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TrueZIP is a Java based Virtual File System (VFS) to enable transparent, multi-threaded read/write access to archive files (ZIP, TAR etc.) as if they were directories. Archive files may be arbitrarily nested and the nesting level is only limited by heap and file system size.

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/*
 * Copyright (C) 2005-2010 Schlichtherle IT Services
 *
 * Licensed 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 de.schlichtherle.io.rof;

import java.io.*;
import java.nio.*;
import java.nio.channels.*;

/**
 * A {@link ReadOnlyFile} implementation using file channels.
 *
 * @author Christian Schlichtherle
 * @version $Id: ChannelReadOnlyFile.java,v 1.3 2010/08/16 10:55:48 christian_schlichtherle Exp $
 */
public class ChannelReadOnlyFile extends AbstractReadOnlyFile {

    /** For use by {@link #read()} only! */
    private final ByteBuffer singleByteBuffer = ByteBuffer.allocate(1);

    private final FileChannel channel;

    public ChannelReadOnlyFile(File file) throws FileNotFoundException {
        channel = new FileInputStream(file).getChannel();
    }

    public long length() throws IOException {
        return channel.size();
    }

    public long getFilePointer() throws IOException {
        return channel.position();
    }

    public void seek(long fp) throws IOException {
        try {
            channel.position(fp);
        } catch (IllegalArgumentException iae) {
            final IOException ioe = new IOException(iae.toString());
            ioe.initCause(iae);
            throw ioe;
        }
    }

    public int read() throws IOException {
        singleByteBuffer.position(0);
        if (channel.read(singleByteBuffer) == 1)
            return singleByteBuffer.array()[0] & 0xff;
        else
            return -1;
    }

    public int read(byte[] buf, int off, int len) throws IOException {
        return channel.read(ByteBuffer.wrap(buf, off, len));
    }

    public void close() throws IOException {
        channel.close();
    }
}