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 SLEntryPtr entry;
269 int retcode = 0;
270
271 entry = SLLocate(list, key, update);
272
273 *prev_key = *next_key = key;
274 *prev_value = *next_value = NULL;
275
276 if (update[0]) {
277 *prev_key = update[0]->key;
278 *prev_value = update[0]->value;
279 ++retcode;
280 if (update[0]->forward[0]) {
281 *next_key = update[0]->forward[0]->key;
282 *next_value = update[0]->forward[0]->value;
283 ++retcode;
284 }
285 }
286 return retcode;
287 }
288
drmSLNext(void * l,unsigned long * key,void ** value)289 int drmSLNext(void *l, unsigned long *key, void **value)
290 {
291 SkipListPtr list = (SkipListPtr)l;
292 SLEntryPtr entry;
293
294 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
295
296 entry = list->p0;
297
298 if (entry) {
299 list->p0 = entry->forward[0];
300 *key = entry->key;
301 *value = entry->value;
302 return 1;
303 }
304 list->p0 = NULL;
305 return 0;
306 }
307
drmSLFirst(void * l,unsigned long * key,void ** value)308 int drmSLFirst(void *l, unsigned long *key, void **value)
309 {
310 SkipListPtr list = (SkipListPtr)l;
311
312 if (list->magic != SL_LIST_MAGIC) return -1; /* Bad magic */
313
314 list->p0 = list->head->forward[0];
315 return drmSLNext(list, key, value);
316 }
317
318 /* Dump internal data structures for debugging. */
drmSLDump(void * l)319 void drmSLDump(void *l)
320 {
321 SkipListPtr list = (SkipListPtr)l;
322 SLEntryPtr entry;
323 int i;
324
325 if (list->magic != SL_LIST_MAGIC) {
326 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
327 list->magic, SL_LIST_MAGIC);
328 return;
329 }
330
331 printf("Level = %d, count = %d\n", list->level, list->count);
332 for (entry = list->head; entry; entry = entry->forward[0]) {
333 if (entry->magic != SL_ENTRY_MAGIC) {
334 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
335 list->magic, SL_ENTRY_MAGIC);
336 }
337 printf("\nEntry %p <0x%08lx, %p> has %2d levels\n",
338 entry, entry->key, entry->value, entry->levels);
339 for (i = 0; i < entry->levels; i++) {
340 if (entry->forward[i]) {
341 printf(" %2d: %p <0x%08lx, %p>\n",
342 i,
343 entry->forward[i],
344 entry->forward[i]->key,
345 entry->forward[i]->value);
346 } else {
347 printf(" %2d: %p\n", i, entry->forward[i]);
348 }
349 }
350 }
351 }
352
353 #if SL_MAIN
print(SkipListPtr list)354 static void print(SkipListPtr list)
355 {
356 unsigned long key;
357 void *value;
358
359 if (drmSLFirst(list, &key, &value)) {
360 do {
361 printf("key = %5lu, value = %p\n", key, value);
362 } while (drmSLNext(list, &key, &value));
363 }
364 }
365
do_time(int size,int iter)366 static double do_time(int size, int iter)
367 {
368 SkipListPtr list;
369 int i, j;
370 unsigned long keys[1000000];
371 unsigned long previous;
372 unsigned long key;
373 void *value;
374 struct timeval start, stop;
375 double usec;
376 SL_RANDOM_DECL;
377
378 SL_RANDOM_INIT(12345);
379
380 list = drmSLCreate();
381
382 for (i = 0; i < size; i++) {
383 keys[i] = SL_RANDOM;
384 drmSLInsert(list, keys[i], NULL);
385 }
386
387 previous = 0;
388 if (drmSLFirst(list, &key, &value)) {
389 do {
390 if (key <= previous) {
391 printf( "%lu !< %lu\n", previous, key);
392 }
393 previous = key;
394 } while (drmSLNext(list, &key, &value));
395 }
396
397 gettimeofday(&start, NULL);
398 for (j = 0; j < iter; j++) {
399 for (i = 0; i < size; i++) {
400 if (drmSLLookup(list, keys[i], &value))
401 printf("Error %lu %d\n", keys[i], i);
402 }
403 }
404 gettimeofday(&stop, NULL);
405
406 usec = (double)(stop.tv_sec * 1000000 + stop.tv_usec
407 - start.tv_sec * 1000000 - start.tv_usec) / (size * iter);
408
409 printf("%0.2f microseconds for list length %d\n", usec, size);
410
411 drmSLDestroy(list);
412
413 return usec;
414 }
415
print_neighbors(void * list,unsigned long key)416 static void print_neighbors(void *list, unsigned long key)
417 {
418 unsigned long prev_key = 0;
419 unsigned long next_key = 0;
420 void *prev_value;
421 void *next_value;
422 int retval;
423
424 retval = drmSLLookupNeighbors(list, key,
425 &prev_key, &prev_value,
426 &next_key, &next_value);
427 printf("Neighbors of %5lu: %d %5lu %5lu\n",
428 key, retval, prev_key, next_key);
429 }
430
main(void)431 int main(void)
432 {
433 SkipListPtr list;
434 double usec, usec2, usec3, usec4;
435
436 list = drmSLCreate();
437 printf( "list at %p\n", list);
438
439 print(list);
440 printf("\n==============================\n\n");
441
442 drmSLInsert(list, 123, NULL);
443 drmSLInsert(list, 213, NULL);
444 drmSLInsert(list, 50, NULL);
445 print(list);
446 printf("\n==============================\n\n");
447
448 print_neighbors(list, 0);
449 print_neighbors(list, 50);
450 print_neighbors(list, 51);
451 print_neighbors(list, 123);
452 print_neighbors(list, 200);
453 print_neighbors(list, 213);
454 print_neighbors(list, 256);
455 printf("\n==============================\n\n");
456
457 drmSLDelete(list, 50);
458 print(list);
459 printf("\n==============================\n\n");
460
461 drmSLDump(list);
462 drmSLDestroy(list);
463 printf("\n==============================\n\n");
464
465 usec = do_time(100, 10000);
466 usec2 = do_time(1000, 500);
467 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
468 1000.0/100.0, usec2 / usec);
469
470 usec3 = do_time(10000, 50);
471 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
472 10000.0/100.0, usec3 / usec);
473
474 usec4 = do_time(100000, 4);
475 printf("Table size increased by %0.2f, search time increased by %0.2f\n",
476 100000.0/100.0, usec4 / usec);
477
478 return 0;
479 }
480 #endif
481