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/*-------------------------------------------------------------------------
*
* hsearch.h
* exported definitions for utils/hash/dynahash.c; see notes therein
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/utils/hsearch.h
*
*-------------------------------------------------------------------------
*/
#ifndef HSEARCH_H
#define HSEARCH_H
/*
* Hash functions must have this signature.
*/
typedef uint32 (*HashValueFunc) (const void *key, Size keysize);
/*
* Key comparison functions must have this signature. Comparison functions
* return zero for match, nonzero for no match. (The comparison function
* definition is designed to allow memcmp() and strncmp() to be used directly
* as key comparison functions.)
*/
typedef int (*HashCompareFunc) (const void *key1, const void *key2,
Size keysize);
/*
* Key copying functions must have this signature. The return value is not
* used. (The definition is set up to allow memcpy() and strlcpy() to be
* used directly.)
*/
typedef void *(*HashCopyFunc) (void *dest, const void *src, Size keysize);
/*
* Space allocation function for a hashtable --- designed to match malloc().
* Note: there is no free function API; can't destroy a hashtable unless you
* use the default allocator.
*/
typedef void *(*HashAllocFunc) (Size request);
/*
* HASHELEMENT is the private part of a hashtable entry. The caller's data
* follows the HASHELEMENT structure (on a MAXALIGN'd boundary). The hash key
* is expected to be at the start of the caller's hash entry data structure.
*/
typedef struct HASHELEMENT
{
struct HASHELEMENT *link; /* link to next entry in same bucket */
uint32 hashvalue; /* hash function result for this entry */
} HASHELEMENT;
/* Hash table header struct is an opaque type known only within dynahash.c */
typedef struct HASHHDR HASHHDR;
/* Hash table control struct is an opaque type known only within dynahash.c */
typedef struct HTAB HTAB;
/* Parameter data structure for hash_create */
/* Only those fields indicated by hash_flags need be set */
typedef struct HASHCTL
{
/* Used if HASH_PARTITION flag is set: */
long num_partitions; /* # partitions (must be power of 2) */
/* Used if HASH_SEGMENT flag is set: */
long ssize; /* segment size */
/* Used if HASH_DIRSIZE flag is set: */
long dsize; /* (initial) directory size */
long max_dsize; /* limit to dsize if dir size is limited */
/* Used if HASH_ELEM flag is set (which is now required): */
Size keysize; /* hash key length in bytes */
Size entrysize; /* total user element size in bytes */
/* Used if HASH_FUNCTION flag is set: */
HashValueFunc hash; /* hash function */
/* Used if HASH_COMPARE flag is set: */
HashCompareFunc match; /* key comparison function */
/* Used if HASH_KEYCOPY flag is set: */
HashCopyFunc keycopy; /* key copying function */
/* Used if HASH_ALLOC flag is set: */
HashAllocFunc alloc; /* memory allocator */
/* Used if HASH_CONTEXT flag is set: */
MemoryContext hcxt; /* memory context to use for allocations */
/* Used if HASH_SHARED_MEM flag is set: */
HASHHDR *hctl; /* location of header in shared mem */
} HASHCTL;
/* Flag bits for hash_create; most indicate which parameters are supplied */
#define HASH_PARTITION 0x0001 /* Hashtable is used w/partitioned locking */
#define HASH_SEGMENT 0x0002 /* Set segment size */
#define HASH_DIRSIZE 0x0004 /* Set directory size (initial and max) */
#define HASH_ELEM 0x0008 /* Set keysize and entrysize (now required!) */
#define HASH_STRINGS 0x0010 /* Select support functions for string keys */
#define HASH_BLOBS 0x0020 /* Select support functions for binary keys */
#define HASH_FUNCTION 0x0040 /* Set user defined hash function */
#define HASH_COMPARE 0x0080 /* Set user defined comparison function */
#define HASH_KEYCOPY 0x0100 /* Set user defined key-copying function */
#define HASH_ALLOC 0x0200 /* Set memory allocator */
#define HASH_CONTEXT 0x0400 /* Set memory allocation context */
#define HASH_SHARED_MEM 0x0800 /* Hashtable is in shared memory */
#define HASH_ATTACH 0x1000 /* Do not initialize hctl */
#define HASH_FIXED_SIZE 0x2000 /* Initial size is a hard limit */
/* max_dsize value to indicate expansible directory */
#define NO_MAX_DSIZE (-1)
/* hash_search operations */
typedef enum
{
HASH_FIND,
HASH_ENTER,
HASH_REMOVE,
HASH_ENTER_NULL
} HASHACTION;
/* hash_seq status (should be considered an opaque type by callers) */
typedef struct
{
HTAB *hashp;
uint32 curBucket; /* index of current bucket */
HASHELEMENT *curEntry; /* current entry in bucket */
} HASH_SEQ_STATUS;
/*
* prototypes for functions in dynahash.c
*/
extern HTAB *hash_create(const char *tabname, long nelem,
const HASHCTL *info, int flags);
extern void hash_destroy(HTAB *hashp);
extern void hash_stats(const char *where, HTAB *hashp);
extern void *hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action,
bool *foundPtr);
extern uint32 get_hash_value(HTAB *hashp, const void *keyPtr);
extern void *hash_search_with_hash_value(HTAB *hashp, const void *keyPtr,
uint32 hashvalue, HASHACTION action,
bool *foundPtr);
extern bool hash_update_hash_key(HTAB *hashp, void *existingEntry,
const void *newKeyPtr);
extern long hash_get_num_entries(HTAB *hashp);
extern void hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp);
extern void *hash_seq_search(HASH_SEQ_STATUS *status);
extern void hash_seq_term(HASH_SEQ_STATUS *status);
extern void hash_freeze(HTAB *hashp);
extern Size hash_estimate_size(long num_entries, Size entrysize);
extern long hash_select_dirsize(long num_entries);
extern Size hash_get_shared_size(HASHCTL *info, int flags);
extern void AtEOXact_HashTables(bool isCommit);
extern void AtEOSubXact_HashTables(bool isCommit, int nestDepth);
#endif /* HSEARCH_H */
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