@link org.apache.lucene.analysis.TokenFilter} chain. For example as in this 
+ * stemming example:
+ * <pre>
+ * PatternAnalyzer pat = ...
+ * TokenStream tokenStream = new SnowballFilter(
+ *     pat.tokenStream("content", "James is running round in the woods"), 
+ *     "English"));
+ * </pre>
+ * 
+ * @author whoschek.AT.lbl.DOT.gov
+ */
+public class PatternAnalyzer extends Analyzer {
+	
+	/** <code>"\\W+"</code>; Divides text at non-letters (Character.isLetter(c))
*/
+	public static final Pattern NON_WORD_PATTERN = Pattern.compile("\\W+");
+	
+	/** <code>"\\s+"</code>; Divides text at whitespaces (Character.isWhitespace(c))
*/
+	public static final Pattern WHITESPACE_PATTERN = Pattern.compile("\\s+");
+	
+	private static final Set EXTENDED_ENGLISH_STOP_WORDS = makeStopSet(new String[] {
+		"a", "about", "above", "across", "adj", "after", "afterwards",
+		"again", "against", "albeit", "all", "almost", "alone", "along",
+		"already", "also", "although", "always", "among", "amongst", "an",
+		"and", "another", "any", "anyhow", "anyone", "anything",
+		"anywhere", "are", "around", "as", "at", "be", "became", "because",
+		"become", "becomes", "becoming", "been", "before", "beforehand",
+		"behind", "being", "below", "beside", "besides", "between",
+		"beyond", "both", "but", "by", "can", "cannot", "co", "could",
+		"down", "during", "each", "eg", "either", "else", "elsewhere",
+		"enough", "etc", "even", "ever", "every", "everyone", "everything",
+		"everywhere", "except", "few", "first", "for", "former",
+		"formerly", "from", "further", "had", "has", "have", "he", "hence",
+		"her", "here", "hereafter", "hereby", "herein", "hereupon", "hers",
+		"herself", "him", "himself", "his", "how", "however", "i", "ie", "if",
+		"in", "inc", "indeed", "into", "is", "it", "its", "itself", "last",
+		"latter", "latterly", "least", "less", "ltd", "many", "may", "me",
+		"meanwhile", "might", "more", "moreover", "most", "mostly", "much",
+		"must", "my", "myself", "namely", "neither", "never",
+		"nevertheless", "next", "no", "nobody", "none", "noone", "nor",
+		"not", "nothing", "now", "nowhere", "of", "off", "often", "on",
+		"once one", "only", "onto", "or", "other", "others", "otherwise",
+		"our", "ours", "ourselves", "out", "over", "own", "per", "perhaps",
+		"rather", "s", "same", "seem", "seemed", "seeming", "seems",
+		"several", "she", "should", "since", "so", "some", "somehow",
+		"someone", "something", "sometime", "sometimes", "somewhere",
+		"still", "such", "t", "than", "that", "the", "their", "them",
+		"themselves", "then", "thence", "there", "thereafter", "thereby",
+		"therefor", "therein", "thereupon", "these", "they", "this",
+		"those", "though", "through", "throughout", "thru", "thus", "to",
+		"together", "too", "toward", "towards", "under", "until", "up",
+		"upon", "us", "very", "via", "was", "we", "well", "were", "what",
+		"whatever", "whatsoever", "when", "whence", "whenever",
+		"whensoever", "where", "whereafter", "whereas", "whereat",
+		"whereby", "wherefrom", "wherein", "whereinto", "whereof",
+		"whereon", "whereto", "whereunto", "whereupon", "wherever",
+		"wherewith", "whether", "which", "whichever", "whichsoever",
+		"while", "whilst", "whither", "who", "whoever", "whole", "whom",
+		"whomever", "whomsoever", "whose", "whosoever", "why", "will",
+		"with", "within", "without", "would", "xsubj", "xcal", "xauthor",
+		"xother ", "xnote", "yet", "you", "your", "yours", "yourself",
+		"yourselves"});
+		
+	/**
+	 * A lower-casing word analyzer with English stop words (can be shared
+	 * freely across threads without harm); global per class loader.
+	 */
+	public static final PatternAnalyzer DEFAULT_ANALYZER = new PatternAnalyzer(
+		NON_WORD_PATTERN, true, makeStopSet(StopAnalyzer.ENGLISH_STOP_WORDS));
+		
+	/**
+	 * A lower-casing word analyzer with <b>extended </b> English stop words
+	 * (can be shared freely across threads without harm); global per class
+	 * loader. The stop words are borrowed from
+	 * http://thomas.loc.gov/home/stopwords.html, see
+	 * http://thomas.loc.gov/home/all.about.inquery.html
+	 */
+	public static final PatternAnalyzer EXTENDED_ANALYZER = new PatternAnalyzer(
+		NON_WORD_PATTERN, true, EXTENDED_ENGLISH_STOP_WORDS);
+		
+	private final Pattern pattern;
+	private final boolean toLowerCase;
+	private final Set stopWords;
+	
+	/**
+	 * Constructs a new instance with the given parameters.
+	 * 
+	 * @param pattern
+	 *            a regular expression delimiting tokens
+	 * @param toLowerCase
+	 *            if <code>true</code> returns tokens after applying
+	 *            String.toLowerCase()
+	 * @param stopWords
+	 *            if non-null, ignores all tokens that are contained in the
+	 *            given stop set (after previously having applied toLowerCase()
+	 *            if applicable). For example, created via
+	 *            {@link StopFilter#makeStopSet(String[])}and/or
+	 *            {@link org.apache.lucene.analysis.WordlistLoader}as in
+	 *            <code>WordlistLoader.getWordSet(new File("samples/fulltext/stopwords.txt")</code>
+	 *            or <a href="http://www.unine.ch/info/clef/">other stop words
+	 *            lists </a>.
+	 */
+	public PatternAnalyzer(Pattern pattern, boolean toLowerCase, Set stopWords) {
+		if (pattern == null) 
+			throw new IllegalArgumentException("pattern must not be null");
+		
+		if (eqPattern(NON_WORD_PATTERN, pattern)) pattern = NON_WORD_PATTERN;
+		else if (eqPattern(WHITESPACE_PATTERN, pattern)) pattern = WHITESPACE_PATTERN;
+		
+		if (stopWords != null && stopWords.size() == 0) stopWords = null;
+		
+		this.pattern = pattern;
+		this.toLowerCase = toLowerCase;
+		this.stopWords = stopWords;
+	}
+	
+	/**
+	 * Creates a token stream that tokenizes the given string into token terms
+	 * (aka words).
+	 * 
+	 * @param fieldName
+	 *            the name of the field to tokenize (currently ignored).
+	 * @param text
+	 *            the string to tokenize
+	 */
+	public TokenStream tokenStream(String fieldName, String text) {
+		// Ideally the Analyzer superclass should have a method with the same signature, 
+		// with a default impl that simply delegates to the StringReader flavour. 
+		if (text == null) 
+			throw new IllegalArgumentException("text must not be null");
+		
+		TokenStream stream;
+		if (pattern == NON_WORD_PATTERN) { // fast path
+			stream = new FastStringTokenizer(text, true, toLowerCase, stopWords);
+		}
+		else if (pattern == WHITESPACE_PATTERN) { // fast path
+			stream = new FastStringTokenizer(text, false, toLowerCase, stopWords);
+		}
+		else {
+			stream = new PatternTokenizer(text, pattern, toLowerCase);
+			if (stopWords != null) stream = new StopFilter(stream, stopWords);
+		}
+		
+		return stream;
+	}
+	
+	/**
+	 * Creates a token stream that tokenizes all the text in the given Reader;
+	 * This implementation forwards to <code>tokenStream(String, String)</code>
and is
+	 * less efficient than <code>tokenStream(String, String)</code>.
+	 */
+	public TokenStream tokenStream(String fieldName, Reader reader) {
+		if (reader instanceof FastStringReader) { // fast path
+			return tokenStream(fieldName, ((FastStringReader)reader).getString());
+		}
+		
+		try {
+			String text = toString(reader);
+			return tokenStream(fieldName, text);
+		} catch (IOException e) {
+			throw new RuntimeException(e);
+		}
+	}
+	
+	/**  Indicates whether some other object is "equal to" this one. */
+	public boolean equals(Object other) {
+		if (this  == other) return true;
+		if (this  == DEFAULT_ANALYZER && other == EXTENDED_ANALYZER) return false;
+		if (other == DEFAULT_ANALYZER && this  == EXTENDED_ANALYZER) return false;
+		
+		if (other instanceof PatternAnalyzer) {
+			PatternAnalyzer p2 = (PatternAnalyzer) other;
+			return 
+				toLowerCase == p2.toLowerCase &&
+				eqPattern(pattern, p2.pattern) &&
+				eq(stopWords, p2.stopWords);
+		}
+		return false;
+	}
+	
+	/** Returns a hash code value for the object. */
+	public int hashCode() {
+		if (this == DEFAULT_ANALYZER) return -1218418418; // fast path
+		if (this == EXTENDED_ANALYZER) return 1303507063; // fast path
+		
+		int h = 1;
+		h = 31*h + pattern.pattern().hashCode();
+		h = 31*h + pattern.flags();
+		h = 31*h + (toLowerCase ? 1231 : 1237);
+		h = 31*h + (stopWords != null ? stopWords.hashCode() : 0);
+		return h;
+	}
+	
+	/** equality where o1 and/or o2 can be null */
+	private static boolean eq(Object o1, Object o2) {
+		return (o1 == o2) || (o1 != null ? o1.equals(o2) : false);
+	}
+	
+	/** assumes p1 and p2 are not null */
+	private static boolean eqPattern(Pattern p1, Pattern p2) {
+		return p1 == p2 || (p1.flags() == p2.flags() && p1.pattern().equals(p2.pattern()));
+	}
+		
+	/**
+	 * Reads until end-of-stream and returns all read chars, finally closes the stream.
+	 * 
+	 * @param input the input stream
+	 * @throws IOException if an I/O error occurs while reading the stream
+	 */
+	private static String toString(Reader input) throws IOException {
+		try {
+			int len = 256;
+			char[] buffer = new char[len];
+			char[] output = new char[len];
+			
+			len = 0;
+			int n;
+			while ((n = input.read(buffer)) >= 0) {
+				if (len + n > output.length) { // grow capacity
+					char[] tmp = new char[Math.max(output.length << 1, len + n)];
+					System.arraycopy(output, 0, tmp, 0, len);
+					System.arraycopy(buffer, 0, tmp, len, n);
+					buffer = output; // use larger buffer for future larger bulk reads
+					output = tmp;
+				} else {
+					System.arraycopy(buffer, 0, output, len, n);
+				}
+				len += n;
+			}
+
+			return new String(output, 0, output.length);
+		} finally {
+			if (input != null) input.close();
+		}
+	}
+		
+	/** somewhat oversized to minimize hash collisions */
+	private static Set makeStopSet(String[] stopWords) {
+		Set stops = new HashSet(stopWords.length * 2, 0.3f); 
+		stops.addAll(Arrays.asList(stopWords));
+		return stops;
+//		return Collections.unmodifiableSet(stops);
+	}
+
+	
+	///////////////////////////////////////////////////////////////////////////////
+	// Nested classes:
+	///////////////////////////////////////////////////////////////////////////////
+	/**
+	 * The work horse; performance isn't fantastic, but it's not nearly as bad
+	 * as one might think - kudos to the Sun regex developers.
+	 */
+	private static final class PatternTokenizer extends TokenStream {
+		
+		private final String str;
+		private final boolean toLowerCase;
+		private Matcher matcher;
+		private int pos = 0;
+		private static final Locale locale = Locale.getDefault();
+		
+		public PatternTokenizer(String str, Pattern pattern, boolean toLowerCase) {
+			this.str = str;
+			this.matcher = pattern.matcher(str);
+			this.toLowerCase = toLowerCase;
+		}
+
+		public Token next() {
+			if (matcher == null) return null;
+			
+			while (true) { // loop takes care of leading and trailing boundary cases
+				int start = pos;
+				int end;
+				boolean isMatch = matcher.find();
+				if (isMatch) {
+					end = matcher.start();
+					pos = matcher.end();
+				} else { 
+					end = str.length();
+					matcher = null; // we're finished
+				}
+				
+				if (start != end) { // non-empty match (header/trailer)
+					String text = str.substring(start, end);
+					if (toLowerCase) text = text.toLowerCase(locale);
+					return new Token(text, start, end);
+				}
+				if (!isMatch) return null;
+			}
+		}
+		
+	}	
+	
+	
+	///////////////////////////////////////////////////////////////////////////////
+	// Nested classes:
+	///////////////////////////////////////////////////////////////////////////////
+	/**
+	 * Special-case class for best performance in common cases; this class is
+	 * otherwise unnecessary.
+	 */
+	private static final class FastStringTokenizer extends TokenStream {
+		
+		private final String str;
+		private int pos;
+		private final boolean isLetter;
+		private final boolean toLowerCase;
+		private final Set stopWords;
+		private static final Locale locale = Locale.getDefault();
+		
+		public FastStringTokenizer(String str, boolean isLetter, boolean toLowerCase, Set stopWords)
{
+			this.str = str;
+			this.isLetter = isLetter;
+			this.toLowerCase = toLowerCase;
+			this.stopWords = stopWords;
+		}
+
+		public Token next() {
+			// cache loop instance vars (performance)
+			String s = str;
+			int len = s.length();
+			int i = pos;
+			boolean letter = isLetter;
+			
+			int start = 0;
+			String text;
+			do {
+				// find beginning of token
+				text = null;
+				while (i < len && !isTokenChar(s.charAt(i), letter)) {
+					i++;
+				}
+				
+				if (i < len) { // found beginning; now find end of token
+					start = i;
+					while (i < len && isTokenChar(s.charAt(i), letter)) {
+						i++;
+					}
+					
+					text = s.substring(start, i);
+					if (toLowerCase) text = text.toLowerCase(locale);
+//					if (toLowerCase) {						
+////						use next line once JDK 1.5 String.toLowerCase() performance regression is fixed
+////						see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6265809
+//						text = s.substring(start, i).toLowerCase(); 
+////						char[] chars = new char[i-start];
+////						for (int j=start; j < i; j++) chars[j-start] = Character.toLowerCase(s.charAt(j));
+////						text = new String(chars);
+//					} else {
+//						text = s.substring(start, i);
+//					}
+				}
+			} while (text != null && isStopWord(text));
+			
+			pos = i;
+			return text != null ? new Token(text, start, i) : null;
+		}
+		
+		private boolean isTokenChar(char c, boolean isLetter) {
+			return isLetter ? Character.isLetter(c) : !Character.isWhitespace(c);
+		}
+		
+		private boolean isStopWord(String text) {
+			return stopWords != null && stopWords.contains(text);
+		}
+		
+	}
+
+	
+	///////////////////////////////////////////////////////////////////////////////
+	// Nested classes:
+	///////////////////////////////////////////////////////////////////////////////
+	/**
+	 * A StringReader that exposes it's contained string for fast direct access.
+	 * Might make sense to generalize this to CharSequence and make it public?
+	 */
+	static final class FastStringReader extends StringReader {
+
+		private final String s;
+		
+		FastStringReader(String s) {
+			super(s);
+			this.s = s;
+		}
+		
+		String getString() {
+			return s;
+		}
+	}
+	
+}



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