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 * 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
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package javax.imageio.stream;

import java.io.File;
import java.io.InputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.file.Files;
import com.sun.imageio.stream.StreamCloser;
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 file is used to cache previously read data. 
/**
 * An implementation of {@code ImageInputStream} that gets its
 * input from a regular {@code InputStream}.  A file is used to
 * cache previously read data.
 *
 */
public class FileCacheImageInputStream extends ImageInputStreamImpl {

    private InputStream stream;

    private File cacheFile;

    private RandomAccessFile cache;

    private static final int BUFFER_LENGTH = 1024;

    private byte[] buf = new byte[BUFFER_LENGTH];

    private long length = 0L;

    private boolean foundEOF = false;

    
The referent to be registered with the Disposer. 
/** The referent to be registered with the Disposer. */
    private final Object disposerReferent;

    
The DisposerRecord that closes the underlying cache. 
/** The DisposerRecord that closes the underlying cache. */
    private final DisposerRecord disposerRecord;

    
The CloseAction that closes the stream in
 the StreamCloser's shutdown hook                     
/** The CloseAction that closes the stream in
     *  the StreamCloser's shutdown hook                     */
    private final StreamCloser.CloseAction closeAction;

    
Constructs a FileCacheImageInputStream that will read from a given InputStream. 
 A temporary file is used as a cache. If cacheDir is non-null and is a directory, the file will be created there. If it is null, the system-dependent default temporary-file directory will be used (see the documentation for File.createTempFile for details). 
Params:
  • stream – an InputStream to read from.
  • cacheDir – a File indicating where the cache file should be created, or null to use the system directory.
Throws:
/**
     * Constructs a {@code FileCacheImageInputStream} that will read
     * from a given {@code InputStream}.
     *
     * <p> A temporary file is used as a cache.  If
     * {@code cacheDir} is non-{@code null} and is a
     * directory, the file will be created there.  If it is
     * {@code null}, the system-dependent default temporary-file
     * directory will be used (see the documentation for
     * {@code File.createTempFile} for details).
     *
     * @param stream an {@code InputStream} to read from.
     * @param cacheDir a {@code File} indicating where the
     * cache file should be created, or {@code null} to use the
     * system directory.
     *
     * @exception IllegalArgumentException if {@code stream} is
     * {@code null}.
     * @exception IllegalArgumentException if {@code cacheDir} is
     * non-{@code null} but is not a directory.
     * @throws IOException if a cache file cannot be created.
     */
    public FileCacheImageInputStream(InputStream stream, File cacheDir)
        throws IOException {
        if (stream == null) {
            throw new IllegalArgumentException("stream == null!");
        }
        if ((cacheDir != null) && !(cacheDir.isDirectory())) {
            throw new IllegalArgumentException("Not a directory!");
        }
        this.stream = stream;
        if (cacheDir == null)
            this.cacheFile = Files.createTempFile("imageio", ".tmp").toFile();
        else
            this.cacheFile = Files.createTempFile(cacheDir.toPath(), "imageio", ".tmp")
                                  .toFile();
        this.cache = new RandomAccessFile(cacheFile, "rw");

        this.closeAction = StreamCloser.createCloseAction(this);
        StreamCloser.addToQueue(closeAction);

        disposerRecord = new StreamDisposerRecord(cacheFile, cache);
        if (getClass() == FileCacheImageInputStream.class) {
            disposerReferent = new Object();
            Disposer.addRecord(disposerReferent, disposerRecord);
        } else {
            disposerReferent = new StreamFinalizer(this);
        }
    }

    
Ensures that at least pos bytes are cached, or the end of the source is reached. The return value is equal to the smaller of pos and the length of the source file. 
Throws:
  • IOException – if an I/O error occurs while reading from the
source file
/**
     * Ensures that at least {@code pos} bytes are cached,
     * or the end of the source is reached.  The return value
     * is equal to the smaller of {@code pos} and the
     * length of the source file.
     *
     * @throws IOException if an I/O error occurs while reading from the
     * source file
     */
    private long readUntil(long pos) throws IOException {
        // We've already got enough data cached
        if (pos < length) {
            return pos;
        }
        // pos >= length but length isn't getting any bigger, so return it
        if (foundEOF) {
            return length;
        }

        long len = pos - length;
        cache.seek(length);
        while (len > 0) {
            // Copy a buffer's worth of data from the source to the cache
            // BUFFER_LENGTH will always fit into an int so this is safe
            int nbytes =
                stream.read(buf, 0, (int)Math.min(len, (long)BUFFER_LENGTH));
            if (nbytes == -1) {
                foundEOF = true;
                return length;
            }

            cache.write(buf, 0, nbytes);
            len -= nbytes;
            length += nbytes;
        }

        return pos;
    }

    public int read() throws IOException {
        checkClosed();
        bitOffset = 0;
        long next = streamPos + 1;
        long pos = readUntil(next);
        if (pos >= next) {
            cache.seek(streamPos++);
            return cache.read();
        } else {
            return -1;
        }
    }

    public int read(byte[] b, int off, int len) throws IOException {
        checkClosed();

        if (b == null) {
            throw new NullPointerException("b == null!");
        }
        // Fix 4430357 - if off + len < 0, overflow occurred
        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 = readUntil(streamPos + len);

        // len will always fit into an int so this is safe
        len = (int)Math.min((long)len, pos - streamPos);
        if (len > 0) {
            cache.seek(streamPos);
            cache.readFully(b, off, len);
            streamPos += len;
            return len;
        } else {
            return -1;
        }
    }

    
Returns true since this ImageInputStream caches data in order to allow seeking backwards. 
See Also:
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 true since this ImageInputStream maintains a file cache. 
See Also:
Returns:true.
/**
     * Returns {@code true} since this
     * {@code ImageInputStream} maintains a file cache.
     *
     * @return {@code true}.
     *
     * @see #isCached
     * @see #isCachedMemory
     */
    public boolean isCachedFile() {
        return true;
    }

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

    
Closes this FileCacheImageInputStream, closing and removing the cache file. The source InputStream is not closed. 
Throws:
/**
     * Closes this {@code FileCacheImageInputStream}, closing
     * and removing the cache file.  The source {@code InputStream}
     * is not closed.
     *
     * @throws IOException if an error occurs.
     */
    public void close() throws IOException {
        super.close();
        disposerRecord.dispose(); // this will close/delete the cache file
        stream = null;
        cache = null;
        cacheFile = null;
        StreamCloser.removeFromQueue(closeAction);
    }

    
{@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
        // RandomAccessFile is closed/deleted prior to garbage collection
    }

    private static class StreamDisposerRecord implements DisposerRecord {
        private File cacheFile;
        private RandomAccessFile cache;

        public StreamDisposerRecord(File cacheFile, RandomAccessFile cache) {
            this.cacheFile = cacheFile;
            this.cache = cache;
        }

        public synchronized void dispose() {
            if (cache != null) {
                try {
                    cache.close();
                } catch (IOException e) {
                } finally {
                    cache = null;
                }
            }
            if (cacheFile != null) {
                cacheFile.delete();
                cacheFile = null;
            }
            // Note: Explicit removal of the stream from the StreamCloser
            // queue is not mandatory in this case, as it will be removed
            // automatically by GC shortly after this method is called.
        }
    }
}