stasis-aries-wal/stasis/logger/logger2.h

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/**
 * @file
 *
 * Interface to Stasis' log file.
 *
 * @ingroup LOGGING_DISCIPLINE
 * 
 * $Id$
 * 
 */


#ifndef __LOGGER2_H__
#define __LOGGER2_H__

#include <stasis/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 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;
} TransactionLog;

/** 
    This is the log implementation that is being used.  
    
    Before Stasis is intialized it will be set to a default value.    
    It may be changed before Tinit() is called by assigning to it.
    The default can be overridden at compile time by defining
    USE_LOGGER.

    (eg: gcc ... -DUSE_LOGGER=LOG_TO_FOO)

    @see constants.h for a list of recognized log implementations. 
         (The constants are named LOG_TO_*)

 */
extern int loggerType;

int  LogInit(int logType);
int  LogDeinit();
void LogForce(lsn_t lsn);
/** 
    @param lsn The first lsn that will be available after truncation.
*/ 
void LogTruncate(lsn_t lsn);

/** This function is guaranteed to return the LSN of the most recent
    log entry that has not been flushed to disk.  (If the entire log
    is flushed, this function returns the LSN of the entry that will
    be allocated the next time the log is appended to. */
lsn_t LogFlushedLSN();
/** Returns the LSN of the first entry of the log, or the LSN of the
    next to be allocated if the log is empty) */
lsn_t LogTruncationPoint();
/** Read a log entry, given its LSN.
    @param lsn  The lsn of the log entry to be read.
*/
const LogEntry * LogReadLSN(lsn_t lsn);
/**
   Given a log entry, return the LSN of the next entry.
*/
lsn_t LogNextEntry(const LogEntry * e);

/**
   Inform the logging layer that a new transaction has begun, and
   obtain a handle.
*/
TransactionLog LogTransBegin(int xid);

/**
  Write a transaction COMMIT to the log tail.  Blocks until the commit
  record is stable.

  @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 UPDATELOG log record to the log tail.  It also interprets
  its operation argument to the extent necessary for allocating and laying out 
  the log entry.  Finally, it updates the state of the parameter l.
*/
LogEntry * LogUpdate(TransactionLog * l, Page * p, recordid rid, int operation,
		     const byte * args);

/**
   Any LogEntry that is returned by a function in logger2.h or
   logHandle.h should be freed using this function.

   @param e The log entry to be freed.  (The "const" here is a hack
            that allows LogReadLSN to return a const *.
*/
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(const LogEntry * e);

lsn_t LogDummyCLR(int xid, lsn_t prevLSN);

/**
   Write a end transaction record @see XEND

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

/**
   Needed by sizeofLogEntry
*/
long LoggerSizeOfInternalLogEntry(const LogEntry * e);

/** 
   For internal use only...  This would be static, but it is called by
   the test cases.
*/
void LogWrite(LogEntry * e);

#endif