1/* glxhash.c -- Small hash table support for integer -> integer mapping
2 * Taken from libdrm.
3 *
4 * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
5 *
6 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
7 * All Rights Reserved.
8 *
9 * Permission is hereby granted, free of charge, to any person obtaining a
10 * copy of this software and associated documentation files (the "Software"),
11 * to deal in the Software without restriction, including without limitation
12 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
13 * and/or sell copies of the Software, and to permit persons to whom the
14 * Software is furnished to do so, subject to the following conditions:
15 *
16 * The above copyright notice and this permission notice (including the next
17 * paragraph) shall be included in all copies or substantial portions of the
18 * Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
23 * PRECISION INSIGHT AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
24 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
25 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
26 * DEALINGS IN THE SOFTWARE.
27 *
28 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
29 *
30 * DESCRIPTION
31 *
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:
36 *
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
40 * resolution.
41 *
42 * 2) The hash computation uses a table of random integers [Hanson97,
43 * pp. 39-41].
44 *
45 * FUTURE ENHANCEMENTS
46 *
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
57 * implementation.
58 *
59 * REFERENCES
60 *
61 * [Hanson97] David R. Hanson.  C Interfaces and Implementations:
62 * Techniques for Creating Reusable Software.  Reading, Massachusetts:
63 * Addison-Wesley, 1997.
64 *
65 * [Knuth73] Donald E. Knuth. The Art of Computer Programming.  Volume 3:
66 * Sorting and Searching.  Reading, Massachusetts: Addison-Wesley, 1973.
67 *
68 * [Larson88] Per-Ake Larson. "Dynamic Hash Tables".  CACM 31(4), April
69 * 1988, pp. 446-457.
70 *
71 */
72
73#include "glxhash.h"
74#include <X11/Xfuncproto.h>
75
76#define HASH_MAIN 0
77
78#include <stdio.h>
79#include <stdlib.h>
80#include <string.h>
81
82#define HASH_MAGIC 0xdeadbeef
83#define HASH_DEBUG 0
84#define HASH_SIZE  512          /* Good for about 100 entries */
85                                /* If you change this value, you probably
86                                   have to change the HashHash hashing
87                                   function! */
88
89#define HASH_ALLOC malloc
90#define HASH_FREE  free
91#ifndef __GLIBC__
92#define HASH_RANDOM_DECL	char *ps, rs[256]
93#define HASH_RANDOM_INIT(seed)	ps = initstate(seed, rs, sizeof(rs))
94#define HASH_RANDOM		random()
95#define HASH_RANDOM_DESTROY	setstate(ps)
96#else
97#define HASH_RANDOM_DECL	struct random_data rd; int32_t rv; char rs[256]
98#define HASH_RANDOM_INIT(seed)					\
99   do {								\
100      (void) memset(&rd, 0, sizeof(rd));			\
101      (void) initstate_r(seed, rs, sizeof(rs), &rd);		\
102   } while(0)
103#define HASH_RANDOM             ((void) random_r(&rd, &rv), rv)
104#define HASH_RANDOM_DESTROY
105#endif
106
107typedef struct __glxHashBucket
108{
109   unsigned long key;
110   void *value;
111   struct __glxHashBucket *next;
112} __glxHashBucket, *__glxHashBucketPtr;
113
114typedef struct __glxHashTable *__glxHashTablePtr;
115struct __glxHashTable
116{
117   unsigned long magic;
118   unsigned long hits;          /* At top of linked list */
119   unsigned long partials;      /* Not at top of linked list */
120   unsigned long misses;        /* Not in table */
121   __glxHashBucketPtr buckets[HASH_SIZE];
122   int p0;
123   __glxHashBucketPtr p1;
124};
125
126static unsigned long
127HashHash(unsigned long key)
128{
129   unsigned long hash = 0;
130   unsigned long tmp = key;
131   static int init = 0;
132   static unsigned long scatter[256];
133   int i;
134
135   if (!init) {
136      HASH_RANDOM_DECL;
137      HASH_RANDOM_INIT(37);
138      for (i = 0; i < 256; i++)
139         scatter[i] = HASH_RANDOM;
140      HASH_RANDOM_DESTROY;
141      ++init;
142   }
143
144   while (tmp) {
145      hash = (hash << 1) + scatter[tmp & 0xff];
146      tmp >>= 8;
147   }
148
149   hash %= HASH_SIZE;
150#if HASH_DEBUG
151   printf("Hash(%d) = %d\n", key, hash);
152#endif
153   return hash;
154}
155
156_X_HIDDEN __glxHashTable *
157__glxHashCreate(void)
158{
159   __glxHashTablePtr table;
160   int i;
161
162   table = HASH_ALLOC(sizeof(*table));
163   if (!table)
164      return NULL;
165   table->magic = HASH_MAGIC;
166   table->hits = 0;
167   table->partials = 0;
168   table->misses = 0;
169
170   for (i = 0; i < HASH_SIZE; i++)
171      table->buckets[i] = NULL;
172   return table;
173}
174
175_X_HIDDEN int
176__glxHashDestroy(__glxHashTable * t)
177{
178   __glxHashTablePtr table = (__glxHashTablePtr) t;
179   __glxHashBucketPtr bucket;
180   __glxHashBucketPtr next;
181   int i;
182
183   if (table->magic != HASH_MAGIC)
184      return -1;                /* Bad magic */
185
186   for (i = 0; i < HASH_SIZE; i++) {
187      for (bucket = table->buckets[i]; bucket;) {
188         next = bucket->next;
189         HASH_FREE(bucket);
190         bucket = next;
191      }
192   }
193   HASH_FREE(table);
194   return 0;
195}
196
197/* Find the bucket and organize the list so that this bucket is at the
198   top. */
199
200static __glxHashBucketPtr
201HashFind(__glxHashTablePtr table, unsigned long key, unsigned long *h)
202{
203   unsigned long hash = HashHash(key);
204   __glxHashBucketPtr prev = NULL;
205   __glxHashBucketPtr bucket;
206
207   if (h)
208      *h = hash;
209
210   for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
211      if (bucket->key == key) {
212         if (prev) {
213            /* Organize */
214            prev->next = bucket->next;
215            bucket->next = table->buckets[hash];
216            table->buckets[hash] = bucket;
217            ++table->partials;
218         }
219         else {
220            ++table->hits;
221         }
222         return bucket;
223      }
224      prev = bucket;
225   }
226   ++table->misses;
227   return NULL;
228}
229
230_X_HIDDEN int
231__glxHashLookup(__glxHashTable * t, unsigned long key, void **value)
232{
233   __glxHashTablePtr table = (__glxHashTablePtr) t;
234   __glxHashBucketPtr bucket;
235
236   if (!table || table->magic != HASH_MAGIC)
237      return -1;                /* Bad magic */
238
239   bucket = HashFind(table, key, NULL);
240   if (!bucket)
241      return 1;                 /* Not found */
242   *value = bucket->value;
243   return 0;                    /* Found */
244}
245
246_X_HIDDEN int
247__glxHashInsert(__glxHashTable * t, unsigned long key, void *value)
248{
249   __glxHashTablePtr table = (__glxHashTablePtr) t;
250   __glxHashBucketPtr bucket;
251   unsigned long hash;
252
253   if (table->magic != HASH_MAGIC)
254      return -1;                /* Bad magic */
255
256   if (HashFind(table, key, &hash))
257      return 1;                 /* Already in table */
258
259   bucket = HASH_ALLOC(sizeof(*bucket));
260   if (!bucket)
261      return -1;                /* Error */
262   bucket->key = key;
263   bucket->value = value;
264   bucket->next = table->buckets[hash];
265   table->buckets[hash] = bucket;
266#if HASH_DEBUG
267   printf("Inserted %d at %d/%p\n", key, hash, bucket);
268#endif
269   return 0;                    /* Added to table */
270}
271
272_X_HIDDEN int
273__glxHashDelete(__glxHashTable * t, unsigned long key)
274{
275   __glxHashTablePtr table = (__glxHashTablePtr) t;
276   unsigned long hash;
277   __glxHashBucketPtr bucket;
278
279   if (table->magic != HASH_MAGIC)
280      return -1;                /* Bad magic */
281
282   bucket = HashFind(table, key, &hash);
283
284   if (!bucket)
285      return 1;                 /* Not found */
286
287   table->buckets[hash] = bucket->next;
288   HASH_FREE(bucket);
289   return 0;
290}
291
292_X_HIDDEN int
293__glxHashNext(__glxHashTable * t, unsigned long *key, void **value)
294{
295   __glxHashTablePtr table = (__glxHashTablePtr) t;
296
297   while (table->p0 < HASH_SIZE) {
298      if (table->p1) {
299         *key = table->p1->key;
300         *value = table->p1->value;
301         table->p1 = table->p1->next;
302         return 1;
303      }
304      table->p1 = table->buckets[table->p0];
305      ++table->p0;
306   }
307   return 0;
308}
309
310_X_HIDDEN int
311__glxHashFirst(__glxHashTable * t, unsigned long *key, void **value)
312{
313   __glxHashTablePtr table = (__glxHashTablePtr) t;
314
315   if (table->magic != HASH_MAGIC)
316      return -1;                /* Bad magic */
317
318   table->p0 = 0;
319   table->p1 = table->buckets[0];
320   return __glxHashNext(table, key, value);
321}
322
323#if HASH_MAIN
324#define DIST_LIMIT 10
325static int dist[DIST_LIMIT];
326
327static void
328clear_dist(void)
329{
330   int i;
331
332   for (i = 0; i < DIST_LIMIT; i++)
333      dist[i] = 0;
334}
335
336static int
337count_entries(__glxHashBucketPtr bucket)
338{
339   int count = 0;
340
341   for (; bucket; bucket = bucket->next)
342      ++count;
343   return count;
344}
345
346static void
347update_dist(int count)
348{
349   if (count >= DIST_LIMIT)
350      ++dist[DIST_LIMIT - 1];
351   else
352      ++dist[count];
353}
354
355static void
356compute_dist(__glxHashTablePtr table)
357{
358   int i;
359   __glxHashBucketPtr bucket;
360
361   printf("Hits = %ld, partials = %ld, misses = %ld\n",
362          table->hits, table->partials, table->misses);
363   clear_dist();
364   for (i = 0; i < HASH_SIZE; i++) {
365      bucket = table->buckets[i];
366      update_dist(count_entries(bucket));
367   }
368   for (i = 0; i < DIST_LIMIT; i++) {
369      if (i != DIST_LIMIT - 1)
370         printf("%5d %10d\n", i, dist[i]);
371      else
372         printf("other %10d\n", dist[i]);
373   }
374}
375
376static void
377check_table(__glxHashTablePtr table, unsigned long key, unsigned long value)
378{
379   unsigned long retval = 0;
380   int retcode = __glxHashLookup(table, key, &retval);
381
382   switch (retcode) {
383   case -1:
384      printf("Bad magic = 0x%08lx:"
385             " key = %lu, expected = %lu, returned = %lu\n",
386             table->magic, key, value, retval);
387      break;
388   case 1:
389      printf("Not found: key = %lu, expected = %lu returned = %lu\n",
390             key, value, retval);
391      break;
392   case 0:
393      if (value != retval)
394         printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
395                key, value, retval);
396      break;
397   default:
398      printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
399             retcode, key, value, retval);
400      break;
401   }
402}
403
404int
405main(void)
406{
407   __glxHashTablePtr table;
408   int i;
409
410   printf("\n***** 256 consecutive integers ****\n");
411   table = __glxHashCreate();
412   for (i = 0; i < 256; i++)
413      __glxHashInsert(table, i, i);
414   for (i = 0; i < 256; i++)
415      check_table(table, i, i);
416   for (i = 256; i >= 0; i--)
417      check_table(table, i, i);
418   compute_dist(table);
419   __glxHashDestroy(table);
420
421   printf("\n***** 1024 consecutive integers ****\n");
422   table = __glxHashCreate();
423   for (i = 0; i < 1024; i++)
424      __glxHashInsert(table, i, i);
425   for (i = 0; i < 1024; i++)
426      check_table(table, i, i);
427   for (i = 1024; i >= 0; i--)
428      check_table(table, i, i);
429   compute_dist(table);
430   __glxHashDestroy(table);
431
432   printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
433   table = __glxHashCreate();
434   for (i = 0; i < 1024; i++)
435      __glxHashInsert(table, i * 4096, i);
436   for (i = 0; i < 1024; i++)
437      check_table(table, i * 4096, i);
438   for (i = 1024; i >= 0; i--)
439      check_table(table, i * 4096, i);
440   compute_dist(table);
441   __glxHashDestroy(table);
442
443   printf("\n***** 1024 random integers ****\n");
444   table = __glxHashCreate();
445   srandom(0xbeefbeef);
446   for (i = 0; i < 1024; i++)
447      __glxHashInsert(table, random(), i);
448   srandom(0xbeefbeef);
449   for (i = 0; i < 1024; i++)
450      check_table(table, random(), i);
451   srandom(0xbeefbeef);
452   for (i = 0; i < 1024; i++)
453      check_table(table, random(), i);
454   compute_dist(table);
455   __glxHashDestroy(table);
456
457   printf("\n***** 5000 random integers ****\n");
458   table = __glxHashCreate();
459   srandom(0xbeefbeef);
460   for (i = 0; i < 5000; i++)
461      __glxHashInsert(table, random(), i);
462   srandom(0xbeefbeef);
463   for (i = 0; i < 5000; i++)
464      check_table(table, random(), i);
465   srandom(0xbeefbeef);
466   for (i = 0; i < 5000; i++)
467      check_table(table, random(), i);
468   compute_dist(table);
469   __glxHashDestroy(table);
470
471   return 0;
472}
473#endif
474