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300 lines
4.4 KiB
C
300 lines
4.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* hashfunc.c--
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* Comparison functions for hash access method.
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*
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* 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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* $Header: /cvsroot/pgsql/src/backend/access/hash/hashfunc.c,v 1.5 1997/09/08 02:20:13 momjian Exp $
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*
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* NOTES
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* These functions are stored in pg_amproc. For each operator class
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* defined on hash tables, they compute the hash value of the argument.
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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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uint32
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hashint2(int16 key)
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{
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return ((uint32) ~ key);
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}
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uint32
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hashint4(uint32 key)
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{
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return (~key);
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}
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/* Hash function from Chris Torek. */
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uint32
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hashfloat4(float32 keyp)
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{
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int len;
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int loop;
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uint32 h;
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char *kp = (char *) keyp;
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len = sizeof(float32data);
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#define HASH4a h = (h << 5) - h + *kp++;
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#define HASH4b h = (h << 5) + h + *kp++;
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#define HASH4 HASH4b
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h = 0;
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if (len > 0)
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{
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loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1))
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{
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case 0:
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do
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{ /* All fall throughs */
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HASH4;
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case 7:
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HASH4;
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case 6:
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HASH4;
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case 5:
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HASH4;
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case 4:
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HASH4;
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case 3:
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HASH4;
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case 2:
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HASH4;
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case 1:
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HASH4;
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} while (--loop);
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}
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}
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return (h);
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}
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uint32
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hashfloat8(float64 keyp)
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{
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int len;
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int loop;
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uint32 h;
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char *kp = (char *) keyp;
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len = sizeof(float64data);
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#define HASH4a h = (h << 5) - h + *kp++;
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#define HASH4b h = (h << 5) + h + *kp++;
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#define HASH4 HASH4b
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h = 0;
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if (len > 0)
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{
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loop = (len + 8 - 1) >> 3;
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switch (len & (8 - 1))
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{
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case 0:
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do
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{ /* All fall throughs */
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HASH4;
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case 7:
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HASH4;
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case 6:
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HASH4;
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case 5:
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HASH4;
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case 4:
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HASH4;
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case 3:
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HASH4;
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case 2:
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HASH4;
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case 1:
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HASH4;
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} while (--loop);
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}
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}
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return (h);
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}
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uint32
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hashoid(Oid key)
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{
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return ((uint32) ~ key);
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}
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uint32
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hashchar(char key)
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{
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int len;
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uint32 h;
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len = sizeof(char);
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#define PRIME1 37
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#define PRIME2 1048583
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h = 0;
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/* Convert char to integer */
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h = h * PRIME1 ^ (key - ' ');
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h %= PRIME2;
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return (h);
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}
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uint32
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hashchar2(uint16 intkey)
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{
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uint32 h;
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int len;
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char *key = (char *) &intkey;
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h = 0;
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len = sizeof(uint16);
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*key++ - ' ');
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h %= PRIME2;
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return (h);
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}
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uint32
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hashchar4(uint32 intkey)
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{
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uint32 h;
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int len;
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char *key = (char *) &intkey;
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h = 0;
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len = sizeof(uint32);
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*key++ - ' ');
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h %= PRIME2;
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return (h);
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}
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uint32
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hashchar8(char *key)
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{
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uint32 h;
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int len;
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h = 0;
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len = sizeof(char8);
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*key++ - ' ');
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h %= PRIME2;
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return (h);
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}
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uint32
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hashname(NameData * n)
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{
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uint32 h;
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int len;
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char *key;
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key = n->data;
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h = 0;
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len = NAMEDATALEN;
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*key++ - ' ');
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h %= PRIME2;
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return (h);
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}
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uint32
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hashchar16(char *key)
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{
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uint32 h;
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int len;
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h = 0;
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len = sizeof(char16);
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/* Convert string to integer */
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while (len--)
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h = h * PRIME1 ^ (*key++ - ' ');
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h %= PRIME2;
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return (h);
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}
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/*
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* (Comment from the original db3 hashing code: )
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*
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* "This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
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* units. On the first time through the loop we get the 'leftover bytes'
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* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
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* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
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* this routine is heavily used enough, it's worth the ugly coding.
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*
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* "OZ's original sdbm hash"
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*/
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uint32
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hashtext(struct varlena * key)
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{
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int keylen;
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char *keydata;
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uint32 n;
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int loop;
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keydata = VARDATA(key);
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keylen = VARSIZE(key);
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/* keylen includes the four bytes in which string keylength is stored */
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keylen -= sizeof(VARSIZE(key));
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#define HASHC n = *keydata++ + 65599 * n
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n = 0;
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if (keylen > 0)
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{
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loop = (keylen + 8 - 1) >> 3;
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switch (keylen & (8 - 1))
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{
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case 0:
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do
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{ /* All fall throughs */
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HASHC;
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case 7:
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HASHC;
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case 6:
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HASHC;
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case 5:
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HASHC;
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case 4:
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HASHC;
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case 3:
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HASHC;
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case 2:
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HASHC;
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case 1:
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HASHC;
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} while (--loop);
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}
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}
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return (n);
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}
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