/*
 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
 * 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.
 */

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.*;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.Path;
import java.nio.file.Files;
import java.nio.file.FileStore;
import java.nio.file.StandardOpenOption;
import com.sun.nio.file.ExtendedOpenOption;

public class DirectIO {

    private static final int SIZE = 4096;

    static {
        System.loadLibrary("DirectIO");
    }

    private static void testWrite(Path p) throws Exception {
        FileChannel fc = FileChannel.open(p, StandardOpenOption.WRITE,
                ExtendedOpenOption.DIRECT);
        FileStore fs = Files.getFileStore(p);
        int alignment = (int)fs.getBlockSize();
        ByteBuffer src = ByteBuffer.allocateDirect(SIZE + alignment -1)
                                   .alignedSlice(alignment);
        for (int j = 0; j < SIZE; j++) {
            src.put((byte)0);
        }
        src.flip();
        try {
            fc.write(src);
        } finally {
            fc.close();
        }
    }

    private static void testRead(Path p) throws Exception {
        FileChannel fc = FileChannel.open(p, ExtendedOpenOption.DIRECT);
        FileStore fs = Files.getFileStore(p);
        int alignment = (int)fs.getBlockSize();

        ByteBuffer dest = ByteBuffer.allocateDirect(SIZE + alignment - 1)
                                    .alignedSlice(alignment);
        fc.read(dest);

        fc.close();
    }

    private static boolean isFileInCache(Path p) {
        String path = p.toString();
        return isFileInCache0(SIZE, path);
    }

    private static native boolean isFileInCache0(int size, String path);

    public static void main(String[] args) throws Exception {
        Path p = Files.createTempFile(Paths.get(
                System.getProperty("test.dir", ".")), "test", null);
        testWrite(p);
        if (isFileInCache(p)) {
            throw new RuntimeException("DirectIO is not working properly with "
                                       + "write. File still exists in cache!");
        }
        testRead(p);
        if (isFileInCache(p)) {
            throw new RuntimeException("DirectIO is not working properly with "
                                       + "read. File still exists in cache!");
        }
        Files.delete(p);
    }
}