src/mesa/drivers/dri/dri_client/xf86drmHash.c

   1 /* xf86drmHash.c -- Small hash table support for integer -> integer mapping
   2  * Created: Sun Apr 18 09:35:45 1999 by faith@precisioninsight.com
   3  *
   4  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
   5  * All Rights Reserved.
   6  *
   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:
  13  *
  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
  16  * Software.
  17  *
  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.
  25  *
  26  * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
  27  *
  28  * $XFree86: xc/programs/Xserver/hw/xfree86/os-support/linux/drm/xf86drmHash.c,v 1.4 2001/03/21 18:08:54 dawes Exp $
  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 #define HASH_MAIN 0
  74
  75 #if HASH_MAIN
  76 # include <stdio.h>
  77 # include <stdlib.h>
  78 #else
  79 # include "xf86drm.h"
  80 # ifdef XFree86LOADER
  81 #  include "xf86.h"
  82 #  include "xf86_ansic.h"
  83 # else
  84 #  include <stdio.h>
  85 #  include <stdlib.h>
  86 # endif
  87 #endif
  88
  89 #define N(x)  drm##x
  90
  91 #define HASH_MAGIC 0xdeadbeef
  92 #define HASH_DEBUG 0
  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
  96                                    function! */
  97
  98 #if HASH_MAIN
  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()
 104 #else
 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)
 110
 111 #endif
 112
 113 typedef struct HashBucket {
 114     unsigned long     key;
 115     void              *value;
 116     struct HashBucket *next;
 117 } HashBucket, *HashBucketPtr;
 118
 119 typedef struct HashTable {
 120     unsigned long    magic;
 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];
 126     int              p0;
 127     HashBucketPtr    p1;
 128 } HashTable, *HashTablePtr;
 129
 130 #if HASH_MAIN
 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);
 136 #endif
 137
 138 static unsigned long HashHash(unsigned long key)
 139 {
 140     unsigned long        hash = 0;
 141     unsigned long        tmp  = key;
 142     static int           init = 0;
 143     static unsigned long scatter[256];
 144     int                  i;
 145
 146     if (!init) {
 147         HASH_RANDOM_DECL;
 148         HASH_RANDOM_INIT(37);
 149         for (i = 0; i < 256; i++) scatter[i] = HASH_RANDOM;
 150         ++init;
 151     }
 152
 153     while (tmp) {
 154         hash = (hash << 1) + scatter[tmp & 0xff];
 155         tmp >>= 8;
 156     }
 157
 158     hash %= HASH_SIZE;
 159 #if HASH_DEBUG
 160     printf( "Hash(%d) = %d\n", key, hash);
 161 #endif
 162     return hash;
 163 }
 164
 165 void *N(HashCreate)(void)
 166 {
 167     HashTablePtr table;
 168     int          i;
 169
 170     table           = HASH_ALLOC(sizeof(*table));
 171     if (!table) return NULL;
 172     table->magic    = HASH_MAGIC;
 173     table->entries  = 0;
 174     table->hits     = 0;
 175     table->partials = 0;
 176     table->misses   = 0;
 177
 178     for (i = 0; i < HASH_SIZE; i++) table->buckets[i] = NULL;
 179     return table;
 180 }
 181
 182 int N(HashDestroy)(void *t)
 183 {
 184     HashTablePtr  table = (HashTablePtr)t;
 185     HashBucketPtr bucket;
 186     HashBucketPtr next;
 187     int           i;
 188
 189     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 190
 191     for (i = 0; i < HASH_SIZE; i++) {
 192         for (bucket = table->buckets[i]; bucket;) {
 193             next = bucket->next;
 194             HASH_FREE(bucket);
 195             bucket = next;
 196         }
 197     }
 198     HASH_FREE(table);
 199     return 0;
 200 }
 201
 202 /* Find the bucket and organize the list so that this bucket is at the
 203    top. */
 204
 205 static HashBucketPtr HashFind(HashTablePtr table,
 206                               unsigned long key, unsigned long *h)
 207 {
 208     unsigned long hash = HashHash(key);
 209     HashBucketPtr prev = NULL;
 210     HashBucketPtr bucket;
 211
 212     if (h) *h = hash;
 213
 214     for (bucket = table->buckets[hash]; bucket; bucket = bucket->next) {
 215         if (bucket->key == key) {
 216             if (prev) {
 217                                 /* Organize */
 218                 prev->next           = bucket->next;
 219                 bucket->next         = table->buckets[hash];
 220                 table->buckets[hash] = bucket;
 221                 ++table->partials;
 222             } else {
 223                 ++table->hits;
 224             }
 225             return bucket;
 226         }
 227         prev = bucket;
 228     }
 229     ++table->misses;
 230     return NULL;
 231 }
 232
 233 int N(HashLookup)(void *t, unsigned long key, void **value)
 234 {
 235     HashTablePtr  table = (HashTablePtr)t;
 236     HashBucketPtr bucket;
 237
 238     if (!table || table->magic != HASH_MAGIC) return -1; /* Bad magic */
 239
 240     bucket = HashFind(table, key, NULL);
 241     if (!bucket) return 1;      /* Not found */
 242     *value = bucket->value;
 243     return 0;                   /* Found */
 244 }
 245
 246 int N(HashInsert)(void *t, unsigned long key, void *value)
 247 {
 248     HashTablePtr  table = (HashTablePtr)t;
 249     HashBucketPtr bucket;
 250     unsigned long hash;
 251
 252     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 253
 254     if (HashFind(table, key, &hash)) return 1; /* Already in table */
 255
 256     bucket               = HASH_ALLOC(sizeof(*bucket));
 257     if (!bucket) return -1;     /* Error */
 258     bucket->key          = key;
 259     bucket->value        = value;
 260     bucket->next         = table->buckets[hash];
 261     table->buckets[hash] = bucket;
 262 #if HASH_DEBUG
 263     printf("Inserted %d at %d/%p\n", key, hash, bucket);
 264 #endif
 265     return 0;                   /* Added to table */
 266 }
 267
 268 int N(HashDelete)(void *t, unsigned long key)
 269 {
 270     HashTablePtr  table = (HashTablePtr)t;
 271     unsigned long hash;
 272     HashBucketPtr bucket;
 273
 274     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 275
 276     bucket = HashFind(table, key, &hash);
 277
 278     if (!bucket) return 1;      /* Not found */
 279
 280     table->buckets[hash] = bucket->next;
 281     HASH_FREE(bucket);
 282     return 0;
 283 }
 284
 285 int N(HashNext)(void *t, unsigned long *key, void **value)
 286 {
 287     HashTablePtr  table = (HashTablePtr)t;
 288
 289     for (; table->p0 < HASH_SIZE;
 290          ++table->p0, table->p1 = table->buckets[table->p0]) {
 291         if (table->p1) {
 292             *key       = table->p1->key;
 293             *value     = table->p1->value;
 294             table->p1  = table->p1->next;
 295             return 1;
 296         }
 297     }
 298     return 0;
 299 }
 300
 301 int N(HashFirst)(void *t, unsigned long *key, void **value)
 302 {
 303     HashTablePtr  table = (HashTablePtr)t;
 304
 305     if (table->magic != HASH_MAGIC) return -1; /* Bad magic */
 306
 307     table->p0 = 0;
 308     table->p1 = table->buckets[0];
 309     return N(HashNext)(table, key, value);
 310 }
 311
 312 #if HASH_MAIN
 313 #define DIST_LIMIT 10
 314 static int dist[DIST_LIMIT];
 315
 316 static void clear_dist(void) {
 317     int i;
 318
 319     for (i = 0; i < DIST_LIMIT; i++) dist[i] = 0;
 320 }
 321
 322 static int count_entries(HashBucketPtr bucket)
 323 {
 324     int count = 0;
 325
 326     for (; bucket; bucket = bucket->next) ++count;
 327     return count;
 328 }
 329
 330 static void update_dist(int count)
 331 {
 332     if (count >= DIST_LIMIT) ++dist[DIST_LIMIT-1];
 333     else                     ++dist[count];
 334 }
 335
 336 static void compute_dist(HashTablePtr table)
 337 {
 338     int           i;
 339     HashBucketPtr bucket;
 340
 341     printf("Entries = %ld, hits = %ld, partials = %ld, misses = %ld\n",
 342            table->entries, table->hits, table->partials, table->misses);
 343     clear_dist();
 344     for (i = 0; i < HASH_SIZE; i++) {
 345         bucket = table->buckets[i];
 346         update_dist(count_entries(bucket));
 347     }
 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]);
 351     }
 352 }
 353
 354 static void check_table(HashTablePtr table,
 355                         unsigned long key, unsigned long value)
 356 {
 357     unsigned long retval  = 0;
 358     int           retcode = N(HashLookup)(table, key, &retval);
 359
 360     switch (retcode) {
 361     case -1:
 362         printf("Bad magic = 0x%08lx:"
 363                " key = %lu, expected = %lu, returned = %lu\n",
 364                table->magic, key, value, retval);
 365         break;
 366     case 1:
 367         printf("Not found: key = %lu, expected = %lu returned = %lu\n",
 368                key, value, retval);
 369         break;
 370     case 0:
 371         if (value != retval)
 372             printf("Bad value: key = %lu, expected = %lu, returned = %lu\n",
 373                    key, value, retval);
 374         break;
 375     default:
 376         printf("Bad retcode = %d: key = %lu, expected = %lu, returned = %lu\n",
 377                retcode, key, value, retval);
 378         break;
 379     }
 380 }
 381
 382 int main(void)
 383 {
 384     HashTablePtr table;
 385     int          i;
 386
 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);
 392     compute_dist(table);
 393     N(HashDestroy)(table);
 394
 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);
 400     compute_dist(table);
 401     N(HashDestroy)(table);
 402
 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);
 408     compute_dist(table);
 409     N(HashDestroy)(table);
 410
 411     printf("\n***** 1024 random integers ****\n");
 412     table = N(HashCreate)();
 413     srandom(0xbeefbeef);
 414     for (i = 0; i < 1024; i++) N(HashInsert)(table, random(), i);
 415     srandom(0xbeefbeef);
 416     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 417     srandom(0xbeefbeef);
 418     for (i = 0; i < 1024; i++) check_table(table, random(), i);
 419     compute_dist(table);
 420     N(HashDestroy)(table);
 421
 422     printf("\n***** 5000 random integers ****\n");
 423     table = N(HashCreate)();
 424     srandom(0xbeefbeef);
 425     for (i = 0; i < 5000; i++) N(HashInsert)(table, random(), i);
 426     srandom(0xbeefbeef);
 427     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 428     srandom(0xbeefbeef);
 429     for (i = 0; i < 5000; i++) check_table(table, random(), i);
 430     compute_dist(table);
 431     N(HashDestroy)(table);
 432
 433     return 0;
 434 }
 435 #endif