001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (C) Alkacon Software (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.jlan;
029
030/**
031 * Buffer class which holds file contents for JLAN file access in memory before they are written to the VFS.<p>
032 *
033 * This is implemented as a CmsByteBuffer instance together with a 'position' index which marks the next write position
034 */
035public class CmsFileBuffer {
036
037    /** The buffer used to store the file contents. */
038    CmsByteBuffer m_buffer = new CmsByteBuffer(8192);
039
040    /** The current write position. */
041    long m_position;
042
043    /**
044     * Gets the contents of this buffer as a byte array.<p>
045     *
046     * @return the file content
047     */
048    public byte[] getContents() {
049
050        byte[] contents = new byte[m_buffer.size()];
051        m_buffer.readBytes(contents, 0, 0, m_buffer.size());
052        return contents;
053    }
054
055    /**
056     * Gets the length of the file content.<p>
057     *
058     * @return the content length
059     *
060     */
061    public long getLength() {
062
063        return m_buffer.size();
064    }
065
066    /**
067     * Gets the current write position.<p>
068     *
069     * @return the current write position
070     */
071    public long getPosition() {
072
073        return m_position;
074    }
075
076    /**
077     * Initializes the file content data.<p>
078     *
079     * @param data the file content data
080     */
081    public void init(byte[] data) {
082
083        m_position = 0;
084        m_buffer.writeBytes(data, 0, 0, data.length);
085    }
086
087    /**
088     * Transfers data from this buffer to a byte array.<p>
089     *
090     * @param dest the target byte array
091     *
092     * @param length the number of bytes to transfer
093     * @param bufferOffset the start index for the target buffer
094     * @param fileOffset the start index for this instance
095     *
096     * @return the number of bytes read, or -1 if we are at the end of the file
097     */
098    public int read(byte[] dest, int length, int bufferOffset, int fileOffset) {
099
100        if (fileOffset >= m_buffer.size()) {
101            return -1;
102        }
103        int readEnd = fileOffset + length;
104        if (readEnd > m_buffer.size()) {
105            length = length - (readEnd - m_buffer.size());
106        }
107        m_buffer.readBytes(dest, fileOffset, bufferOffset, length);
108        return length;
109    }
110
111    /**
112     * Changes the write position.<p>
113     *
114     * @param newPos the new write position
115     */
116    public void seek(long newPos) {
117
118        m_position = newPos;
119    }
120
121    /**
122     * Changes the size of this buffer.<p>
123     *
124     * @param size the new size
125     */
126    public void truncate(int size) {
127
128        m_buffer.truncate(size);
129        m_position = Math.min(size, m_position);
130    }
131
132    /**
133     * Writes the data to the internal buffer.<p>
134     *
135     * @param data the data to write
136     */
137    public void write(byte[] data) {
138
139        m_buffer.writeBytes(data, 0, (int)m_position, data.length);
140    }
141}