src/glx/x11/glxhash.c

   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
  81 #define HASH_MAGIC 0xdeadbeef
  82 #define HASH_DEBUG 0
  83 #define HASH_SIZE  512          /* Good for about 100 entries */
  84                                 /* If you change this value, you probably
  85                                    have to change the HashHash hashing
  86                                    function! */
  87
  88 #define HASH_ALLOC malloc
  89 #define HASH_FREE  free
  90 #define HASH_RANDOM_DECL
  91 #define HASH_RANDOM_INIT(seed)  srandom(seed)
  92 #define HASH_RANDOM             random()
  93 #define HASH_RANDOM_DESTROY
  94
  95 typedef struct __glxHashBucket {
  96     unsigned long     key;
  97     void              *value;
  98     struct __glxHashBucket *next;
  99 } __glxHashBucket, *__glxHashBucketPtr;
 100
 101 typedef struct __glxHashTable *__glxHashTablePtr;
 102 struct __glxHashTable {
 103     unsigned long    magic;
 104     unsigned long    hits;      /* At top of linked list */
 105     unsigned long    partials;  /* Not at top of linked list */
 106     unsigned long    misses;    /* Not in table */
 107     __glxHashBucketPtr    buckets[HASH_SIZE];
 108     int              p0;
 109     __glxHashBucketPtr    p1;
 110 };
 111
 112 static unsigned long HashHash(unsigned long key)
 113 {
 114     unsigned long        hash = 0;
 115     unsigned long        tmp  = key;
 116     static int           init = 0;
 117     static unsigned long scatter[256];
 118     int                  i;
 119
 120     if (!init) {
 121         HASH_RANDOM_DECL;
 122         HASH_RANDOM_INIT(37);
 123         for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
 124         HASH_RANDOM_DESTROY;
 125         ++init;
 126     }
 127
 128     while (tmp) {
 129         hash = (hash << 1) + scatter[tmp & 0xff];
 130         tmp >>= 8;
 131     }
 132
 133     hash %= HASH_SIZE;
 134 #if HASH_DEBUG
 135     printf( "Hash(%d) = %d\n", key, hash);
 136 #endif
 137     return hash;
 138 }
 139
 140 _X_HIDDEN __glxHashTable *__glxHashCreate(void)
 141 {
 142     __glxHashTablePtr table;
 143     int          i;
 144
 145     table           = HASH_ALLOC(sizeof(*table));
 146     if (!table) return NULL;
 147     table->magic    = HASH_MAGIC;
 148     table->hits     = 0;
 149     table->partials = 0;
 150     table->misses   = 0;
 151
 152     for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
 153     return table;
 154 }
 155
 156 _X_HIDDEN int __glxHashDestroy(__glxHashTable *t)
 157 {
 158     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 159     __glxHashBucketPtr bucket;
 160     __glxHashBucketPtr next;
 161     int           i;
 162
 163     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 164
 165     for (i = 0; i < HASH_SIZE; i++) {
 166         for (bucket = table->buckets[i]; bucket;) {
 167             next = bucket->next;
 168             HASH_FREE(bucket);
 169             bucket = next;
 170         }
 171     }
 172     HASH_FREE(table);
 173     return 0;
 174 }
 175
 176 /* Find the bucket and organize the list so that this bucket is at the
 177    top. */
 178
 179 static __glxHashBucketPtr HashFind(__glxHashTablePtr table,
 180                               unsigned long key, unsigned long *h)
 181 {
 182     unsigned long hash = HashHash(key);
 183     __glxHashBucketPtr prev = NULL;
 184     __glxHashBucketPtr bucket;
 185
 186     if (h) *h = hash;
 187
 188     for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
 189         if (bucket->key == key) {
 190             if (prev) {
 191                                 /* Organize */
 192                 prev->next           = bucket->next;
 193                 bucket->next         = table->buckets[hash];
 194                 table->buckets[hash] = bucket;
 195                 ++table->partials;
 196             } else {
 197                 ++table->hits;
 198             }
 199             return bucket;
 200         }
 201         prev = bucket;
 202     }
 203     ++table->misses;
 204     return NULL;
 205 }
 206
 207 _X_HIDDEN int __glxHashLookup(__glxHashTable *t,
 208                               unsigned long key, void **value)
 209 {
 210     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 211     __glxHashBucketPtr bucket;
 212
 213     if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */
 214
 215     bucket = HashFind(table, key, NULL);
 216     if (!bucket) return 1;      /* Not found */
 217     *value = bucket->value;
 218     return 0;                   /* Found */
 219 }
 220
 221 _X_HIDDEN int __glxHashInsert(__glxHashTable *t,
 222                               unsigned long key, void *value)
 223 {
 224     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 225     __glxHashBucketPtr bucket;
 226     unsigned long hash;
 227
 228     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 229
 230     if (HashFind(table, key, &hash)) return 1; /* Already in table */
 231
 232     bucket               = HASH_ALLOC(sizeof(*bucket));
 233     if (!bucket) return -1;     /* Error */
 234     bucket->key          = key;
 235     bucket->value        = value;
 236     bucket->next         = table->buckets[hash];
 237     table->buckets[hash] = bucket;
 238 #if HASH_DEBUG
 239     printf("Inserted %d at %d/%p\n", key, hash, bucket);
 240 #endif
 241     return 0;                   /* Added to table */
 242 }
 243
 244 _X_HIDDEN int __glxHashDelete(__glxHashTable *t, unsigned long key)
 245 {
 246     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 247     unsigned long hash;
 248     __glxHashBucketPtr bucket;
 249
 250     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 251
 252     bucket = HashFind(table, key, &hash);
 253
 254     if (!bucket) return 1;      /* Not found */
 255
 256     table->buckets[hash] = bucket->next;
 257     HASH_FREE(bucket);
 258     return 0;
 259 }
 260
 261 _X_HIDDEN int __glxHashNext(__glxHashTable *t,
 262                             unsigned long *key, void **value)
 263 {
 264     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 265
 266     while (table->p0 < HASH_SIZE) {
 267         if (table->p1) {
 268             *key       = table->p1->key;
 269             *value     = table->p1->value;
 270             table->p1  = table->p1->next;
 271             return 1;
 272         }
 273         table->p1 = table->buckets[table->p0];
 274         ++table->p0;
 275     }
 276     return 0;
 277 }
 278
 279 _X_HIDDEN int __glxHashFirst(__glxHashTable *t,
 280                              unsigned long *key, void **value)
 281 {
 282     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 283
 284     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 285
 286     table->p0 = 0;
 287     table->p1 = table->buckets[0];
 288     return __glxHashNext(table, key, value);
 289 }
 290
 291 #if HASH_MAIN
 292 #define DIST_LIMIT 10
 293 static int dist[DIST_LIMIT];
 294
 295 static void clear_dist(void) {
 296     int i;
 297
 298     for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
 299 }
 300
 301 static int count_entries(__glxHashBucketPtr bucket)
 302 {
 303     int count = 0;
 304
 305     for (; bucket; bucket = bucket->next) ++count;
 306     return count;
 307 }
 308
 309 static void update_dist(int count)
 310 {
 311     if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
 312     else                     ++dist[count];
 313 }
 314
 315 static void compute_dist(__glxHashTablePtr table)
 316 {
 317     int           i;
 318     __glxHashBucketPtr bucket;
 319
 320     printf("Hits = %ld, partials = %ld, misses = %ld\n",
 321            table->hits, table->partials, table->misses);
 322     clear_dist();
 323     for (i = 0; i < HASH_SIZE; i++) {
 324         bucket = table->buckets[i];
 325         update_dist(count_entries(bucket));
 326     }
 327     for (i = 0; i < DIST_LIMIT; i++) {
 328         if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
 329         else                   printf("other %10d\n", dist[i]);
 330     }
 331 }
 332
 333 static void check_table(__glxHashTablePtr table,
 334                         unsigned long key, unsigned long value)
 335 {
 336     unsigned long retval  = 0;
 337     int           retcode = __glxHashLookup(table, key, &retval);
 338
 339     switch (retcode) {
 340     case -1:
 341         printf("Bad magic = 0x%08lx:"
 342                " key = %lu, expected = %lu, returned = %lu\n",
 343                table->magic, key, value, retval);
 344         break;
 345     case 1:
 346         printf("Not found: key = %lu, expected = %lu returned = %lu\n",
 347                key, value, retval);
 348         break;
 349     case 0:
 350         if (value != retval)
 351             printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
 352                    key, value, retval);
 353         break;
 354     default:
 355         printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
 356                retcode, key, value, retval);
 357         break;
 358     }
 359 }
 360
 361 int main(void)
 362 {
 363     __glxHashTablePtr table;
 364     int          i;
 365
 366     printf("\n***** 256 consecutive integers ****\n");
 367     table = __glxHashCreate();
 368     for (i = 0; i < 256; i++) __glxHashInsert(table, i, i);
 369     for (i = 0; i < 256; i++) check_table(table, i, i);
 370     for (i = 256; i >= 0; i--) check_table(table, i, i);
 371     compute_dist(table);
 372     __glxHashDestroy(table);
 373
 374     printf("\n***** 1024 consecutive integers ****\n");
 375     table = __glxHashCreate();
 376     for (i = 0; i < 1024; i++) __glxHashInsert(table, i, i);
 377     for (i = 0; i < 1024; i++) check_table(table, i, i);
 378     for (i = 1024; i >= 0; i--) check_table(table, i, i);
 379     compute_dist(table);
 380     __glxHashDestroy(table);
 381
 382     printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
 383     table = __glxHashCreate();
 384     for (i = 0; i < 1024; i++) __glxHashInsert(table, i*4096, i);
 385     for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
 386     for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
 387     compute_dist(table);
 388     __glxHashDestroy(table);
 389
 390     printf("\n***** 1024 random integers ****\n");
 391     table = __glxHashCreate();
 392     srandom(0xbeefbeef);
 393     for (i = 0; i < 1024; i++) __glxHashInsert(table, random(), i);
 394     srandom(0xbeefbeef);
 395     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 396     srandom(0xbeefbeef);
 397     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 398     compute_dist(table);
 399     __glxHashDestroy(table);
 400
 401     printf("\n***** 5000 random integers ****\n");
 402     table = __glxHashCreate();
 403     srandom(0xbeefbeef);
 404     for (i = 0; i < 5000; i++) __glxHashInsert(table, random(), i);
 405     srandom(0xbeefbeef);
 406     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 407     srandom(0xbeefbeef);
 408     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 409     compute_dist(table);
 410     __glxHashDestroy(table);
 411
 412     return 0;
 413 }
 414 #endif