/*
* @(#)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;
}
}
}
}