1 /* xf86drmHash.c -- Small hash table support for integer -> integer mapping
2 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
4 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
7 * Permission is hereby granted, free of charge, to any person obtaining a
8 * copy of this software and associated documentation files (the "Software"),
9 * to deal in the Software without restriction, including without limitation
10 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
11 * and/or sell copies of the Software, and to permit persons to whom the
12 * Software is furnished to do so, subject to the following conditions:
14 * The above copyright notice and this permission notice (including the next
15 * paragraph) shall be included in all copies or substantial portions of the
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
21 * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
22 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
23 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
24 * DEALINGS IN THE SOFTWARE.
26 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
28 * $XFree86: xc/programs/Xserver/hw/xfree86/os-support/linux/drm/xf86drmHash.c,v 1.3 2000/06/17 00:03:34 martin Exp $
32 * This file contains a straightforward implementation of a fixed-sized
33 * hash table using self-organizing linked lists [Knuth73, pp. 398-399] for
34 * collision resolution. There are two potentially interesting things
35 * about this implementation:
37 * 1) The table is power-of-two sized. Prime sized tables are more
38 * traditional, but do not have a significant advantage over power-of-two
39 * sized table, especially when double hashing is not used for collision
42 * 2) The hash computation uses a table of random integers [Hanson97,
47 * With a table size of 512, the current implementation is sufficient for a
48 * few hundred keys. Since this is well above the expected size of the
49 * tables for which this implementation was designed, the implementation of
50 * dynamic hash tables was postponed until the need arises. A common (and
51 * naive) approach to dynamic hash table implementation simply creates a
52 * new hash table when necessary, rehashes all the data into the new table,
53 * and destroys the old table. The approach in [Larson88] is superior in
54 * two ways: 1) only a portion of the table is expanded when needed,
55 * distributing the expansion cost over several insertions, and 2) portions
56 * of the table can be locked, enabling a scalable thread-safe
61 * [Hanson97] David R. Hanson. C Interfaces and Implementations:
62 * Techniques for Creating Reusable Software. Reading, Massachusetts:
63 * Addison-Wesley, 1997.
65 * [Knuth73] Donald E. Knuth. The Art of Computer Programming. Volume 3:
66 * Sorting and Searching. Reading, Massachusetts: Addison-Wesley, 1973.
68 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables". CACM 31(4), April
82 # include "xf86_ansic.h"
91 #define HASH_MAGIC 0xdeadbeef
93 #define HASH_SIZE 512 /* Good for about 100 entries */
94 /* If you change this value, you probably
95 have to change the HashHash hashing
99 #define HASH_ALLOC malloc
100 #define HASH_FREE free
101 #define HASH_RANDOM_DECL
102 #define HASH_RANDOM_INIT(seed) srandom(seed)
103 #define HASH_RANDOM random()
105 #define HASH_ALLOC drmMalloc
106 #define HASH_FREE drmFree
107 #define HASH_RANDOM_DECL void *state
108 #define HASH_RANDOM_INIT(seed) state = drmRandomCreate(seed)
109 #define HASH_RANDOM drmRandom(state)
113 typedef struct HashBucket {
116 struct HashBucket *next;
117 } HashBucket, *HashBucketPtr;
119 typedef struct HashTable {
121 unsigned long entries;
122 unsigned long hits; /* At top of linked list */
123 unsigned long partials; /* Not at top of linked list */
124 unsigned long misses; /* Not in table */
125 HashBucketPtr buckets[HASH_SIZE];
128 } HashTable, *HashTablePtr;
131 extern void *N(HashCreate)(void);
132 extern int N(HashDestroy)(void *t);
133 extern int N(HashLookup)(void *t, unsigned long key, unsigned long *value);
134 extern int N(HashInsert)(void *t, unsigned long key, unsigned long value);
135 extern int N(HashDelete)(void *t, unsigned long key);
138 static unsigned long HashHash(unsigned long key)
140 unsigned long hash = 0;
141 unsigned long tmp = key;
143 static unsigned long scatter[256];
148 HASH_RANDOM_INIT(37);
149 for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
154 hash = (hash << 1) + scatter[tmp & 0xff];
160 printf( "Hash(%d) = %d\n", key, hash);
165 void *N(HashCreate)(void)
170 table = HASH_ALLOC(sizeof(*table));
171 if (!table) return NULL;
172 table->magic = HASH_MAGIC;
178 for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
182 int N(HashDestroy)(void *t)
184 HashTablePtr table = (HashTablePtr)t;
185 HashBucketPtr bucket;
189 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
191 for (i = 0; i < HASH_SIZE; i++) {
192 for (bucket = table->buckets[i]; bucket;) {
202 /* Find the bucket and organize the list so that this bucket is at the
205 static HashBucketPtr HashFind(HashTablePtr table,
206 unsigned long key, unsigned long *h)
208 unsigned long hash = HashHash(key);
209 HashBucketPtr prev = NULL;
210 HashBucketPtr bucket;
214 for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
215 if (bucket->key == key) {
218 prev->next = bucket->next;
219 bucket->next = table->buckets[hash];
220 table->buckets[hash] = bucket;
233 int N(HashLookup)(void *t, unsigned long key, void **value)
235 HashTablePtr table = (HashTablePtr)t;
236 HashBucketPtr bucket;
238 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
240 bucket = HashFind(table, key, NULL);
241 if (!bucket) return 1; /* Not found */
242 *value = bucket->value;
243 return 0; /* Found */
246 int N(HashInsert)(void *t, unsigned long key, void *value)
248 HashTablePtr table = (HashTablePtr)t;
249 HashBucketPtr bucket;
252 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
254 if (HashFind(table, key, &hash)) return 1; /* Already in table */
256 bucket = HASH_ALLOC(sizeof(*bucket));
257 if (!bucket) return -1; /* Error */
259 bucket->value = value;
260 bucket->next = table->buckets[hash];
261 table->buckets[hash] = bucket;
263 printf("Inserted %d at %d/%p\n", key, hash, bucket);
265 return 0; /* Added to table */
268 int N(HashDelete)(void *t, unsigned long key)
270 HashTablePtr table = (HashTablePtr)t;
272 HashBucketPtr bucket;
274 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
276 bucket = HashFind(table, key, &hash);
278 if (!bucket) return 1; /* Not found */
280 table->buckets[hash] = bucket->next;
285 int N(HashNext)(void *t, unsigned long *key, void **value)
287 HashTablePtr table = (HashTablePtr)t;
289 for (; table->p0 < HASH_SIZE;
290 ++table->p0, table->p1 = table->buckets[table->p0]) {
292 *key = table->p1->key;
293 *value = table->p1->value;
294 table->p1 = table->p1->next;
301 int N(HashFirst)(void *t, unsigned long *key, void **value)
303 HashTablePtr table = (HashTablePtr)t;
305 if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
308 table->p1 = table->buckets[0];
309 return N(HashNext)(table, key, value);
313 #define DIST_LIMIT 10
314 static int dist[DIST_LIMIT];
316 static void clear_dist(void) {
319 for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
322 static int count_entries(HashBucketPtr bucket)
326 for (; bucket; bucket = bucket->next) ++count;
330 static void update_dist(int count)
332 if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
336 static void compute_dist(HashTablePtr table)
339 HashBucketPtr bucket;
341 printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
342 table->entries, table->hits, table->partials, table->misses);
344 for (i = 0; i < HASH_SIZE; i++) {
345 bucket = table->buckets[i];
346 update_dist(count_entries(bucket));
348 for (i = 0; i < DIST_LIMIT; i++) {
349 if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
350 else printf("other %10d\n", dist[i]);
354 static void check_table(HashTablePtr table,
355 unsigned long key, unsigned long value)
357 unsigned long retval = 0;
358 int retcode = N(HashLookup)(table, key, &retval);
362 printf("Bad magic = 0x%08lx:"
363 " key = %lu, expected = %lu, returned = %lu\n",
364 table->magic, key, value, retval);
367 printf("Not found: key = %lu, expected = %lu returned = %lu\n",
372 printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
376 printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
377 retcode, key, value, retval);
387 printf("\n***** 256 consecutive integers ****\n");
388 table = N(HashCreate)();
389 for (i = 0; i < 256; i++) N(HashInsert)(table, i, i);
390 for (i = 0; i < 256; i++) check_table(table, i, i);
391 for (i = 256; i >= 0; i--) check_table(table, i, i);
393 N(HashDestroy)(table);
395 printf("\n***** 1024 consecutive integers ****\n");
396 table = N(HashCreate)();
397 for (i = 0; i < 1024; i++) N(HashInsert)(table, i, i);
398 for (i = 0; i < 1024; i++) check_table(table, i, i);
399 for (i = 1024; i >= 0; i--) check_table(table, i, i);
401 N(HashDestroy)(table);
403 printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
404 table = N(HashCreate)();
405 for (i = 0; i < 1024; i++) N(HashInsert)(table, i*4096, i);
406 for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
407 for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
409 N(HashDestroy)(table);
411 printf("\n***** 1024 random integers ****\n");
412 table = N(HashCreate)();
414 for (i = 0; i < 1024; i++) N(HashInsert)(table, random(), i);
416 for (i = 0; i < 1024; i++) check_table(table, random(), i);
418 for (i = 0; i < 1024; i++) check_table(table, random(), i);
420 N(HashDestroy)(table);
422 printf("\n***** 5000 random integers ****\n");
423 table = N(HashCreate)();
425 for (i = 0; i < 5000; i++) N(HashInsert)(table, random(), i);
427 for (i = 0; i < 5000; i++) check_table(table, random(), i);
429 for (i = 0; i < 5000; i++) check_table(table, random(), i);
431 N(HashDestroy)(table);