1 /*
   2  * Copyright (c) 2000, 2007, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package javax.imageio.stream;
  27 
  28 import java.io.InputStream;
  29 import java.io.IOException;
  30 import com.sun.imageio.stream.StreamFinalizer;
  31 import sun.java2d.Disposer;
  32 import sun.java2d.DisposerRecord;
  33 
  34 /**
  35  * An implementation of {@code ImageInputStream} that gets its
  36  * input from a regular {@code InputStream}.  A memory buffer is
  37  * used to cache at least the data between the discard position and
  38  * the current read position.
  39  *
  40  * <p> In general, it is preferable to use a
  41  * {@code FileCacheImageInputStream} when reading from a regular
  42  * {@code InputStream}.  This class is provided for cases where
  43  * it is not possible to create a writable temporary file.
  44  *
  45  */
  46 public class MemoryCacheImageInputStream extends ImageInputStreamImpl {
  47 
  48     private InputStream stream;
  49 
  50     private MemoryCache cache = new MemoryCache();
  51 
  52     /** The referent to be registered with the Disposer. */
  53     private final Object disposerReferent;
  54 
  55     /** The DisposerRecord that resets the underlying MemoryCache. */
  56     private final DisposerRecord disposerRecord;
  57 
  58     /**
  59      * Constructs a {@code MemoryCacheImageInputStream} that will read
  60      * from a given {@code InputStream}.
  61      *
  62      * @param stream an {@code InputStream} to read from.
  63      *
  64      * @exception IllegalArgumentException if {@code stream} is
  65      * {@code null}.
  66      */
  67     public MemoryCacheImageInputStream(InputStream stream) {
  68         if (stream == null) {
  69             throw new IllegalArgumentException("stream == null!");
  70         }
  71         this.stream = stream;
  72 
  73         disposerRecord = new StreamDisposerRecord(cache);
  74         if (getClass() == MemoryCacheImageInputStream.class) {
  75             disposerReferent = new Object();
  76             Disposer.addRecord(disposerReferent, disposerRecord);
  77         } else {
  78             disposerReferent = new StreamFinalizer(this);
  79         }
  80     }
  81 
  82     public int read() throws IOException {
  83         checkClosed();
  84         bitOffset = 0;
  85         long pos = cache.loadFromStream(stream, streamPos+1);
  86         if (pos >= streamPos+1) {
  87             return cache.read(streamPos++);
  88         } else {
  89             return -1;
  90         }
  91     }
  92 
  93     public int read(byte[] b, int off, int len) throws IOException {
  94         checkClosed();
  95 
  96         if (b == null) {
  97             throw new NullPointerException("b == null!");
  98         }
  99         if (off < 0 || len < 0 || off + len > b.length || off + len < 0) {
 100             throw new IndexOutOfBoundsException
 101                 ("off < 0 || len < 0 || off+len > b.length || off+len < 0!");
 102         }
 103 
 104         bitOffset = 0;
 105 
 106         if (len == 0) {
 107             return 0;
 108         }
 109 
 110         long pos = cache.loadFromStream(stream, streamPos+len);
 111 
 112         len = (int)(pos - streamPos);  // In case stream ended early
 113 
 114         if (len > 0) {
 115             cache.read(b, off, len, streamPos);
 116             streamPos += len;
 117             return len;
 118         } else {
 119             return -1;
 120         }
 121     }
 122 
 123     public void flushBefore(long pos) throws IOException {
 124         super.flushBefore(pos); // this will call checkClosed() for us
 125         cache.disposeBefore(pos);
 126     }
 127 
 128     /**
 129      * Returns {@code true} since this
 130      * {@code ImageInputStream} caches data in order to allow
 131      * seeking backwards.
 132      *
 133      * @return {@code true}.
 134      *
 135      * @see #isCachedMemory
 136      * @see #isCachedFile
 137      */
 138     public boolean isCached() {
 139         return true;
 140     }
 141 
 142     /**
 143      * Returns {@code false} since this
 144      * {@code ImageInputStream} does not maintain a file cache.
 145      *
 146      * @return {@code false}.
 147      *
 148      * @see #isCached
 149      * @see #isCachedMemory
 150      */
 151     public boolean isCachedFile() {
 152         return false;
 153     }
 154 
 155     /**
 156      * Returns {@code true} since this
 157      * {@code ImageInputStream} maintains a main memory cache.
 158      *
 159      * @return {@code true}.
 160      *
 161      * @see #isCached
 162      * @see #isCachedFile
 163      */
 164     public boolean isCachedMemory() {
 165         return true;
 166     }
 167 
 168     /**
 169      * Closes this {@code MemoryCacheImageInputStream}, freeing
 170      * the cache.  The source {@code InputStream} is not closed.
 171      */
 172     public void close() throws IOException {
 173         super.close();
 174         disposerRecord.dispose(); // this resets the MemoryCache
 175         stream = null;
 176         cache = null;
 177     }
 178 
 179     /**
 180      * {@inheritDoc}
 181      */
 182     protected void finalize() throws Throwable {
 183         // Empty finalizer: for performance reasons we instead use the
 184         // Disposer mechanism for ensuring that the underlying
 185         // MemoryCache is reset prior to garbage collection
 186     }
 187 
 188     private static class StreamDisposerRecord implements DisposerRecord {
 189         private MemoryCache cache;
 190 
 191         public StreamDisposerRecord(MemoryCache cache) {
 192             this.cache = cache;
 193         }
 194 
 195         public synchronized void dispose() {
 196             if (cache != null) {
 197                 cache.reset();
 198                 cache = null;
 199             }
 200         }
 201     }
 202 }
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