test/jdk/java/nio/file/Files/NulDevice.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * 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).
 *
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.FileChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import static java.nio.file.StandardOpenOption.*;
import java.util.concurrent.ExecutionException;

/* @test
 * @bug 8263898
 * @summary Verify stream and channel behavior with NUL device
 * @requires os.family == "windows"
 * @run main NulDevice
*/
public class NulDevice {
    public static void main(String[] args)
        throws ExecutionException, InterruptedException, IOException {
        Path path = Path.of("nul");

        try (OutputStream os = Files.newOutputStream(path)) {
            os.write(0x02);
            try (InputStream is = Files.newInputStream(path);) {
                if (is.available() != 0) {
                    throw new RuntimeException("No bytes should be available");
                }
                int aByte = is.read();
                if (aByte != -1) {
                    throw new RuntimeException("Should only read -1 from NUL");
                }
            }
        }

        try (OutputStream os = Files.newOutputStream(path, WRITE)) {
            os.write(0x02);
        }

        try (FileChannel ch = FileChannel.open(path, CREATE, TRUNCATE_EXISTING, WRITE)) {
            byte[] bytes = "Whatever".getBytes();
            ByteBuffer buf = ByteBuffer.allocate(2*bytes.length);
            buf.put(bytes);
            int nw = ch.write(buf);
            if (nw != bytes.length) {
                throw new RuntimeException("Should write " + bytes.length +
                    " to NUL");
            }
        }

        try (FileChannel ch = FileChannel.open(path, READ)) {
            if (ch.size() != 0) {
                throw new RuntimeException("Size should be zero");
            }
            ByteBuffer buf = ByteBuffer.allocate(10);
            int nr = ch.read(buf);
            if (nr != -1) {
                throw new RuntimeException("Read returns " + nr + " not -1");
            }
        }

        try (AsynchronousFileChannel ch = AsynchronousFileChannel.open(path, READ, WRITE)) {
            if (ch.size() != 0) {
                throw new RuntimeException("Size should be zero");
            }
            int nw = ch.write(ByteBuffer.wrap(new byte[] {(byte)0x02}), 0L).get();
            if (nw != 1) {
                throw new RuntimeException("Wrote " + nw + " bytes, not one");
            }
            ByteBuffer buf = ByteBuffer.allocate(10);
            int nr = ch.read(buf, 0L).get();
            if (nr != -1) {
                throw new RuntimeException("Read returns " + nr + " not -1");
            }
        }
    }
}