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Robert Haas authored
This interface is intended to make it simple to divide a dynamic shared memory segment into different regions with distinct purposes. It therefore serves much the same purpose that ShmemIndex accomplishes for the main shared memory segment, but it is intended to be more lightweight. Patch by me. Review by Andres Freund.
Robert Haas authoredThis interface is intended to make it simple to divide a dynamic shared memory segment into different regions with distinct purposes. It therefore serves much the same purpose that ShmemIndex accomplishes for the main shared memory segment, but it is intended to be more lightweight. Patch by me. Review by Andres Freund.
shm_toc.h 2.00 KiB
/*-------------------------------------------------------------------------
*
* shm_toc.h
* shared memory segment table of contents
*
* This is intended to provide a simple way to divide a chunk of shared
* memory (probably dynamic shared memory allocated via dsm_create) into
* a number of regions and keep track of the addreses of those regions or
* key data structures within those regions. This is not intended to
* scale to a large number of keys and will perform poorly if used that
* way; if you need a large number of pointers, store them within some
* other data structure within the segment and only put the pointer to
* the data structure itself in the table of contents.
*
* Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/storage/shm_toc.h
*
*-------------------------------------------------------------------------
*/
#ifndef SHM_TOC_H
#define SHM_TOC_H
#include "storage/shmem.h"
struct shm_toc;
typedef struct shm_toc shm_toc;
extern shm_toc *shm_toc_create(uint64 magic, void *address, Size nbytes);
extern shm_toc *shm_toc_attach(uint64 magic, void *address);
extern void *shm_toc_allocate(shm_toc *toc, Size nbytes);
extern Size shm_toc_freespace(shm_toc *toc);
extern void shm_toc_insert(shm_toc *toc, uint64 key, void *address);
extern void *shm_toc_lookup(shm_toc *toc, uint64 key);
/*
* Tools for estimating how large a chunk of shared memory will be needed
* to store a TOC and its dependent objects.
*/
typedef struct
{
Size space_for_chunks;
Size number_of_keys;
} shm_toc_estimator;
#define shm_toc_initialize_estimator(e) \
((e)->space_for_chunks = 0, (e)->number_of_keys = 0)
#define shm_toc_estimate_chunk(e, sz) \
((e)->space_for_chunks = add_size((e)->space_for_chunks, \
BUFFERALIGN((sz))))
#define shm_toc_estimate_keys(e, cnt) \
((e)->number_of_keys = add_size((e)->number_of_keys, (cnt)))
extern Size shm_toc_estimate(shm_toc_estimator *);
#endif /* SHM_TOC_H */