/*-------------------------------------------------------------------------
 *
 * sinvaladt.h--
 *    POSTGRES shared cache invalidation segment definitions.
 *
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 * $Id: sinvaladt.h,v 1.3 1996/11/05 06:11:06 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef SINVALADT_H
#define SINVALADT_H

#include <storage/itemptr.h>
#include <storage/ipc.h>
 
/*
 * The structure of the shared cache invaidation segment
 *
 */
/*
A------------- Header info --------------
    criticalSectionSemaphoreId
    generalSemaphoreId
    startEntrySection   (offset a)
    endEntrySection     (offset a + b)
    startFreeSpace      (offset relative to B)
    startEntryChain     (offset relatiev to B)
    endEntryChain       (offset relative to B)
    numEntries
    maxNumEntries
    procState[MaxBackendId] --> limit
				resetState (bool)
a				tag (POSTID)
B------------- Start entry section -------
    SISegEntry  --> entryData --> ... (see  SharedInvalidData!)
                    isfree  (bool)
                    next  (offset to next entry in chain )
b     .... (dynamically growing down)
C----------------End shared segment -------  

*/

/* Parameters (configurable)  *******************************************/
#define MaxBackendId 32      	    /* maximum number of backends   	*/
#define MAXNUMMESSAGES 1000 	    /* maximum number of messages in seg*/


#define	InvalidOffset	1000000000  /* a invalid offset  (End of chain)	*/

typedef struct ProcState {
    int 	limit;      	/* the number of read messages	    	*/
    bool 	resetState; 	/* true, if backend has to reset its state */
    int		tag;		/* special tag, recieved from the postmaster */
} ProcState;


typedef struct SISeg {
    IpcSemaphoreId  	criticalSectionSemaphoreId; /* semaphore id     */
    IpcSemaphoreId  	generalSemaphoreId; 	    /* semaphore id     */
    Offset      startEntrySection;  	/* (offset a)	    	    	*/
    Offset      endEntrySection;    	/* (offset a + b)   	    	*/
    Offset      startFreeSpace;	    	/* (offset relative to B)   	*/
    Offset      startEntryChain;    	/* (offset relative to B)   	*/
    Offset      endEntryChain;          /* (offset relative to B)   	*/
    int         numEntries;
    int         maxNumEntries;
    ProcState   procState[MaxBackendId]; /* reflects the invalidation state */
    /* here starts the entry section, controlled by offsets */
} SISeg;
#define SizeSISeg     sizeof(SISeg)

typedef struct SharedInvalidData {
    int	    	    	cacheId;    /* XXX */
    Index   	    	hashIndex;
    ItemPointerData 	pointerData;
} SharedInvalidData;

typedef SharedInvalidData   *SharedInvalid;


typedef struct SISegEntry {
    SharedInvalidData	entryData;  	    	    /* the message data */
    bool                isfree;	    	    	    /* entry free? */
    Offset  	    	next;	    	    	    /* offset to next entry*/
} SISegEntry;

#define SizeOfOneSISegEntry   sizeof(SISegEntry)
    
typedef struct SISegOffsets {
    Offset  startSegment;   	    	/* always 0 (for now) */
    Offset  offsetToFirstEntry;         /* A + a = B */
    Offset  offsetToEndOfSegemnt;       /* A + a + b */
} SISegOffsets;


/****************************************************************************/
/* synchronization of the shared buffer access	    	    	    	    */
/*    access to the buffer is synchronized by the lock manager !!   	    */
/****************************************************************************/

#define SI_LockStartValue  255
#define SI_SharedLock     (-1)
#define SI_ExclusiveLock  (-255)

extern SISeg *shmInvalBuffer;	

/*
 * prototypes for functions in sinvaladt.c
 */
extern int SIBackendInit(SISeg *segInOutP);
extern int SISegmentInit(bool killExistingSegment, IPCKey key);

extern bool SISetDataEntry(SISeg *segP, SharedInvalidData  *data);
extern void SISetProcStateInvalid(SISeg *segP);
extern bool SIDelDataEntry(SISeg *segP);
extern void SIReadEntryData(SISeg *segP, int backendId,
		void (*invalFunction)(), void (*resetFunction)());
extern void SIDelExpiredDataEntries(SISeg *segP);

#endif	/* SINVALADT_H */
