xref: /illumos-gate/usr/src/lib/libipmi/common/ipmi_hash.c (revision 1da57d551424de5a9d469760be7c4b4d4f10a755)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  */
25 
26 #include <strings.h>
27 
28 #include <assert.h>
29 #include <ipmi_impl.h>
30 #include <string.h>
31 #include <strings.h>
32 
33 /*
34  * The (prime) number 137 happens to have the nice property that -- when
35  * multiplied by two and added to 33 -- one gets a pretty long series of
36  * primes:
37  *
38  *   307, 647, 1327, 2687, 5407, 10847, 21727, 43487
39  *
40  * And beyond 43487, the numbers in the series have few factors or are prime.
41  * That is, one can have a prime number and roughly double it to get another
42  * prime number -- but the series starts at 137.  A size of 137 buckets doesn't
43  * particularly accommodate small hash tables, but we note that 13 also yields
44  * a reasonable sequence when doubling it and adding 5:
45  *
46  *   13, 31, 67, 139, 283, 571
47  *
48  * So we start with this second sequence, crossing over to the first when
49  * the size is greater than 137.  (And when reducing the size of the hash
50  * table, we cross back when the size gets below 67.)
51  */
52 #define	IPMI_HASHCROSSOVER	137
53 #define	IPMI_HASHCROSSUNDER	67
54 #define	IPMI_HASHMINSIZE		13
55 
56 static ulong_t
ipmi_hash_double(ulong_t size)57 ipmi_hash_double(ulong_t size)
58 {
59 	ulong_t nsize;
60 
61 	if (size < IPMI_HASHCROSSOVER) {
62 		nsize = (size * 2) + 5;
63 		return (nsize < IPMI_HASHCROSSOVER ? nsize :
64 		    IPMI_HASHCROSSOVER);
65 	}
66 
67 	return ((size * 2) + 33);
68 }
69 
70 static ulong_t
ipmi_hash_half(ulong_t size)71 ipmi_hash_half(ulong_t size)
72 {
73 	ulong_t nsize;
74 
75 	if (size > IPMI_HASHCROSSUNDER) {
76 		nsize = (size - 33) / 2;
77 		return (nsize > IPMI_HASHCROSSUNDER ? nsize :
78 		    IPMI_HASHCROSSUNDER);
79 	}
80 
81 	nsize = (size - 5) / 2;
82 
83 	return (nsize > IPMI_HASHMINSIZE ? nsize : IPMI_HASHMINSIZE);
84 }
85 
86 ipmi_hash_t *
ipmi_hash_create(ipmi_handle_t * hp,size_t linkoffs,const void * (* convert)(const void * elem),ulong_t (* compute)(const void * key),int (* compare)(const void * lkey,const void * rkey))87 ipmi_hash_create(ipmi_handle_t *hp, size_t linkoffs,
88     const void *(*convert)(const void *elem),
89     ulong_t (*compute)(const void *key),
90     int (*compare)(const void *lkey, const void *rkey))
91 {
92 	ipmi_hash_t *ihp;
93 
94 	if ((ihp = ipmi_zalloc(hp, sizeof (ipmi_hash_t))) == NULL)
95 		return (NULL);
96 
97 	ihp->ih_handle = hp;
98 	ihp->ih_nbuckets = IPMI_HASHMINSIZE;
99 	ihp->ih_linkoffs = linkoffs;
100 	ihp->ih_convert = convert;
101 	ihp->ih_compute = compute;
102 	ihp->ih_compare = compare;
103 
104 	if ((ihp->ih_buckets = ipmi_zalloc(hp,
105 	    ihp->ih_nbuckets * sizeof (void *))) == NULL) {
106 		ipmi_free(hp, ihp);
107 		return (NULL);
108 	}
109 
110 	return (ihp);
111 }
112 
113 void
ipmi_hash_destroy(ipmi_hash_t * ihp)114 ipmi_hash_destroy(ipmi_hash_t *ihp)
115 {
116 	if (ihp != NULL) {
117 		ipmi_free(ihp->ih_handle, ihp->ih_buckets);
118 		ipmi_free(ihp->ih_handle, ihp);
119 	}
120 }
121 
122 ulong_t
ipmi_hash_strhash(const void * key)123 ipmi_hash_strhash(const void *key)
124 {
125 	ulong_t g, h = 0;
126 	const char *p;
127 
128 	for (p = key; *p != '\0'; p++) {
129 		h = (h << 4) + *p;
130 
131 		if ((g = (h & 0xf0000000)) != 0) {
132 			h ^= (g >> 24);
133 			h ^= g;
134 		}
135 	}
136 
137 	return (h);
138 }
139 
140 int
ipmi_hash_strcmp(const void * lhs,const void * rhs)141 ipmi_hash_strcmp(const void *lhs, const void *rhs)
142 {
143 	return (strcmp(lhs, rhs));
144 }
145 
146 ulong_t
ipmi_hash_ptrhash(const void * key)147 ipmi_hash_ptrhash(const void *key)
148 {
149 	return (*((const uintptr_t *)key) >> 4);
150 }
151 
152 int
ipmi_hash_ptrcmp(const void * lhs,const void * rhs)153 ipmi_hash_ptrcmp(const void *lhs, const void *rhs)
154 {
155 	const uintptr_t *l = lhs, *r = rhs;
156 
157 	return (*l == *r ? 0 : -1);
158 }
159 
160 
161 static ulong_t
ipmi_hash_compute(ipmi_hash_t * ihp,const void * elem)162 ipmi_hash_compute(ipmi_hash_t *ihp, const void *elem)
163 {
164 	return (ihp->ih_compute(ihp->ih_convert(elem)) % ihp->ih_nbuckets);
165 }
166 
167 static void
ipmi_hash_resize(ipmi_hash_t * ihp,ulong_t nsize)168 ipmi_hash_resize(ipmi_hash_t *ihp, ulong_t nsize)
169 {
170 	size_t osize = ihp->ih_nbuckets;
171 	ipmi_handle_t *hp = ihp->ih_handle;
172 	ipmi_hash_link_t *link, **nbuckets;
173 	ulong_t idx, nidx;
174 
175 	assert(nsize >= IPMI_HASHMINSIZE);
176 
177 	if (nsize == osize)
178 		return;
179 
180 	if ((nbuckets = ipmi_zalloc(hp, nsize * sizeof (void *))) == NULL) {
181 		/*
182 		 * This routine can't fail, so we just eat the failure here.
183 		 * The consequences of this failing are only for performance;
184 		 * correctness is not affected by our inability to resize
185 		 * the hash table.
186 		 */
187 		return;
188 	}
189 
190 	ihp->ih_nbuckets = nsize;
191 
192 	for (idx = 0; idx < osize; idx++) {
193 		while ((link = ihp->ih_buckets[idx]) != NULL) {
194 			void *elem;
195 
196 			/*
197 			 * For every hash element, we need to remove it from
198 			 * this bucket, and rehash it given the new bucket
199 			 * size.
200 			 */
201 			ihp->ih_buckets[idx] = link->ihl_next;
202 			elem = (void *)((uintptr_t)link - ihp->ih_linkoffs);
203 			nidx = ipmi_hash_compute(ihp, elem);
204 
205 			link->ihl_next = nbuckets[nidx];
206 			nbuckets[nidx] = link;
207 		}
208 	}
209 
210 	ipmi_free(hp, ihp->ih_buckets);
211 	ihp->ih_buckets = nbuckets;
212 }
213 
214 void *
ipmi_hash_lookup(ipmi_hash_t * ihp,const void * search)215 ipmi_hash_lookup(ipmi_hash_t *ihp, const void *search)
216 {
217 	ulong_t idx = ihp->ih_compute(search) % ihp->ih_nbuckets;
218 	ipmi_hash_link_t *hl;
219 
220 	for (hl = ihp->ih_buckets[idx]; hl != NULL; hl = hl->ihl_next) {
221 		void *elem = (void *)((uintptr_t)hl - ihp->ih_linkoffs);
222 
223 		if (ihp->ih_compare(ihp->ih_convert(elem), search) == 0)
224 			return (elem);
225 	}
226 
227 	return (NULL);
228 }
229 
230 void *
ipmi_hash_first(ipmi_hash_t * ihp)231 ipmi_hash_first(ipmi_hash_t *ihp)
232 {
233 	void *link = ipmi_list_next(&(ihp)->ih_list);
234 
235 	if (link == NULL)
236 		return (NULL);
237 
238 	return ((void *)((uintptr_t)link - ihp->ih_linkoffs));
239 }
240 
241 void *
ipmi_hash_next(ipmi_hash_t * ihp,void * elem)242 ipmi_hash_next(ipmi_hash_t *ihp, void *elem)
243 {
244 	void *link = ipmi_list_next((uintptr_t)elem + ihp->ih_linkoffs);
245 
246 	if (link == NULL)
247 		return (NULL);
248 
249 	return ((void *)((uintptr_t)link - ihp->ih_linkoffs));
250 }
251 
252 void
ipmi_hash_insert(ipmi_hash_t * ihp,void * elem)253 ipmi_hash_insert(ipmi_hash_t *ihp, void *elem)
254 {
255 	ipmi_hash_link_t *link = (void *)((uintptr_t)elem + ihp->ih_linkoffs);
256 	ulong_t idx = ipmi_hash_compute(ihp, elem);
257 
258 	assert(ipmi_hash_lookup(ihp, ihp->ih_convert(elem)) == NULL);
259 
260 	link->ihl_next = ihp->ih_buckets[idx];
261 	ihp->ih_buckets[idx] = link;
262 
263 	ipmi_list_append(&ihp->ih_list, link);
264 
265 	if (++ihp->ih_nelements > ihp->ih_nbuckets / 2)
266 		ipmi_hash_resize(ihp, ipmi_hash_double(ihp->ih_nbuckets));
267 }
268 
269 void
ipmi_hash_remove(ipmi_hash_t * ihp,void * elem)270 ipmi_hash_remove(ipmi_hash_t *ihp, void *elem)
271 {
272 	ulong_t idx = ipmi_hash_compute(ihp, elem);
273 	ipmi_hash_link_t *link = (void *)((uintptr_t)elem + ihp->ih_linkoffs);
274 	ipmi_hash_link_t **hlp = &ihp->ih_buckets[idx];
275 
276 	for (; *hlp != NULL; hlp = &(*hlp)->ihl_next) {
277 		if (*hlp == link)
278 			break;
279 	}
280 
281 	assert(*hlp != NULL);
282 	*hlp = (*hlp)->ihl_next;
283 
284 	ipmi_list_delete(&ihp->ih_list, link);
285 
286 	assert(ihp->ih_nelements > 0);
287 
288 	if (--ihp->ih_nelements < ihp->ih_nbuckets / 4)
289 		ipmi_hash_resize(ihp, ipmi_hash_half(ihp->ih_nbuckets));
290 }
291 
292 size_t
ipmi_hash_count(ipmi_hash_t * ihp)293 ipmi_hash_count(ipmi_hash_t *ihp)
294 {
295 	return (ihp->ih_nelements);
296 }
297