svn commit: r1063778 - /commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java

[si...@apache.org]

Author: simonetripodi
Date: Wed Jan 26 16:23:32 2011
New Revision: 1063778

URL: http://svn.apache.org/viewvc?rev=1063778&view=rev
Log:
first checkin of SimpleRegexMatcher, a polished version of the one on proper /trunk

Added:
    commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java   (with props)

Added: commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java
URL: http://svn.apache.org/viewvc/commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java?rev=1063778&view=auto
==============================================================================
--- commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java (added)
+++ commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/SimpleRegexMatcher.java Wed Jan 26 16:23:32 2011
@@ -0,0 +1,101 @@
+/* $Id$
+ *
+ * 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 org.apache.commons.digester3.rules;
+
+/**
+ * <p>Simple regex pattern matching algorithm.</p>
+ * 
+ * <p>This uses just two wildcards:
+ * <ul>
+ *  <li><code>*</code> matches any sequence of none, one or more characters
+ *  <li><code>?</code> matches any one character 
+ * </ul>
+ * Escaping these wildcards is not supported .</p>
+ */
+public class SimpleRegexMatcher implements RegexMatcher {
+
+    /**
+     * {@inheritDoc}
+     */
+    public boolean match(String basePattern, String regexPattern) {
+        // check for nulls
+        if (basePattern == null || regexPattern == null) {
+            return false;
+        }
+        return match(basePattern, regexPattern, 0, 0);
+    }
+
+    /**
+     * Implementation of regex matching algorithm.
+     * This calls itself recursively.
+     */
+    private boolean match(String basePattern, String regexPattern, int baseAt, int regexAt) {
+        // check bounds
+        if (regexAt >= regexPattern.length()) {
+            // maybe we've got a match
+            if (baseAt >= basePattern.length()) {
+                // ok!
+                return true;
+            }
+            // run out early
+            return false;
+            
+        } else {
+            if (baseAt >= basePattern.length()) {
+                // run out early
+                return false;
+            }
+        }
+
+        // ok both within bounds
+        char regexCurrent = regexPattern.charAt(regexAt);
+        switch (regexCurrent) {
+            case '*':
+                // this is the tricky case
+                // check for terminal 
+                if (++regexAt >= regexPattern.length()) {
+                    // this matches anything let - so return true
+                    return true;
+                }
+                // go through every subsequent apperance of the next character
+                // and so if the rest of the regex matches
+                char nextRegex = regexPattern.charAt(regexAt);
+
+                int nextMatch = basePattern.indexOf(nextRegex, baseAt);
+                while (nextMatch != -1) {
+                    if (match(basePattern, regexPattern, nextMatch, regexAt)) {
+                        return true;
+                    }
+                    nextMatch = basePattern.indexOf(nextRegex, nextMatch + 1);
+                }
+                return false;
+
+            case '?':
+                // this matches anything
+                return match(basePattern, regexPattern, ++baseAt, ++regexAt);
+
+            default:
+                if (regexCurrent == basePattern.charAt(baseAt)) {
+                    // still got more to go
+                    return match(basePattern, regexPattern, ++baseAt, ++regexAt);
+                }
+                return false;
+        }
+    }
+
+}

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