/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 * Driven by: 3GBZipFiles.sh

 */

import java.io.RandomAccessFile;

import java.io.IOException;

import java.util.Random;

public class FileBuilder {

    private static void usageError() {

        System.err.println("Usage: FileBuilder filetype filename filesize");

        System.err.println("");

        System.err.println("Makes a file named FILENAME of size FILESIZE.");

        System.err.println("If FILETYPE is \"MostlyEmpty\", the file contents is mostly null bytes");

        System.err.println("(which might occupy no disk space if the right OS support exists).");

        System.err.println("If FILETYPE is \"SlightlyCompressible\", the file contents are");

        System.err.println("approximately 90% random data.");

        System.exit(1);

    }

    public static void main (String[] args) throws IOException {

        if (args.length != 3)

            usageError();

        String filetype = args[0];

        String filename = args[1];

        long   filesize = Long.parseLong(args[2]);

        if (! (filetype.equals("MostlyEmpty") ||

               filetype.equals("SlightlyCompressible")))

            usageError();

        try (RandomAccessFile raf = new RandomAccessFile(filename, "rw")) {

            if (filetype.equals("SlightlyCompressible")) {

                byte[] randomBytes = new byte[16384];

                byte[] nullBytes   = new byte[randomBytes.length/10];

                Random rand = new Random();

                for (int i = 0; raf.length() < filesize; ++i) {

                    rand.nextBytes(randomBytes);

                    raf.write(nullBytes);

                    raf.write(randomBytes);

                }

            }

            // Make sure file is exactly the requested size, and that

            // a unique identifying trailer is written.

            byte[] filenameBytes = filename.getBytes("UTF8");

            raf.seek(filesize-filenameBytes.length);

            raf.write(filenameBytes);

            raf.setLength(filesize);

        }

    }

}