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/RandomAccessSourceFactory.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 com.itextpdf.io.IOException;
import com.itextpdf.io.util.ResourceUtil;
import com.itextpdf.io.util.StreamUtil;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.io.Serializable;
import java.net.URL;
import java.nio.channels.FileChannel;
import com.itextpdf.io.util.MessageFormatUtil;

/**
 * Factory to create {@link IRandomAccessSource} objects based on various types of sources
 */
public final class RandomAccessSourceFactory implements Serializable {

    private static final long serialVersionUID = -8958482579413233761L;

    /**
     * Whether the full content of the source should be read into memory at construction
     */
    private boolean forceRead = false;

    /**
     * Whether {@link java.io.RandomAccessFile} should be used instead of a {@link java.nio.channels.FileChannel}, where applicable
     */
    private boolean usePlainRandomAccess = false;

    /**
     * Whether the underlying file should have a RW lock on it or just an R lock
     */
    private boolean exclusivelyLockFile = false;

    /**
     * Creates a factory that will give preference to accessing the underling data source using memory mapped files
     */
    public RandomAccessSourceFactory() {
    }

    /**
     * Determines whether the full content of the source will be read into memory
     * @param forceRead true if the full content will be read, false otherwise
     * @return this object (this allows chaining of method calls)
     */
    public RandomAccessSourceFactory setForceRead(boolean forceRead){
        this.forceRead = forceRead;
        return this;
    }

    /**
     * Determines whether {@link java.io.RandomAccessFile} should be used as the primary data access mechanism
     * @param usePlainRandomAccess whether {@link java.io.RandomAccessFile} should be used as the primary data access mechanism
     * @return this object (this allows chaining of method calls)
     */
    public RandomAccessSourceFactory setUsePlainRandomAccess(boolean usePlainRandomAccess){
        this.usePlainRandomAccess = usePlainRandomAccess;
        return this;
    }

    public RandomAccessSourceFactory setExclusivelyLockFile(boolean exclusivelyLockFile){
        this.exclusivelyLockFile = exclusivelyLockFile;
        return this;
    }

    /**
     * Creates a {@link IRandomAccessSource} based on a byte array
     * @param data the byte array
     * @return the newly created {@link IRandomAccessSource}
     */
    public IRandomAccessSource createSource(byte[] data){
        return new ArrayRandomAccessSource(data);
    }

    public IRandomAccessSource createSource(RandomAccessFile raf) throws java.io.IOException {
        return new RAFRandomAccessSource(raf);
    }

    /**
     * Creates a {@link IRandomAccessSource} based on a URL.  The data available at the URL is read into memory and used
     * as the source for the {@link IRandomAccessSource}
     * @param url the url to read from
     * @return the newly created {@link IRandomAccessSource}
     */
    public IRandomAccessSource createSource(URL url) throws java.io.IOException{
        InputStream stream = url.openStream();
        try {
            return createSource(stream);
        }
        finally {
            try {
                stream.close();
            } catch(java.io.IOException ignored) { }
        }
    }

    /**
     * Creates a {@link IRandomAccessSource} based on an {@link InputStream}.  The full content of the InputStream is read into memory and used
     * as the source for the {@link IRandomAccessSource}
     * @param inputStream the stream to read from
     * @return the newly created {@link IRandomAccessSource}
     */
    public IRandomAccessSource createSource(InputStream inputStream) throws java.io.IOException{
        return createSource(StreamUtil.inputStreamToArray(inputStream));
    }

    /**
     * Creates a {@link IRandomAccessSource} based on a filename string.
     * If the filename describes a URL, a URL based source is created
     * If the filename describes a file on disk, the contents may be read into memory (if {@code forceRead} is true),
     * opened using memory mapped file channel (if usePlainRandomAccess is false), or
     * opened using {@link RandomAccessFile} access (if usePlainRandomAccess is true)
     * This call will automatically fail over to using {@link RandomAccessFile} if the memory map operation fails
     * @param filename the name of the file or resource to create the {@link IRandomAccessSource} for
     * @return the newly created {@link IRandomAccessSource}
     */
    public IRandomAccessSource createBestSource(String filename) throws java.io.IOException{
        File file = new File(filename);
        if (!file.canRead()) {
            if (filename.startsWith("file:/")
                    || filename.startsWith("http://")
                    || filename.startsWith("https://")
                    || filename.startsWith("jar:")
                    || filename.startsWith("wsjar:")
                    || filename.startsWith("wsjar:")
                    || filename.startsWith("vfszip:")) {
                return createSource(new URL(filename));
            } else {
                return createByReadingToMemory(filename);
            }
        }

        if (forceRead){
            return createByReadingToMemory(new FileInputStream(filename));
        }

        String openMode = exclusivelyLockFile ? "rw" : "r";

        RandomAccessFile raf = new RandomAccessFile(file, openMode);
        if (exclusivelyLockFile){
            raf.getChannel().lock();
        }

        if (usePlainRandomAccess){
            return new RAFRandomAccessSource(raf);
        }

        try{
            if (raf.length() <= 0) // files with zero length can't be mapped and will throw an IllegalArgumentException.  Just open using a simple RAF source.
                return new RAFRandomAccessSource(raf);

            try {
                // ownership of the RAF passes to whatever source is created by createBestSource.
                return createBestSource(raf.getChannel());
            } catch (java.io.IOException e){
                if (exceptionIsMapFailureException(e)) {
                    return new RAFRandomAccessSource(raf);
                }
                throw e;
            }
        } catch (Exception e) { // If RAFRandomAccessSource constructor or createBestSource throws, then we must close the RAF we created.
            try {
                raf.close();
            } catch (java.io.IOException ignore){}
            throw e;
        }
    }

    /**
     * Creates a {@link IRandomAccessSource} based on memory mapping a file channel.
     * Unless you are explicitly working with a {@code FileChannel} already, it is better to use
     * {@link RandomAccessSourceFactory#createBestSource(String)}.
     * If the file is large, it will be opened using a paging strategy.
     * @param channel the name of the file or resource to create the {@link IRandomAccessSource} for
     * @return the newly created {@link IRandomAccessSource}
     */
    public IRandomAccessSource createBestSource(FileChannel channel) throws java.io.IOException {
        if (channel.size() <= PagedChannelRandomAccessSource.DEFAULT_TOTAL_BUFSIZE){ // if less than the fully mapped usage of PagedFileChannelRandomAccessSource, just map the whole thing and be done with it
            return new GetBufferedRandomAccessSource(new FileChannelRandomAccessSource(channel));
        } else {
            return new GetBufferedRandomAccessSource(new PagedChannelRandomAccessSource(channel));
        }
    }

    public IRandomAccessSource createRanged(IRandomAccessSource source, long[] ranges) throws java.io.IOException {
        IRandomAccessSource[] sources = new IRandomAccessSource[ranges.length/2];
        for(int i = 0; i < ranges.length; i+=2){
            sources[i/2] = new WindowRandomAccessSource(source, ranges[i], ranges[i+1]);
        }
        return new GroupedRandomAccessSource(sources);
    }

    /**
     * Creates a new {@link IRandomAccessSource} by reading the specified file/resource into memory
     * @param filename the name of the resource to read
     * @return the newly created {@link IRandomAccessSource}
     * @throws java.io.IOException if reading the underling file or stream fails
     */
    private IRandomAccessSource createByReadingToMemory(String filename) throws java.io.IOException {
        InputStream stream = ResourceUtil.getResourceStream(filename);
        if (stream == null) {
            throw new java.io.IOException(MessageFormatUtil.format(IOException._1NotFoundAsFileOrResource, filename));
        }
        return createByReadingToMemory(stream);
    }

    /**
     * Creates a new {@link IRandomAccessSource} by reading the specified file/resource into memory
     * @param stream the name of the resource to read
     * @return the newly created {@link IRandomAccessSource}
     * @throws java.io.IOException if reading the underling file or stream fails
     */
    private IRandomAccessSource createByReadingToMemory(InputStream stream) throws java.io.IOException {
        try {
            return new ArrayRandomAccessSource(StreamUtil.inputStreamToArray(stream));
        }
        finally {
            try {
                stream.close();
            } catch (java.io.IOException ignored) { }
        }
    }

    /**
     * Utility method that determines whether a given java.io.IOException is the result
     * of a failure to map a memory mapped file.  It would be better if the runtime
     * provided a special exception for this case, but it doesn't, so we have to rely
     * on parsing the exception message.
     * @param e the exception to check
     * @return true if the exception was the result of a failure to map a memory mapped file
     */
    private static boolean exceptionIsMapFailureException(java.io.IOException e){
        if (e.getMessage() != null && e.getMessage().contains("Map failed"))
            return true;
        return false;
    }
}

⏎ com/itextpdf/io/source/RandomAccessSourceFactory.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

⇐ iText kernel.jar Source Code

⇑ Download and Install iText Java Library

⇑⇑ iText for PDF Generation