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 #define SL_MAIN 0
45
46 #if !SL_MAIN
47 # include "xf86drm.h"
48 #else
49 # include <sys/time.h>
50 #endif
51
52 #define SL_LIST_MAGIC 0xfacade00LU
53 #define SL_ENTRY_MAGIC 0x00fab1edLU
54 #define SL_FREED_MAGIC 0xdecea5edLU
55 #define SL_MAX_LEVEL 16
56 #define SL_DEBUG 0
57 #define SL_RANDOM_SEED 0xc01055a1LU
58
59 #if SL_MAIN
60 #define SL_ALLOC malloc
61 #define SL_FREE free
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()
65 #else
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)
71
72 #endif
73
74 typedef struct SLEntry {
75 unsigned long magic; /* SL_ENTRY_MAGIC */
76 unsigned long key;
77 void *value;
78 int levels;
79 struct SLEntry *forward[1]; /* variable sized array */
80 } SLEntry, *SLEntryPtr;
81
82 typedef struct SkipList {
83 unsigned long magic; /* SL_LIST_MAGIC */
84 int level;
85 int count;
86 SLEntryPtr head;
87 SLEntryPtr p0; /* Position for iteration */
88 } SkipList, *SkipListPtr;
89
90 #if SL_MAIN
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);
102 #endif
103
SLCreateEntry(int max_level,unsigned long key,void * value)104 static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
105 {
106 SLEntryPtr entry;
107
108 if (max_level < 0 || max_level > SL_MAX_LEVEL) max_level = SL_MAX_LEVEL;
109
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;
114 entry->key = key;
115 entry->value = value;
116 entry->levels = max_level + 1;
117
118 return entry;
119 }
120
SLRandomLevel(void)121 static int SLRandomLevel(void)
122 {
123 int level = 1;
124 SL_RANDOM_DECL;
125
126 SL_RANDOM_INIT(SL_RANDOM_SEED);
127
128 while ((SL_RANDOM & 0x01) && level < SL_MAX_LEVEL) ++level;
129 return level;
130 }
131
drmSLCreate(void)132 void *drmSLCreate(void)
133 {
134 SkipListPtr list;
135 int i;
136
137 list = SL_ALLOC(sizeof(*list));
138 if (!list) return NULL;
139 list->magic = SL_LIST_MAGIC;
140 list->level = 0;
141 list->head = SLCreateEntry(SL_MAX_LEVEL, 0, NULL);
142 list->count = 0;
143
144 for (i = 0; i <= SL_MAX_LEVEL; i++) list->head->forward[i] = NULL;
145
146 return list;
147 }
148
drmSLDestroy(void * l)149 int drmSLDestroy(void *l)
150 {
151 SkipListPtr list = (SkipListPtr)l;
152 SLEntryPtr entry;
153 SLEntryPtr next;
154
155 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
156
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;
161 SL_FREE(entry);
162 }
163
164 list->magic = SL_FREED_MAGIC;
165 SL_FREE(list);
166 return 0;
167 }
168
SLLocate(void * l,unsigned long key,SLEntryPtr * update)169 static SLEntryPtr SLLocate(void *l, unsigned long key, SLEntryPtr *update)
170 {
171 SkipListPtr list = (SkipListPtr)l;
172 SLEntryPtr entry;
173 int i;
174
175 if (list->magic != SL_LIST_MAGIC) return NULL;
176
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];
180 update[i] = entry;
181 }
182
183 return entry->forward[0];
184 }
185
drmSLInsert(void * l,unsigned long key,void * value)186 int drmSLInsert(void *l, unsigned long key, void *value)
187 {
188 SkipListPtr list = (SkipListPtr)l;
189 SLEntryPtr entry;
190 SLEntryPtr update[SL_MAX_LEVEL + 1];
191 int level;
192 int i;
193
194 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
195
196 entry = SLLocate(list, key, update);
197
198 if (entry && entry->key == key) return 1; /* Already in list */
199
200
201 level = SLRandomLevel();
202 if (level > list->level) {
203 level = ++list->level;
204 update[level] = list->head;
205 }
206
207 entry = SLCreateEntry(level, key, value);
208
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;
213 }
214
215 ++list->count;
216 return 0; /* Added to table */
217 }
218
drmSLDelete(void * l,unsigned long key)219 int drmSLDelete(void *l, unsigned long key)
220 {
221 SkipListPtr list = (SkipListPtr)l;
222 SLEntryPtr update[SL_MAX_LEVEL + 1];
223 SLEntryPtr entry;
224 int i;
225
226 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
227
228 entry = SLLocate(list, key, update);
229
230 if (!entry || entry->key != key) return 1; /* Not found */
231
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];
236 }
237
238 entry->magic = SL_FREED_MAGIC;
239 SL_FREE(entry);
240
241 while (list->level && !list->head->forward[list->level]) --list->level;
242 --list->count;
243 return 0;
244 }
245
drmSLLookup(void * l,unsigned long key,void ** value)246 int drmSLLookup(void *l, unsigned long key, void **value)
247 {
248 SkipListPtr list = (SkipListPtr)l;
249 SLEntryPtr update[SL_MAX_LEVEL + 1];
250 SLEntryPtr entry;
251
252 entry = SLLocate(list, key, update);
253
254 if (entry && entry->key == key) {
255 *value = entry;
256 return 0;
257 }
258 *value = NULL;
259 return -1;
260 }
261
drmSLLookupNeighbors(void * l,unsigned long key,unsigned long * prev_key,void ** prev_value,unsigned long * next_key,void ** next_value)262 int drmSLLookupNeighbors(void *l, unsigned long key,
263 unsigned long *prev_key, void **prev_value,
264 unsigned long *next_key, void **next_value)
265 {
266 SkipListPtr list = (SkipListPtr)l;
267 SLEntryPtr update[SL_MAX_LEVEL + 1];
268 int retcode = 0;
269
270 *prev_key = *next_key = key;
271 *prev_value = *next_value = NULL;
272
273 if (update[0]) {
274 *prev_key = update[0]->key;
275 *prev_value = update[0]->value;
276 ++retcode;
277 if (update[0]->forward[0]) {
278 *next_key = update[0]->forward[0]->key;
279 *next_value = update[0]->forward[0]->value;
280 ++retcode;
281 }
282 }
283 return retcode;
284 }
285
drmSLNext(void * l,unsigned long * key,void ** value)286 int drmSLNext(void *l, unsigned long *key, void **value)
287 {
288 SkipListPtr list = (SkipListPtr)l;
289 SLEntryPtr entry;
290
291 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
292
293 entry = list->p0;
294
295 if (entry) {
296 list->p0 = entry->forward[0];
297 *key = entry->key;
298 *value = entry->value;
299 return 1;
300 }
301 list->p0 = NULL;
302 return 0;
303 }
304
drmSLFirst(void * l,unsigned long * key,void ** value)305 int drmSLFirst(void *l, unsigned long *key, void **value)
306 {
307 SkipListPtr list = (SkipListPtr)l;
308
309 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
310
311 list->p0 = list->head->forward[0];
312 return drmSLNext(list, key, value);
313 }
314
315 /* Dump internal data structures for debugging. */
drmSLDump(void * l)316 void drmSLDump(void *l)
317 {
318 SkipListPtr list = (SkipListPtr)l;
319 SLEntryPtr entry;
320 int i;
321
322 if (list->magic != SL_LIST_MAGIC) {
323 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
324 list->magic, SL_LIST_MAGIC);
325 return;
326 }
327
328 printf("Level = %d, count = %d\n", list->level, list->count);
329 for (entry = list->head; entry; entry = entry->forward[0]) {
330 if (entry->magic != SL_ENTRY_MAGIC) {
331 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
332 list->magic, SL_ENTRY_MAGIC);
333 }
334 printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
335 entry, entry->key, entry->value, entry->levels);
336 for (i = 0; i < entry->levels; i++) {
337 if (entry->forward[i]) {
338 printf(" %2d: %p <0x%08lx, %p>\n",
339 i,
340 entry->forward[i],
341 entry->forward[i]->key,
342 entry->forward[i]->value);
343 } else {
344 printf(" %2d: %p\n", i, entry->forward[i]);
345 }
346 }
347 }
348 }
349
350 #if SL_MAIN
print(SkipListPtr list)351 static void print(SkipListPtr list)
352 {
353 unsigned long key;
354 void *value;
355
356 if (drmSLFirst(list, &key, &value)) {
357 do {
358 printf("key = %5lu, value = %p\n", key, value);
359 } while (drmSLNext(list, &key, &value));
360 }
361 }
362
do_time(int size,int iter)363 static double do_time(int size, int iter)
364 {
365 SkipListPtr list;
366 int i, j;
367 unsigned long keys[1000000];
368 unsigned long previous;
369 unsigned long key;
370 void *value;
371 struct timeval start, stop;
372 double usec;
373 SL_RANDOM_DECL;
374
375 SL_RANDOM_INIT(12345);
376
377 list = drmSLCreate();
378
379 for (i = 0; i < size; i++) {
380 keys[i] = SL_RANDOM;
381 drmSLInsert(list, keys[i], NULL);
382 }
383
384 previous = 0;
385 if (drmSLFirst(list, &key, &value)) {
386 do {
387 if (key <= previous) {
388 printf( "%lu !< %lu\n", previous, key);
389 }
390 previous = key;
391 } while (drmSLNext(list, &key, &value));
392 }
393
394 gettimeofday(&start, NULL);
395 for (j = 0; j < iter; j++) {
396 for (i = 0; i < size; i++) {
397 if (drmSLLookup(list, keys[i], &value))
398 printf("Error %lu %d\n", keys[i], i);
399 }
400 }
401 gettimeofday(&stop, NULL);
402
403 usec = (double)(stop.tv_sec * 1000000 + stop.tv_usec
404 - start.tv_sec * 1000000 - start.tv_usec) / (size * iter);
405
406 printf("%0.2f microseconds for list length %d\n", usec, size);
407
408 drmSLDestroy(list);
409
410 return usec;
411 }
412
print_neighbors(void * list,unsigned long key)413 static void print_neighbors(void *list, unsigned long key)
414 {
415 unsigned long prev_key = 0;
416 unsigned long next_key = 0;
417 void *prev_value;
418 void *next_value;
419 int retval;
420
421 retval = drmSLLookupNeighbors(list, key,
422 &prev_key, &prev_value,
423 &next_key, &next_value);
424 printf("Neighbors of %5lu: %d %5lu %5lu\n",
425 key, retval, prev_key, next_key);
426 }
427
main(void)428 int main(void)
429 {
430 SkipListPtr list;
431 double usec, usec2, usec3, usec4;
432
433 list = drmSLCreate();
434 printf( "list at %p\n", list);
435
436 print(list);
437 printf("\n==============================\n\n");
438
439 drmSLInsert(list, 123, NULL);
440 drmSLInsert(list, 213, NULL);
441 drmSLInsert(list, 50, NULL);
442 print(list);
443 printf("\n==============================\n\n");
444
445 print_neighbors(list, 0);
446 print_neighbors(list, 50);
447 print_neighbors(list, 51);
448 print_neighbors(list, 123);
449 print_neighbors(list, 200);
450 print_neighbors(list, 213);
451 print_neighbors(list, 256);
452 printf("\n==============================\n\n");
453
454 drmSLDelete(list, 50);
455 print(list);
456 printf("\n==============================\n\n");
457
458 drmSLDump(list);
459 drmSLDestroy(list);
460 printf("\n==============================\n\n");
461
462 usec = do_time(100, 10000);
463 usec2 = do_time(1000, 500);
464 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
465 1000.0/100.0, usec2 / usec);
466
467 usec3 = do_time(10000, 50);
468 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
469 10000.0/100.0, usec3 / usec);
470
471 usec4 = do_time(100000, 4);
472 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
473 100000.0/100.0, usec4 / usec);
474
475 return 0;
476 }
477 #endif
478