/*

 * 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.

 */

/* @test

 * @summary Test read method of FileChannel

 */

import java.io.*;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.channels.*;

import java.nio.channels.FileChannel;

import java.util.Random;

/**

 * Testing FileChannel's mapping capabilities.

 */

public class Read {

    private static PrintStream err = System.err;

    private static Random generator = new Random();

    private static int CHARS_PER_LINE = File.separatorChar == '/' ? 5 : 6;

    private static File blah;

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

        StringBuffer sb = new StringBuffer();

        sb.setLength(4);

        blah = File.createTempFile("blah", null);

        blah.deleteOnExit();

        initTestFile(blah);

        FileInputStream fis = new FileInputStream(blah);

        FileChannel c = fis.getChannel();

        for (int x=0; x<1000; x++) {

            long offset = x * CHARS_PER_LINE;

            long expectedResult = offset / CHARS_PER_LINE;

            offset = expectedResult * CHARS_PER_LINE;

            ByteBuffer bleck = ByteBuffer.allocateDirect(CHARS_PER_LINE);

            c.read(bleck);

            for (int i=0; i<4; i++) {

                byte aByte = bleck.get(i);

                sb.setCharAt(i, (char)aByte);

            }

            int result = Integer.parseInt(sb.toString());

            if (result != expectedResult) {

                err.println("I expected "+expectedResult);

                err.println("I got "+ result);

                throw new Exception("Read test failed");

            }

        }

        c.close();

        fis.close();

        blah.delete();

    }

    /**

     * Creates file blah:

     * 0000

     * 0001

     * 0002

     * 0003

     * .

     * .

     * .

     * 3999

     *

     * Blah extends beyond a single page of memory so that the

     * ability to index into a file of multiple pages is tested.

     */

    private static void initTestFile(File blah) throws Exception {

        FileOutputStream fos = new FileOutputStream(blah);

        BufferedWriter awriter

            = new BufferedWriter(new OutputStreamWriter(fos, "8859_1"));

        for(int i=0; i<4000; i++) {

            String number = new Integer(i).toString();

            for (int h=0; h<4-number.length(); h++)

                awriter.write("0");

            awriter.write(""+i);

            awriter.newLine();

        }

       awriter.flush();

       awriter.close();

    }

}