001    /*
002     * Copyright (c) Andrey Kuznetsov. All Rights Reserved.
003     *
004     * http://uio.imagero.com
005     *
006     * Redistribution and use in source and binary forms, with or without
007     * modification, are permitted provided that the following conditions are met:
008     *
009     *  o Redistributions of source code must retain the above copyright notice,
010     *    this list of conditions and the following disclaimer.
011     *
012     *  o Redistributions in binary form must reproduce the above copyright notice,
013     *    this list of conditions and the following disclaimer in the documentation
014     *    and/or other materials provided with the distribution.
015     *
016     *  o Neither the name of Andrey Kuznetsov nor the names of
017     *    its contributors may be used to endorse or promote products derived
018     *    from this software without specific prior written permission.
019     *
020     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
021     * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
022     * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
023     * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
024     * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
025     * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
026     * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
027     * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
028     * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
029     * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
030     * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
031     */
032    
033    package com.imagero.uio.impl;
034    
035    import java.io.File;
036    import java.io.IOException;
037    
038    /**
039     * OffsetRandomAccessFile.java
040     * <br>
041     * Usefull for reading EXIF files<br>
042     * However this class has bad performance, bacause the data is unbuffered.
043     *
044     * @author Andrei Kouznetsov
045     */
046    public class OffsetRandomAccessFile extends RandomAccessFileX {
047            protected long offset;
048            protected long length;
049    
050            public OffsetRandomAccessFile(File file, String mode, long offset) throws IOException {
051                    this(file, mode, offset, file.length() - offset);
052            }
053    
054            public OffsetRandomAccessFile(File file, String mode, long offset, long length) throws IOException {
055                    super(file, mode);
056                    this.offset = offset;
057                    this.length = length;
058                    seek(0);
059            }
060    
061            public OffsetRandomAccessFile(String name, String mode, long offset) throws IOException {
062                    this(new File(name), mode, offset);
063            }
064    
065            public OffsetRandomAccessFile(String name, String mode, long offset, long length) throws IOException {
066                    this(new File(name), mode, offset, length);
067            }
068    
069            public void seek(long pos) throws IOException {
070                    if(pos < 0) {
071                            throw new IOException();
072                    }
073                    super.seek(pos + offset);
074            }
075    
076            public int read() throws IOException {
077                    if(getFilePointer() >= length) {
078                            return -1;
079                    }
080                    return super.read();
081            }
082    
083            public long length() throws IOException {
084                    return length;
085            }
086    
087            public long getFilePointer() throws IOException {
088                    return super.getFilePointer() - offset;
089            }
090    
091            public int skip(int n) throws IOException {
092                    return skipBytes(n);
093            }
094    }