src/common/lookup.c

/* Copyright (c) 1997 Silicon Graphics, Inc. */

#ifndef lint
static char SCCSid[] = "$SunId$ SGI";
#endif

/*
 * Table lookup routines
 */

#include <stdio.h>
#include "lookup.h"

#define MEM_PTR         char *

extern MEM_PTR  calloc();


int
lu_init(tbl, nel)               /* initialize tbl for at least nel elements */
register LUTAB  *tbl;
int     nel;
{
        static int  hsiztab[] = {
                31, 61, 127, 251, 509, 1021, 2039, 4093, 8191, 16381, 
                32749, 65521, 131071, 262139, 524287, 1048573, 2097143, 
                4194301, 8388593, 0
        };
        register int  *hsp;

        nel += nel>>1;                  /* 66% occupancy */
        for (hsp = hsiztab; *hsp; hsp++)
                if (*hsp > nel)
                        break;
        if (!(tbl->tsiz = *hsp))
                tbl->tsiz = nel*2 + 1;          /* not always prime */
        tbl->tabl = (LUENT *)calloc(tbl->tsiz, sizeof(LUENT));
        if (tbl->tabl == NULL)
                tbl->tsiz = 0;
        tbl->ndel = 0;
        return(tbl->tsiz);
}


long
lu_shash(s)                     /* hash a nul-terminated string */
char    *s;
{
        static unsigned char shuffle[256] = {
                0, 157, 58, 215, 116, 17, 174, 75, 232, 133, 34,
                191, 92, 249, 150, 51, 208, 109, 10, 167, 68, 225,
                126, 27, 184, 85, 242, 143, 44, 201, 102, 3, 160,
                61, 218, 119, 20, 177, 78, 235, 136, 37, 194, 95,
                252, 153, 54, 211, 112, 13, 170, 71, 228, 129, 30,
                187, 88, 245, 146, 47, 204, 105, 6, 163, 64, 221,
                122, 23, 180, 81, 238, 139, 40, 197, 98, 255, 156,
                57, 214, 115, 16, 173, 74, 231, 132, 33, 190, 91,
                248, 149, 50, 207, 108, 9, 166, 67, 224, 125, 26,
                183, 84, 241, 142, 43, 200, 101, 2, 159, 60, 217,
                118, 19, 176, 77, 234, 135, 36, 193, 94, 251, 152,
                53, 210, 111, 12, 169, 70, 227, 128, 29, 186, 87,
                244, 145, 46, 203, 104, 5, 162, 63, 220, 121, 22,
                179, 80, 237, 138, 39, 196, 97, 254, 155, 56, 213,
                114, 15, 172, 73, 230, 131, 32, 189, 90, 247, 148,
                49, 206, 107, 8, 165, 66, 223, 124, 25, 182, 83,
                240, 141, 42, 199, 100, 1, 158, 59, 216, 117, 18,
                175, 76, 233, 134, 35, 192, 93, 250, 151, 52, 209,
                110, 11, 168, 69, 226, 127, 28, 185, 86, 243, 144,
                45, 202, 103, 4, 161, 62, 219, 120, 21, 178, 79,
                236, 137, 38, 195, 96, 253, 154, 55, 212, 113, 14,
                171, 72, 229, 130, 31, 188, 89, 246, 147, 48, 205,
                106, 7, 164, 65, 222, 123, 24, 181, 82, 239, 140,
                41, 198, 99
        };
        register int    i = 0;
        register long   h = 0;
        register unsigned char *t = (unsigned char *)s;

        while (*t)
                h ^= (long)shuffle[*t++] << ((i+=11) & 0xf);

        return(h);
}


LUENT *
lu_find(tbl, key)               /* find a table entry */
register LUTAB  *tbl;
char    *key;
{
        long    hval;
        int     i, n;
        register int    ndx;
        register LUENT  *le;
                                        /* look up object */
        if (tbl->tsiz == 0)
                lu_init(tbl, 1);
        hval = (*tbl->hashf)(key);
tryagain:
        ndx = hval % tbl->tsiz;
        le = &tbl->tabl[ndx];
        for (i = 0, n = 1; i < tbl->tsiz; i++, n += 2) {
                if (le->key == NULL) {
                        le->hval = hval;
                        return(le);
                }
                if (le->hval == hval && 
                      (tbl->keycmp == NULL || !(*tbl->keycmp)(le->key, key))) {
                        return(le);
                }
                le += n;
                if ((ndx += n) >= tbl->tsiz) {  /* this happens rarely */
                        ndx = ndx % tbl->tsiz;
                        le = &tbl->tabl[ndx];
                }
        }
                                        /* table is full, reallocate */
        le = tbl->tabl;
        ndx = tbl->tsiz;
        i = tbl->ndel;
        if (!lu_init(tbl, ndx-i+1)) {   /* no more memory! */
                tbl->tabl = le;
                tbl->tsiz = ndx;
                tbl->ndel = i;
                return(NULL);
        }
        if (!ndx)
                goto tryagain;
        /*
         * The following code may fail if the user has reclaimed many
         * deleted entries and the system runs out of memory in a
         * recursive call to lu_find().
         */
        while (ndx--)
                if (le[ndx].key != NULL)
                        if (le[ndx].data != NULL)
                                *lu_find(tbl, le[ndx].key) = le[ndx];
                        else if (tbl->freek != NULL)
                                (*tbl->freek)(le[ndx].key);
        free((MEM_PTR)le);
        goto tryagain;                  /* should happen only once! */
}


void
lu_delete(tbl, key)             /* delete a table entry */
register LUTAB  *tbl;
char    *key;
{
        register LUENT  *le;

        if ((le = lu_find(tbl, key)) == NULL)
                return;
        if (le->key == NULL || le->data == NULL)
                return;
        if (tbl->freed != NULL)
                (*tbl->freed)(le->data);
        le->data = NULL;
        tbl->ndel++;
}


void
lu_done(tbl)                    /* free table and contents */
register LUTAB  *tbl;
{
        register LUENT  *tp;

        if (!tbl->tsiz)
                return;
        for (tp = tbl->tabl + tbl->tsiz; tp-- > tbl->tabl; )
                if (tp->key != NULL) {
                        if (tbl->freek != NULL)
                                (*tbl->freek)(tp->key);
                        if (tp->data != NULL && tbl->freed != NULL)
                                (*tbl->freed)(tp->data);
                }
        free((MEM_PTR)tbl->tabl);
        tbl->tabl = NULL;
        tbl->tsiz = 0;
        tbl->ndel = 0;
}
Revision:	2.3
Committed:	Wed Dec 3 10:59:30 1997 UTC (27 years, 11 months ago) by gregl
Content type:	text/plain
Branch:	MAIN
Changes since 2.2:	+62 -23 lines
Log Message:	Added Philippe Bekaert's improvements to lu_hash() and lu_find()
#	User	Rev	Content
1	gregl	2.3	/* Copyright (c) 1997 Silicon Graphics, Inc. */
2	greg	2.1
3			#ifndef lint
4	gregl	2.3	static char SCCSid[] = "$SunId$ SGI";
5	greg	2.1	#endif
6
7			/*
8			* Table lookup routines
9			*/
10
11			#include <stdio.h>
12			#include "lookup.h"
13
14			#define MEM_PTR char *
15
16			extern MEM_PTR calloc();
17
18
19			int
20			lu_init(tbl, nel) /* initialize tbl for at least nel elements */
21			register LUTAB *tbl;
22			int nel;
23			{
24			static int hsiztab[] = {
25	gregl	2.3	31, 61, 127, 251, 509, 1021, 2039, 4093, 8191, 16381,
26			32749, 65521, 131071, 262139, 524287, 1048573, 2097143,
27			4194301, 8388593, 0
28	greg	2.1	};
29			register int *hsp;
30
31			nel += nel>>1; /* 66% occupancy */
32			for (hsp = hsiztab; *hsp; hsp++)
33			if (*hsp > nel)
34			break;
35			if (!(tbl->tsiz = *hsp))
36			tbl->tsiz = nel2 + 1; / not always prime */
37			tbl->tabl = (LUENT *)calloc(tbl->tsiz, sizeof(LUENT));
38			if (tbl->tabl == NULL)
39			tbl->tsiz = 0;
40			tbl->ndel = 0;
41			return(tbl->tsiz);
42			}
43
44
45			long
46			lu_shash(s) /* hash a nul-terminated string */
47	gregl	2.3	char *s;
48	greg	2.1	{
49	gregl	2.3	static unsigned char shuffle[256] = {
50			0, 157, 58, 215, 116, 17, 174, 75, 232, 133, 34,
51			191, 92, 249, 150, 51, 208, 109, 10, 167, 68, 225,
52			126, 27, 184, 85, 242, 143, 44, 201, 102, 3, 160,
53			61, 218, 119, 20, 177, 78, 235, 136, 37, 194, 95,
54			252, 153, 54, 211, 112, 13, 170, 71, 228, 129, 30,
55			187, 88, 245, 146, 47, 204, 105, 6, 163, 64, 221,
56			122, 23, 180, 81, 238, 139, 40, 197, 98, 255, 156,
57			57, 214, 115, 16, 173, 74, 231, 132, 33, 190, 91,
58			248, 149, 50, 207, 108, 9, 166, 67, 224, 125, 26,
59			183, 84, 241, 142, 43, 200, 101, 2, 159, 60, 217,
60			118, 19, 176, 77, 234, 135, 36, 193, 94, 251, 152,
61			53, 210, 111, 12, 169, 70, 227, 128, 29, 186, 87,
62			244, 145, 46, 203, 104, 5, 162, 63, 220, 121, 22,
63			179, 80, 237, 138, 39, 196, 97, 254, 155, 56, 213,
64			114, 15, 172, 73, 230, 131, 32, 189, 90, 247, 148,
65			49, 206, 107, 8, 165, 66, 223, 124, 25, 182, 83,
66			240, 141, 42, 199, 100, 1, 158, 59, 216, 117, 18,
67			175, 76, 233, 134, 35, 192, 93, 250, 151, 52, 209,
68			110, 11, 168, 69, 226, 127, 28, 185, 86, 243, 144,
69			45, 202, 103, 4, 161, 62, 219, 120, 21, 178, 79,
70			236, 137, 38, 195, 96, 253, 154, 55, 212, 113, 14,
71			171, 72, 229, 130, 31, 188, 89, 246, 147, 48, 205,
72			106, 7, 164, 65, 222, 123, 24, 181, 82, 239, 140,
73			41, 198, 99
74			};
75	greg	2.1	register int i = 0;
76			register long h = 0;
77	gregl	2.3	register unsigned char t = (unsigned char )s;
78	greg	2.1
79	gregl	2.3	while (*t)
80			h ^= (long)shuffle[*t++] << ((i+=11) & 0xf);
81
82	greg	2.1	return(h);
83			}
84
85
86			LUENT *
87			lu_find(tbl, key) /* find a table entry */
88			register LUTAB *tbl;
89			char *key;
90			{
91			long hval;
92	gregl	2.3	int i, n;
93	greg	2.1	register int ndx;
94	gregl	2.3	register LUENT *le;
95	greg	2.1	/* look up object */
96	gregl	2.3	if (tbl->tsiz == 0)
97			lu_init(tbl, 1);
98	greg	2.1	hval = (*tbl->hashf)(key);
99			tryagain:
100	gregl	2.3	ndx = hval % tbl->tsiz;
101			le = &tbl->tabl[ndx];
102			for (i = 0, n = 1; i < tbl->tsiz; i++, n += 2) {
103			if (le->key == NULL) {
104			le->hval = hval;
105			return(le);
106	greg	2.1	}
107	gregl	2.3	if (le->hval == hval &&
108			(tbl->keycmp == NULL \|\| !(*tbl->keycmp)(le->key, key))) {
109			return(le);
110			}
111			le += n;
112			if ((ndx += n) >= tbl->tsiz) { /* this happens rarely */
113			ndx = ndx % tbl->tsiz;
114			le = &tbl->tabl[ndx];
115			}
116	greg	2.1	}
117			/* table is full, reallocate */
118	gregl	2.3	le = tbl->tabl;
119	greg	2.1	ndx = tbl->tsiz;
120			i = tbl->ndel;
121	greg	2.2	if (!lu_init(tbl, ndx-i+1)) { /* no more memory! */
122	gregl	2.3	tbl->tabl = le;
123	greg	2.1	tbl->tsiz = ndx;
124			tbl->ndel = i;
125			return(NULL);
126			}
127			if (!ndx)
128			goto tryagain;
129			/*
130			* The following code may fail if the user has reclaimed many
131			* deleted entries and the system runs out of memory in a
132			* recursive call to lu_find().
133			*/
134			while (ndx--)
135	gregl	2.3	if (le[ndx].key != NULL)
136			if (le[ndx].data != NULL)
137			*lu_find(tbl, le[ndx].key) = le[ndx];
138	greg	2.1	else if (tbl->freek != NULL)
139	gregl	2.3	(*tbl->freek)(le[ndx].key);
140			free((MEM_PTR)le);
141	greg	2.1	goto tryagain; /* should happen only once! */
142			}
143
144
145			void
146			lu_delete(tbl, key) /* delete a table entry */
147			register LUTAB *tbl;
148			char *key;
149			{
150			register LUENT *le;
151
152			if ((le = lu_find(tbl, key)) == NULL)
153			return;
154			if (le->key == NULL \|\| le->data == NULL)
155			return;
156			if (tbl->freed != NULL)
157			(*tbl->freed)(le->data);
158			le->data = NULL;
159			tbl->ndel++;
160			}
161
162
163			void
164			lu_done(tbl) /* free table and contents */
165			register LUTAB *tbl;
166			{
167			register LUENT *tp;
168
169			if (!tbl->tsiz)
170			return;
171			for (tp = tbl->tabl + tbl->tsiz; tp-- > tbl->tabl; )
172			if (tp->key != NULL) {
173			if (tbl->freek != NULL)
174			(*tbl->freek)(tp->key);
175			if (tp->data != NULL && tbl->freed != NULL)
176			(*tbl->freed)(tp->data);
177			}
178			free((MEM_PTR)tbl->tabl);
179			tbl->tabl = NULL;
180			tbl->tsiz = 0;
181			tbl->ndel = 0;
182			}