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