Class CheckpointingLogger

java.lang.Object
java.io.OutputStream
org.ka2ddo.yaac.util.CheckpointingLogger
All Implemented Interfaces:
Closeable, Flushable, AutoCloseable

public class CheckpointingLogger extends OutputStream
This class defines a rolling logger that checkpoints the last N bytes of a log file to a disk file.
Author:
Andrew Pavlin, KA2DDO
  • Constructor Summary

    Constructors
    Constructor
    Description
    CheckpointingLogger(int bufSize, File logFile)
    Create a CheckpointingLogger stream with the specified maximum file size and path to the file.
  • Method Summary

    Modifier and Type
    Method
    Description
    void
    Closes this output stream and releases any system resources associated with this stream.
    void
    Flushes this output stream and forces any buffered output bytes to be written out.
    void
    Really flush this output stream and forces any buffered output bytes to be written out.
    int
    Get the last-written size of the log file.
    int
    Get the current position in the buffer for the next character to write (may be end of buffer).
    Get the current contents of the logger's buffer.
    Report the pathname of the file where this logger will checkpoint the log data.
    int
    Return the maximum number of bytes this logger can hold.
    void
    write(byte[] b, int off, int len)
    Writes len bytes from the specified byte array starting at offset off to this output stream.
    void
    write(int b)
    Writes the specified byte to this output stream.

    Methods inherited from class java.io.OutputStream

    nullOutputStream, write

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Constructor Details

    • CheckpointingLogger

      public CheckpointingLogger(int bufSize, File logFile)
      Create a CheckpointingLogger stream with the specified maximum file size and path to the file.
      Parameters:
      bufSize - int maximum file size in bytes
      logFile - File pointing to where the data should be checkpointed
  • Method Details

    • close

      public void close() throws IOException
      Closes this output stream and releases any system resources associated with this stream. The general contract of close is that it closes the output stream. A closed stream cannot perform output operations and cannot be reopened.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Overrides:
      close in class OutputStream
      Throws:
      IOException - if an I/O error occurs.
    • write

      public void write(byte[] b, int off, int len) throws IOException
      Writes len bytes from the specified byte array starting at offset off to this output stream. The general contract for write(b, off, len) is that some of the bytes in the array b are written to the output stream in order; element b[off] is the first byte written and b[off+len-1] is the last byte written by this operation.

      If b is null, a NullPointerException is thrown.

      If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

      Overrides:
      write in class OutputStream
      Parameters:
      b - the data.
      off - the start offset in the data.
      len - the number of bytes to write.
      Throws:
      IOException - if an I/O error occurs. In particular, an IOException is thrown if the output stream is closed.
    • write

      public void write(int b) throws IOException
      Writes the specified byte to this output stream. The general contract for write is that one byte is written to the output stream. The byte to be written is the eight low-order bits of the argument b. The 24 high-order bits of b are ignored.
      Specified by:
      write in class OutputStream
      Parameters:
      b - the byte.
      Throws:
      IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.
    • flush

      public void flush()
      Flushes this output stream and forces any buffered output bytes to be written out. The general contract of flush is that calling it is an indication that, if any bytes previously written have been buffered by the implementation of the output stream, such bytes should immediately be written to their intended destination.

      If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive.

      Specified by:
      flush in interface Flushable
      Overrides:
      flush in class OutputStream
    • flushImpl

      public void flushImpl() throws IOException
      Really flush this output stream and forces any buffered output bytes to be written out.
      Throws:
      IOException - if an I/O error occurs.
    • getLogPathName

      public String getLogPathName()
      Report the pathname of the file where this logger will checkpoint the log data.
      Returns:
      absolute pathname of log file
    • getLoggerContents

      public String getLoggerContents()
      Get the current contents of the logger's buffer.
      Returns:
      the String contents of the log buffer
    • getFileLength

      public int getFileLength()
      Get the last-written size of the log file.
      Returns:
      file size in bytes
    • getLength

      public int getLength()
      Get the current position in the buffer for the next character to write (may be end of buffer).
      Returns:
      current length of buffer contents
    • getMaxSize

      public int getMaxSize()
      Return the maximum number of bytes this logger can hold.
      Returns:
      byte size of logger's buffer