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/*
 * @(#)TransactionLogRecord.java	1.2 06/29/07
 */ 

package com.sun.messaging.jmq.util.txnlog;

/**
 * Encapsulates a log entry. Used by the TransactionLogWriter to store and 
 * retrieve as a transaction record.
 *<p>
 * Format of data for writing (48 byte header) is specified as follows:
 * <p>
 * 1. Record Magic # (int, 0-3)
 * <p>
 * 2. Record Type (int, 4-7)
 * <p>
 * 3. Record Body Size (int, 8-11)  
 * <p>
 * 4. Timestamp (long, 12-19)
 * <p>
 * 5. Record Sequence Number (long, 20-28)
 * <p>
 * 6. Check Point Sequence (long, 29-36)
 * <p>
 * 7. Record Body Check Sum (long, 37-44)
 * <p>
 * 8. Record Header Reserve (int, 45-48)
 * <p>
 * 9. Record body data (byte[], size defined in #3 above)
 *
 *<p>
 * 
 * @see TransactionLogWriter
 */

public interface TransactionLogRecord {
 
   /**
    * Get the timestamp of the log record.
    * This value is set by the TransactionLogWriter
    * when writing the entry to the log file.
    *
    * @see #setTimestamp
    * @return the timestamp that this record is created.
    */
   public long getTimestamp();
   
   /**
    * Set the timestamp for this log record.
    * This value is set by the TransactionLogWriter
    * when writing the entry to the log file.
    *
    * @see #getTimestamp
    */
   public void setTimestamp (long timestamp);

   /**
    * Get the sequence number of the log record.
    *
    * @return the sequence number of this log record.
    */
   public long getSequence();
   
   /**
    * Set the sequence number for this log record.
    * This value is set by the TransactionLogWriter
    * when writing the entry to the log file.
    *
    * @param sequenceNumber the number assigned to this 
    * log entry.
    */
   public void setSequence (long sequenceNumber);
   
   /**
    * Get the check point sequence number.  The
    * value is assigned by the TransactionLogWriter
    * right before TransactionLogWriter.write()
    * returns.
    * <p>
    * All records added after a check point contains the same 
    * check point sequence number until a new checkpoint is
    * called.
    * <p>
    * @see TransactionLogWriter#write
    *
    * @return the assigned check point sequence.
    * 
    */
   public long getCheckPointSequence ();

   /**
    * Set the specified check point sequence to the log
    * entry.
    * <p>
    * Each log record is assigned the same check point sequence
    * number until a new checkpoint is called.
    * <p>
    *
    * @see TransactionLogWriter#write
    */
   public void setCheckPointSequence (long cpSequence);
   
   /**
    * Get the record type of the log entry.
    *  
    * @see TransactionLogType
    * @return the type of the log record. 
    */
   public int getType();
   
   /**
    * Set the entry type of this log record.
    * @param type the transaction type of this log entry.
    */
   public void setType(int type);

   /**
    *  Set the log record body bytes to this log record.
    */
   public void setBody(byte[] body);

   /** 
    * Get the log record body bytes from this log entry.
    *
    * @return the body data of this entry.
    */
   public byte[] getBody();
   
   /** 
    * Get the associated exception for this log entry.
    *
    * @return the body data of this entry.
    */
   public Exception getException();
   
   /**
    * Set the associated exception for this log entry.
    * @param exception the exception for this log entry.
    */
   public void setException(Exception exception);

   /**
    * Get the written flag for this log entry.
    * @return true if this record has been written to the log.
    */
   public boolean isWritten();
   
   /**
    * Set the written flag for this log entry.
   * @param flag the written flag for this log entry.
    */
   public void setWritten(boolean flag);

}

