Examples of java.nio.MappedByteBuffer

java.nio.MappedByteBuffer
A direct byte buffer whose content is a memory-mapped region of a file.
Mapped byte buffers are created via the {@link java.nio.channels.FileChannel#map FileChannel.map} method. This classextends the {@link ByteBuffer} class with operations that are specific tomemory-mapped file regions.
A mapped byte buffer and the file mapping that it represents remain valid until the buffer itself is garbage-collected.
The content of a mapped byte buffer can change at any time, for example if the content of the corresponding region of the mapped file is changed by this program or another. Whether or not such changes occur, and when they occur, is operating-system dependent and therefore unspecified.
All or part of a mapped byte buffer may become inaccessible at any time, for example if the mapped file is truncated. An attempt to access an inaccessible region of a mapped byte buffer will not change the buffer's content and will cause an unspecified exception to be thrown either at the time of the access or at some later time. It is therefore strongly recommended that appropriate precautions be taken to avoid the manipulation of a mapped file by this program, or by a concurrently running program, except to read or write the file's content.
Mapped byte buffers otherwise behave no differently than ordinary direct byte buffers.
@author Mark Reinhold @author JSR-51 Expert Group @version 1.25, 09/02/26 @since 1.4

    /**
     * @tests java.nio.channels.FileChannel#map(MapMode,long,long)
     */
    public void test_map_Private() throws IOException {
        this.writeDataToFile(fileOfReadWriteFileChannel);
        MappedByteBuffer mapped = readWriteFileChannel.map(MapMode.PRIVATE, 0,
                CONTENT_LENGTH);
        assertEquals(CONTENT_LENGTH, mapped.limit());
        // test copy on write if private
        ByteBuffer returnByPut = mapped.put(TEST_BYTES);
        assertSame(returnByPut, mapped);
        ByteBuffer checkBuffer = ByteBuffer.allocate(CONTENT_LENGTH);
        mapped.force();
        readWriteFileChannel.read(checkBuffer);
        assertEquals(CONTENT, new String(checkBuffer.array(), "iso8859-1"));


        // test overflow
        try {
            mapped.put(("test" + CONTENT).getBytes("iso8859-1"));
            fail("should throw BufferOverflowException.");
        } catch (BufferOverflowException ex) {
            // expected;
        }
    }

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    /**
     * @tests java.nio.channels.FileChannel#map(MapMode,long,long)
     */
    public void test_map_Private_NonZeroPosition() throws IOException {
        MappedByteBuffer mapped = readWriteFileChannel.map(MapMode.PRIVATE, 10,
                CONTENT_LENGTH - 10);
        assertEquals(CONTENT_LENGTH - 10, mapped.limit());
        assertEquals(CONTENT_LENGTH - 10, mapped.capacity());
        assertEquals(0, mapped.position());
    }

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    /**
     * @tests java.nio.channels.FileChannel#map(MapMode,long,long)
     */
    public void test_map_ReadWrite() throws IOException {
        MappedByteBuffer mapped = null;
        writeDataToFile(fileOfReadWriteFileChannel);
        mapped = readWriteFileChannel.map(MapMode.READ_WRITE, 0, CONTENT
                .length());


        // put something will change its channel
        ByteBuffer returnByPut = mapped.put(TEST_BYTES);
        assertSame(returnByPut, mapped);
        String checkString = "test" + CONTENT.substring(4);
        ByteBuffer checkBuffer = ByteBuffer.allocate(CONTENT_LENGTH);
        mapped.force();
        readWriteFileChannel.position(0);
        readWriteFileChannel.read(checkBuffer);
        assertEquals(checkString, new String(checkBuffer.array(), "iso8859-1"));


        try {
            mapped.put(("test" + CONTENT).getBytes("iso8859-1"));
            fail("should throw BufferOverflowException.");
        } catch (BufferOverflowException ex) {
            // expected;
        }
    }

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     * @tests java.nio.channels.FileChannel#map(MapMode,long,long)
     */
    public void test_map_ReadWrite_NonZeroPosition() throws IOException {
        // test position non-zero
        writeDataToFile(fileOfReadWriteFileChannel);
        MappedByteBuffer mapped = readWriteFileChannel.map(MapMode.READ_WRITE,
                10, CONTENT_LENGTH - 10);
        assertEquals(CONTENT_LENGTH - 10, mapped.limit());
        assertEquals(CONTENT.length() - 10, mapped.capacity());
        assertEquals(0, mapped.position());
        mapped.put(TEST_BYTES);
        ByteBuffer checkBuffer = ByteBuffer.allocate(CONTENT_LENGTH);
        readWriteFileChannel.read(checkBuffer);
        String expected = CONTENT.substring(0, 10) + "test"
                + CONTENT.substring(10 + "test".length());
        assertEquals(expected, new String(checkBuffer.array(), "iso8859-1"));

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                readOnlyFileChannel = new FileInputStream(fileOfReadOnlyFileChannel)
                        .getChannel();
            }


            writeLargeDataToFile(fileOfReadOnlyFileChannel, sizes[i] + 2 * CONTENT_LEN);
            MappedByteBuffer mapped = readOnlyFileChannel.map(MapMode.READ_ONLY,
                    sizes[i], CONTENT_LEN);
            assertEquals("Incorrectly mapped file channel for " + sizes[i]
                    + " position (capacity)", CONTENT_LEN, mapped.capacity());
            assertEquals("Incorrectly mapped file channel for " + sizes[i]
                    + " position (limit)", CONTENT_LEN, mapped.limit());
            assertEquals("Incorrectly mapped file channel for " + sizes[i]
                    + " position (position)", 0, mapped.position());


            // map not change channel's position
            assertEquals(0, readOnlyFileChannel.position());


            // Close the file and the channel before the next iteration

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                       || (start>0 && start<=logFileTime && end>0 && end>=logFileTime)) {


                        // It's in the range, so process the file
                        RandomAccessFile raf = new RandomAccessFile(logFiles[i], "r");
                        FileChannel fc = raf.getChannel();
                        MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
                        CharBuffer cb = Charset.forName("US-ASCII").decode(bb); //todo: does Jetty use a different charset on a foreign PC?
                        Matcher lines = FULL_LINE_PATTERN.matcher(cb);
                        Matcher target = ACCESS_LOG_PATTERN.matcher("");
                        SimpleDateFormat format = (start == 0 && end == 0) ? null : new SimpleDateFormat(ACCESS_LOG_DATE_FORMAT);
                        int max = maxResults == null ? MAX_SEARCH_RESULTS : Math.min(maxResults.intValue(), MAX_SEARCH_RESULTS);

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                       || (start>0 && start<=logFileTime && end>0 && end>=logFileTime)) {


                        // It's in the range, so process the file
                        RandomAccessFile raf = new RandomAccessFile(logFiles[i], "r");
                        FileChannel fc = raf.getChannel();
                        MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
                        CharBuffer cb = Charset.forName("US-ASCII").decode(bb); //todo: does Jetty use a different charset on a foreign PC?
                        Matcher lines = FULL_LINE_PATTERN.matcher(cb);
                        Matcher target = ACCESS_LOG_PATTERN.matcher("");
                        SimpleDateFormat format = (start == 0 && end == 0) ? null : new SimpleDateFormat(ACCESS_LOG_DATE_FORMAT);
                        int max = maxResults == null ? MAX_SEARCH_RESULTS : Math.min(maxResults.intValue(), MAX_SEARCH_RESULTS);

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        boolean capped = false;
        int lineCount = 0;
        try {
            RandomAccessFile raf = new RandomAccessFile(file, "r");
            FileChannel fc = raf.getChannel();
            MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
            CharBuffer cb = Charset.forName(System.getProperty("file.encoding")).decode(bb);
            Matcher target = null;
            Matcher any = null;
            Matcher lines = FULL_LINE_PATTERN.matcher(cb);
            Matcher text = textSearch == null ? null : textSearch.matcher("");

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  public List<Long> fetchData(String path) throws IOException {
    List<Long> input = new ArrayList<Long>();
    FileInputStream stream = new FileInputStream(new File(path));
    try {
      FileChannel fc = stream.getChannel();
      MappedByteBuffer bb = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
      /* Instead of using default, pass in a decoder. */
      String[] lines = Charset.defaultCharset().decode(bb).toString()
          .split("\n");
      for(String line : lines) {
        long val = 0;

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    }


    private MappedByteBuffer mapFile(File file) {
        try {
            FileChannel channel = new FileInputStream(file).getChannel();
            MappedByteBuffer buffer = channel.map(MapMode.READ_ONLY, 0, file.length());
            channel.close();
            return buffer;
        } catch(IOException e) {
            throw new VoldemortException(e);
        }

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