FileToBytesConverter.java

/*
 * ProActive Parallel Suite(TM):
 * The Open Source library for parallel and distributed
 * Workflows & Scheduling, Orchestration, Cloud Automation
 * and Big Data Analysis on Enterprise Grids & Clouds.
 *
 * Copyright (c) 2007 - 2017 ActiveEon
 * Contact: contact@activeeon.com
 *
 * This library is free software: you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation: version 3 of
 * the License.
 *
 * 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/>.
 *
 * If needed, contact us to obtain a release under GPL Version 2 or 3
 * or a different license than the AGPL.
 */
package org.ow2.proactive.utils;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import org.objectweb.proactive.annotation.PublicAPI;


/**
 * Utility functions for converting files contents to a byte array,
 * and vis versa.
 *
 * @author The ProActive Team
 *
 */
@PublicAPI
public class FileToBytesConverter {

    /** Read contents of a file and return it as a byte array
     * @param file the file to read
     * @return an array of bytes containing file's data.
     * @throws IOException
     */
    public static byte[] convertFileToByteArray(File file) throws IOException {
        FileInputStream fis = new FileInputStream(file);
        try {
            long length = file.length();
            if (length > 0) {
                return fastConversion(fis, length);
            } else {
                return slowConversion(fis);
            }
        } finally {
            try {
                fis.close();
            } catch (IOException e) {
                // We want to throw the exception thrown by the outer try block
                // not by the close()
            }
        }
    }

    /**
     * Read content of a file of known length and return it as a byte array
     *  
     * @param fis The stream to read
     * @param length The number of byte to read
     * @return an array of bytes containing file's data
     * @throws IOException If an I/O error occurs, the file is too large or less bytes than length can be read
     */
    private static byte[] fastConversion(final FileInputStream fis, long length) throws IOException {
        if (length > Integer.MAX_VALUE) {
            throw new IOException("File too large to fit in a byte array");
        }

        final byte[] buf = new byte[(int) length];
        int offset = 0;
        while (offset < buf.length) {
            int r = fis.read(buf, offset, buf.length - offset);
            if (r >= 0) {
                offset += r;
            } else {
                throw new IOException("EOF encountered but fewer bits than expected has been read");
            }
        }

        return buf;
    }

    /**
     * Read content of a file of unknown length (or empty file) and return it as a byte array
     *  
     * @param fis the stream to read
     * @return an array of bytes containing file's data
     * @throws IOException If an I/O error occurs
     */
    private static byte[] slowConversion(final FileInputStream fis) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();

        byte[] buffer = new byte[1024];
        long count = 0;
        int n = 0;
        while (-1 != (n = fis.read(buffer))) {
            output.write(buffer, 0, n);
            count += n;
        }
        return output.toByteArray();
    }

    /** write contents of a byte array in a file
     * @param array Array of bytes to write
     * @param file object in which bytes will be written
     * @throws IOException
     */
    public static void convertByteArrayToFile(byte[] array, File file) throws IOException {
        FileOutputStream outStream = new FileOutputStream(file);
        outStream.write(array);
        outStream.close();
    }
}