org.ka2ddo.yaac.util

Class CheckpointingLogger

java.lang.Object

java.io.OutputStream

org.ka2ddo.yaac.util.CheckpointingLogger

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

public class CheckpointingLogger
extends java.io.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 and Description
CheckpointingLogger(int bufSize, java.io.File logFile) Create a CheckpointingLogger stream with the specified maximum file size and path to the file.

Method Summary

Modifier and Type	Method and Description
void	close() Closes this output stream and releases any system resources associated with this stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out.
void	flushImpl() Really flush this output stream and forces any buffered output bytes to be written out.
int	getFileLength() Get the last-written size of the log file.
int	getLength() Get the current position in the buffer for the next character to write (may be end of buffer).
java.lang.String	getLoggerContents() Get the current contents of the logger's buffer.
java.lang.String	getLogPathName() Report the pathname of the file where this logger will checkpoint the log data.
int	getMaxSize() 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

write

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CheckpointingLogger

public CheckpointingLogger(int bufSize,
                           java.io.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 Detail

close

public void close()
           throws java.io.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 java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.OutputStream

Throws:

java.io.IOException - if an I/O error occurs.

write

public void write(byte[] b,
                  int off,
                  int len)
           throws java.io.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 java.io.OutputStream

Parameters:

b - the data.

off - the start offset in the data.

len - the number of bytes to write.

Throws:

java.io.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 java.io.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 java.io.OutputStream

Parameters:

b - the byte.

Throws:

java.io.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 java.io.Flushable

Overrides:

flush in class java.io.OutputStream

flushImpl

public void flushImpl()
               throws java.io.IOException

Really flush this output stream and forces any buffered output bytes to be written out.

Throws:

java.io.IOException - if an I/O error occurs.

getLogPathName

public java.lang.String getLogPathName()

Report the pathname of the file where this logger will checkpoint the log data.

Returns:

absolute pathname of log file

getLoggerContents

public java.lang.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