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/*------------------------------------------------------------------------- * * 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) 1996-2012, 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); #endif /* SHMEM_H */