codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * pg_shmem.h4 *	  Platform-independent API for shared memory support.5 *6 * Every port is expected to support shared memory with approximately7 * SysV-ish semantics; in particular, a memory block is not anonymous8 * but has an ID, and we must be able to tell whether there are any9 * remaining processes attached to a block of a specified ID.10 *11 * To simplify life for the SysV implementation, the ID is assumed to12 * consist of two unsigned long values (these are key and ID in SysV13 * terms).  Other platforms may ignore the second value if they need14 * only one ID number.15 *16 *17 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group18 * Portions Copyright (c) 1994, Regents of the University of California19 *20 * src/include/storage/pg_shmem.h21 *22 *-------------------------------------------------------------------------23 */24#ifndef PG_SHMEM_H25#define PG_SHMEM_H26 27#include "storage/dsm_impl.h"28 29typedef struct PGShmemHeader	/* standard header for all Postgres shmem */30{31	int32		magic;			/* magic # to identify Postgres segments */32#define PGShmemMagic  67983489433	pid_t		creatorPID;		/* PID of creating process (set but unread) */34	Size		totalsize;		/* total size of segment */35	Size		freeoffset;		/* offset to first free space */36	dsm_handle	dsm_control;	/* ID of dynamic shared memory control seg */37	void	   *index;			/* pointer to ShmemIndex table */38#ifndef WIN32					/* Windows doesn't have useful inode#s */39	dev_t		device;			/* device data directory is on */40	ino_t		inode;			/* inode number of data directory */41#endif42} PGShmemHeader;43 44/* GUC variables */45extern PGDLLIMPORT int shared_memory_type;46extern PGDLLIMPORT int huge_pages;47extern PGDLLIMPORT int huge_page_size;48 49/* Possible values for huge_pages */50typedef enum51{52	HUGE_PAGES_OFF,53	HUGE_PAGES_ON,54	HUGE_PAGES_TRY55}			HugePagesType;56 57/* Possible values for shared_memory_type */58typedef enum59{60	SHMEM_TYPE_WINDOWS,61	SHMEM_TYPE_SYSV,62	SHMEM_TYPE_MMAP63}			PGShmemType;64 65#ifndef WIN3266extern PGDLLIMPORT unsigned long UsedShmemSegID;67#else68extern PGDLLIMPORT HANDLE UsedShmemSegID;69extern PGDLLIMPORT void *ShmemProtectiveRegion;70#endif71extern PGDLLIMPORT void *UsedShmemSegAddr;72 73#if !defined(WIN32) && !defined(EXEC_BACKEND)74#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_MMAP75#elif !defined(WIN32)76#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_SYSV77#else78#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_WINDOWS79#endif80 81#ifdef EXEC_BACKEND82extern void PGSharedMemoryReAttach(void);83extern void PGSharedMemoryNoReAttach(void);84#endif85 86extern PGShmemHeader *PGSharedMemoryCreate(Size size,87										   PGShmemHeader **shim);88extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);89extern void PGSharedMemoryDetach(void);90extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags);91 92#endif							/* PG_SHMEM_H */93