1 /*-------------------------------------------------------------------------
4 * shared memory management structures
7 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * $PostgreSQL: pgsql/src/include/storage/shmem.h,v 1.44 2004/12/31 22:03:42 pgsql Exp $
12 *-------------------------------------------------------------------------
17 #include "utils/hsearch.h"
21 * The shared memory region can start at a different address
22 * in every process. Shared memory "pointers" are actually
23 * offsets relative to the start of the shared memory region(s).
25 * In current usage, this is not actually a problem, but we keep
26 * the code that used to handle it...
28 typedef unsigned long SHMEM_OFFSET;
30 #define INVALID_OFFSET (-1)
31 #define BAD_LOCATION (-1)
34 * Start of the primary shared memory region, in this process' address space.
35 * The macros in this header file can only cope with offsets into this
36 * shared memory region!
38 extern DLLIMPORT SHMEM_OFFSET ShmemBase;
41 /* coerce an offset into a pointer in this process's address space */
42 #define MAKE_PTR(xx_offs)\
43 (ShmemBase+((unsigned long)(xx_offs)))
45 /* coerce a pointer into a shmem offset */
46 #define MAKE_OFFSET(xx_ptr)\
47 ((SHMEM_OFFSET) (((unsigned long)(xx_ptr))-ShmemBase))
49 #define SHM_PTR_VALID(xx_ptr)\
50 (((unsigned long)(xx_ptr)) > ShmemBase)
52 /* cannot have an offset to ShmemFreeStart (offset 0) */
53 #define SHM_OFFSET_VALID(xx_offs)\
54 (((xx_offs) != 0) && ((xx_offs) != INVALID_OFFSET))
57 typedef struct SHM_QUEUE
64 extern void InitShmemAllocation(void *seghdr, bool init);
65 extern void *ShmemAlloc(Size size);
66 extern bool ShmemIsValid(unsigned long addr);
67 extern void InitShmemIndex(void);
68 extern HTAB *ShmemInitHash(const char *name, long init_size, long max_size,
69 HASHCTL *infoP, int hash_flags);
70 extern void *ShmemInitStruct(const char *name, Size size, bool *foundPtr);
73 /* size constants for the shmem index table */
74 /* max size of data structure string name */
75 #define SHMEM_INDEX_KEYSIZE (48)
76 /* max size of the shmem index table (not a hard limit) */
77 #define SHMEM_INDEX_SIZE (32)
79 /* this is a hash bucket in the shmem index table */
82 char key[SHMEM_INDEX_KEYSIZE]; /* string name */
83 unsigned long location; /* location in shared mem */
84 unsigned long size; /* numbytes allocated for the structure */
88 * prototypes for functions in shmqueue.c
90 extern void SHMQueueInit(SHM_QUEUE *queue);
91 extern void SHMQueueElemInit(SHM_QUEUE *queue);
92 extern void SHMQueueDelete(SHM_QUEUE *queue);
93 extern void SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem);
94 extern Pointer SHMQueueNext(SHM_QUEUE *queue, SHM_QUEUE *curElem,
96 extern bool SHMQueueEmpty(SHM_QUEUE *queue);