/*
* Copyright (c) 2000, 2007, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
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*
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*/
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;
}
}
}
}