/*---
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---*/
/**
 * @file
 * Manages the page buffer

    pageManager - Provides cached page handling, delegates to blob
    manager when necessary.  Doesn't implement an eviction policy.
    That is left to a cacheManager.  (Multiple cacheManagers can be
    used with a single page manager.)

 
  @todo Allow error checking!  
 
  @todo Make linux provide a better version of malloc().  We need to
  directly DMA pages into and out of userland, or setup mmap() so
  that it takes a flag that makes it page mmapped() pages to swap
  instead of back to disk. (munmap() and msync() would still hit the
  on-disk copy)
 
  @todo Refactoring for lock manager
 
  Possible interface for lockManager:

       Define three classes of objects that the lock manager is interested in:

         Transactions,
	 Operations,
	 Predicates.

       LLADD already has operations and transactions, and these can be
       relatively unchanged.  Predicates are read only operations that
       return a set of tuples.  Tread() is the simplest predicate.
       Index scans provide a motivating example.  

       See http://research.microsoft.com/%7Eadya/pubs/icde00.pdf
       (Generalized Isolation Level Definitions, Adya, Liskov, O'Neil,
       2000) for a theoretical discussion of general locking schemes..

       Locking functions can return errors such as DEADLOCK, etc.
       When such a value is returned, the transaction aborts, and an
       error is passed up to the application.

 * @ingroup LLADD_CORE
 * $Id$
 */

#ifndef __BUFFERMANAGER_H__
#define __BUFFERMANAGER_H__


#include <lladd/constants.h>
#include <lladd/transactional.h>
/**
 * initialize buffer manager
 * @return 0 on success
 * @return error code on failure
 */
int bufInit();

/**
 * allocate a record.  This must be done in two phases.  The first
 * phase reserves a slot, and produces a log entry.  The second phase
 * sets up the slot according to the contents of the log entry.
 *
 * Ralloc implements the first phase.
 *
 * @param xid The active transaction.
 * @param size The size of the new record
 * @return allocated record
 *
 * @see slotRalloc the implementation of the second phase.
 */
recordid ralloc(int xid, long size);


/**
 * allocate a record at a given slot.  (Useful for recovery.)
 * 
 * @see ralloc
 */
void slotRalloc(int pageid, lsn_t lsn, recordid rid);

/**
 * @param pageid ID of page you want to read
 * @return LSN found on disk
 */
long readLSN(int pageid);

/**
 * @param xid transaction id @param lsn the lsn that the updated
 * record will reflect.  This is needed by recovery, and undo.  (The
 * lsn of a page must always increase.  Undos are handled by passing
 * in the LSN of the CLR that records the undo.)
 *
 * @param rid recordid where you want to write @param dat data you
 * wish to write
 */
void writeRecord(int xid, lsn_t lsn, recordid rid, const void *dat);

/**
 * @param xid transaction ID
 * @param rid
 * @param dat buffer for data
 */
void readRecord(int xid, recordid rid, void *dat);

/**
 * all actions necessary when committing a transaction. Can assume that the log
 * has been written as well as any other actions that do not depend on the
 * buffer manager
 *
 * Basicly, this call is here because we used to do copy on write, and
 * it might be useful when locking is implemented.
 *
 * @param xid transaction ID
 * @param lsn the lsn at which the transaction aborted.  (Currently
 * unused, but may be useful for other implementations of the buffer
 * manager.)
 * @return 0 on success
 * @return error code on failure
 */
int bufTransCommit(int xid, lsn_t lsn);

/**
 * 
 * Currently identical to bufTransCommit.
 * 
 * @param xid transaction ID 
 * 
 * @param lsn the lsn at which the transaction aborted.  (Currently
 * unused, but may be useful for other implementations of the buffer
 * manager.)
 *
 * @return 0 on success
 *  
 * @return error code on failure
 */
int bufTransAbort(int xid, lsn_t lsn);

/**
 * will write out any dirty pages, assumes that there are no running
 * transactions
 */
void bufDeinit();

void setSlotType(int pageid, int slot, int type);

void addPendingEvent(int pageid);
void removePendingEvent(int pageid);

#endif