/* -------------------------------------------------------------------------
 *
 * shmem.h
 *	  shared memory management structures
 *
 * Historical note:
 * A long time ago, openGauss' shared memory region was allowed to be mapped
 * at a different address in each process, and shared memory "pointers" were
 * passed around as offsets relative to the start of the shared memory region.
 * That is no longer the case: each process must map the shared memory region
 * at the same address.  This means shared memory pointers can be passed
 * around directly between different processes.
 *
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/shmem.h
 *
 * -------------------------------------------------------------------------
 */
#ifndef SHMEM_H
#define SHMEM_H

#include "utils/hsearch.h"

/* shmqueue.c */
typedef struct SHM_QUEUE {
    struct SHM_QUEUE* prev;
    struct SHM_QUEUE* next;
} SHM_QUEUE;

/* shmem.c */
extern void InitShmemAccess(void* seghdr);
extern void InitShmemAllocation(void);
extern void* ShmemAlloc(Size size);
extern bool ShmemAddrIsValid(const void* addr);
extern void InitShmemIndex(void);
extern HTAB* ShmemInitHash(const char* name, long init_size, long max_size, HASHCTL* infoP, int hash_flags);
extern void* ShmemInitStruct(const char* name, Size size, bool* foundPtr);
extern Size add_size(Size s1, Size s2);
extern Size mul_size(Size s1, Size s2);

/* ipci.c */
extern void RequestAddinShmemSpace(Size size);

/* size constants for the shmem index table */
/* max size of data structure string name */
#define SHMEM_INDEX_KEYSIZE (48)
/* estimated size of the shmem index table (not a hard limit) */
#define SHMEM_INDEX_SIZE (64)

/* this is a hash bucket in the shmem index table */
typedef struct {
    char key[SHMEM_INDEX_KEYSIZE]; /* string name */
    void* location;                /* location in shared mem */
    Size size;                     /* # bytes allocated for the structure */
} ShmemIndexEnt;

/*
 * prototypes for functions in shmqueue.c
 */
extern void SHMQueueInit(SHM_QUEUE* queue);
extern void SHMQueueElemInit(SHM_QUEUE* queue);
extern void SHMQueueDelete(SHM_QUEUE* queue);
extern void SHMQueueInsertBefore(SHM_QUEUE* queue, SHM_QUEUE* elem);
extern void SHMQueueInsertAfter(SHM_QUEUE* queue, SHM_QUEUE* elem);
extern Pointer SHMQueueNext(const SHM_QUEUE* queue, const SHM_QUEUE* curElem, Size linkOffset);
extern Pointer SHMQueuePrev(const SHM_QUEUE* queue, const SHM_QUEUE* curElem, Size linkOffset);
extern bool SHMQueueEmpty(const SHM_QUEUE* queue);
extern bool SHMQueueIsDetached(const SHM_QUEUE* queue);

// Heap memory allocation
//
extern void* HeapMemAlloc(Size size);
extern HTAB* HeapMemInitHash(const char* name, long init_size, long max_size, HASHCTL* infoP, int hash_flags);
extern void HeapMemResetHash(HTAB* hashtbl, const char* tabname);

#endif /* SHMEM_H */