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Java > Open Source Codes > org > openlaszlo > iv > flash > cache > GenericCache


1 /*
2  * $Id: GenericCache.java,v 1.5 2002/06/12 23:54:14 skavish Exp $
3  *
4  * ==========================================================================
5  *
6  * The JGenerator Software License, Version 1.0
7  *
8  * Copyright (c) 2000 Dmitry Skavish (skavish@usa.net). All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright
14  * notice, this list of conditions and the following disclaimer.
15  *
16  * 2. Redistributions in binary form must reproduce the above copyright
17  * notice, this list of conditions and the following disclaimer in
18  * the documentation and/or other materials provided with the
19  * distribution.
20  *
21  * 3. The end-user documentation included with the redistribution, if
22  * any, must include the following acknowlegement:
23  * "This product includes software developed by Dmitry Skavish
24  * (skavish@usa.net, http://www.flashgap.com/)."
25  * Alternately, this acknowlegement may appear in the software itself,
26  * if and wherever such third-party acknowlegements normally appear.
27  *
28  * 4. The name "The JGenerator" must not be used to endorse or promote
29  * products derived from this software without prior written permission.
30  * For written permission, please contact skavish@usa.net.
31  *
32  * 5. Products derived from this software may not be called "The JGenerator"
33  * nor may "The JGenerator" appear in their names without prior written
34  * permission of Dmitry Skavish.
35  *
36  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
37  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
38  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
39  * DISCLAIMED. IN NO EVENT SHALL DMITRY SKAVISH OR THE OTHER
40  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
41  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
42  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
43  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
44  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
45  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
46  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
47  * SUCH DAMAGE.
48  *
49  */
50
51 package org.openlaszlo.iv.flash.cache;
52
53 import org.openlaszlo.iv.flash.api.*;
54 import org.openlaszlo.iv.flash.util.*;
55
56 import java.util.*;
57
58 public abstract class GenericCache {
59
60     protected Hashtable cache = new Hashtable();
61     protected int cacheSize = 0;
62     protected CacheSettings settings = new CacheSettings();
63
64     public CacheSettings getMySettings() {
65         return settings;
66     }
67
68     public int getSize() {
69         return cacheSize;
70     }
71
72     public synchronized void clear() {
73         cache.clear();
74         cacheSize = 0;
75     }
76
77     protected synchronized boolean addItem( CacheItem item ) {
78         //Log.debug("adding item to cache: "+getClass().getName()+", cachesize="+cacheSize+", key='"+item.getKey()+"', expireAfter="+(new Date(item.getExpireAfter()))+", size="+item.getSize() );
79 if( !checkCacheSize( item.getSize() ) ) {
80             //Log.debug(" ... failed. cachesize="+cacheSize);
81 return false;
82         }
83         cache.put( item.getKey(), item );
84         cacheSize += item.getSize();
85         //Log.debug(" ... succeed. cachesize="+cacheSize);
86 return true;
87     }
88
89     protected synchronized CacheItem getItem( Object JavaDoc key ) {
90         CacheItem item = (CacheItem) cache.get( key );
91         if( item == null ) return null;
92         if( !isModified( item ) &&
93             System.currentTimeMillis() <= item.getExpireAfter()
94           ) return item;
95
96         // modified or expired - remove from the cache
97 removeItem( item );
98         return null;
99     }
100
101     protected boolean isModified( CacheItem item ) {
102         return false;
103     }
104
105     /**
106      * Returns true if there is enough place
107      */
108     protected boolean checkCacheSize( int size ) {
109         if( cacheSize + size <= settings.getMaxSize() ) return true;
110         if( !settings.isRecycle() ) return false;
111         recycle( size );
112         return cacheSize + size <= settings.getMaxSize();
113     }
114
115     /**
116      * Try to recycle at least 'size' bytes
117      */
118     protected synchronized void recycle( int size ) {
119         if( cache.size() == 0 ) return;
120         //Log.log( Resource.STR, "Recycling cache("+cacheSize+")" );
121
122         // sort list in ascending order, so older elements come first
123 ArrayList l = new ArrayList( cache.values() );
124         Collections.sort( l, new Comparator() {
125                 public int compare( Object JavaDoc o1, Object JavaDoc o2 ) {
126                     return (int) (((CacheItem)o1).getCacheTime() - ((CacheItem)o2).getCacheTime());
127                 }
128             }
129         );
130
131         // recycle cache and remove stale objects at the same time
132 long now = System.currentTimeMillis();
133         for( int i=0; i<l.size(); i++ ) {
134             CacheItem item = (CacheItem) l.get(i);
135             if( size > 0 || now > item.getExpireAfter() ) {
136                 size -= item.getSize();
137                 removeItem( item );
138             }
139         }
140         //Log.log( Resource.STR, "Recycling cache("+cacheSize+") DONE" );
141 }
142
143     protected synchronized void removeItem( CacheItem item ) {
144         cacheSize -= item.getSize();
145         cache.remove( item.getKey() );
146     }
147
148 }
149
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