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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
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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 ImageInputStream that gets its input from a regular InputStream. A memory buffer is used to cache at least the data between the discard position and the current read position. 
 In general, it is preferable to use a FileCacheImageInputStream when reading from a regular InputStream. This class is provided for cases where it is not possible to create a writable temporary file. /**
 * An implementation of {@code ImageInputStream} that gets its
 * input from a regular {@code InputStream}.  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} when reading from a regular
 * {@code InputStream}.  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. /** The referent to be registered with the Disposer. */
    private final Object disposerReferent;

    
The DisposerRecord that resets the underlying MemoryCache. /** The DisposerRecord that resets the underlying MemoryCache. */
    private final DisposerRecord disposerRecord;

    
Constructs a MemoryCacheImageInputStream that will read from a given InputStream. 
Params:
stream – an InputStream to read from.
Throws:
IllegalArgumentException – if stream is null./**
     * Constructs a {@code MemoryCacheImageInputStream} that will read
     * from a given {@code InputStream}.
     *
     * @param stream an {@code InputStream} to read from.
     *
     * @exception IllegalArgumentException if {@code stream} is
     * {@code null}.
     */
    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 true since this ImageInputStream caches data in order to allow seeking backwards. 
See Also:
isCachedMemory
isCachedFile
Returns:
true./**
     * Returns {@code true} since this
     * {@code ImageInputStream} caches data in order to allow
     * seeking backwards.
     *
     * @return {@code true}.
     *
     * @see #isCachedMemory
     * @see #isCachedFile
     */
    public boolean isCached() {
        return true;
    }

    
Returns false since this ImageInputStream does not maintain a file cache. 
See Also:
isCached
isCachedMemory
Returns:
false./**
     * Returns {@code false} since this
     * {@code ImageInputStream} does not maintain a file cache.
     *
     * @return {@code false}.
     *
     * @see #isCached
     * @see #isCachedMemory
     */
    public boolean isCachedFile() {
        return false;
    }

    
Returns true since this ImageInputStream maintains a main memory cache. 
See Also:
isCached
isCachedFile
Returns:
true./**
     * Returns {@code true} since this
     * {@code ImageInputStream} maintains a main memory cache.
     *
     * @return {@code true}.
     *
     * @see #isCached
     * @see #isCachedFile
     */
    public boolean isCachedMemory() {
        return true;
    }

    
Closes this MemoryCacheImageInputStream, freeing the cache. The source InputStream is not closed. /**
     * Closes this {@code MemoryCacheImageInputStream}, freeing
     * the cache.  The source {@code InputStream} is not closed.
     */
    public void close() throws IOException {
        super.close();
        disposerRecord.dispose(); // this resets the MemoryCache
        stream = null;
        cache = null;
    }

    
{@inheritDoc}
Deprecated:
The finalize method has been deprecated. Subclasses that override finalize in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overriding finalize method. When overriding the finalize method, its implementation must explicitly ensure that super.finalize() is invoked as described in Object.finalize. See the specification for Object.finalize() for further information about migration options./**
     * {@inheritDoc}
     *
     * @deprecated The {@code finalize} method has been deprecated.
     *     Subclasses that override {@code finalize} in order to perform cleanup
     *     should be modified to use alternative cleanup mechanisms and
     *     to remove the overriding {@code finalize} method.
     *     When overriding the {@code finalize} method, its implementation must explicitly
     *     ensure that {@code super.finalize()} is invoked as described in {@link Object#finalize}.
     *     See the specification for {@link Object#finalize()} for further
     *     information about migration options.
     */
    @Deprecated(since="9")
    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;
            }
        }
    }
}