/*
 * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

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</code> that gets its
 * input from a regular <code>InputStream</code>.  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
cacheDiris 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:
IllegalArgumentException – if stream is
null.
IllegalArgumentException – if cacheDir is
non-null but is not a directory.
IOException – if a cache file cannot be created./**
     * Constructs a <code>FileCacheImageInputStream</code> that will read
     * from a given <code>InputStream</code>.
     *
     * <p> A temporary file is used as a cache.  If
     * <code>cacheDir</code>is non-<code>null</code> and is a
     * directory, the file will be created there.  If it is
     * <code>null</code>, the system-dependent default temporary-file
     * directory will be used (see the documentation for
     * <code>File.createTempFile</code> for details).
     *
     * @param stream an <code>InputStream</code> to read from.
     * @param cacheDir a <code>File</code> indicating where the
     * cache file should be created, or <code>null</code> to use the
     * system directory.
     *
     * @exception IllegalArgumentException if <code>stream</code> is
     * <code>null</code>.
     * @exception IllegalArgumentException if <code>cacheDir</code> is
     * non-<code>null</code> but is not a directory.
     * @exception 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.
/**
     * Ensures that at least <code>pos</code> bytes are cached,
     * or the end of the source is reached.  The return value
     * is equal to the smaller of <code>pos</code> and the
     * length of 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:
isCachedMemory
isCachedFile
Returns:
true./**
     * 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 true since this
ImageInputStream maintains a file cache.
See Also:
isCached
isCachedMemory
Returns:
true./**
     * Returns <code>true</code> since this
     * <code>ImageInputStream</code> maintains a file cache.
     *
     * @return <code>true</code>.
     *
     * @see #isCached
     * @see #isCachedMemory
     */
    public boolean isCachedFile() {
        return true;
    }

    
Returns false since this
ImageInputStream does not maintain a main memory
cache.
See Also:
isCached
isCachedFile
Returns:
false./**
     * Returns <code>false</code> since this
     * <code>ImageInputStream</code> does not maintain a main memory
     * cache.
     *
     * @return <code>false</code>.
     *
     * @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:
IOException – if an error occurs./**
     * Closes this <code>FileCacheImageInputStream</code>, closing
     * and removing the cache file.  The source <code>InputStream</code>
     * is not closed.
     *
     * @exception 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}
/**
     * {@inheritDoc}
     */
    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.
        }
    }
}