56 lines
1.4 KiB
C
56 lines
1.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* hashfn.c
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* Hash functions for use in dynahash.c hashtables
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*
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*
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* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/hash/hashfn.c,v 1.23 2005/04/14 20:32:43 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/hash.h"
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#include "utils/hsearch.h"
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/*
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* string_hash: hash function for keys that are null-terminated strings.
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*
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* NOTE: this is the default hash function if none is specified.
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*/
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uint32
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string_hash(const void *key, Size keysize)
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{
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return DatumGetUInt32(hash_any((const unsigned char *) key,
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(int) strlen((const char *) key)));
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}
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/*
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* tag_hash: hash function for fixed-size tag values
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*/
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uint32
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tag_hash(const void *key, Size keysize)
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{
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return DatumGetUInt32(hash_any((const unsigned char *) key,
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(int) keysize));
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}
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/*
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* oid_hash: hash function for keys that are OIDs
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*
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* (tag_hash works for this case too, but is slower)
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*/
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uint32
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oid_hash(const void *key, Size keysize)
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{
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Assert(keysize == sizeof(Oid));
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/* We don't actually bother to do anything to the OID value ... */
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return (uint32) *((const Oid *) key);
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}
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