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shm_toc.h
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1 /*-------------------------------------------------------------------------
2  *
3  * shm_toc.h
4  * shared memory segment table of contents
5  *
6  * This is intended to provide a simple way to divide a chunk of shared
7  * memory (probably dynamic shared memory allocated via dsm_create) into
8  * a number of regions and keep track of the addresses of those regions or
9  * key data structures within those regions. This is not intended to
10  * scale to a large number of keys and will perform poorly if used that
11  * way; if you need a large number of pointers, store them within some
12  * other data structure within the segment and only put the pointer to
13  * the data structure itself in the table of contents.
14  *
15  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
16  * Portions Copyright (c) 1994, Regents of the University of California
17  *
18  * src/include/storage/shm_toc.h
19  *
20  *-------------------------------------------------------------------------
21  */
22 #ifndef SHM_TOC_H
23 #define SHM_TOC_H
24 
25 #include "storage/shmem.h" /* for add_size() */
26 
27 /* shm_toc is an opaque type known only within shm_toc.c */
28 typedef struct shm_toc shm_toc;
29 
30 extern shm_toc *shm_toc_create(uint64 magic, void *address, Size nbytes);
31 extern shm_toc *shm_toc_attach(uint64 magic, void *address);
32 extern void *shm_toc_allocate(shm_toc *toc, Size nbytes);
33 extern Size shm_toc_freespace(shm_toc *toc);
34 extern void shm_toc_insert(shm_toc *toc, uint64 key, void *address);
35 extern void *shm_toc_lookup(shm_toc *toc, uint64 key, bool noError);
36 
37 /*
38  * Tools for estimating how large a chunk of shared memory will be needed
39  * to store a TOC and its dependent objects. Note: we don't really support
40  * large numbers of keys, but it's convenient to declare number_of_keys
41  * as a Size anyway.
42  */
43 typedef struct
44 {
48 
49 #define shm_toc_initialize_estimator(e) \
50  ((e)->space_for_chunks = 0, (e)->number_of_keys = 0)
51 #define shm_toc_estimate_chunk(e, sz) \
52  ((e)->space_for_chunks = add_size((e)->space_for_chunks, BUFFERALIGN(sz)))
53 #define shm_toc_estimate_keys(e, cnt) \
54  ((e)->number_of_keys = add_size((e)->number_of_keys, cnt))
55 
57 
58 #endif /* SHM_TOC_H */
Size number_of_keys
Definition: shm_toc.h:46
Size shm_toc_freespace(shm_toc *toc)
Definition: shm_toc.c:131
void * shm_toc_allocate(shm_toc *toc, Size nbytes)
Definition: shm_toc.c:88
shm_toc * shm_toc_create(uint64 magic, void *address, Size nbytes)
Definition: shm_toc.c:40
void shm_toc_insert(shm_toc *toc, uint64 key, void *address)
Definition: shm_toc.c:171
Size shm_toc_estimate(shm_toc_estimator *e)
Definition: shm_toc.c:263
Size space_for_chunks
Definition: shm_toc.h:45
void * shm_toc_lookup(shm_toc *toc, uint64 key, bool noError)
Definition: shm_toc.c:232
size_t Size
Definition: c.h:350
e
Definition: preproc-init.c:82
shm_toc * shm_toc_attach(uint64 magic, void *address)
Definition: shm_toc.c:64