Java Code Examples for java.nio.channels.FileChannel#truncate()

@Test
public void whenTruncateFile_thenCorrect() throws IOException {
    String input = "this is a test input";

    FileOutputStream fout = new FileOutputStream("src/test/resources/test_truncate.txt");
    FileChannel channel = fout.getChannel();

    ByteBuffer buff = ByteBuffer.wrap(input.getBytes());
    channel.write(buff);
    buff.flip();

    channel = channel.truncate(5);
    assertEquals(5, channel.size());

    fout.close();
    channel.close();
}
 

@Override
public long truncateFileAtURL(LocalFilesystemURL inputURL, long size) throws IOException {
       File file = new File(filesystemPathForURL(inputURL));

       if (!file.exists()) {
           throw new FileNotFoundException("File at " + inputURL.uri + " does not exist.");
       }

       RandomAccessFile raf = new RandomAccessFile(filesystemPathForURL(inputURL), "rw");
       try {
           if (raf.length() >= size) {
               FileChannel channel = raf.getChannel();
               channel.truncate(size);
               return size;
           }

           return raf.length();
       } finally {
           raf.close();
       }


}
 

@Test
public void readPrematureEndOfFile1() throws Exception {
	final FileChannel fc = tmpFileChannel();
	final Buffer buffer = createTestBuffer();
	final MemorySegment readBuffer = MemorySegmentFactory.allocateUnpooledOffHeapMemory(buffer.getSize(), null);

	BufferReaderWriterUtil.writeToByteChannel(fc, buffer, BufferReaderWriterUtil.allocatedWriteBufferArray());
	fc.truncate(fc.position() - 1);
	fc.position(0);

	try {
		BufferReaderWriterUtil.readFromByteChannel(
				fc, BufferReaderWriterUtil.allocatedHeaderBuffer(), readBuffer, FreeingBufferRecycler.INSTANCE);
		fail();
	}
	catch (IOException e) {
		// expected
	}
}
 

@Override
public long truncateFileAtURL(LocalFilesystemURL inputURL, long size) throws IOException {
       File file = new File(filesystemPathForURL(inputURL));

       if (!file.exists()) {
           throw new FileNotFoundException("File at " + inputURL.uri + " does not exist.");
       }

       RandomAccessFile raf = new RandomAccessFile(filesystemPathForURL(inputURL), "rw");
       try {
           if (raf.length() >= size) {
               FileChannel channel = raf.getChannel();
               channel.truncate(size);
               return size;
           }

           return raf.length();
       } finally {
           raf.close();
       }


}
 

/**
 * Truncate the file to size
 *
 * @param filename
 * @param size
 * @throws FileNotFoundException, IOException
 * @throws NoModificationAllowedException
 */
private long truncateFile(String filename, long size) throws FileNotFoundException, IOException, NoModificationAllowedException {
    if (filename.startsWith("content://")) {
        throw new NoModificationAllowedException("Couldn't truncate file given its content URI");
    }

    filename = FileHelper.getRealPath(filename, cordova);

    RandomAccessFile raf = new RandomAccessFile(filename, "rw");
    try {
        if (raf.length() >= size) {
            FileChannel channel = raf.getChannel();
            channel.truncate(size);
            return size;
        }

        return raf.length();
    } finally {
        raf.close();
    }
}
 

@Test
public void readPrematureEndOfFile2() throws Exception {
	final FileChannel fc = tmpFileChannel();
	final Buffer buffer = createTestBuffer();
	final MemorySegment readBuffer = MemorySegmentFactory.allocateUnpooledOffHeapMemory(buffer.getSize(), null);

	BufferReaderWriterUtil.writeToByteChannel(fc, buffer, BufferReaderWriterUtil.allocatedWriteBufferArray());
	fc.truncate(2); // less than a header size
	fc.position(0);

	try {
		BufferReaderWriterUtil.readFromByteChannel(
				fc, BufferReaderWriterUtil.allocatedHeaderBuffer(), readBuffer, FreeingBufferRecycler.INSTANCE);
		fail();
	}
	catch (IOException e) {
		// expected
	}
}
 

@Test
public void readPrematureEndOfFile2() throws Exception {
	final FileChannel fc = tmpFileChannel();
	final Buffer buffer = createTestBuffer();
	final MemorySegment readBuffer = MemorySegmentFactory.allocateUnpooledOffHeapMemory(buffer.getSize(), null);

	BufferReaderWriterUtil.writeToByteChannel(fc, buffer, BufferReaderWriterUtil.allocatedWriteBufferArray());
	fc.truncate(2); // less than a header size
	fc.position(0);

	try {
		BufferReaderWriterUtil.readFromByteChannel(
				fc, BufferReaderWriterUtil.allocatedHeaderBuffer(), readBuffer, FreeingBufferRecycler.INSTANCE);
		fail();
	}
	catch (IOException e) {
		// expected
	}
}
 

@Override
public long truncateFileAtURL(LocalFilesystemURL inputURL, long size) throws IOException {
       File file = new File(filesystemPathForURL(inputURL));

       if (!file.exists()) {
           throw new FileNotFoundException("File at " + inputURL.URL + " does not exist.");
       }
       
       RandomAccessFile raf = new RandomAccessFile(filesystemPathForURL(inputURL), "rw");
       try {
           if (raf.length() >= size) {
               FileChannel channel = raf.getChannel();
               channel.truncate(size);
               return size;
           }

           return raf.length();
       } finally {
           raf.close();
       }


}
 

/**
 * Create a new Database for the given fileFormat
 * @param fileFormat version of new database.
 * @param mdbFile Location to write the new database to.  <b>If this file
 *                already exists, it will be overwritten.</b>
 * @param channel  pre-opened FileChannel.  if provided explicitly, it will
 *                 not be closed by this Database instance
 * @param autoSync whether or not to enable auto-syncing on write.  if
 *                 {@code true}, writes will be immediately flushed to disk.
 *                 This leaves the database in a (fairly) consistent state
 *                 on each write, but can be very inefficient for many
 *                 updates.  if {@code false}, flushing to disk happens at
 *                 the jvm's leisure, which can be much faster, but may
 *                 leave the database in an inconsistent state if failures
 *                 are encountered during writing.  Writes may be flushed at
 *                 any time using {@link #flush}.
 * @param charset  Charset to use, if {@code null}, uses default
 * @param timeZone TimeZone to use, if {@code null}, uses default
 * @usage _advanced_method_
 */
public static DatabaseImpl create(FileFormat fileFormat, Path mdbFile,
                                  FileChannel channel, boolean autoSync,
                                  Charset charset, TimeZone timeZone)
  throws IOException
{
  FileFormatDetails details = getFileFormatDetails(fileFormat);
  if (details.getFormat().READ_ONLY) {
    throw new IOException("File format " + fileFormat +
                          " does not support writing for " + mdbFile);
  }
  if(details.getEmptyFilePath() == null) {
    throw new IOException("File format " + fileFormat +
                          " does not support file creation for " + mdbFile);
  }

  boolean closeChannel = false;
  if(channel == null) {
    channel = openChannel(mdbFile, false, true);
    closeChannel = true;
  }

  boolean success = false;
  try {
    channel.truncate(0);
    transferDbFrom(channel, getResourceAsStream(details.getEmptyFilePath()));
    channel.force(true);
    DatabaseImpl db = new DatabaseImpl(mdbFile, channel, closeChannel, autoSync,
                                       fileFormat, charset, timeZone, null,
                                       false);
    success = true;
    return db;
  } finally {
    if(!success && closeChannel) {
      // something blew up, shutdown the channel (quietly)
      ByteUtil.closeQuietly(channel);
    }
  }
}
 

public void trunk(long pos) {
    try {
        FileChannel outChan = new FileOutputStream(in, true).getChannel();
        outChan.truncate(getBufferLen(pos));
        outChan.close();
    } catch (IOException e) {
        throw new RuntimeException(e);
    }
}
 

@BeforeClass
public static void setUpOnce() {
  new File("target/test").mkdirs();
  
  try {
    FileChannel channel = FileChannel.open(path, StandardOpenOption.APPEND);
    channel.truncate(0);
    channel.close();
  } catch (IOException e) {

  }
}
 

private void truncateFiles() throws IOException {
  logger.info("{} truncating {} files", taskName, analyzer.getFileLastPositions().size());
  for (Entry<File, Long> entry : analyzer.getFileLastPositions().entrySet()) {
    File file = entry.getKey();
    Long lastPosition = entry.getValue();
    if (file.exists() && file.length() != lastPosition) {
      try (FileInputStream fileInputStream = new FileInputStream(file)) {
        FileChannel channel = fileInputStream.getChannel();
        channel.truncate(lastPosition);
        channel.close();
      }
    }
  }
  analyzer.setFileLastPositions(null);
}
 

private String readAndClearFileEntries() throws IOException {
    handler.flush();
    String currentFileName = handler.getCurrentFileName();
    String contents = Files.contentOf(new File(currentFileName), Charset.forName("UTF-8"));
    FileChannel outChan = new FileOutputStream(currentFileName, true).getChannel();
    outChan.truncate(0);
    outChan.close();
    return contents;
}
 

private void truncateFile() {
	FileChannel channel = out.getChannel();
	try {
		channel.truncate(offset);
	} catch (IOException e) {
		LOGGER.error("R:truncate file failed", e);
	}
}
 

static void truncateFileToConsistentSize(FileOutputStream fos, long size) {
    try {
        FileChannel fch = fos.getChannel();
        fch.truncate(size);
        fch.force(true);
    } catch (IOException ex) {
        Logger.getLogger(DataConsistentFileOutputStream.class.getName()).log(
                Level.INFO,
                "Not able to truncate file to the data consistent size of "+size+" bytes.",
                ex);
    }
}
 

@Test
public void testRecoveryMode() throws IOException {
  // edits generated by nnHelper (MiniDFSCluster), should have all op codes
  // binary, XML, reparsed binary
  String edits = nnHelper.generateEdits();
  FileOutputStream os = new FileOutputStream(edits, true);
  // Corrupt the file by truncating the end
  FileChannel editsFile = os.getChannel();
  editsFile.truncate(editsFile.size() - 5);

  String editsParsedXml = folder.newFile("editsRecoveredParsed.xml")
      .getAbsolutePath();
  String editsReparsed = folder.newFile("editsRecoveredReparsed")
      .getAbsolutePath();
  String editsParsedXml2 = folder.newFile("editsRecoveredParsed2.xml")
      .getAbsolutePath();

  // Can't read the corrupted file without recovery mode
  assertEquals(-1, runOev(edits, editsParsedXml, "xml", false));

  // parse to XML then back to binary
  assertEquals(0, runOev(edits, editsParsedXml, "xml", true));
  assertEquals(0, runOev(editsParsedXml, editsReparsed, "binary", false));
  assertEquals(0, runOev(editsReparsed, editsParsedXml2, "xml", false));

  // judgment time
  assertTrue("Test round trip", FileUtils.contentEqualsIgnoreEOL(
      new File(editsParsedXml), new File(editsParsedXml2), "UTF-8"));

  os.close();
}
 

@Override
public void truncate() throws IOException {
    if ( isOpen.get() ) {
        throw new IOException( "Cannot truncate while log is open for writing. Close the log then truncate." );
    }

    // Synchronize on isOpen to prevent re-opening while truncating (rare)
    synchronized ( isOpen ) {
        File results = new File( resultsFile.get() );
        FileChannel channel = new FileOutputStream( results, true ).getChannel();
        channel.truncate( 0 );
        channel.close();
        resultCount.set( 0 );
    }
}
 

@Test
public void xferTest03() throws Exception { // for bug 4559072
    byte[] srcData = new byte[] {1,2,3,4} ;

    // get filechannel for the source file.
    File source = File.createTempFile("source", null);
    source.deleteOnExit();
    RandomAccessFile raf1 = new RandomAccessFile(source, "rw");
    FileChannel fc1 = raf1.getChannel();
    fc1.truncate(0);

    // write out data to the file channel
    int bytesWritten = 0;
    while (bytesWritten < 4) {
        bytesWritten = fc1.write(ByteBuffer.wrap(srcData));
    }

    // get filechannel for the dst file.
    File dest = File.createTempFile("dest", null);
    dest.deleteOnExit();
    RandomAccessFile raf2 = new RandomAccessFile(dest, "rw");
    FileChannel fc2 = raf2.getChannel();
    fc2.truncate(0);

    fc1.transferTo(0, srcData.length + 1, fc2);

    if (fc2.size() > 4)
        throw new Exception("xferTest03 failed");

    fc1.close();
    fc2.close();
    raf1.close();
    raf2.close();

    source.delete();
    dest.delete();
}
 

@Test
public void testRecoveryMode() throws IOException {
  // edits generated by nnHelper (MiniDFSCluster), should have all op codes
  // binary, XML, reparsed binary
  String edits = nnHelper.generateEdits();
  FileOutputStream os = new FileOutputStream(edits, true);
  // Corrupt the file by truncating the end
  FileChannel editsFile = os.getChannel();
  editsFile.truncate(editsFile.size() - 5);

  String editsParsedXml = folder.newFile("editsRecoveredParsed.xml")
      .getAbsolutePath();
  String editsReparsed = folder.newFile("editsRecoveredReparsed")
      .getAbsolutePath();
  String editsParsedXml2 = folder.newFile("editsRecoveredParsed2.xml")
      .getAbsolutePath();

  // Can't read the corrupted file without recovery mode
  assertEquals(-1, runOev(edits, editsParsedXml, "xml", false));

  // parse to XML then back to binary
  assertEquals(0, runOev(edits, editsParsedXml, "xml", true));
  assertEquals(0, runOev(editsParsedXml, editsReparsed, "binary", false));
  assertEquals(0, runOev(editsReparsed, editsParsedXml2, "xml", false));

  // judgment time
  assertTrue("Test round trip", FileUtils.contentEqualsIgnoreEOL(
      new File(editsParsedXml), new File(editsParsedXml2), "UTF-8"));

  os.close();
}
 

@SuppressWarnings( "resource" )
@Override
public void copyFile(
        String sourceFile,
        String destinationFile,
        boolean failOnError ) {

    File inputFile = new File(sourceFile);
    checkFileExistence(inputFile);

    FileChannel srcChannel = null;
    FileChannel dstChannel = null;

    try {
        // Create channel on the source
        srcChannel = new FileInputStream(sourceFile).getChannel();

        // Create channel on the destination
        dstChannel = new FileOutputStream(destinationFile).getChannel();

        // Copy file contents from source to destination
        dstChannel.truncate(0);

        if (log.isDebugEnabled()) {
            log.debug("Copying file '" + sourceFile + "' of " + srcChannel.size() + "bytes to '"
                      + destinationFile + "'");
        }

        /* Copy the file in chunks.
         * If we provide the whole file at once, the copy process does not start or does not
         * copy the whole file on some systems when the file is a very large one - usually
         * bigger than 2 GBs
         */
        final long CHUNK = 16 * 1024 * 1024; // 16 MB chunks
        for (long pos = 0; pos < srcChannel.size(); ) {
            pos += dstChannel.transferFrom(srcChannel, pos, CHUNK);
        }

        if (srcChannel.size() != dstChannel.size()) {
            throw new FileSystemOperationException("Size of the destination file \"" + destinationFile
                                                   + "\" and the source file \"" + sourceFile
                                                   + "\" mismatch!");
        }

        if (osType.isUnix()) {
            // set the original file permission to the new file
            setFilePermissions(destinationFile, getFilePermissions(sourceFile));
        }

    } catch (IOException e) {
        throw new FileSystemOperationException("Unable to copy file '" + sourceFile + "' to '"
                                               + destinationFile + "'", e);
    } finally {
        // Close the channels
        IoUtils.closeStream(srcChannel,
                            "Unable to close input channel while copying file '" + sourceFile + "' to '"
                            + destinationFile + "'");
        IoUtils.closeStream(dstChannel,
                            "Unable to close destination channel while copying file '" + sourceFile
                            + "' to '" + destinationFile + "'");
    }
}