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
  75 #define HASH_MAIN 0
  76
  77 #include <stdio.h>
  78 #include <stdlib.h>
  79
  80 #define HASH_MAGIC 0xdeadbeef
  81 #define HASH_DEBUG 0
  82 #define HASH_SIZE  512          /* Good for about 100 entries */
  83                                 /* If you change this value, you probably
  84                                    have to change the HashHash hashing
  85                                    function! */
  86
  87 #define HASH_ALLOC malloc
  88 #define HASH_FREE  free
  89 #define HASH_RANDOM_DECL
  90 #define HASH_RANDOM_INIT(seed)  srandom(seed)
  91 #define HASH_RANDOM             random()
  92 #define HASH_RANDOM_DESTROY
  93
  94 typedef struct __glxHashBucket {
  95     unsigned long     key;
  96     void              *value;
  97     struct __glxHashBucket *next;
  98 } __glxHashBucket, *__glxHashBucketPtr;
  99
 100 typedef struct __glxHashTable *__glxHashTablePtr;
 101 struct __glxHashTable {
 102     unsigned long    magic;
 103     unsigned long    entries;
 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 __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->entries  = 0;
 149     table->hits     = 0;
 150     table->partials = 0;
 151     table->misses   = 0;
 152
 153     for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
 154     return table;
 155 }
 156
 157 int __glxHashDestroy(__glxHashTable *t)
 158 {
 159     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 160     __glxHashBucketPtr bucket;
 161     __glxHashBucketPtr next;
 162     int           i;
 163
 164     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 165
 166     for (i = 0; i < HASH_SIZE; i++) {
 167         for (bucket = table->buckets[i]; bucket;) {
 168             next = bucket->next;
 169             HASH_FREE(bucket);
 170             bucket = next;
 171         }
 172     }
 173     HASH_FREE(table);
 174     return 0;
 175 }
 176
 177 /* Find the bucket and organize the list so that this bucket is at the
 178    top. */
 179
 180 static __glxHashBucketPtr HashFind(__glxHashTablePtr table,
 181                               unsigned long key, unsigned long *h)
 182 {
 183     unsigned long hash = HashHash(key);
 184     __glxHashBucketPtr prev = NULL;
 185     __glxHashBucketPtr bucket;
 186
 187     if (h) *h = hash;
 188
 189     for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
 190         if (bucket->key == key) {
 191             if (prev) {
 192                                 /* Organize */
 193                 prev->next           = bucket->next;
 194                 bucket->next         = table->buckets[hash];
 195                 table->buckets[hash] = bucket;
 196                 ++table->partials;
 197             } else {
 198                 ++table->hits;
 199             }
 200             return bucket;
 201         }
 202         prev = bucket;
 203     }
 204     ++table->misses;
 205     return NULL;
 206 }
 207
 208 int __glxHashLookup(__glxHashTable *t, 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 int __glxHashInsert(__glxHashTable *t, unsigned long key, void *value)
 222 {
 223     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 224     __glxHashBucketPtr bucket;
 225     unsigned long hash;
 226
 227     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 228
 229     if (HashFind(table, key, &hash)) return 1; /* Already in table */
 230
 231     bucket               = HASH_ALLOC(sizeof(*bucket));
 232     if (!bucket) return -1;     /* Error */
 233     bucket->key          = key;
 234     bucket->value        = value;
 235     bucket->next         = table->buckets[hash];
 236     table->buckets[hash] = bucket;
 237 #if HASH_DEBUG
 238     printf("Inserted %d at %d/%p\n", key, hash, bucket);
 239 #endif
 240     return 0;                   /* Added to table */
 241 }
 242
 243 int __glxHashDelete(__glxHashTable *t, unsigned long key)
 244 {
 245     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 246     unsigned long hash;
 247     __glxHashBucketPtr bucket;
 248
 249     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 250
 251     bucket = HashFind(table, key, &hash);
 252
 253     if (!bucket) return 1;      /* Not found */
 254
 255     table->buckets[hash] = bucket->next;
 256     HASH_FREE(bucket);
 257     return 0;
 258 }
 259
 260 int __glxHashNext(__glxHashTable *t, unsigned long *key, void **value)
 261 {
 262     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 263
 264     while (table->p0 < HASH_SIZE) {
 265         if (table->p1) {
 266             *key       = table->p1->key;
 267             *value     = table->p1->value;
 268             table->p1  = table->p1->next;
 269             return 1;
 270         }
 271         table->p1 = table->buckets[table->p0];
 272         ++table->p0;
 273     }
 274     return 0;
 275 }
 276
 277 int __glxHashFirst(__glxHashTable *t, unsigned long *key, void **value)
 278 {
 279     __glxHashTablePtr  table = (__glxHashTablePtr)t;
 280
 281     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 282
 283     table->p0 = 0;
 284     table->p1 = table->buckets[0];
 285     return __glxHashNext(table, key, value);
 286 }
 287
 288 #if HASH_MAIN
 289 #define DIST_LIMIT 10
 290 static int dist[DIST_LIMIT];
 291
 292 static void clear_dist(void) {
 293     int i;
 294
 295     for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
 296 }
 297
 298 static int count_entries(__glxHashBucketPtr bucket)
 299 {
 300     int count = 0;
 301
 302     for (; bucket; bucket = bucket->next) ++count;
 303     return count;
 304 }
 305
 306 static void update_dist(int count)
 307 {
 308     if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
 309     else                     ++dist[count];
 310 }
 311
 312 static void compute_dist(__glxHashTablePtr table)
 313 {
 314     int           i;
 315     __glxHashBucketPtr bucket;
 316
 317     printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
 318            table->entries, table->hits, table->partials, table->misses);
 319     clear_dist();
 320     for (i = 0; i < HASH_SIZE; i++) {
 321         bucket = table->buckets[i];
 322         update_dist(count_entries(bucket));
 323     }
 324     for (i = 0; i < DIST_LIMIT; i++) {
 325         if (i != DIST_LIMIT-1) printf("%5d %10d\n", i, dist[i]);
 326         else                   printf("other %10d\n", dist[i]);
 327     }
 328 }
 329
 330 static void check_table(__glxHashTablePtr table,
 331                         unsigned long key, unsigned long value)
 332 {
 333     unsigned long retval  = 0;
 334     int           retcode = __glxHashLookup(table, key, &retval);
 335
 336     switch (retcode) {
 337     case -1:
 338         printf("Bad magic = 0x%08lx:"
 339                " key = %lu, expected = %lu, returned = %lu\n",
 340                table->magic, key, value, retval);
 341         break;
 342     case 1:
 343         printf("Not found: key = %lu, expected = %lu returned = %lu\n",
 344                key, value, retval);
 345         break;
 346     case 0:
 347         if (value != retval)
 348             printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
 349                    key, value, retval);
 350         break;
 351     default:
 352         printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
 353                retcode, key, value, retval);
 354         break;
 355     }
 356 }
 357
 358 int main(void)
 359 {
 360     __glxHashTablePtr table;
 361     int          i;
 362
 363     printf("\n***** 256 consecutive integers ****\n");
 364     table = __glxHashCreate();
 365     for (i = 0; i < 256; i++) __glxHashInsert(table, i, i);
 366     for (i = 0; i < 256; i++) check_table(table, i, i);
 367     for (i = 256; i >= 0; i--) check_table(table, i, i);
 368     compute_dist(table);
 369     __glxHashDestroy(table);
 370
 371     printf("\n***** 1024 consecutive integers ****\n");
 372     table = __glxHashCreate();
 373     for (i = 0; i < 1024; i++) __glxHashInsert(table, i, i);
 374     for (i = 0; i < 1024; i++) check_table(table, i, i);
 375     for (i = 1024; i >= 0; i--) check_table(table, i, i);
 376     compute_dist(table);
 377     __glxHashDestroy(table);
 378
 379     printf("\n***** 1024 consecutive page addresses (4k pages) ****\n");
 380     table = __glxHashCreate();
 381     for (i = 0; i < 1024; i++) __glxHashInsert(table, i*4096, i);
 382     for (i = 0; i < 1024; i++) check_table(table, i*4096, i);
 383     for (i = 1024; i >= 0; i--) check_table(table, i*4096, i);
 384     compute_dist(table);
 385     __glxHashDestroy(table);
 386
 387     printf("\n***** 1024 random integers ****\n");
 388     table = __glxHashCreate();
 389     srandom(0xbeefbeef);
 390     for (i = 0; i < 1024; i++) __glxHashInsert(table, random(), i);
 391     srandom(0xbeefbeef);
 392     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 393     srandom(0xbeefbeef);
 394     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 395     compute_dist(table);
 396     __glxHashDestroy(table);
 397
 398     printf("\n***** 5000 random integers ****\n");
 399     table = __glxHashCreate();
 400     srandom(0xbeefbeef);
 401     for (i = 0; i < 5000; i++) __glxHashInsert(table, random(), i);
 402     srandom(0xbeefbeef);
 403     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 404     srandom(0xbeefbeef);
 405     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 406     compute_dist(table);
 407     __glxHashDestroy(table);
 408
 409     return 0;
 410 }
 411 #endif