| /*------------------------------------------------------------------------- |
| * |
| * shmem.h |
| * shared memory management structures |
| * |
| * Historical note: |
| * A long time ago, Postgres' 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) 1996-2009, PostgreSQL Global Development Group |
| * Portions Copyright (c) 1994, Regents of the University of California |
| * |
| * $PostgreSQL: pgsql/src/include/storage/shmem.h,v 1.49 2006/10/15 22:04:08 tgl Exp $ |
| * |
| *------------------------------------------------------------------------- |
| */ |
| #ifndef SHMEM_H |
| #define SHMEM_H |
| |
| #include "utils/hsearch.h" |
| #include "utils/size.h" |
| |
| /* |
| * The shared memory region can start at a different address |
| * in every process. Shared memory "pointers" are actually |
| * offsets relative to the start of the shared memory region(s). |
| * |
| * In current usage, this is not actually a problem, but we keep |
| * the code that used to handle it... |
| */ |
| typedef unsigned long SHMEM_OFFSET; |
| |
| #define INVALID_OFFSET (-1) |
| #define BAD_LOCATION (-1) |
| |
| /* |
| * Start of the primary shared memory region, in this process' address space. |
| * The macros in this header file can only cope with offsets into this |
| * shared memory region! |
| */ |
| extern PGDLLIMPORT SHMEM_OFFSET ShmemBase; |
| |
| |
| /* coerce an offset into a pointer in this process's address space */ |
| #define MAKE_PTR(xx_offs)\ |
| (ShmemBase+((unsigned long)(xx_offs))) |
| |
| /* coerce a pointer into a shmem offset */ |
| #define MAKE_OFFSET(xx_ptr)\ |
| ((SHMEM_OFFSET) (((unsigned long)(xx_ptr))-ShmemBase)) |
| |
| #define SHM_PTR_VALID(xx_ptr)\ |
| (((unsigned long)(xx_ptr)) > ShmemBase) |
| |
| /* cannot have an offset to ShmemFreeStart (offset 0) */ |
| #define SHM_OFFSET_VALID(xx_offs)\ |
| (((xx_offs) != 0) && ((xx_offs) != INVALID_OFFSET)) |
| |
| /* shmqueue.c */ |
| typedef struct SHM_QUEUE |
| { |
| SHMEM_OFFSET prev; |
| SHMEM_OFFSET next; |
| } SHM_QUEUE; |
| |
| /* shmem.c */ |
| extern void InitShmemAccess(void *seghdr); |
| extern void InitShmemAllocation(void); |
| extern void *ShmemAlloc(Size size); |
| extern bool ShmemIsValid(unsigned long 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); |
| |
| /* 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) |
| /* max size of the shmem index table (not a hard limit) */ |
| #define SHMEM_INDEX_SIZE (40) |
| |
| /* this is a hash bucket in the shmem index table */ |
| typedef struct |
| { |
| char key[SHMEM_INDEX_KEYSIZE]; /* string name */ |
| unsigned long location; /* location in shared mem */ |
| unsigned long size; /* numbytes allocated for the structure */ |
| } ShmemIndexEnt; |
| |
| /* |
| * prototypes for functions in shmqueue.c |
| */ |
| extern void SHMQueueInit(SHM_QUEUE *queue); |
| extern bool SHMQueueIsDetached(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 Pointer SHMQueueNext(SHM_QUEUE *queue, SHM_QUEUE *curElem, |
| Size linkOffset); |
| extern bool SHMQueueEmpty(SHM_QUEUE *queue); |
| |
| #endif /* SHMEM_H */ |