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Apache Commons VFS is a Virtual File System library - Sandbox.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.vfs2.util;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashSet;
import java.util.Set;

import javax.mail.internet.SharedInputStream;

import org.apache.commons.vfs2.Capability;
import org.apache.commons.vfs2.FileObject;
import org.apache.commons.vfs2.FileSystemException;
import org.apache.commons.vfs2.RandomAccessContent;

/**
 * (Sandbox) A wrapper to an FileObject to get a {@link javax.mail.internet.SharedInputStream}.
 */
public class SharedRandomContentInputStream extends BufferedInputStream implements SharedInputStream {
    private final Set createdStreams;
    private final FileObject fo;
    private final long fileStart;
    private final long fileEnd;

    private long pos;
    private long resetCount;

    private SharedRandomContentInputStream(final Set createdStreams,
            final FileObject fo, final long fileStart, final long fileEnd, final InputStream is)
            throws FileSystemException {
        super(is);

        if (!fo.getFileSystem().hasCapability(Capability.RANDOM_ACCESS_READ)) {
            throw new FileSystemException("vfs.util/missing-capability.error", Capability.RANDOM_ACCESS_READ);
        }

        this.fo = fo;
        this.fileStart = fileStart;
        this.fileEnd = fileEnd;
        this.createdStreams = createdStreams;

        synchronized (createdStreams) {
            createdStreams.add(this);
        }
    }

    public SharedRandomContentInputStream(final FileObject fo) throws FileSystemException {
        this(new HashSet(), fo, 0, -1, fo.getContent().getInputStream());
    }

    @Override
    public synchronized int read() throws IOException {
        if (checkEnd()) {
            return -1;
        }
        final int r = super.read();
        pos++;
        resetCount++;
        return r;
    }

    @Override
    public synchronized int read(final byte[] b, final int off, int len) throws IOException {
        if (checkEnd()) {
            return -1;
        }

        if (fileEnd > -1 && calcFilePosition(len) > fileEnd) {
            // we can not read past our end
            len = (int) (fileEnd - getFilePosition());
        }

        final int nread = super.read(b, off, len);
        pos += nread;
        resetCount += nread;
        return nread;
    }

    @Override
    public synchronized long skip(long n) throws IOException {
        if (checkEnd()) {
            return -1;
        }

        if (fileEnd > -1 && calcFilePosition(n) > fileEnd) {
            // we can not skip past our end
            n = fileEnd - getFilePosition();
        }

        final long nskip = super.skip(n);
        pos += nskip;
        resetCount += nskip;
        return nskip;
    }

    /*
     * public synchronized int available() throws IOException { long realFileEnd = fileEnd; if (realFileEnd < 0) {
     * realFileEnd = fo.getContent().getSize(); } if (realFileEnd < 0) { // we cant determine if there is really
     * something available return 8192; }
     *
     * long available = realFileEnd - (fileStart + pos); if (available > Integer.MAX_VALUE) { return Integer.MAX_VALUE;
     * }
     *
     * return (int) available; }
     */

    private boolean checkEnd() {
        return fileEnd > -1 && (getFilePosition() >= fileEnd);
    }

    protected long getFilePosition() {
        return fileStart + pos;
    }

    protected long calcFilePosition(final long nadd) {
        return getFilePosition() + nadd;
    }

    @Override
    public synchronized void mark(final int readlimit) {
        super.mark(readlimit);
        resetCount = 0;
    }

    @Override
    public synchronized void reset() throws IOException {
        super.reset();
        pos -= resetCount;
        resetCount = 0;
    }

    public long getPosition() {
        return pos;
    }

    @Override
    public void close() throws IOException {
        super.close();

        synchronized (createdStreams) {
            createdStreams.remove(this);
        }
    }

    public InputStream newStream(final long start, final long end) {
        try {
            final long newFileStart = this.fileStart + start;
            final long newFileEnd = end < 0 ? this.fileEnd : this.fileStart + end;

            final RandomAccessContent rac = fo.getContent().getRandomAccessContent(RandomAccessMode.READ);
            rac.seek(newFileStart);
            return new SharedRandomContentInputStream(createdStreams, fo, newFileStart, newFileEnd,
                    rac.getInputStream());
        } catch (final IOException e) {
            throw new RuntimeException(e);
        }
    }

    public void closeAll() throws IOException {
        synchronized (createdStreams) {
            final SharedRandomContentInputStream[] streams = new SharedRandomContentInputStream[createdStreams.size()];
            createdStreams.toArray(streams);
            for (final SharedRandomContentInputStream stream : streams) {
                stream.close();
            }
        }
    }
}