/*---
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and license this software and its documentation for any purpose,
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FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
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GOVERNMENT USE: If you are acquiring this software on behalf of the
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the software and related documentation as defined in the Federal
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---*/

/**
 * @file
 *
 * New version of logger.  Based on logger.h
 * 
 * $Id$
 * 
 */


#ifndef __LOGGER2_H__
#define __LOGGER2_H__

#include <lladd/operations.h>

/**
   A callback function that allows logHandle's iterator to stop
   returning log entries depending on the context in which it was
   called.
*/
typedef int (guard_fcn_t)(const LogEntry *, void *);

typedef struct { 
  /** The LSN of the last log entry returned.*/
  /*  lsn_t       file_offset; */ /* Unneeded? */
  /** The LSN of the log entry that we would return if next is called. */
  lsn_t       next_offset; 
  /** The LSN of the log entry that we would return if previous is called. */
  lsn_t       prev_offset;
  guard_fcn_t * guard;
  void * guard_state;
} LogHandle;

/**
   Contains the state needed by the logging layer to perform
   operations on a transaction.
 */
typedef struct {
  int xid; 
  lsn_t prevLSN;
  lsn_t recLSN;
  LogHandle lh;
} TransactionLog;

#define LOG_TO_FILE   0
#define LOG_TO_MEMORY 1

extern int loggerType;

int  LogInit(int logType);

int  LogDeinit();


void LogForce(lsn_t lsn);
void LogTruncate(lsn_t lsn);
lsn_t LogFlushedLSN();


lsn_t LogTruncationPoint();

const LogEntry * LogReadLSN(lsn_t lsn);

/**
   Inform the logging layer that a new transaction has begun.
   Currently a no-op.
*/
TransactionLog LogTransBegin(int xid);

/**
  Write a transaction COMMIT to the log tail, then flush the log tail immediately to disk

  @return The lsn of the commit log entry.  
*/
lsn_t LogTransCommit(TransactionLog * l);

/**
  Write a transaction ABORT to the log tail

  @return The lsn of the abort log entry.
*/
lsn_t LogTransAbort(TransactionLog * l);

/**
  LogUpdate writes an UPDATE log record to the log tail
*/
LogEntry * LogUpdate(TransactionLog * l, Page * p, recordid rid, int operation, const byte * args);

/**
   Whenever a LogEntry is returned by a function that is defined by
   logger2.h or logHandle.h, the caller should eventually call this
   function to release any resources held by that entry.
   
   @todo The 'const' modifier on FreeLogEntry's parameter is a hack;
   for some log types (in memory) it is very important that the caller
   does not modify LogEntries returned by this API, so we always
   return 'const' pointers to callers.  The implementation of
   FreeLogEntry knows whether the const is important, and ignores it
   if appropriate, so const isn't really the right concept...
*/
void FreeLogEntry(const LogEntry * e);

/**
   Write a compensation log record.  These records are used to allow
   for efficient recovery, and possibly for log truncation.  They
   record the completion of undo operations, amongst other things.

   @return the lsn of the CLR entry that was written to the log.
   (Needed so that the lsn slot of the page in question can be
   updated.)  
*/
//lsn_t LogCLR (LogEntry * undone);
lsn_t LogCLR(int xid, lsn_t LSN, recordid rid, lsn_t prevLSN);

/**
   Write a end transaction record @see XEND

   @todo Implement LogEnd
*/
void LogEnd (TransactionLog * l);

/** 
  (For internal use only..)
*/
void genericLogWrite(LogEntry * e);

#endif