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