Bug Summary

File:xf86drmSL.c
Location:line 273, column 9
Description:Branch condition evaluates to a garbage value

Annotated Source Code

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_MAIN0 0
45
46#if !SL_MAIN0
47# include "xf86drm.h"
48#else
49# include <sys/time.h>
50#endif
51
52#define SL_LIST_MAGIC0xfacade00LU 0xfacade00LU
53#define SL_ENTRY_MAGIC0x00fab1edLU 0x00fab1edLU
54#define SL_FREED_MAGIC0xdecea5edLU 0xdecea5edLU
55#define SL_MAX_LEVEL16 16
56#define SL_DEBUG0 0
57#define SL_RANDOM_SEED0xc01055a1LU 0xc01055a1LU
58
59#if SL_MAIN0
60#define SL_ALLOCdrmMalloc malloc
61#define SL_FREEdrmFree free
62#define SL_RANDOM_DECLstatic void *state = ((void *)0) static int state = 0;
63#define SL_RANDOM_INIT(seed)if (!state) state = drmRandomCreate(seed) if (!state) { srandom(seed); ++state; }
64#define SL_RANDOMdrmRandom(state) random()
65#else
66#define SL_ALLOCdrmMalloc drmMalloc
67#define SL_FREEdrmFree drmFree
68#define SL_RANDOM_DECLstatic void *state = ((void *)0) static void *state = NULL((void *)0)
69#define SL_RANDOM_INIT(seed)if (!state) state = drmRandomCreate(seed) if (!state) state = drmRandomCreate(seed)
70#define SL_RANDOMdrmRandom(state) drmRandom(state)
71
72#endif
73
74typedef 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
82typedef 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_MAIN0
91extern void *drmSLCreate(void);
92extern int drmSLDestroy(void *l);
93extern int drmSLLookup(void *l, unsigned long key, void **value);
94extern int drmSLInsert(void *l, unsigned long key, void *value);
95extern int drmSLDelete(void *l, unsigned long key);
96extern int drmSLNext(void *l, unsigned long *key, void **value);
97extern int drmSLFirst(void *l, unsigned long *key, void **value);
98extern void drmSLDump(void *l);
99extern 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
104static SLEntryPtr SLCreateEntry(int max_level, unsigned long key, void *value)
105{
106 SLEntryPtr entry;
107
108 if (max_level < 0 || max_level > SL_MAX_LEVEL16) max_level = SL_MAX_LEVEL16;
109
110 entry = SL_ALLOCdrmMalloc(sizeof(*entry)
111 + (max_level + 1) * sizeof(entry->forward[0]));
112 if (!entry) return NULL((void *)0);
113 entry->magic = SL_ENTRY_MAGIC0x00fab1edLU;
114 entry->key = key;
115 entry->value = value;
116 entry->levels = max_level + 1;
117
118 return entry;
119}
120
121static int SLRandomLevel(void)
122{
123 int level = 1;
124 SL_RANDOM_DECLstatic void *state = ((void *)0);
125
126 SL_RANDOM_INIT(SL_RANDOM_SEED)if (!state) state = drmRandomCreate(0xc01055a1LU);
127
128 while ((SL_RANDOMdrmRandom(state) & 0x01) && level < SL_MAX_LEVEL16) ++level;
129 return level;
130}
131
132void *drmSLCreate(void)
133{
134 SkipListPtr list;
135 int i;
136
137 list = SL_ALLOCdrmMalloc(sizeof(*list));
138 if (!list) return NULL((void *)0);
139 list->magic = SL_LIST_MAGIC0xfacade00LU;
140 list->level = 0;
141 list->head = SLCreateEntry(SL_MAX_LEVEL16, 0, NULL((void *)0));
142 list->count = 0;
143
144 for (i = 0; i <= SL_MAX_LEVEL16; i++) list->head->forward[i] = NULL((void *)0);
145
146 return list;
147}
148
149int drmSLDestroy(void *l)
150{
151 SkipListPtr list = (SkipListPtr)l;
152 SLEntryPtr entry;
153 SLEntryPtr next;
154
155 if (list->magic != SL_LIST_MAGIC0xfacade00LU) return -1; /* Bad magic */
156
157 for (entry = list->head; entry; entry = next) {
158 if (entry->magic != SL_ENTRY_MAGIC0x00fab1edLU) return -1; /* Bad magic */
159 next = entry->forward[0];
160 entry->magic = SL_FREED_MAGIC0xdecea5edLU;
161 SL_FREEdrmFree(entry);
162 }
163
164 list->magic = SL_FREED_MAGIC0xdecea5edLU;
165 SL_FREEdrmFree(list);
166 return 0;
167}
168
169static 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_MAGIC0xfacade00LU) return NULL((void *)0);
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
186int drmSLInsert(void *l, unsigned long key, void *value)
187{
188 SkipListPtr list = (SkipListPtr)l;
189 SLEntryPtr entry;
190 SLEntryPtr update[SL_MAX_LEVEL16 + 1];
191 int level;
192 int i;
193
194 if (list->magic != SL_LIST_MAGIC0xfacade00LU) 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
219int drmSLDelete(void *l, unsigned long key)
220{
221 SkipListPtr list = (SkipListPtr)l;
222 SLEntryPtr update[SL_MAX_LEVEL16 + 1];
223 SLEntryPtr entry;
224 int i;
225
226 if (list->magic != SL_LIST_MAGIC0xfacade00LU) 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_MAGIC0xdecea5edLU;
239 SL_FREEdrmFree(entry);
240
241 while (list->level && !list->head->forward[list->level]) --list->level;
242 --list->count;
243 return 0;
244}
245
246int drmSLLookup(void *l, unsigned long key, void **value)
247{
248 SkipListPtr list = (SkipListPtr)l;
249 SLEntryPtr update[SL_MAX_LEVEL16 + 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((void *)0);
259 return -1;
260}
261
262int 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_LEVEL16 + 1];
268 int retcode = 0;
269
270 *prev_key = *next_key = key;
271 *prev_value = *next_value = NULL((void *)0);
272
273 if (update[0]) {
Branch condition evaluates to a garbage value
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
286int drmSLNext(void *l, unsigned long *key, void **value)
287{
288 SkipListPtr list = (SkipListPtr)l;
289 SLEntryPtr entry;
290
291 if (list->magic != SL_LIST_MAGIC0xfacade00LU) 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((void *)0);
302 return 0;
303}
304
305int drmSLFirst(void *l, unsigned long *key, void **value)
306{
307 SkipListPtr list = (SkipListPtr)l;
308
309 if (list->magic != SL_LIST_MAGIC0xfacade00LU) 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. */
316void drmSLDump(void *l)
317{
318 SkipListPtr list = (SkipListPtr)l;
319 SLEntryPtr entry;
320 int i;
321
322 if (list->magic != SL_LIST_MAGIC0xfacade00LU) {
323 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
324 list->magic, SL_LIST_MAGIC0xfacade00LU);
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_MAGIC0x00fab1edLU) {
331 printf("Bad magic: 0x%08lx (expected 0x%08lx)\n",
332 list->magic, SL_ENTRY_MAGIC0x00fab1edLU);
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_MAIN0
351static 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
363static 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_DECLstatic void *state = ((void *)0);
374
375 SL_RANDOM_INIT(12345)if (!state) state = drmRandomCreate(12345);
376
377 list = drmSLCreate();
378
379 for (i = 0; i < size; i++) {
380 keys[i] = SL_RANDOMdrmRandom(state);
381 drmSLInsert(list, keys[i], NULL((void *)0));
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((void *)0));
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((void *)0));
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
413static 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
428int 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((void *)0));
440 drmSLInsert(list, 213, NULL((void *)0));
441 drmSLInsert(list, 50, NULL((void *)0));
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