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.
50 # include <sys/time.h>
53 #define SL_LIST_MAGIC 0xfacade00LU
54 #define SL_ENTRY_MAGIC 0x00fab1edLU
55 #define SL_FREED_MAGIC 0xdecea5edLU
56 #define SL_MAX_LEVEL 16
58 #define SL_RANDOM_SEED 0xc01055a1LU
61 #define SL_ALLOC malloc
63 #define SL_RANDOM_DECL static int state = 0;
64 #define SL_RANDOM_INIT(seed) if (!state) { srandom(seed); ++state; }
65 #define SL_RANDOM random()
67 #define SL_ALLOC drmMalloc
68 #define SL_FREE drmFree
69 #define SL_RANDOM_DECL static void *state = NULL
70 #define SL_RANDOM_INIT(seed) if (!state) state = drmRandomCreate(seed)
71 #define SL_RANDOM drmRandom(state)
75 typedef struct SLEntry {
76 unsigned long magic; /* SL_ENTRY_MAGIC */
80 struct SLEntry *forward[1]; /* variable sized array */
81 } SLEntry, *SLEntryPtr;
83 typedef struct SkipList {
84 unsigned long magic; /* SL_LIST_MAGIC */
88 SLEntryPtr p0; /* Position for iteration */
89 } SkipList, *SkipListPtr;
92 extern void *drmSLCreate(void);
93 extern int drmSLDestroy(void *l);
94 extern int drmSLLookup(void *l, unsigned long key, void **value);
95 extern int drmSLInsert(void *l, unsigned long key, void *value);
96 extern int drmSLDelete(void *l, unsigned long key);
97 extern int drmSLNext(void *l, unsigned long *key, void **value);
98 extern int drmSLFirst(void *l, unsigned long *key, void **value);
99 extern void drmSLDump(void *l);
100 extern int drmSLLookupNeighbors(void *l, unsigned long key,
101 unsigned long *prev_key, void **prev_value,
102 unsigned long *next_key, void **next_value);
105 static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
109 if (max_level < 0 || max_level > SL_MAX_LEVEL) max_level = SL_MAX_LEVEL;
111 entry = SL_ALLOC(sizeof(*entry)
112 + (max_level + 1) * sizeof(entry->forward[0]));
113 if (!entry) return NULL;
114 entry->magic = SL_ENTRY_MAGIC;
116 entry->value = value;
117 entry->levels = max_level + 1;
122 static int SLRandomLevel(void)
127 SL_RANDOM_INIT(SL_RANDOM_SEED);
129 while ((SL_RANDOM & 0x01) && level < SL_MAX_LEVEL) ++level;
133 void *drmSLCreate(void)
138 list = SL_ALLOC(sizeof(*list));
139 if (!list) return NULL;
140 list->magic = SL_LIST_MAGIC;
142 list->head = SLCreateEntry(SL_MAX_LEVEL, 0, NULL);
145 for (i = 0; i <= SL_MAX_LEVEL; i++) list->head->forward[i] = NULL;
150 int drmSLDestroy(void *l)
152 SkipListPtr list = (SkipListPtr)l;
156 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
158 for (entry = list->head; entry; entry = next) {
159 if (entry->magic != SL_ENTRY_MAGIC) return -1; /* Bad magic */
160 next = entry->forward[0];
161 entry->magic = SL_FREED_MAGIC;
165 list->magic = SL_FREED_MAGIC;
170 static SLEntryPtr SLLocate(void *l, unsigned long key, SLEntryPtr *update)
172 SkipListPtr list = (SkipListPtr)l;
176 if (list->magic != SL_LIST_MAGIC) return NULL;
178 for (i = list->level, entry = list->head; i >= 0; i--) {
179 while (entry->forward[i] && entry->forward[i]->key < key)
180 entry = entry->forward[i];
184 return entry->forward[0];
187 int drmSLInsert(void *l, unsigned long key, void *value)
189 SkipListPtr list = (SkipListPtr)l;
191 SLEntryPtr update[SL_MAX_LEVEL + 1];
195 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
197 entry = SLLocate(list, key, update);
199 if (entry && entry->key == key) return 1; /* Already in list */
202 level = SLRandomLevel();
203 if (level > list->level) {
204 level = ++list->level;
205 update[level] = list->head;
208 entry = SLCreateEntry(level, key, value);
210 /* Fix up forward pointers */
211 for (i = 0; i <= level; i++) {
212 entry->forward[i] = update[i]->forward[i];
213 update[i]->forward[i] = entry;
217 return 0; /* Added to table */
220 int drmSLDelete(void *l, unsigned long key)
222 SkipListPtr list = (SkipListPtr)l;
223 SLEntryPtr update[SL_MAX_LEVEL + 1];
227 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
229 entry = SLLocate(list, key, update);
231 if (!entry || entry->key != key) return 1; /* Not found */
233 /* Fix up forward pointers */
234 for (i = 0; i <= list->level; i++) {
235 if (update[i]->forward[i] == entry)
236 update[i]->forward[i] = entry->forward[i];
239 entry->magic = SL_FREED_MAGIC;
242 while (list->level && !list->head->forward[list->level]) --list->level;
247 int drmSLLookup(void *l, unsigned long key, void **value)
249 SkipListPtr list = (SkipListPtr)l;
250 SLEntryPtr update[SL_MAX_LEVEL + 1];
253 entry = SLLocate(list, key, update);
255 if (entry && entry->key == key) {
263 int drmSLLookupNeighbors(void *l, unsigned long key,
264 unsigned long *prev_key, void **prev_value,
265 unsigned long *next_key, void **next_value)
267 SkipListPtr list = (SkipListPtr)l;
268 SLEntryPtr update[SL_MAX_LEVEL + 1];
272 entry = SLLocate(list, key, update);
274 *prev_key = *next_key = key;
275 *prev_value = *next_value = NULL;
278 *prev_key = update[0]->key;
279 *prev_value = update[0]->value;
281 if (update[0]->forward[0]) {
282 *next_key = update[0]->forward[0]->key;
283 *next_value = update[0]->forward[0]->value;
290 int drmSLNext(void *l, unsigned long *key, void **value)
292 SkipListPtr list = (SkipListPtr)l;
295 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
300 list->p0 = entry->forward[0];
302 *value = entry->value;
309 int drmSLFirst(void *l, unsigned long *key, void **value)
311 SkipListPtr list = (SkipListPtr)l;
313 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
315 list->p0 = list->head->forward[0];
316 return drmSLNext(list, key, value);
319 /* Dump internal data structures for debugging. */
320 void drmSLDump(void *l)
322 SkipListPtr list = (SkipListPtr)l;
326 if (list->magic != SL_LIST_MAGIC) {
327 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
328 list->magic, SL_LIST_MAGIC);
332 printf("Level = %d, count = %d\n", list->level, list->count);
333 for (entry = list->head; entry; entry = entry->forward[0]) {
334 if (entry->magic != SL_ENTRY_MAGIC) {
335 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
336 list->magic, SL_ENTRY_MAGIC);
338 printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
339 entry, entry->key, entry->value, entry->levels);
340 for (i = 0; i < entry->levels; i++) {
341 if (entry->forward[i]) {
342 printf(" %2d: %p <0x%08lx, %p>\n",
345 entry->forward[i]->key,
346 entry->forward[i]->value);
348 printf(" %2d: %p\n", i, entry->forward[i]);
355 static void print(SkipListPtr list)
360 if (drmSLFirst(list, &key, &value)) {
362 printf("key = %5lu, value = %p\n", key, value);
363 } while (drmSLNext(list, &key, &value));
367 static double do_time(int size, int iter)
371 unsigned long keys[1000000];
372 unsigned long previous;
375 struct timeval start, stop;
379 SL_RANDOM_INIT(12345);
381 list = drmSLCreate();
383 for (i = 0; i < size; i++) {
385 drmSLInsert(list, keys[i], NULL);
389 if (drmSLFirst(list, &key, &value)) {
391 if (key <= previous) {
392 printf( "%lu !< %lu\n", previous, key);
395 } while (drmSLNext(list, &key, &value));
398 gettimeofday(&start, NULL);
399 for (j = 0; j < iter; j++) {
400 for (i = 0; i < size; i++) {
401 if (drmSLLookup(list, keys[i], &value))
402 printf("Error %lu %d\n", keys[i], i);
405 gettimeofday(&stop, NULL);
407 usec = (double)(stop.tv_sec * 1000000 + stop.tv_usec
408 - start.tv_sec * 1000000 - start.tv_usec) / (size * iter);
410 printf("%0.2f microseconds for list length %d\n", usec, size);
417 static void print_neighbors(void *list, unsigned long key)
419 unsigned long prev_key = 0;
420 unsigned long next_key = 0;
425 retval = drmSLLookupNeighbors(list, key,
426 &prev_key, &prev_value,
427 &next_key, &next_value);
428 printf("Neighbors of %5lu: %d %5lu %5lu\n",
429 key, retval, prev_key, next_key);
435 double usec, usec2, usec3, usec4;
437 list = drmSLCreate();
438 printf( "list at %p\n", list);
441 printf("\n==============================\n\n");
443 drmSLInsert(list, 123, NULL);
444 drmSLInsert(list, 213, NULL);
445 drmSLInsert(list, 50, NULL);
447 printf("\n==============================\n\n");
449 print_neighbors(list, 0);
450 print_neighbors(list, 50);
451 print_neighbors(list, 51);
452 print_neighbors(list, 123);
453 print_neighbors(list, 200);
454 print_neighbors(list, 213);
455 print_neighbors(list, 256);
456 printf("\n==============================\n\n");
458 drmSLDelete(list, 50);
460 printf("\n==============================\n\n");
464 printf("\n==============================\n\n");
466 usec = do_time(100, 10000);
467 usec2 = do_time(1000, 500);
468 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
469 1000.0/100.0, usec2 / usec);
471 usec3 = do_time(10000, 50);
472 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
473 10000.0/100.0, usec3 / usec);
475 usec4 = do_time(100000, 4);
476 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
477 100000.0/100.0, usec4 / usec);