1 /* xf86drmSL.c -- Skip list support
2 * Created: Mon May 10 09:28:13 1999 by faith@precisioninsight.com
4 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
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:
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
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.
26 * Authors: Rickard E. (Rik) Faith <faith@valinux.com>
30 * This file contains a straightforward skip list implementation.n
36 * [Pugh90] William Pugh. Skip Lists: A Probabilistic Alternative to
37 * Balanced Trees. CACM 33(6), June 1990, pp. 668-676.
49 # include <sys/time.h>
52 #define SL_LIST_MAGIC 0xfacade00LU
53 #define SL_ENTRY_MAGIC 0x00fab1edLU
54 #define SL_FREED_MAGIC 0xdecea5edLU
55 #define SL_MAX_LEVEL 16
57 #define SL_RANDOM_SEED 0xc01055a1LU
60 #define SL_ALLOC malloc
62 #define SL_RANDOM_DECL static int state = 0;
63 #define SL_RANDOM_INIT(seed) if (!state) { srandom(seed); ++state; }
64 #define SL_RANDOM random()
66 #define SL_ALLOC drmMalloc
67 #define SL_FREE drmFree
68 #define SL_RANDOM_DECL static void *state = NULL
69 #define SL_RANDOM_INIT(seed) if (!state) state = drmRandomCreate(seed)
70 #define SL_RANDOM drmRandom(state)
74 typedef struct SLEntry {
75 unsigned long magic; /* SL_ENTRY_MAGIC */
79 struct SLEntry *forward[1]; /* variable sized array */
80 } SLEntry, *SLEntryPtr;
82 typedef struct SkipList {
83 unsigned long magic; /* SL_LIST_MAGIC */
87 SLEntryPtr p0; /* Position for iteration */
88 } SkipList, *SkipListPtr;
91 extern void *drmSLCreate(void);
92 extern int drmSLDestroy(void *l);
93 extern int drmSLLookup(void *l, unsigned long key, void **value);
94 extern int drmSLInsert(void *l, unsigned long key, void *value);
95 extern int drmSLDelete(void *l, unsigned long key);
96 extern int drmSLNext(void *l, unsigned long *key, void **value);
97 extern int drmSLFirst(void *l, unsigned long *key, void **value);
98 extern void drmSLDump(void *l);
99 extern int drmSLLookupNeighbors(void *l, unsigned long key,
100 unsigned long *prev_key, void **prev_value,
101 unsigned long *next_key, void **next_value);
104 static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
108 if (max_level < 0 || max_level > SL_MAX_LEVEL) max_level = SL_MAX_LEVEL;
110 entry = SL_ALLOC(sizeof(*entry)
111 + (max_level + 1) * sizeof(entry->forward[0]));
112 if (!entry) return NULL;
113 entry->magic = SL_ENTRY_MAGIC;
115 entry->value = value;
116 entry->levels = max_level + 1;
121 static int SLRandomLevel(void)
126 SL_RANDOM_INIT(SL_RANDOM_SEED);
128 while ((SL_RANDOM & 0x01) && level < SL_MAX_LEVEL) ++level;
132 void *drmSLCreate(void)
137 list = SL_ALLOC(sizeof(*list));
138 if (!list) return NULL;
139 list->magic = SL_LIST_MAGIC;
141 list->head = SLCreateEntry(SL_MAX_LEVEL, 0, NULL);
144 for (i = 0; i <= SL_MAX_LEVEL; i++) list->head->forward[i] = NULL;
149 int drmSLDestroy(void *l)
151 SkipListPtr list = (SkipListPtr)l;
155 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
157 for (entry = list->head; entry; entry = next) {
158 if (entry->magic != SL_ENTRY_MAGIC) return -1; /* Bad magic */
159 next = entry->forward[0];
160 entry->magic = SL_FREED_MAGIC;
164 list->magic = SL_FREED_MAGIC;
169 static SLEntryPtr SLLocate(void *l, unsigned long key, SLEntryPtr *update)
171 SkipListPtr list = (SkipListPtr)l;
175 if (list->magic != SL_LIST_MAGIC) return NULL;
177 for (i = list->level, entry = list->head; i >= 0; i--) {
178 while (entry->forward[i] && entry->forward[i]->key < key)
179 entry = entry->forward[i];
183 return entry->forward[0];
186 int drmSLInsert(void *l, unsigned long key, void *value)
188 SkipListPtr list = (SkipListPtr)l;
190 SLEntryPtr update[SL_MAX_LEVEL + 1];
194 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
196 entry = SLLocate(list, key, update);
198 if (entry && entry->key == key) return 1; /* Already in list */
201 level = SLRandomLevel();
202 if (level > list->level) {
203 level = ++list->level;
204 update[level] = list->head;
207 entry = SLCreateEntry(level, key, value);
209 /* Fix up forward pointers */
210 for (i = 0; i <= level; i++) {
211 entry->forward[i] = update[i]->forward[i];
212 update[i]->forward[i] = entry;
216 return 0; /* Added to table */
219 int drmSLDelete(void *l, unsigned long key)
221 SkipListPtr list = (SkipListPtr)l;
222 SLEntryPtr update[SL_MAX_LEVEL + 1];
226 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
228 entry = SLLocate(list, key, update);
230 if (!entry || entry->key != key) return 1; /* Not found */
232 /* Fix up forward pointers */
233 for (i = 0; i <= list->level; i++) {
234 if (update[i]->forward[i] == entry)
235 update[i]->forward[i] = entry->forward[i];
238 entry->magic = SL_FREED_MAGIC;
241 while (list->level && !list->head->forward[list->level]) --list->level;
246 int drmSLLookup(void *l, unsigned long key, void **value)
248 SkipListPtr list = (SkipListPtr)l;
249 SLEntryPtr update[SL_MAX_LEVEL + 1];
252 entry = SLLocate(list, key, update);
254 if (entry && entry->key == key) {
262 int drmSLLookupNeighbors(void *l, unsigned long key,
263 unsigned long *prev_key, void **prev_value,
264 unsigned long *next_key, void **next_value)
266 SkipListPtr list = (SkipListPtr)l;
267 SLEntryPtr update[SL_MAX_LEVEL + 1] = {0};
270 SLLocate(list, key, update);
272 *prev_key = *next_key = key;
273 *prev_value = *next_value = NULL;
276 *prev_key = update[0]->key;
277 *prev_value = update[0]->value;
279 if (update[0]->forward[0]) {
280 *next_key = update[0]->forward[0]->key;
281 *next_value = update[0]->forward[0]->value;
288 int drmSLNext(void *l, unsigned long *key, void **value)
290 SkipListPtr list = (SkipListPtr)l;
293 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
298 list->p0 = entry->forward[0];
300 *value = entry->value;
307 int drmSLFirst(void *l, unsigned long *key, void **value)
309 SkipListPtr list = (SkipListPtr)l;
311 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
313 list->p0 = list->head->forward[0];
314 return drmSLNext(list, key, value);
317 /* Dump internal data structures for debugging. */
318 void drmSLDump(void *l)
320 SkipListPtr list = (SkipListPtr)l;
324 if (list->magic != SL_LIST_MAGIC) {
325 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
326 list->magic, SL_LIST_MAGIC);
330 printf("Level = %d, count = %d\n", list->level, list->count);
331 for (entry = list->head; entry; entry = entry->forward[0]) {
332 if (entry->magic != SL_ENTRY_MAGIC) {
333 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
334 list->magic, SL_ENTRY_MAGIC);
336 printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
337 entry, entry->key, entry->value, entry->levels);
338 for (i = 0; i < entry->levels; i++) {
339 if (entry->forward[i]) {
340 printf(" %2d: %p <0x%08lx, %p>\n",
343 entry->forward[i]->key,
344 entry->forward[i]->value);
346 printf(" %2d: %p\n", i, entry->forward[i]);
353 static void print(SkipListPtr list)
358 if (drmSLFirst(list, &key, &value)) {
360 printf("key = %5lu, value = %p\n", key, value);
361 } while (drmSLNext(list, &key, &value));
365 static double do_time(int size, int iter)
369 unsigned long keys[1000000];
370 unsigned long previous;
373 struct timeval start, stop;
377 SL_RANDOM_INIT(12345);
379 list = drmSLCreate();
381 for (i = 0; i < size; i++) {
383 drmSLInsert(list, keys[i], NULL);
387 if (drmSLFirst(list, &key, &value)) {
389 if (key <= previous) {
390 printf( "%lu !< %lu\n", previous, key);
393 } while (drmSLNext(list, &key, &value));
396 gettimeofday(&start, NULL);
397 for (j = 0; j < iter; j++) {
398 for (i = 0; i < size; i++) {
399 if (drmSLLookup(list, keys[i], &value))
400 printf("Error %lu %d\n", keys[i], i);
403 gettimeofday(&stop, NULL);
405 usec = (double)(stop.tv_sec * 1000000 + stop.tv_usec
406 - start.tv_sec * 1000000 - start.tv_usec) / (size * iter);
408 printf("%0.2f microseconds for list length %d\n", usec, size);
415 static void print_neighbors(void *list, unsigned long key)
417 unsigned long prev_key = 0;
418 unsigned long next_key = 0;
423 retval = drmSLLookupNeighbors(list, key,
424 &prev_key, &prev_value,
425 &next_key, &next_value);
426 printf("Neighbors of %5lu: %d %5lu %5lu\n",
427 key, retval, prev_key, next_key);
433 double usec, usec2, usec3, usec4;
435 list = drmSLCreate();
436 printf( "list at %p\n", list);
439 printf("\n==============================\n\n");
441 drmSLInsert(list, 123, NULL);
442 drmSLInsert(list, 213, NULL);
443 drmSLInsert(list, 50, NULL);
445 printf("\n==============================\n\n");
447 print_neighbors(list, 0);
448 print_neighbors(list, 50);
449 print_neighbors(list, 51);
450 print_neighbors(list, 123);
451 print_neighbors(list, 200);
452 print_neighbors(list, 213);
453 print_neighbors(list, 256);
454 printf("\n==============================\n\n");
456 drmSLDelete(list, 50);
458 printf("\n==============================\n\n");
462 printf("\n==============================\n\n");
464 usec = do_time(100, 10000);
465 usec2 = do_time(1000, 500);
466 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
467 1000.0/100.0, usec2 / usec);
469 usec3 = do_time(10000, 50);
470 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
471 10000.0/100.0, usec3 / usec);
473 usec4 = do_time(100000, 4);
474 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
475 100000.0/100.0, usec4 / usec);