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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.util.logging.*;

/**
 * An adapter class turning a provided {@link ReadOnlyFile} into
 * an {@link InputStream}.
 * Note that this stream supports marking.
 * Note that any of the methods in this class throw a
 * {@link NullPointerException} if {@link #rof} hasn't been initialized.
 *
 * @author Christian Schlichtherle
 * @version $Id: ReadOnlyFileInputStream.java,v 1.4 2010/08/20 13:09:47 christian_schlichtherle Exp $
 * @since TrueZIP 6.4 Support for marking.
 */
public class ReadOnlyFileInputStream extends InputStream {

    /**
     * The underlying {@link ReadOnlyFile}.
     * Any of the methods in this class throw a {@link NullPointerException}
     * if this hasn't been initialized.
     */
    protected ReadOnlyFile rof;

    /**
     * The position of the last mark.
     * Initialized to {@code -1} to indicate that no mark has been set.
     */
    private long mark = -1;

    /**
     * Adapts the given {@code ReadOnlyFile}.
     *
     * @param rof The underlying {@code ReadOnlyFile}. May be
     *        {@code null}, but must be initialized before any method
     *        of this class can be used.
     */
    public ReadOnlyFileInputStream(ReadOnlyFile rof) {
        this.rof = rof;
    }

    public int read() throws IOException {
        return rof.read();
    }

    public int read(byte[] b) throws IOException {
        return rof.read(b);
    }

    public int read(byte[] b, int off, int len) throws IOException {
        return rof.read(b, off, len);
    }

    public long skip(long n) throws IOException {
        if (n <= 0)
            return 0; // for compatibility to RandomAccessFile

        final long fp = rof.getFilePointer(); // should fail when closed
        final long len = rof.length(); // may succeed when closed
        final long rem = len - fp;
        if (n > rem)
            n = (int) rem;
        rof.seek(fp + n);
        return n;
    }

    public int available() throws IOException {
        final long rem = rof.length() - rof.getFilePointer();
        return rem > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) rem;
    }

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

    public void mark(int readlimit) {
        try {
            mark = rof.getFilePointer();
        } catch (IOException failure) {
            Logger.getLogger(ReadOnlyFileInputStream.class.getName())
                .log(Level.WARNING, "mark()/reset() not supported", failure);
            mark = -2;
        }
    }

    public void reset() throws IOException {
        if (mark < 0)
            throw new IOException(mark == -1
                    ? "no mark set"
                    : "mark()/reset() not supported by underlying file");
        rof.seek(mark);
    }

    public boolean markSupported() {
        try {
            rof.seek(rof.getFilePointer());
            return true;
        } catch (IOException failure) {
            return false;
        }
    }
}