Back to index...

	/*
	* Copyright (c) 2000, 2007, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package javax.imageio.stream;

	import java.io.InputStream;
	import java.io.IOException;
	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.
	*
	*/
	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;
	}
	}
	}
	}

Back to index...