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/* * @(#)MemoryCacheImageInputStream.java 1.26 06/01/05 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.imageio.stream; import java.io.InputStream; import java.io.IOException; import java.io.RandomAccessFile; import java.util.ArrayList; import com.sun.imageio.stream.StreamFinalizer; import sun.java2d.Disposer; import sun.java2d.DisposerRecord; /** * An implementation of <code>ImageInputStream</code> that gets its * input from a regular <code>InputStream</code>. A memory buffer is * used to cache at least the data between the discard position and * the current read position. * * <p> In general, it is preferable to use a * <code>FileCacheImageInputStream</code> when reading from a regular * <code>InputStream</code>. This class is provided for cases where * it is not possible to create a writable temporary file. * * @version 0.5 */ public class MemoryCacheImageInputStream extends ImageInputStreamImpl { private InputStream stream; private MemoryCache cache = new MemoryCache(); /** The referent to be registered with the Disposer. */ private final Object disposerReferent; /** The DisposerRecord that resets the underlying MemoryCache. */ private final DisposerRecord disposerRecord; /** * Constructs a <code>MemoryCacheImageInputStream</code> that will read * from a given <code>InputStream</code>. * * @param stream an <code>InputStream</code> to read from. * * @exception IllegalArgumentException if <code>stream</code> is * <code>null</code>. */ public MemoryCacheImageInputStream(InputStream stream) { if (stream == null) { throw new IllegalArgumentException("stream == null!"); } this.stream = stream; disposerRecord = new StreamDisposerRecord(cache); if (getClass() == MemoryCacheImageInputStream.class) { disposerReferent = new Object(); Disposer.addRecord(disposerReferent, disposerRecord); } else { disposerReferent = new StreamFinalizer(this); } } public int read() throws IOException { checkClosed(); bitOffset = 0; long pos = cache.loadFromStream(stream, streamPos+1); if (pos >= streamPos+1) { return cache.read(streamPos++); } else { return -1; } } public int read(byte[] b, int off, int len) throws IOException { checkClosed(); if (b == null) { throw new NullPointerException("b == null!"); } if (off < 0 || len < 0 || off + len > b.length || off + len < 0) { throw new IndexOutOfBoundsException ("off < 0 || len < 0 || off+len > b.length || off+len < 0!"); } bitOffset = 0; if (len == 0) { return 0; } long pos = cache.loadFromStream(stream, streamPos+len); len = (int)(pos - streamPos); // In case stream ended early if (len > 0) { cache.read(b, off, len, streamPos); streamPos += len; return len; } else { return -1; } } public void flushBefore(long pos) throws IOException { super.flushBefore(pos); // this will call checkClosed() for us cache.disposeBefore(pos); } /** * Returns <code>true</code> since this * <code>ImageInputStream</code> caches data in order to allow * seeking backwards. * * @return <code>true</code>. * * @see #isCachedMemory * @see #isCachedFile */ public boolean isCached() { return true; } /** * Returns <code>false</code> since this * <code>ImageInputStream</code> does not maintain a file cache. * * @return <code>false</code>. * * @see #isCached * @see #isCachedMemory */ public boolean isCachedFile() { return false; } /** * Returns <code>true</code> since this * <code>ImageInputStream</code> maintains a main memory cache. * * @return <code>true</code>. * * @see #isCached * @see #isCachedFile */ public boolean isCachedMemory() { return true; } /** * Closes this <code>MemoryCacheImageInputStream</code>, freeing * the cache. The source <code>InputStream</code> is not closed. */ public void close() throws IOException { super.close(); disposerRecord.dispose(); // this resets the MemoryCache stream = null; cache = null; } /** * {@inheritDoc} */ protected void finalize() throws Throwable { // Empty finalizer: for performance reasons we instead use the // Disposer mechanism for ensuring that the underlying // MemoryCache is reset prior to garbage collection } private static class StreamDisposerRecord implements DisposerRecord { private MemoryCache cache; public StreamDisposerRecord(MemoryCache cache) { this.cache = cache; } public synchronized void dispose() { if (cache != null) { cache.reset(); cache = null; } } } }