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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: sym.c,v 1.6 1999/05/26 21:08:31 mdw Exp $ |
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4 | * |
5 | * Symbol table management |
6 | * |
7 | * (c) 1998 Straylight/Edgeware |
8 | */ |
9 | |
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10 | /*----- Licensing notice --------------------------------------------------* |
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11 | * |
12 | * This file is part of the mLib utilities library. |
13 | * |
14 | * mLib is free software; you can redistribute it and/or modify |
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15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
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19 | * mLib is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
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25 | * License along with mLib; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
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28 | */ |
29 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: sym.c,v $ |
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33 | * Revision 1.6 1999/05/26 21:08:31 mdw |
34 | * Rename symbols in line with newer conventions. |
35 | * |
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36 | * Revision 1.5 1999/05/13 22:48:37 mdw |
37 | * Twiddle the extension threshold. Change `-ise' to `-ize' throughout. |
38 | * |
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39 | * Revision 1.4 1999/05/06 19:51:35 mdw |
40 | * Reformatted the LGPL notice a little bit. |
41 | * |
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42 | * Revision 1.3 1999/05/05 18:50:31 mdw |
43 | * Change licensing conditions to LGPL. |
44 | * |
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45 | * Revision 1.2 1998/11/26 19:27:33 mdw |
46 | * Move SYM_NAME into the header file. Fix bugs. |
47 | * |
48 | * Revision 1.1.1.1 1998/06/17 23:44:42 mdw |
49 | * Initial version of mLib |
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50 | * |
51 | */ |
52 | |
53 | /*----- Header files ------------------------------------------------------*/ |
54 | |
55 | /* --- ANSI headers --- */ |
56 | |
57 | #include <stdio.h> |
58 | #include <stdlib.h> |
59 | #include <string.h> |
60 | |
61 | /* --- Local headers --- */ |
62 | |
63 | #include "alloc.h" |
64 | #include "crc32.h" |
65 | #include "exc.h" |
66 | #include "sub.h" |
67 | #include "sym.h" |
68 | #include "track.h" |
69 | |
70 | /*----- Tuning parameters -------------------------------------------------*/ |
71 | |
72 | /* --- Initial hash table size --- * |
73 | * |
74 | * This is the initial @mask@ value. It must be of the form %$2^n - 1$%, |
75 | * so that it can be used to mask of the bottom bits of a hash value. |
76 | */ |
77 | |
78 | #define SYM_INITSZ 255 /* Size of a new hash table */ |
79 | |
80 | /* --- Maximum load factor --- * |
81 | * |
82 | * This parameter controls how much the table has to be loaded before the |
83 | * table is extended. The number of elements %$n$%, the number of bins %$b$% |
84 | * and the limit %$l$% satisfy the relation %$n < bl$%; if a new item is |
85 | * added to the table and this relation is found to be false, the table is |
86 | * doubled in size. |
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87 | */ |
88 | |
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89 | #define SYM_LIMIT(n) ((n) * 4) /* Load factor for growing table */ |
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90 | |
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91 | /*----- Main code ---------------------------------------------------------*/ |
92 | |
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93 | /* --- @sym_create@ --- * |
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94 | * |
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95 | * Arguments: @sym_table *t@ = symbol table to initialize |
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96 | * |
97 | * Returns: --- |
98 | * |
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99 | * Use: Initializes the given symbol table. Raises @EXC_NOMEM@ if |
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100 | * there isn't enough memory. |
101 | */ |
102 | |
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103 | void sym_create(sym_table *t) |
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104 | { |
105 | size_t i; |
106 | |
107 | TRACK_CTX("symbol table creation"); |
108 | TRACK_PUSH; |
109 | |
110 | t->mask = SYM_INITSZ; |
111 | t->c = SYM_LIMIT(SYM_INITSZ); |
112 | t->a = xmalloc((t->mask + 1) * sizeof(sym_base *)); |
113 | |
114 | for (i = 0; i < SYM_INITSZ + 1; i++) |
115 | t->a[i] = 0; |
116 | |
117 | TRACK_POP; |
118 | } |
119 | |
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120 | /* --- @sym_destroy@ --- * |
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121 | * |
122 | * Arguments: @sym_table *t@ = pointer to symbol table in question |
123 | * |
124 | * Returns: --- |
125 | * |
126 | * Use: Destroys a symbol table, freeing all the memory it used to |
127 | * occupy. |
128 | */ |
129 | |
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130 | void sym_destroy(sym_table *t) |
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131 | { |
132 | size_t i; |
133 | sym_base *p, *q; |
134 | |
135 | TRACK_CTX("symbol table deletion"); |
136 | TRACK_PUSH; |
137 | |
138 | for (i = 0; i <= t->mask; i++) { |
139 | p = t->a[i]; |
140 | while (p) { |
141 | q = p->next; |
142 | if (p->len > SYM_BUFSZ) |
143 | sub_free(p->name.p, p->len); |
144 | free(p); |
145 | p = q; |
146 | } |
147 | } |
148 | free(t->a); |
149 | |
150 | TRACK_POP; |
151 | } |
152 | |
153 | /* --- @sym_find@ --- * |
154 | * |
155 | * Arguments: @sym_table *t@ = pointer to symbol table in question |
156 | * @const char *n@ = pointer to symbol table to look up |
157 | * @long l@ = length of the name string or negative to measure |
158 | * @size_t sz@ = size of desired symbol object, or zero |
159 | * @unsigned *f@ = pointer to a flag, or null. |
160 | * |
161 | * Returns: The address of a @sym_base@ structure, or null if not found |
162 | * and @sz@ is zero. |
163 | * |
164 | * Use: Looks up a symbol in a given symbol table. The name is |
165 | * passed by the address of its first character. The length |
166 | * may be given, in which case the name may contain arbitrary |
167 | * binary data, or it may be given as a negative number, in |
168 | * which case the length of the name is calculated as |
169 | * @strlen(n) + 1@. |
170 | * |
171 | * The return value is the address of a pointer to a @sym_base@ |
172 | * block (which may have other things on the end, as above). If |
173 | * the symbol could be found, the return value points to the |
174 | * symbol block. If the symbol wasn't there, then if @sz@ is |
175 | * nonzero, a new symbol is created and its address is returned; |
176 | * otherwise a null pointer is returned. The exception |
177 | * @EXC_NOMEM@ is raised if the block can't be allocated. |
178 | * |
179 | * The value of @*f@ indicates whether a new symbol entry was |
180 | * created: a nonzero value indicates that an old value was |
181 | * found. |
182 | */ |
183 | |
184 | void *sym_find(sym_table *t, const char *n, long l, size_t sz, unsigned *f) |
185 | { |
186 | unsigned long hash; /* Hash value for user's name */ |
187 | size_t len = l < 0 ? strlen(n) + 1 : l; /* Find length of user's name */ |
188 | sym_base *bin; /* Bin containing our item */ |
189 | sym_base *p, *q; /* Pointer wandering through list */ |
190 | |
191 | /* --- Find the correct bin --- */ |
192 | |
193 | CRC32(hash, 0, n, len); /* Find hash value for this name */ |
194 | bin = p = (sym_base *)(t->a + (hash & t->mask)); |
195 | |
196 | /* --- Search the bin list --- */ |
197 | |
198 | while (p->next) { |
199 | if (hash == p->next->hash && /* Check full hash values first */ |
200 | len == p->next->len && /* Then compare string lengths */ |
201 | !memcmp(n, SYM_NAME(p->next), len)) /* And finally compare names */ |
202 | { |
203 | /* --- Found a match --- * |
204 | * |
205 | * As a minor, and probably pointless, tweak, move the item to the |
206 | * front of its bin list. |
207 | */ |
208 | |
209 | q = p->next; /* Find the actual symbol block */ |
210 | p->next = q->next; /* Extract block from bin list */ |
211 | q->next = bin->next; /* Set up symbol's next pointer */ |
212 | bin->next = q; /* And reinsert the block */ |
213 | |
214 | /* --- Return the block --- */ |
215 | |
216 | if (f) *f = 1; /* Didn't fail to find the item */ |
217 | return (q); /* And return the block */ |
218 | } |
219 | |
220 | p = p->next; /* Move onto the next item */ |
221 | } |
222 | |
223 | /* --- Couldn't find the item there --- */ |
224 | |
225 | if (f) *f = 0; /* Failed to find the block */ |
226 | if (!sz) return (0); /* Return zero if not creating */ |
227 | |
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228 | /* --- Create a new symbol block and initialize it --- */ |
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229 | |
230 | { |
231 | TRACK_CTX("new symbol creation"); |
232 | TRACK_PUSH; |
233 | |
234 | p = xmalloc(sz); /* Create a new symbol block */ |
235 | p->next = bin->next; /* Set up the next pointer */ |
236 | p->hash = hash; /* Set up the hash value too */ |
237 | p->len = len; /* And set up the string length */ |
238 | if (len <= SYM_BUFSZ) |
239 | memcpy(p->name.b, n, len); /* And copy the string over */ |
240 | else { |
241 | TRY { |
242 | p->name.p = sub_alloc(len); /* Allocate a block for the name */ |
243 | memcpy(p->name.p, n, len); /* And copy the string over */ |
244 | } CATCH { |
245 | free(p); |
246 | TRACK_POP; |
247 | RETHROW; |
248 | } END_TRY; |
249 | } |
250 | |
251 | TRACK_POP; |
252 | } |
253 | |
254 | bin->next = p; /* Put the pointer into the bin */ |
255 | |
256 | /* --- Consider growing the array --- */ |
257 | |
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258 | if (t->c) |
259 | t->c--; |
260 | if (!t->c) { |
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261 | unsigned long m = t->mask + 1; /* Next set bit in has word */ |
262 | sym_base *p, *q, *r; /* More useful pointers */ |
263 | size_t i, lim; /* Loop counter and limit */ |
264 | |
265 | TRACK_CTX("symbol table extension"); |
266 | TRACK_PUSH; |
267 | |
268 | /* --- Update values in the anchor block --- */ |
269 | |
270 | TRY { |
271 | t->a = xrealloc(t->a, (t->mask + 1) * 2 * sizeof(sym_base *)); |
272 | } CATCH switch (exc_type) { |
273 | case EXC_NOMEM: |
274 | TRACK_POP; |
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275 | return (bin->next); |
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276 | default: |
277 | TRACK_POP; |
278 | RETHROW; |
279 | } END_TRY; |
280 | |
281 | t->c = SYM_LIMIT(t->mask + 1); /* Set load value */ |
282 | t->mask = (t->mask + 1) * 2 - 1; /* Set the new mask value */ |
283 | |
284 | /* --- Now wander through the table rehashing things --- * |
285 | * |
286 | * This loop is very careful to avoid problems with aliasing. The items |
287 | * are dealt with from the end backwards to avoid overwriting bins before |
288 | * they've been processed. |
289 | */ |
290 | |
291 | lim = (t->mask + 1) >> 1; |
292 | for (i = 0; i < lim; i++) { |
293 | |
294 | /* --- Some initialisation --- */ |
295 | |
296 | r = t->a[i]; /* Find the list we're dissecting */ |
297 | p = (sym_base *)(t->a + i); /* Find bit-clear list */ |
298 | q = (sym_base *)(t->a + i + lim); /* And the bit-set lsit */ |
299 | |
300 | /* --- Now go through the @r@ list --- */ |
301 | |
302 | while (r) { |
303 | if (r->hash & m) /* Is the next bit set? */ |
304 | q = q->next = r; /* Yes, so fit up previous link */ |
305 | else |
306 | p = p->next = r; /* No, so fit up previous link */ |
307 | r = r->next; /* Move onto the next item */ |
308 | } |
309 | p->next = q->next = 0; /* Null terminate the new lists */ |
310 | } |
311 | |
312 | TRACK_POP; |
313 | } |
314 | |
315 | /* --- Finished that, so return the new symbol block --- */ |
316 | |
317 | return (p); |
318 | } |
319 | |
320 | /* --- @sym_remove@ --- * |
321 | * |
322 | * Arguments: @sym_table *i@ = pointer to a symbol table object |
323 | * @void *b@ = pointer to symbol table entry |
324 | * |
325 | * Returns: --- |
326 | * |
327 | * Use: Removes the object from the symbol table. The space occupied |
328 | * by the object and its name is freed; anything else attached |
329 | * to the entry should already be gone by this point. |
330 | */ |
331 | |
332 | void sym_remove(sym_table *t, void *b) |
333 | { |
334 | /* --- A quick comment --- * |
335 | * |
336 | * Since the @sym_base@ block contains the hash, finding the element in the |
337 | * bin list is really quick -- it's not worth bothering with things like |
338 | * doubly linked lists. |
339 | */ |
340 | |
341 | sym_base *p = b; |
342 | sym_base *bin = (sym_base *)(t->a + (p->hash & t->mask)); |
343 | |
344 | /* --- Find the item in the bin list --- */ |
345 | |
346 | while (bin->next) { |
347 | if (bin->next == p) |
348 | break; |
349 | bin = bin->next; |
350 | } |
351 | if (!bin->next) |
352 | return; |
353 | |
354 | /* --- Now just remove the item from the list and free it --- * |
355 | * |
356 | * Oh, and bump the load counter. |
357 | */ |
358 | |
359 | bin->next = p->next; |
360 | if (p->len > SYM_BUFSZ) |
361 | sub_free(p->name.p, p->len); |
362 | free(p); |
363 | t->c++; |
364 | } |
365 | |
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366 | /* --- @sym_mkiter@ --- * |
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367 | * |
368 | * Arguments: @sym_iter *i@ = pointer to an iterator object |
369 | * @sym_table *t@ = pointer to a symbol table object |
370 | * |
371 | * Returns: --- |
372 | * |
373 | * Use: Creates a new symbol table iterator which may be used to |
374 | * iterate through a symbol table. |
375 | */ |
376 | |
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377 | void sym_mkiter(sym_iter *i, sym_table *t) |
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378 | { |
379 | i->t = t; |
380 | i->i = 0; |
381 | i->n = 0; |
382 | } |
383 | |
384 | /* --- @sym_next@ --- * |
385 | * |
386 | * Arguments: @sym_iter *i@ = pointer to iterator object |
387 | * |
388 | * Returns: Pointer to the next symbol found, or null when finished. |
389 | * |
390 | * Use: Returns the next symbol from the table. Symbols are not |
391 | * returned in any particular order. |
392 | */ |
393 | |
394 | void *sym_next(sym_iter *i) |
395 | { |
396 | sym_base *p; |
397 | |
398 | /* --- Find the next item --- */ |
399 | |
400 | while (!i->n) { |
401 | if (i->i > i->t->mask) |
402 | return (0); |
403 | i->n = i->t->a[i->i++]; |
404 | } |
405 | |
406 | /* --- Update the iterator block --- */ |
407 | |
408 | p = i->n; |
409 | i->n = p->next; |
410 | |
411 | /* --- Done --- */ |
412 | |
413 | return (p); |
414 | } |
415 | |
416 | /*----- Symbol table test code --------------------------------------------*/ |
417 | |
418 | #ifdef TEST_RIG |
419 | |
420 | #include <errno.h> |
421 | #include <time.h> |
422 | |
423 | typedef struct sym_word { |
424 | sym_base base; |
425 | size_t i; |
426 | } sym_word; |
427 | |
428 | |
429 | /* --- What it does --- * |
430 | * |
431 | * Reads the file /usr/dict/words (change to some other file full of |
432 | * interesting and appropriate bits of text to taste) into a big buffer and |
433 | * picks apart into lines. Then picks lines at random and enters them into |
434 | * the symbol table. |
435 | */ |
436 | |
437 | int main(void) |
438 | { |
439 | char *buff, *p, *lim; |
440 | size_t sz, done; |
441 | FILE *fp; |
442 | int i; |
443 | char **line; |
444 | sym_word **flag; |
445 | sym_table tbl; |
446 | int entries; |
447 | |
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448 | /* --- Initialize for reading the file --- */ |
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449 | |
450 | sz = BUFSIZ; |
451 | buff = xmalloc(sz + 1); |
452 | done = 0; |
453 | sub_init(); |
454 | |
455 | if ((fp = fopen("/usr/dict/words", "r")) == 0) |
456 | fprintf(stderr, "buggered ;-( (%s)\n", strerror(errno)); |
457 | |
458 | /* --- Read buffers of text --- * |
459 | * |
460 | * Read a buffer. If more to come, double the buffer size and try again. |
461 | * This is the method I recommended to comp.lang.c, so I may as well try |
462 | * it. |
463 | */ |
464 | |
465 | for (;;) { |
466 | i = fread(buff + done, 1, sz - done, fp); |
467 | done += i; |
468 | if (done != sz) |
469 | break; |
470 | sz <<= 1; |
471 | buff = xrealloc(buff, sz + 1); |
472 | } |
473 | |
474 | /* --- Count the lines --- */ |
475 | |
476 | lim = buff + done; |
477 | |
478 | sz = 1; |
479 | for (p = buff; p < lim; p++) |
480 | if (*p == '\n') sz++; |
481 | |
482 | /* --- Build a table of line starts --- */ |
483 | |
484 | line = xmalloc(sz * sizeof(char *)); |
485 | i = 0; |
486 | line[i++] = buff; |
487 | for (p = buff; p < lim; p++) |
488 | if (*p == '\n') *p = 0, line[i++] = p + 1; |
489 | *lim = 0; |
490 | |
491 | /* --- Build a table of lines --- * |
492 | * |
493 | * This reverses the mapping which the symbol table performs, so that its |
494 | * accuracy can be tested. |
495 | */ |
496 | |
497 | flag = xmalloc(sz * sizeof(sym_word *)); |
498 | for (i = 0; i < sz; i++) |
499 | flag[i] = 0; |
500 | entries = 0; |
501 | |
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502 | sym_create(&tbl); |
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503 | |
504 | for (;;) { |
505 | i = (unsigned)rand() % sz; |
506 | |
507 | switch (rand() % 5) |
508 | { |
509 | case 0: { |
510 | sym_word *w; |
511 | |
512 | printf("find `%s'\n", line[i]); |
513 | if ((rand() & 1023) == 0) { |
514 | putchar('.'); fflush(stdout); |
515 | } |
516 | |
517 | w = sym_find(&tbl, line[i], -1, 0, 0); |
518 | if (w != flag[i]) |
519 | printf("*** error: find `%s' gave %p not %p\n", |
520 | line[i], (void *)w, (void *)flag[i]); |
521 | else if (w && w->i != i) |
522 | printf("*** error: find sym for `%s' gives index %i not %i\n", |
523 | line[i], w->i, i); |
524 | } break; |
525 | |
526 | case 1: { |
527 | unsigned f; |
528 | sym_word *w; |
529 | |
530 | printf("create `%s'\n", line[i]); |
531 | if ((rand() & 1023) == 0) { |
532 | putchar('+'); fflush(stdout); |
533 | } |
534 | |
535 | w = sym_find(&tbl, line[i], -1, sizeof(sym_word), &f); |
536 | if (f) |
537 | { |
538 | if (w != flag[i]) |
539 | printf("*** error: create `%s' gave %p not %p\n", |
540 | line[i], (void *)w, (void *)flag[i]); |
541 | else if (w && w->i != i) |
542 | printf("*** error: create sym for `%s' gives index %i not %i\n", |
543 | line[i], w->i, i); |
544 | } |
545 | else |
546 | { |
547 | if (flag[i]) |
548 | printf("*** error: create `%s' gave new block, should be %p\n", |
549 | line[i], (void *)flag[i]); |
550 | else { |
551 | flag[i] = w; |
552 | w->i = i; |
553 | entries++; |
554 | } |
555 | } |
556 | } break; |
557 | |
558 | case 2: { |
559 | sym_iter it; |
560 | sym_word *w, **ntbl; |
561 | int v; |
562 | |
563 | if (!entries) |
564 | break; |
565 | v = (rand() % entries) == 0; |
566 | if (!v) |
567 | break; |
568 | printf("\niterated %i entries\n", entries); |
569 | break; |
570 | |
571 | printf("iterate\n"); |
572 | |
573 | ntbl = xmalloc(sz * sizeof(sym_word *)); |
574 | memcpy(ntbl, flag, sz * sizeof(sym_word *)); |
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575 | sym_mkiter(&it, &tbl); |
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576 | |
577 | while ((w = sym_next(&it)) != 0) { |
578 | if (ntbl[w->i] == 0) |
579 | printf("*** error: iterate returned duff item %i\n", w->i); |
580 | else |
581 | ntbl[w->i] = 0; |
582 | } |
583 | |
584 | for (i = 0; i < sz; i++) |
585 | if (ntbl[i]) printf("*** error: iterate didn't return item %i\n", |
586 | i); |
587 | free(ntbl); |
588 | } break; |
589 | |
590 | case 3: { |
591 | sym_base *b; |
592 | int v = rand() & 255 ? 0 : 1; |
593 | break; |
594 | |
595 | printf("dump\n"); |
596 | |
597 | for (i = 0; i <= tbl.mask; i++) { |
598 | if (!tbl.a[i]) continue; |
599 | if (v) printf(" %i: ", i); |
600 | b = tbl.a[i]; |
601 | while (b) { |
602 | if ((b->hash & tbl.mask) != i) |
603 | printf("*** error: bad hash value found"); |
604 | if (v) printf("`%s'(%08lx:%lu) ", |
605 | line[((sym_word *)b)->i], |
606 | b->hash, |
607 | b->hash & tbl.mask); |
608 | b = b->next; |
609 | } |
610 | if (v) putchar('\n'); |
611 | } |
612 | } break; |
613 | |
614 | case 4: { |
615 | if (flag[i]) { |
616 | printf("remove `%s'\n", SYM_NAME(&flag[i]->base)); |
617 | if ((rand() & 1023) == 0) { |
618 | putchar('-'); fflush(stdout); |
619 | } |
620 | sym_remove(&tbl, flag[i]); |
621 | flag[i] = 0; |
622 | entries--; |
623 | } |
624 | } break; |
625 | } |
626 | |
627 | } |
628 | |
629 | return (0); |
630 | } |
631 | |
632 | #endif |
633 | |
634 | /*----- That's all, folks -------------------------------------------------*/ |