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/*
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* Copyright 2000-2007 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Sun designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Sun in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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package javax.imageio.stream;
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import java.io.InputStream;
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import java.io.IOException;
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import com.sun.imageio.stream.StreamFinalizer;
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import sun.java2d.Disposer;
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import sun.java2d.DisposerRecord;
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/**
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* An implementation of <code>ImageInputStream</code> that gets its
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* input from a regular <code>InputStream</code>. A memory buffer is
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* used to cache at least the data between the discard position and
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* the current read position.
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*
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* <p> In general, it is preferable to use a
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* <code>FileCacheImageInputStream</code> when reading from a regular
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* <code>InputStream</code>. This class is provided for cases where
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* it is not possible to create a writable temporary file.
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*
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*/
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public class MemoryCacheImageInputStream extends ImageInputStreamImpl {
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private InputStream stream;
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private MemoryCache cache = new MemoryCache();
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/** The referent to be registered with the Disposer. */
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private final Object disposerReferent;
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/** The DisposerRecord that resets the underlying MemoryCache. */
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private final DisposerRecord disposerRecord;
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/**
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* Constructs a <code>MemoryCacheImageInputStream</code> that will read
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* from a given <code>InputStream</code>.
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*
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* @param stream an <code>InputStream</code> to read from.
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*
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* @exception IllegalArgumentException if <code>stream</code> is
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* <code>null</code>.
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*/
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public MemoryCacheImageInputStream(InputStream stream) {
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if (stream == null) {
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throw new IllegalArgumentException("stream == null!");
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}
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this.stream = stream;
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disposerRecord = new StreamDisposerRecord(cache);
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if (getClass() == MemoryCacheImageInputStream.class) {
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disposerReferent = new Object();
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Disposer.addRecord(disposerReferent, disposerRecord);
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} else {
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disposerReferent = new StreamFinalizer(this);
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}
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}
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public int read() throws IOException {
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checkClosed();
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bitOffset = 0;
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long pos = cache.loadFromStream(stream, streamPos+1);
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if (pos >= streamPos+1) {
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return cache.read(streamPos++);
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} else {
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return -1;
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}
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}
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public int read(byte[] b, int off, int len) throws IOException {
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checkClosed();
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if (b == null) {
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throw new NullPointerException("b == null!");
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}
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if (off < 0 || len < 0 || off + len > b.length || off + len < 0) {
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throw new IndexOutOfBoundsException
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("off < 0 || len < 0 || off+len > b.length || off+len < 0!");
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}
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bitOffset = 0;
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if (len == 0) {
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return 0;
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}
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long pos = cache.loadFromStream(stream, streamPos+len);
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len = (int)(pos - streamPos); // In case stream ended early
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if (len > 0) {
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cache.read(b, off, len, streamPos);
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streamPos += len;
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return len;
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} else {
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return -1;
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}
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}
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public void flushBefore(long pos) throws IOException {
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super.flushBefore(pos); // this will call checkClosed() for us
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cache.disposeBefore(pos);
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}
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/**
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* Returns <code>true</code> since this
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* <code>ImageInputStream</code> caches data in order to allow
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* seeking backwards.
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*
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* @return <code>true</code>.
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*
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* @see #isCachedMemory
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* @see #isCachedFile
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*/
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public boolean isCached() {
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return true;
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}
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/**
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* Returns <code>false</code> since this
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* <code>ImageInputStream</code> does not maintain a file cache.
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*
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* @return <code>false</code>.
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*
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* @see #isCached
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* @see #isCachedMemory
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*/
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public boolean isCachedFile() {
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return false;
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}
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/**
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* Returns <code>true</code> since this
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* <code>ImageInputStream</code> maintains a main memory cache.
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*
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* @return <code>true</code>.
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*
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* @see #isCached
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* @see #isCachedFile
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*/
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public boolean isCachedMemory() {
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return true;
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}
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/**
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* Closes this <code>MemoryCacheImageInputStream</code>, freeing
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* the cache. The source <code>InputStream</code> is not closed.
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*/
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public void close() throws IOException {
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super.close();
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disposerRecord.dispose(); // this resets the MemoryCache
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stream = null;
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cache = null;
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}
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/**
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* {@inheritDoc}
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*/
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protected void finalize() throws Throwable {
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// Empty finalizer: for performance reasons we instead use the
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// Disposer mechanism for ensuring that the underlying
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// MemoryCache is reset prior to garbage collection
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}
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private static class StreamDisposerRecord implements DisposerRecord {
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private MemoryCache cache;
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public StreamDisposerRecord(MemoryCache cache) {
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this.cache = cache;
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}
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public synchronized void dispose() {
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if (cache != null) {
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cache.reset();
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cache = null;
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}
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}
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}
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}
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