chiark / gitweb /
Minor tidying and typo correction.
[mLib] / sym.c
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0875b58f 1/* -*-c-*-
2 *
d4d7a053 3 * $Id: sym.c,v 1.7 1999/06/01 09:49:08 mdw Exp $
0875b58f 4 *
5 * Symbol table management
6 *
7 * (c) 1998 Straylight/Edgeware
8 */
9
c846879c 10/*----- Licensing notice --------------------------------------------------*
0875b58f 11 *
12 * This file is part of the mLib utilities library.
13 *
14 * mLib is free software; you can redistribute it and/or modify
c846879c 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 *
0875b58f 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
c846879c 22 * GNU Library General Public License for more details.
23 *
24 * You should have received a copy of the GNU Library General Public
0bd98442 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.
0875b58f 28 */
29
30/*----- Revision history --------------------------------------------------*
31 *
32 * $Log: sym.c,v $
d4d7a053 33 * Revision 1.7 1999/06/01 09:49:08 mdw
34 * Allow things to be looked up by just their caller-supplied hashes. This
35 * actually needs to be thought through better.
36 *
34b97201 37 * Revision 1.6 1999/05/26 21:08:31 mdw
38 * Rename symbols in line with newer conventions.
39 *
a7a37c4a 40 * Revision 1.5 1999/05/13 22:48:37 mdw
41 * Twiddle the extension threshold. Change `-ise' to `-ize' throughout.
42 *
0bd98442 43 * Revision 1.4 1999/05/06 19:51:35 mdw
44 * Reformatted the LGPL notice a little bit.
45 *
c846879c 46 * Revision 1.3 1999/05/05 18:50:31 mdw
47 * Change licensing conditions to LGPL.
48 *
a5d14ede 49 * Revision 1.2 1998/11/26 19:27:33 mdw
50 * Move SYM_NAME into the header file. Fix bugs.
51 *
52 * Revision 1.1.1.1 1998/06/17 23:44:42 mdw
53 * Initial version of mLib
0875b58f 54 *
55 */
56
57/*----- Header files ------------------------------------------------------*/
58
59/* --- ANSI headers --- */
60
61#include <stdio.h>
62#include <stdlib.h>
63#include <string.h>
64
65/* --- Local headers --- */
66
67#include "alloc.h"
d4d7a053 68#include "bits.h"
0875b58f 69#include "crc32.h"
70#include "exc.h"
71#include "sub.h"
72#include "sym.h"
73#include "track.h"
74
75/*----- Tuning parameters -------------------------------------------------*/
76
77/* --- Initial hash table size --- *
78 *
79 * This is the initial @mask@ value. It must be of the form %$2^n - 1$%,
80 * so that it can be used to mask of the bottom bits of a hash value.
81 */
82
83#define SYM_INITSZ 255 /* Size of a new hash table */
84
85/* --- Maximum load factor --- *
86 *
87 * This parameter controls how much the table has to be loaded before the
88 * table is extended. The number of elements %$n$%, the number of bins %$b$%
89 * and the limit %$l$% satisfy the relation %$n < bl$%; if a new item is
90 * added to the table and this relation is found to be false, the table is
91 * doubled in size.
0875b58f 92 */
93
a7a37c4a 94#define SYM_LIMIT(n) ((n) * 4) /* Load factor for growing table */
0875b58f 95
0875b58f 96/*----- Main code ---------------------------------------------------------*/
97
34b97201 98/* --- @sym_create@ --- *
0875b58f 99 *
a7a37c4a 100 * Arguments: @sym_table *t@ = symbol table to initialize
0875b58f 101 *
102 * Returns: ---
103 *
a7a37c4a 104 * Use: Initializes the given symbol table. Raises @EXC_NOMEM@ if
0875b58f 105 * there isn't enough memory.
106 */
107
34b97201 108void sym_create(sym_table *t)
0875b58f 109{
110 size_t i;
111
112 TRACK_CTX("symbol table creation");
113 TRACK_PUSH;
114
115 t->mask = SYM_INITSZ;
116 t->c = SYM_LIMIT(SYM_INITSZ);
117 t->a = xmalloc((t->mask + 1) * sizeof(sym_base *));
118
119 for (i = 0; i < SYM_INITSZ + 1; i++)
120 t->a[i] = 0;
121
122 TRACK_POP;
123}
124
34b97201 125/* --- @sym_destroy@ --- *
0875b58f 126 *
127 * Arguments: @sym_table *t@ = pointer to symbol table in question
128 *
129 * Returns: ---
130 *
131 * Use: Destroys a symbol table, freeing all the memory it used to
132 * occupy.
133 */
134
34b97201 135void sym_destroy(sym_table *t)
0875b58f 136{
137 size_t i;
138 sym_base *p, *q;
139
140 TRACK_CTX("symbol table deletion");
141 TRACK_PUSH;
142
143 for (i = 0; i <= t->mask; i++) {
144 p = t->a[i];
145 while (p) {
146 q = p->next;
147 if (p->len > SYM_BUFSZ)
148 sub_free(p->name.p, p->len);
149 free(p);
150 p = q;
151 }
152 }
153 free(t->a);
154
155 TRACK_POP;
156}
157
158/* --- @sym_find@ --- *
159 *
160 * Arguments: @sym_table *t@ = pointer to symbol table in question
161 * @const char *n@ = pointer to symbol table to look up
162 * @long l@ = length of the name string or negative to measure
163 * @size_t sz@ = size of desired symbol object, or zero
164 * @unsigned *f@ = pointer to a flag, or null.
165 *
166 * Returns: The address of a @sym_base@ structure, or null if not found
167 * and @sz@ is zero.
168 *
169 * Use: Looks up a symbol in a given symbol table. The name is
170 * passed by the address of its first character. The length
171 * may be given, in which case the name may contain arbitrary
172 * binary data, or it may be given as a negative number, in
173 * which case the length of the name is calculated as
d4d7a053 174 * @strlen(n) + 1@. The name pointer @n@ may also be zero; in
175 * this case, @l@ is taken to be a raw hash, and any element
176 * with a matching hash is taken to be the one wanted.
0875b58f 177 *
178 * The return value is the address of a pointer to a @sym_base@
179 * block (which may have other things on the end, as above). If
180 * the symbol could be found, the return value points to the
181 * symbol block. If the symbol wasn't there, then if @sz@ is
182 * nonzero, a new symbol is created and its address is returned;
183 * otherwise a null pointer is returned. The exception
184 * @EXC_NOMEM@ is raised if the block can't be allocated.
185 *
186 * The value of @*f@ indicates whether a new symbol entry was
187 * created: a nonzero value indicates that an old value was
188 * found.
189 */
190
191void *sym_find(sym_table *t, const char *n, long l, size_t sz, unsigned *f)
192{
d4d7a053 193 uint32 hash;
194 size_t len = 0;
195 sym_base *bin;
196 sym_base *p, *q;
0875b58f 197
198 /* --- Find the correct bin --- */
199
d4d7a053 200 if (n) {
201 len = l < 0 ? strlen(n) + 1 : l;
202 CRC32(hash, 0, n, len);
203 } else
204 hash = (uint32)l;
0875b58f 205 bin = p = (sym_base *)(t->a + (hash & t->mask));
206
207 /* --- Search the bin list --- */
208
209 while (p->next) {
d4d7a053 210 if (hash == p->next->hash &&
211 (n == 0 || (len == p->next->len &&
212 !memcmp(n, SYM_NAME(p->next), len))))
0875b58f 213 {
214 /* --- Found a match --- *
215 *
216 * As a minor, and probably pointless, tweak, move the item to the
217 * front of its bin list.
218 */
219
d4d7a053 220 q = p->next;
221 p->next = q->next;
222 q->next = bin->next;
223 bin->next = q;
0875b58f 224
225 /* --- Return the block --- */
226
d4d7a053 227 if (f) *f = 1;
228 return (q);
0875b58f 229 }
230
d4d7a053 231 p = p->next;
0875b58f 232 }
233
234 /* --- Couldn't find the item there --- */
235
d4d7a053 236 if (f) *f = 0;
237 if (!sz) return (0);
0875b58f 238
a7a37c4a 239 /* --- Create a new symbol block and initialize it --- */
0875b58f 240
241 {
242 TRACK_CTX("new symbol creation");
243 TRACK_PUSH;
244
d4d7a053 245 p = xmalloc(sz);
246 p->next = bin->next;
247 p->hash = hash;
248 p->len = len;
249 if (n) {
250 if (len <= SYM_BUFSZ)
251 memcpy(p->name.b, n, len);
252 else {
253 TRY {
254 p->name.p = sub_alloc(len);
255 memcpy(p->name.p, n, len);
256 } CATCH {
257 free(p);
258 TRACK_POP;
259 RETHROW;
260 } END_TRY;
261 }
0875b58f 262 }
263
264 TRACK_POP;
265 }
266
d4d7a053 267 bin->next = p;
0875b58f 268
269 /* --- Consider growing the array --- */
270
a5d14ede 271 if (t->c)
272 t->c--;
273 if (!t->c) {
d4d7a053 274 uint32 m = t->mask + 1;
275 sym_base *p, *q, *r;
276 size_t i, lim;
0875b58f 277
278 TRACK_CTX("symbol table extension");
279 TRACK_PUSH;
280
281 /* --- Update values in the anchor block --- */
282
283 TRY {
284 t->a = xrealloc(t->a, (t->mask + 1) * 2 * sizeof(sym_base *));
285 } CATCH switch (exc_type) {
286 case EXC_NOMEM:
287 TRACK_POP;
a5d14ede 288 return (bin->next);
0875b58f 289 default:
290 TRACK_POP;
291 RETHROW;
292 } END_TRY;
293
d4d7a053 294 t->c = SYM_LIMIT(t->mask + 1);
295 t->mask = (t->mask + 1) * 2 - 1;
0875b58f 296
297 /* --- Now wander through the table rehashing things --- *
298 *
299 * This loop is very careful to avoid problems with aliasing. The items
300 * are dealt with from the end backwards to avoid overwriting bins before
301 * they've been processed.
302 */
303
304 lim = (t->mask + 1) >> 1;
305 for (i = 0; i < lim; i++) {
306
d4d7a053 307 /* --- Some initialization --- */
0875b58f 308
d4d7a053 309 r = t->a[i];
310 p = (sym_base *)(t->a + i);
311 q = (sym_base *)(t->a + i + lim);
0875b58f 312
313 /* --- Now go through the @r@ list --- */
314
315 while (r) {
d4d7a053 316 if (r->hash & m)
317 q = q->next = r;
0875b58f 318 else
d4d7a053 319 p = p->next = r;
320 r = r->next;
0875b58f 321 }
d4d7a053 322 p->next = q->next = 0;
0875b58f 323 }
324
325 TRACK_POP;
326 }
327
328 /* --- Finished that, so return the new symbol block --- */
329
330 return (p);
331}
332
333/* --- @sym_remove@ --- *
334 *
335 * Arguments: @sym_table *i@ = pointer to a symbol table object
336 * @void *b@ = pointer to symbol table entry
337 *
338 * Returns: ---
339 *
340 * Use: Removes the object from the symbol table. The space occupied
341 * by the object and its name is freed; anything else attached
342 * to the entry should already be gone by this point.
343 */
344
345void sym_remove(sym_table *t, void *b)
346{
347 /* --- A quick comment --- *
348 *
349 * Since the @sym_base@ block contains the hash, finding the element in the
350 * bin list is really quick -- it's not worth bothering with things like
351 * doubly linked lists.
352 */
353
354 sym_base *p = b;
355 sym_base *bin = (sym_base *)(t->a + (p->hash & t->mask));
356
357 /* --- Find the item in the bin list --- */
358
359 while (bin->next) {
360 if (bin->next == p)
361 break;
362 bin = bin->next;
363 }
364 if (!bin->next)
365 return;
366
367 /* --- Now just remove the item from the list and free it --- *
368 *
369 * Oh, and bump the load counter.
370 */
371
372 bin->next = p->next;
373 if (p->len > SYM_BUFSZ)
374 sub_free(p->name.p, p->len);
375 free(p);
376 t->c++;
377}
378
34b97201 379/* --- @sym_mkiter@ --- *
0875b58f 380 *
381 * Arguments: @sym_iter *i@ = pointer to an iterator object
382 * @sym_table *t@ = pointer to a symbol table object
383 *
384 * Returns: ---
385 *
386 * Use: Creates a new symbol table iterator which may be used to
387 * iterate through a symbol table.
388 */
389
34b97201 390void sym_mkiter(sym_iter *i, sym_table *t)
0875b58f 391{
392 i->t = t;
393 i->i = 0;
394 i->n = 0;
395}
396
397/* --- @sym_next@ --- *
398 *
399 * Arguments: @sym_iter *i@ = pointer to iterator object
400 *
401 * Returns: Pointer to the next symbol found, or null when finished.
402 *
403 * Use: Returns the next symbol from the table. Symbols are not
404 * returned in any particular order.
405 */
406
407void *sym_next(sym_iter *i)
408{
409 sym_base *p;
410
411 /* --- Find the next item --- */
412
413 while (!i->n) {
414 if (i->i > i->t->mask)
415 return (0);
416 i->n = i->t->a[i->i++];
417 }
418
419 /* --- Update the iterator block --- */
420
421 p = i->n;
422 i->n = p->next;
423
424 /* --- Done --- */
425
426 return (p);
427}
428
429/*----- Symbol table test code --------------------------------------------*/
430
431#ifdef TEST_RIG
432
433#include <errno.h>
434#include <time.h>
435
436typedef struct sym_word {
437 sym_base base;
438 size_t i;
439} sym_word;
440
441
442/* --- What it does --- *
443 *
444 * Reads the file /usr/dict/words (change to some other file full of
445 * interesting and appropriate bits of text to taste) into a big buffer and
446 * picks apart into lines. Then picks lines at random and enters them into
447 * the symbol table.
448 */
449
450int main(void)
451{
452 char *buff, *p, *lim;
453 size_t sz, done;
454 FILE *fp;
455 int i;
456 char **line;
457 sym_word **flag;
458 sym_table tbl;
459 int entries;
460
a7a37c4a 461 /* --- Initialize for reading the file --- */
0875b58f 462
463 sz = BUFSIZ;
464 buff = xmalloc(sz + 1);
465 done = 0;
466 sub_init();
467
468 if ((fp = fopen("/usr/dict/words", "r")) == 0)
469 fprintf(stderr, "buggered ;-( (%s)\n", strerror(errno));
470
471 /* --- Read buffers of text --- *
472 *
473 * Read a buffer. If more to come, double the buffer size and try again.
474 * This is the method I recommended to comp.lang.c, so I may as well try
475 * it.
476 */
477
478 for (;;) {
479 i = fread(buff + done, 1, sz - done, fp);
480 done += i;
481 if (done != sz)
482 break;
483 sz <<= 1;
484 buff = xrealloc(buff, sz + 1);
485 }
486
487 /* --- Count the lines --- */
488
489 lim = buff + done;
490
491 sz = 1;
492 for (p = buff; p < lim; p++)
493 if (*p == '\n') sz++;
494
495 /* --- Build a table of line starts --- */
496
497 line = xmalloc(sz * sizeof(char *));
498 i = 0;
499 line[i++] = buff;
500 for (p = buff; p < lim; p++)
501 if (*p == '\n') *p = 0, line[i++] = p + 1;
502 *lim = 0;
503
504 /* --- Build a table of lines --- *
505 *
506 * This reverses the mapping which the symbol table performs, so that its
507 * accuracy can be tested.
508 */
509
510 flag = xmalloc(sz * sizeof(sym_word *));
511 for (i = 0; i < sz; i++)
512 flag[i] = 0;
513 entries = 0;
514
34b97201 515 sym_create(&tbl);
0875b58f 516
517 for (;;) {
518 i = (unsigned)rand() % sz;
519
520 switch (rand() % 5)
521 {
522 case 0: {
523 sym_word *w;
524
525 printf("find `%s'\n", line[i]);
526 if ((rand() & 1023) == 0) {
527 putchar('.'); fflush(stdout);
528 }
529
530 w = sym_find(&tbl, line[i], -1, 0, 0);
531 if (w != flag[i])
532 printf("*** error: find `%s' gave %p not %p\n",
533 line[i], (void *)w, (void *)flag[i]);
534 else if (w && w->i != i)
535 printf("*** error: find sym for `%s' gives index %i not %i\n",
536 line[i], w->i, i);
537 } break;
538
539 case 1: {
540 unsigned f;
541 sym_word *w;
542
543 printf("create `%s'\n", line[i]);
544 if ((rand() & 1023) == 0) {
545 putchar('+'); fflush(stdout);
546 }
547
548 w = sym_find(&tbl, line[i], -1, sizeof(sym_word), &f);
549 if (f)
550 {
551 if (w != flag[i])
552 printf("*** error: create `%s' gave %p not %p\n",
553 line[i], (void *)w, (void *)flag[i]);
554 else if (w && w->i != i)
555 printf("*** error: create sym for `%s' gives index %i not %i\n",
556 line[i], w->i, i);
557 }
558 else
559 {
560 if (flag[i])
561 printf("*** error: create `%s' gave new block, should be %p\n",
562 line[i], (void *)flag[i]);
563 else {
564 flag[i] = w;
565 w->i = i;
566 entries++;
567 }
568 }
569 } break;
570
571 case 2: {
572 sym_iter it;
573 sym_word *w, **ntbl;
574 int v;
575
576 if (!entries)
577 break;
578 v = (rand() % entries) == 0;
579 if (!v)
580 break;
581 printf("\niterated %i entries\n", entries);
582 break;
583
584 printf("iterate\n");
585
586 ntbl = xmalloc(sz * sizeof(sym_word *));
587 memcpy(ntbl, flag, sz * sizeof(sym_word *));
34b97201 588 sym_mkiter(&it, &tbl);
0875b58f 589
590 while ((w = sym_next(&it)) != 0) {
591 if (ntbl[w->i] == 0)
592 printf("*** error: iterate returned duff item %i\n", w->i);
593 else
594 ntbl[w->i] = 0;
595 }
596
597 for (i = 0; i < sz; i++)
598 if (ntbl[i]) printf("*** error: iterate didn't return item %i\n",
599 i);
600 free(ntbl);
601 } break;
602
603 case 3: {
604 sym_base *b;
605 int v = rand() & 255 ? 0 : 1;
606 break;
607
608 printf("dump\n");
609
610 for (i = 0; i <= tbl.mask; i++) {
611 if (!tbl.a[i]) continue;
612 if (v) printf(" %i: ", i);
613 b = tbl.a[i];
614 while (b) {
615 if ((b->hash & tbl.mask) != i)
616 printf("*** error: bad hash value found");
617 if (v) printf("`%s'(%08lx:%lu) ",
618 line[((sym_word *)b)->i],
619 b->hash,
620 b->hash & tbl.mask);
621 b = b->next;
622 }
623 if (v) putchar('\n');
624 }
625 } break;
626
627 case 4: {
628 if (flag[i]) {
629 printf("remove `%s'\n", SYM_NAME(&flag[i]->base));
630 if ((rand() & 1023) == 0) {
631 putchar('-'); fflush(stdout);
632 }
633 sym_remove(&tbl, flag[i]);
634 flag[i] = 0;
635 entries--;
636 }
637 } break;
638 }
639
640 }
641
642 return (0);
643}
644
645#endif
646
647/*----- That's all, folks -------------------------------------------------*/