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dshash.h
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1/*-------------------------------------------------------------------------
2 *
3 * dshash.h
4 * Concurrent hash tables backed by dynamic shared memory areas.
5 *
6 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 * IDENTIFICATION
10 * src/include/lib/dshash.h
11 *
12 *-------------------------------------------------------------------------
13 */
14#ifndef DSHASH_H
15#define DSHASH_H
16
17#include "utils/dsa.h"
18
19/* The opaque type representing a hash table. */
20struct dshash_table;
22
23/* A handle for a dshash_table which can be shared with other processes. */
25
26/* Sentinel value to use for invalid dshash_table handles. */
27#define DSHASH_HANDLE_INVALID ((dshash_table_handle) InvalidDsaPointer)
28
29/* The type for hash values. */
31
32/* A function type for comparing keys. */
33typedef int (*dshash_compare_function) (const void *a, const void *b,
34 size_t size, void *arg);
35
36/* A function type for computing hash values for keys. */
37typedef dshash_hash (*dshash_hash_function) (const void *v, size_t size,
38 void *arg);
39
40/* A function type for copying keys. */
41typedef void (*dshash_copy_function) (void *dest, const void *src, size_t size,
42 void *arg);
43
44/*
45 * The set of parameters needed to create or attach to a hash table. The
46 * tranche_id member does not need to be initialized when attaching to an
47 * existing hash table.
48 *
49 * Compare, hash, and copy functions must be supplied even when attaching,
50 * because we can't safely share function pointers between backends in general.
51 * The user data pointer supplied to the create and attach functions will be
52 * passed to these functions.
53 */
54typedef struct dshash_parameters
55{
56 size_t key_size; /* Size of the key (initial bytes of entry) */
57 size_t entry_size; /* Total size of entry */
61 int tranche_id; /* The tranche ID to use for locks */
63
64/* Forward declaration of private types for use only by dshash.c. */
67
68/*
69 * Sequential scan state. The detail is exposed to let users know the storage
70 * size but it should be considered as an opaque type by callers.
71 */
72typedef struct dshash_seq_status
73{
74 dshash_table *hash_table; /* dshash table working on */
75 int curbucket; /* bucket number we are at */
76 int nbuckets; /* total number of buckets in the dshash */
77 dshash_table_item *curitem; /* item we are currently at */
78 dsa_pointer pnextitem; /* dsa-pointer to the next item */
79 int curpartition; /* partition number we are at */
80 bool exclusive; /* locking mode */
82
83/* Creating, sharing and destroying from hash tables. */
85 const dshash_parameters *params,
86 void *arg);
88 const dshash_parameters *params,
90 void *arg);
91extern void dshash_detach(dshash_table *hash_table);
93extern void dshash_destroy(dshash_table *hash_table);
94
95/* Finding, creating, deleting entries. */
96extern void *dshash_find(dshash_table *hash_table,
97 const void *key, bool exclusive);
98extern void *dshash_find_or_insert(dshash_table *hash_table,
99 const void *key, bool *found);
100extern bool dshash_delete_key(dshash_table *hash_table, const void *key);
101extern void dshash_delete_entry(dshash_table *hash_table, void *entry);
102extern void dshash_release_lock(dshash_table *hash_table, void *entry);
103
104/* seq scan support */
105extern void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table,
106 bool exclusive);
107extern void *dshash_seq_next(dshash_seq_status *status);
108extern void dshash_seq_term(dshash_seq_status *status);
109extern void dshash_delete_current(dshash_seq_status *status);
110
111/*
112 * Convenience hash, compare, and copy functions wrapping memcmp, tag_hash, and
113 * memcpy.
114 */
115extern int dshash_memcmp(const void *a, const void *b, size_t size, void *arg);
116extern dshash_hash dshash_memhash(const void *v, size_t size, void *arg);
117extern void dshash_memcpy(void *dest, const void *src, size_t size, void *arg);
118
119/*
120 * Convenience hash, compare, and copy functions wrapping strcmp, string_hash,
121 * and strcpy.
122 */
123extern int dshash_strcmp(const void *a, const void *b, size_t size, void *arg);
124extern dshash_hash dshash_strhash(const void *v, size_t size, void *arg);
125extern void dshash_strcpy(void *dest, const void *src, size_t size, void *arg);
126
127/* Debugging support. */
128extern void dshash_dump(dshash_table *hash_table);
129
130#endif /* DSHASH_H */
uint32_t uint32
Definition: c.h:488
uint64 dsa_pointer
Definition: dsa.h:62
bool dshash_delete_key(dshash_table *hash_table, const void *key)
Definition: dshash.c:503
void dshash_memcpy(void *dest, const void *src, size_t size, void *arg)
Definition: dshash.c:590
void dshash_delete_entry(dshash_table *hash_table, void *entry)
Definition: dshash.c:541
void dshash_strcpy(void *dest, const void *src, size_t size, void *arg)
Definition: dshash.c:622
void dshash_destroy(dshash_table *hash_table)
Definition: dshash.c:323
void dshash_release_lock(dshash_table *hash_table, void *entry)
Definition: dshash.c:558
void dshash_detach(dshash_table *hash_table)
Definition: dshash.c:307
void dshash_seq_init(dshash_seq_status *status, dshash_table *hash_table, bool exclusive)
Definition: dshash.c:638
void * dshash_find(dshash_table *hash_table, const void *key, bool exclusive)
Definition: dshash.c:390
dshash_hash dshash_strhash(const void *v, size_t size, void *arg)
Definition: dshash.c:611
dsa_pointer dshash_table_handle
Definition: dshash.h:24
dshash_table_handle dshash_get_hash_table_handle(dshash_table *hash_table)
Definition: dshash.c:367
void dshash_dump(dshash_table *hash_table)
Definition: dshash.c:778
int(* dshash_compare_function)(const void *a, const void *b, size_t size, void *arg)
Definition: dshash.h:33
struct dshash_parameters dshash_parameters
dshash_table * dshash_attach(dsa_area *area, const dshash_parameters *params, dshash_table_handle handle, void *arg)
Definition: dshash.c:270
void dshash_seq_term(dshash_seq_status *status)
Definition: dshash.c:747
uint32 dshash_hash
Definition: dshash.h:30
void(* dshash_copy_function)(void *dest, const void *src, size_t size, void *arg)
Definition: dshash.h:41
int dshash_strcmp(const void *a, const void *b, size_t size, void *arg)
Definition: dshash.c:599
void * dshash_find_or_insert(dshash_table *hash_table, const void *key, bool *found)
Definition: dshash.c:433
struct dshash_seq_status dshash_seq_status
dshash_hash dshash_memhash(const void *v, size_t size, void *arg)
Definition: dshash.c:581
void * dshash_seq_next(dshash_seq_status *status)
Definition: dshash.c:657
dshash_hash(* dshash_hash_function)(const void *v, size_t size, void *arg)
Definition: dshash.h:37
dshash_table * dshash_create(dsa_area *area, const dshash_parameters *params, void *arg)
Definition: dshash.c:206
int dshash_memcmp(const void *a, const void *b, size_t size, void *arg)
Definition: dshash.c:572
void dshash_delete_current(dshash_seq_status *status)
Definition: dshash.c:757
int b
Definition: isn.c:69
int a
Definition: isn.c:68
void * arg
static pg_noinline void Size size
Definition: slab.c:607
Definition: dsa.c:348
dshash_hash_function hash_function
Definition: dshash.h:59
size_t key_size
Definition: dshash.h:56
dshash_compare_function compare_function
Definition: dshash.h:58
dshash_copy_function copy_function
Definition: dshash.h:60
size_t entry_size
Definition: dshash.h:57
bool exclusive
Definition: dshash.h:80
dshash_table_item * curitem
Definition: dshash.h:77
dsa_pointer pnextitem
Definition: dshash.h:78
int curpartition
Definition: dshash.h:79
dshash_table * hash_table
Definition: dshash.h:74