Class LogBufferElement

java.lang.Object
org.apache.derby.impl.store.replication.buffer.LogBufferElement
class LogBufferElement extends Object
ReplicationLogBuffer consists of n LogBufferElements, each of which can store a number of log records in a single byte[].

The format of each log record in the LogBufferElement is the same as is written to log file in LogAccessFile:
(int) total_length (data[].length + optionaldata[].length)
(long) instant
(byte[]) data+optionaldata
(int) total_length

In addition to adding a chunk of log records to the byte[], the greatestInstant variable is updated for every append so that getLastInstant can be used to get the highest log instant in this LogBufferElement.

  • Field Details

    • bufferdata

      private final byte[] bufferdata

    • position

      private int position

    • greatestInstant

      private long greatestInstant

    • recycleMe

      private boolean recycleMe

  • Constructor Details

    • LogBufferElement

      protected LogBufferElement(int bufferSize)

  • Method Details

    • init

      protected void init()
      Resets all variables to default values. Should be called before a LogBufferElement is reused.

    • appendLog

      protected void appendLog(long greatestInstant, byte[] log, int logOffset, int logLength)
      Append a chunk of log records to this LogBufferElement.
      Parameters:
      greatestInstant - the instant of the log record that was added last to this chunk of log
      log - the chunk of log records
      logOffset - offset in log to start copy from
      logLength - number of bytes to copy, starting from logOffset

    • getData

      protected byte[] getData()
      Returns:
      A byte[] representation of the log records appended to this LogBufferElement

    • getLastInstant

      protected long getLastInstant()
      Returns:
      The highest log instant appended to this LogBufferElement

    • freeSize

      protected int freeSize()
      Returns:
      Number of unused bytes in this LogBufferElement

    • size

      protected int size()
      Returns:
      Number of used bytes in this LogBufferElement

    • isRecyclable

      protected boolean isRecyclable()
      Returns:
      true if this LogBufferElement should be reused, i.e. added to freeBuffers after being consumed.

    • setRecyclable

      protected void setRecyclable(boolean r)

    • appendBytes

      private int appendBytes(byte[] b, int offset, int pos, int length)
      Append a byte[] to this LogBufferElement.
      Parameters:
      b - where the bytes are copied from
      offset - offset in b to start copying from
      pos - the position in this LogBufferElement to start copying to
      length - number of bytes to copy from b, starting from offset
      Returns:
      new position