io.jar is a component in iText Java library to provide input/output functionalities. iText Java library allows you to generate and manage PDF documents.

The Source Code files are provided together with the JAR file in the binary packge like iText7-Core-7.1.4.zip. You can download it at iText 7 Core Download site.

You can compile it to generate your JAR file, using io.pom as the build configuration file.

The source code of io-7.1.4.jar is provided below:

⏎ com/itextpdf/io/source/MappedChannelRandomAccessSource.java

/*

    This file is part of the iText (R) project.
    Copyright (c) 1998-2018 iText Group NV
    Authors: Bruno Lowagie, Paulo Soares, et al.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License version 3
    as published by the Free Software Foundation with the addition of the
    following permission added to Section 15 as permitted in Section 7(a):
    FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
    ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
    OF THIRD PARTY RIGHTS

    This program is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE.
    See the GNU Affero General Public License for more details.
    You should have received a copy of the GNU Affero General Public License
    along with this program; if not, see http://www.gnu.org/licenses or write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA, 02110-1301 USA, or download the license from the following URL:
    http://itextpdf.com/terms-of-use/

    The interactive user interfaces in modified source and object code versions
    of this program must display Appropriate Legal Notices, as required under
    Section 5 of the GNU Affero General Public License.

    In accordance with Section 7(b) of the GNU Affero General Public License,
    a covered work must retain the producer line in every PDF that is created
    or manipulated using iText.

    You can be released from the requirements of the license by purchasing
    a commercial license. Buying such a license is mandatory as soon as you
    develop commercial activities involving the iText software without
    disclosing the source code of your own applications.
    These activities include: offering paid services to customers as an ASP,
    serving PDFs on the fly in a web application, shipping iText with a closed
    source product.

    For more information, please contact iText Software Corp. at this
    address: sales@itextpdf.com
 */
package com.itextpdf.io.source;

import java.nio.channels.FileChannel;

/**
 * A RandomAccessSource that represents a memory mapped section of an underlying FileChannel.
 * This source can be closed and will automatically re-open as needed.
 * This class is an internal implementation detail of the {@link FileChannelRandomAccessSource} class and
 * shouldn't be used by general iText users.
 */
class MappedChannelRandomAccessSource implements IRandomAccessSource {
    /**
     * The underlying channel
     */
    private final FileChannel channel;
    /**
     * The offset into the channel that this source maps to
     */
    private final long offset;
    /**
     * The number of bytes this source maps to
     */
    private final long length;

    /**
     * If the map is active, the actual map.  null other wise.
     */
    private ByteBufferRandomAccessSource source;

    /**
     * Create a new source based on the channel.  Mapping will not occur until data is actually read.
     * @param channel the underlying channel
     * @param offset the offset of the map
     * @param length the length of the map
     */
    public MappedChannelRandomAccessSource(FileChannel channel, long offset, long length) {
        if (offset < 0)
            throw new IllegalArgumentException(offset + " is negative");
        if (length <= 0)
            throw new IllegalArgumentException(length + " is zero or negative");

        this.channel = channel;
        this.offset = offset;
        this.length = length;
        this.source = null;
    }

    /**
     * Map the region of the channel
     * @throws java.io.IOException if there is a problem with creating the map
     */
    void open() throws java.io.IOException {
        if (source != null)
            return;

        if (!channel.isOpen())
            throw new IllegalStateException("Channel is closed");

        source = new ByteBufferRandomAccessSource(channel.map(FileChannel.MapMode.READ_ONLY, offset, length));
    }



    /**
     * {@inheritDoc}
     */
    public int get(long position) throws java.io.IOException {
        if (source == null)
            throw new java.io.IOException("RandomAccessSource not opened");
        return source.get(position);
    }

    /**
     * {@inheritDoc}
     */
    public int get(long position, byte[] bytes, int off, int len) throws java.io.IOException {
        if (source == null)
            throw new java.io.IOException("RandomAccessSource not opened");
        return source.get(position, bytes, off, len);
    }

    /**
     * {@inheritDoc}
     */
    public long length() {
        return length;
    }

    /**
     * {@inheritDoc}
     */
    public void close() throws java.io.IOException {
        if (source == null)
            return;
        source.close();
        source = null;
    }

    @Override
    public String toString() {
        return getClass().getName() + " (" + offset + ", " + length + ")";
    }
}

⏎ com/itextpdf/io/source/MappedChannelRandomAccessSource.java

Or download all of them as a single archive file:

File name: io-7.1.4-sources.jar
File size: 608762 bytes
Release date: 2018-10-09
Download 

⇒ iText layout.jar Source Code

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