001/**
002 * Java Web Archive Toolkit - Software to read and validate ARC, WARC
003 * and GZip files. (http://jwat.org/)
004 * Copyright 2011-2012 Netarkivet.dk (http://netarkivet.dk/)
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.jwat.common;
019
020import java.io.IOException;
021import java.io.InputStream;
022import java.io.RandomAccessFile;
023
024/**
025 * This class wraps a <code>RandomAccessFile</code> into a usable
026 * <code>InputStream</code> which supports random re-position.
027 * Re-positioning is done by using seek() on the <code>RandomAccessFile</code>
028 * object. (@see RandomAccessFile#seek())
029 *
030 * @author nicl
031 */
032public class RandomAccessFileInputStream extends InputStream {
033
034    /** Encapsulated <code>RandomAccessFile</code> used for stream data. */
035    protected RandomAccessFile raf;
036
037    /** Current mark position in file. */
038    protected long mark_position = -1;
039
040    /**
041     * Create a new random access <code>InputStream</code> with repositioning
042     * capabilities.
043     * @param raf <code>RandomAccessFile</code> used for stream data
044     */
045    public RandomAccessFileInputStream(RandomAccessFile raf) {
046        this.raf = raf;
047    }
048
049    /**
050     * Closing this stream has no effect.
051     * @throws IOException if an I/O error occurs while closing stream
052     */
053    @Override
054    public void close() throws IOException {
055        raf = null;
056    }
057
058    @Override
059    public boolean markSupported() {
060        return true;
061    }
062
063    @Override
064    public synchronized void mark(int readlimit) {
065        try {
066            mark_position = raf.getFilePointer();
067        } catch (IOException e) {
068            throw new IllegalStateException();
069        }
070    }
071
072    @Override
073    public synchronized void reset() throws IOException {
074        if (mark_position == -1) {
075            throw new IOException("Mark not set or is invalid");
076        }
077        raf.seek(mark_position);
078    }
079
080    @Override
081    public int available() throws IOException {
082        long avail = raf.length() - raf.getFilePointer();
083        return (int) (Math.min(avail, Integer.MAX_VALUE));
084    }
085
086    @Override
087    public long skip(long n) throws IOException {
088        long skip = Math.min(n, raf.length() - raf.getFilePointer());
089        raf.seek(raf.getFilePointer() + skip);
090        return skip;
091    }
092
093    @Override
094    public int read() throws IOException {
095        return raf.read();
096    }
097
098    @Override
099    public int read(byte[] b) throws IOException {
100        return raf.read(b);
101    }
102
103    @Override
104    public int read(byte[] b, int off, int len) throws IOException {
105        return raf.read(b, off, len);
106    }
107
108}