xf86drmSL.c

   1 /* xf86drmSL.c -- Skip list support
   2  * Created: Mon May 10 09:28:13 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  * DESCRIPTION
  29  *
  30  * This file contains a straightforward skip list implementation.n
  31  *
  32  * FUTURE ENHANCEMENTS
  33  *
  34  * REFERENCES
  35  *
  36  * [Pugh90] William Pugh.  Skip Lists: A Probabilistic Alternative to
  37  * Balanced Trees. CACM 33(6), June 1990, pp. 668-676.
  38  *
  39  */
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43
  44 #include "libdrm_macros.h"
  45 #include "xf86drm.h"
  46
  47 #define SL_LIST_MAGIC  0xfacade00LU
  48 #define SL_ENTRY_MAGIC 0x00fab1edLU
  49 #define SL_FREED_MAGIC 0xdecea5edLU
  50 #define SL_MAX_LEVEL   16
  51 #define SL_RANDOM_SEED 0xc01055a1LU
  52
  53 #define SL_RANDOM_DECL        static void *state = NULL
  54 #define SL_RANDOM_INIT(seed)  if (!state) state = drmRandomCreate(seed)
  55 #define SL_RANDOM             drmRandom(state)
  56
  57 typedef struct SLEntry {
  58     unsigned long     magic;       /* SL_ENTRY_MAGIC */
  59     unsigned long     key;
  60     void              *value;
  61     int               levels;
  62     struct SLEntry    *forward[1]; /* variable sized array */
  63 } SLEntry, *SLEntryPtr;
  64
  65 typedef struct SkipList {
  66     unsigned long    magic;     /* SL_LIST_MAGIC */
  67     int              level;
  68     int              count;
  69     SLEntryPtr       head;
  70     SLEntryPtr       p0;        /* Position for iteration */
  71 } SkipList, *SkipListPtr;
  72
  73 static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
  74 {
  75     SLEntryPtr entry;
  76
  77     if (max_level < 0 || max_level > SL_MAX_LEVEL) max_level = SL_MAX_LEVEL;
  78
  79     entry         = drmMalloc(sizeof(*entry)
  80                              + (max_level + 1) * sizeof(entry->forward[0]));
  81     if (!entry) return NULL;
  82     entry->magic  = SL_ENTRY_MAGIC;
  83     entry->key    = key;
  84     entry->value  = value;
  85     entry->levels = max_level + 1;
  86
  87     return entry;
  88 }
  89
  90 static int SLRandomLevel(void)
  91 {
  92     int level = 1;
  93     SL_RANDOM_DECL;
  94
  95     SL_RANDOM_INIT(SL_RANDOM_SEED);
  96
  97     while ((SL_RANDOM & 0x01) && level < SL_MAX_LEVEL) ++level;
  98     return level;
  99 }
 100
 101 drm_public void *drmSLCreate(void)
 102 {
 103     SkipListPtr  list;
 104     int          i;
 105
 106     list           = drmMalloc(sizeof(*list));
 107     if (!list) return NULL;
 108     list->magic    = SL_LIST_MAGIC;
 109     list->level    = 0;
 110     list->head     = SLCreateEntry(SL_MAX_LEVEL, 0, NULL);
 111     list->count    = 0;
 112
 113     for (i = 0; i <= SL_MAX_LEVEL; i++) list->head->forward[i] = NULL;
 114
 115     return list;
 116 }
 117
 118 drm_public int drmSLDestroy(void *l)
 119 {
 120     SkipListPtr   list  = (SkipListPtr)l;
 121     SLEntryPtr    entry;
 122     SLEntryPtr    next;
 123
 124     if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
 125
 126     for (entry = list->head; entry; entry = next) {
 127         if (entry->magic != SL_ENTRY_MAGIC) return -1; /* Bad magic */
 128         next         = entry->forward[0];
 129         entry->magic = SL_FREED_MAGIC;
 130         drmFree(entry);
 131     }
 132
 133     list->magic = SL_FREED_MAGIC;
 134     drmFree(list);
 135     return 0;
 136 }
 137
 138 static SLEntryPtr SLLocate(void *l, unsigned long key, SLEntryPtr *update)
 139 {
 140     SkipListPtr   list  = (SkipListPtr)l;
 141     SLEntryPtr    entry;
 142     int           i;
 143
 144     if (list->magic != SL_LIST_MAGIC) return NULL;
 145
 146     for (i = list->level, entry = list->head; i >= 0; i--) {
 147         while (entry->forward[i] && entry->forward[i]->key < key)
 148             entry = entry->forward[i];
 149         update[i] = entry;
 150     }
 151
 152     return entry->forward[0];
 153 }
 154
 155 drm_public int drmSLInsert(void *l, unsigned long key, void *value)
 156 {
 157     SkipListPtr   list  = (SkipListPtr)l;
 158     SLEntryPtr    entry;
 159     SLEntryPtr    update[SL_MAX_LEVEL + 1];
 160     int           level;
 161     int           i;
 162
 163     if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
 164
 165     entry = SLLocate(list, key, update);
 166
 167     if (entry && entry->key == key) return 1; /* Already in list */
 168
 169
 170     level = SLRandomLevel();
 171     if (level > list->level) {
 172         level = ++list->level;
 173         update[level] = list->head;
 174     }
 175
 176     entry = SLCreateEntry(level, key, value);
 177
 178                                 /* Fix up forward pointers */
 179     for (i = 0; i <= level; i++) {
 180         entry->forward[i]     = update[i]->forward[i];
 181         update[i]->forward[i] = entry;
 182     }
 183
 184     ++list->count;
 185     return 0;                   /* Added to table */
 186 }
 187
 188 drm_public int drmSLDelete(void *l, unsigned long key)
 189 {
 190     SkipListPtr   list = (SkipListPtr)l;
 191     SLEntryPtr    update[SL_MAX_LEVEL + 1];
 192     SLEntryPtr    entry;
 193     int           i;
 194
 195     if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
 196
 197     entry = SLLocate(list, key, update);
 198
 199     if (!entry || entry->key != key) return 1; /* Not found */
 200
 201                                 /* Fix up forward pointers */
 202     for (i = 0; i <= list->level; i++) {
 203         if (update[i]->forward[i] == entry)
 204             update[i]->forward[i] = entry->forward[i];
 205     }
 206
 207     entry->magic = SL_FREED_MAGIC;
 208     drmFree(entry);
 209
 210     while (list->level && !list->head->forward[list->level]) --list->level;
 211     --list->count;
 212     return 0;
 213 }
 214
 215 drm_public int drmSLLookup(void *l, unsigned long key, void **value)
 216 {
 217     SkipListPtr   list = (SkipListPtr)l;
 218     SLEntryPtr    update[SL_MAX_LEVEL + 1];
 219     SLEntryPtr    entry;
 220
 221     entry = SLLocate(list, key, update);
 222
 223     if (entry && entry->key == key) {
 224         *value = entry;
 225         return 0;
 226     }
 227     *value = NULL;
 228     return -1;
 229 }
 230
 231 drm_public int drmSLLookupNeighbors(void *l, unsigned long key,
 232                                     unsigned long *prev_key, void **prev_value,
 233                                     unsigned long *next_key, void **next_value)
 234 {
 235     SkipListPtr   list = (SkipListPtr)l;
 236     SLEntryPtr    update[SL_MAX_LEVEL + 1] = {0};
 237     int           retcode = 0;
 238
 239     SLLocate(list, key, update);
 240
 241     *prev_key   = *next_key   = key;
 242     *prev_value = *next_value = NULL;
 243
 244     if (update[0]) {
 245         *prev_key   = update[0]->key;
 246         *prev_value = update[0]->value;
 247         ++retcode;
 248         if (update[0]->forward[0]) {
 249             *next_key   = update[0]->forward[0]->key;
 250             *next_value = update[0]->forward[0]->value;
 251             ++retcode;
 252         }
 253     }
 254     return retcode;
 255 }
 256
 257 drm_public int drmSLNext(void *l, unsigned long *key, void **value)
 258 {
 259     SkipListPtr   list = (SkipListPtr)l;
 260     SLEntryPtr    entry;
 261
 262     if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
 263
 264     entry    = list->p0;
 265
 266     if (entry) {
 267         list->p0 = entry->forward[0];
 268         *key     = entry->key;
 269         *value   = entry->value;
 270         return 1;
 271     }
 272     list->p0 = NULL;
 273     return 0;
 274 }
 275
 276 drm_public int drmSLFirst(void *l, unsigned long *key, void **value)
 277 {
 278     SkipListPtr   list = (SkipListPtr)l;
 279
 280     if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
 281
 282     list->p0 = list->head->forward[0];
 283     return drmSLNext(list, key, value);
 284 }
 285
 286 /* Dump internal data structures for debugging. */
 287 drm_public void drmSLDump(void *l)
 288 {
 289     SkipListPtr   list = (SkipListPtr)l;
 290     SLEntryPtr    entry;
 291     int           i;
 292
 293     if (list->magic != SL_LIST_MAGIC) {
 294         printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
 295                list->magic, SL_LIST_MAGIC);
 296         return;
 297     }
 298
 299     printf("Level = %d, count = %d\n", list->level, list->count);
 300     for (entry = list->head; entry; entry = entry->forward[0]) {
 301         if (entry->magic != SL_ENTRY_MAGIC) {
 302             printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
 303                    list->magic, SL_ENTRY_MAGIC);
 304         }
 305         printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
 306                entry, entry->key, entry->value, entry->levels);
 307         for (i = 0; i < entry->levels; i++) {
 308             if (entry->forward[i]) {
 309                 printf("   %2d: %p <0x%08lx, %p>\n",
 310                        i,
 311                        entry->forward[i],
 312                        entry->forward[i]->key,
 313                        entry->forward[i]->value);
 314             } else {
 315                 printf("   %2d: %p\n", i, entry->forward[i]);
 316             }
 317         }
 318     }
 319 }