/*
* $Id: GenericPatternCache.java,v 1.7 2003/11/07 20:16:24 dfs Exp $
*
* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2000 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation", "Jakarta-Oro"
* must not be used to endorse or promote products derived from this
* software without prior written permission. For written
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*
* 5. Products derived from this software may not be called "Apache"
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*
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.oro.text;
import java.util.*;
import org.apache.oro.text.regex.*;
import org.apache.oro.util.*;
/**
* This is the base class for all cache implementations provided in the
* org.apache.oro.text package.
* Although 4 subclasses of GenericPatternCache are provided with this
* package, users may not derive subclasses from this class.
* Rather, users should create their own implmentations of the
* {@link PatternCache} interface.
*
* @version @version@
* @since 1.0
* @see PatternCache
* @see PatternCacheLRU
* @see PatternCacheFIFO
* @see PatternCacheFIFO2
* @see PatternCacheRandom
*/
public abstract class GenericPatternCache implements PatternCache {
PatternCompiler _compiler;
Cache _cache;
/**
* The default capacity to be used by the GenericPatternCache subclasses
* provided with this package. Its value is 20.
*/
public static final int DEFAULT_CAPACITY = 20;
/**
* The primary constructor for GenericPatternCache. It has default
* access so it will only be used within the package. It initializes
* _cache and _compiler to the arguments provided.
* <p>
* @param cache The cache with which to store patterns.
* @param compiler The PatternCompiler that should be used to compile
* patterns.
*/
GenericPatternCache(Cache cache, PatternCompiler compiler) {
_cache = cache;
_compiler = compiler;
}
/**
* Adds a pattern to the cache and returns the compiled pattern. This
* method is in principle almost identical to
* {@link #getPattern getPattern()} except for the fact that
* it throws a MalformedPatternException if an expression cannot be
* compiled.
* <p>
* addPattern() is meant to be used when you expressly intend to add
* an expression to the cache and is useful for front-loading a cache
* with expressions before use. If the expression added does not
* already exist in the cache, it is compiled, added to the cache,
* and returned. If the compiled expression is already in the cache, it
* is simply returned.
* <p>
* The expected behavior of this method should be to start replacing
* patterns in the cache only after the cache has been filled to capacity.
* <p>
* @param expression The regular expression to add to the cache.
* @param options The compilation options to use when compiling the
* expression.
* @return The Pattern corresponding to the String representation of the
* regular expression.
* @exception MalformedPatternException If there is an error in compiling
* the regular expression.
*/
public final synchronized Pattern addPattern(String expression, int options)
throws MalformedPatternException
{
Object obj;
Pattern pattern;
obj = _cache.getElement(expression);
if(obj != null) {
pattern = (Pattern)obj;
if(pattern.getOptions() == options)
return pattern;
}
pattern = _compiler.compile(expression, options);
_cache.addElement(expression, pattern);
return pattern;
}
/**
* Same as calling
* <blockquote><pre>
* addPattern(expression, 0);
* </pre></blockquote>
* @exception MalformedPatternException If there is an error in compiling
* the regular expression.
*/
public final synchronized Pattern addPattern(String expression)
throws MalformedPatternException
{
return addPattern(expression, 0);
}
/**
* This method fetches a pattern from the cache. It is nearly identical
* to {@link #addPattern addPattern()} except that it doesn't
* throw a MalformedPatternException. If the pattern is not in the
* cache, it is compiled, placed in the cache, and returned. If
* the pattern cannot be compiled successfully, it
* throws a MalformedCachePatternException.
* Note that this exception is derived from RuntimeException, which means
* you are NOT forced to catch it by the compiler. Please refer to
* {@link MalformedCachePatternException} for a discussion of
* when you should and shouldn't catch this exception.
* <p>
* @param expression The regular expression to fetch from the cache in
* compiled form.
* @param options The compilation options to use when compiling the
* expression.
* @return The Pattern corresponding to the String representation of the
* regular expression.
* @exception MalformedCachePatternException If there is an error in
* compiling the regular expression.
*/
public final synchronized Pattern getPattern(String expression, int options)
throws MalformedCachePatternException
{
Pattern result = null;
try {
result = addPattern(expression, options);
} catch(MalformedPatternException e) {
throw new MalformedCachePatternException("Invalid expression: " +
expression + "\n" +
e.getMessage());
}
return result;
}
/**
* Same as calling
* <blockquote><pre>
* getPattern(expression, 0)
* </pre></blockquote>
*/
public final synchronized Pattern getPattern(String expression)
throws MalformedCachePatternException
{
return getPattern(expression, 0);
}
/**
* Returns the number of elements in the cache, not to be confused with
* the {@link #capacity()} which returns the number
* of elements that can be held in the cache at one time.
* <p>
* @return The current size of the cache (i.e., the number of elements
* currently cached).
*/
public final int size() { return _cache.size(); }
/**
* Returns the maximum number of patterns that can be cached at one time.
* <p>
* @return The maximum number of patterns that can be cached at one time.
*/
public final int capacity() { return _cache.capacity(); }
}
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