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</code> that gets its 36 * input from a regular <code>InputStream</code>. 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</code> when reading from a regular 42 * <code>InputStream</code>. 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</code> that will read 60 * from a given <code>InputStream</code>. 61 * 62 * @param stream an <code>InputStream</code> to read from. 63 * 64 * @exception IllegalArgumentException if <code>stream</code> is 65 * <code>null</code>. 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</code> since this 130 * <code>ImageInputStream</code> caches data in order to allow 131 * seeking backwards. 132 * 133 * @return <code>true</code>. 134 * 135 * @see #isCachedMemory 136 * @see #isCachedFile 137 */ 138 public boolean isCached() { 139 return true; 140 } 141 142 /** 143 * Returns <code>false</code> since this 144 * <code>ImageInputStream</code> does not maintain a file cache. 145 * 146 * @return <code>false</code>. 147 * 148 * @see #isCached 149 * @see #isCachedMemory 150 */ 151 public boolean isCachedFile() { 152 return false; 153 } 154 155 /** 156 * Returns <code>true</code> since this 157 * <code>ImageInputStream</code> maintains a main memory cache. 158 * 159 * @return <code>true</code>. 160 * 161 * @see #isCached 162 * @see #isCachedFile 163 */ 164 public boolean isCachedMemory() { 165 return true; 166 } 167 168 /** 169 * Closes this <code>MemoryCacheImageInputStream</code>, freeing 170 * the cache. The source <code>InputStream</code> 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 }