3 * $Id: sym.c,v 1.3 1999/05/05 18:50:31 mdw Exp $
5 * Symbol table management
7 * (c) 1998 Straylight/Edgeware
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of the mLib utilities library.
14 * mLib is free software; you can redistribute it and/or modify
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.
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
22 * GNU Library General Public License for more details.
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.
29 /*----- Revision history --------------------------------------------------*
32 * Revision 1.3 1999/05/05 18:50:31 mdw
33 * Change licensing conditions to LGPL.
35 * Revision 1.2 1998/11/26 19:27:33 mdw
36 * Move SYM_NAME into the header file. Fix bugs.
38 * Revision 1.1.1.1 1998/06/17 23:44:42 mdw
39 * Initial version of mLib
43 /*----- Header files ------------------------------------------------------*/
45 /* --- ANSI headers --- */
51 /* --- Local headers --- */
60 /*----- Tuning parameters -------------------------------------------------*/
62 /* --- Initial hash table size --- *
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.
68 #define SYM_INITSZ 255 /* Size of a new hash table */
70 /* --- Maximum load factor --- *
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
78 * The current function gives %$l = {3n \over 4}$%, which appears to be
79 * reasonable on the face of things.
82 #define SYM_LIMIT(n) (((n) * 3) >> 2) /* Load factor for growing table */
84 /*----- Main code ---------------------------------------------------------*/
86 /* --- @sym_createTable@ --- *
88 * Arguments: @sym_table *t@ = symbol table to initialise
92 * Use: Initialises the given symbol table. Raises @EXC_NOMEM@ if
93 * there isn't enough memory.
96 void sym_createTable(sym_table *t)
100 TRACK_CTX("symbol table creation");
103 t->mask = SYM_INITSZ;
104 t->c = SYM_LIMIT(SYM_INITSZ);
105 t->a = xmalloc((t->mask + 1) * sizeof(sym_base *));
107 for (i = 0; i < SYM_INITSZ + 1; i++)
113 /* --- @sym_destroyTable@ --- *
115 * Arguments: @sym_table *t@ = pointer to symbol table in question
119 * Use: Destroys a symbol table, freeing all the memory it used to
123 void sym_destroyTable(sym_table *t)
128 TRACK_CTX("symbol table deletion");
131 for (i = 0; i <= t->mask; i++) {
135 if (p->len > SYM_BUFSZ)
136 sub_free(p->name.p, p->len);
146 /* --- @sym_find@ --- *
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.
154 * Returns: The address of a @sym_base@ structure, or null if not found
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
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.
172 * The value of @*f@ indicates whether a new symbol entry was
173 * created: a nonzero value indicates that an old value was
177 void *sym_find(sym_table *t, const char *n, long l, size_t sz, unsigned *f)
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 */
184 /* --- Find the correct bin --- */
186 CRC32(hash, 0, n, len); /* Find hash value for this name */
187 bin = p = (sym_base *)(t->a + (hash & t->mask));
189 /* --- Search the bin list --- */
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 */
196 /* --- Found a match --- *
198 * As a minor, and probably pointless, tweak, move the item to the
199 * front of its bin list.
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 */
207 /* --- Return the block --- */
209 if (f) *f = 1; /* Didn't fail to find the item */
210 return (q); /* And return the block */
213 p = p->next; /* Move onto the next item */
216 /* --- Couldn't find the item there --- */
218 if (f) *f = 0; /* Failed to find the block */
219 if (!sz) return (0); /* Return zero if not creating */
221 /* --- Create a new symbol block and initialise it --- */
224 TRACK_CTX("new symbol creation");
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 */
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 */
247 bin->next = p; /* Put the pointer into the bin */
249 /* --- Consider growing the array --- */
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 */
258 TRACK_CTX("symbol table extension");
261 /* --- Update values in the anchor block --- */
264 t->a = xrealloc(t->a, (t->mask + 1) * 2 * sizeof(sym_base *));
265 } CATCH switch (exc_type) {
274 t->c = SYM_LIMIT(t->mask + 1); /* Set load value */
275 t->mask = (t->mask + 1) * 2 - 1; /* Set the new mask value */
277 /* --- Now wander through the table rehashing things --- *
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.
284 lim = (t->mask + 1) >> 1;
285 for (i = 0; i < lim; i++) {
287 /* --- Some initialisation --- */
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 */
293 /* --- Now go through the @r@ list --- */
296 if (r->hash & m) /* Is the next bit set? */
297 q = q->next = r; /* Yes, so fit up previous link */
299 p = p->next = r; /* No, so fit up previous link */
300 r = r->next; /* Move onto the next item */
302 p->next = q->next = 0; /* Null terminate the new lists */
308 /* --- Finished that, so return the new symbol block --- */
313 /* --- @sym_remove@ --- *
315 * Arguments: @sym_table *i@ = pointer to a symbol table object
316 * @void *b@ = pointer to symbol table entry
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.
325 void sym_remove(sym_table *t, void *b)
327 /* --- A quick comment --- *
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.
335 sym_base *bin = (sym_base *)(t->a + (p->hash & t->mask));
337 /* --- Find the item in the bin list --- */
347 /* --- Now just remove the item from the list and free it --- *
349 * Oh, and bump the load counter.
353 if (p->len > SYM_BUFSZ)
354 sub_free(p->name.p, p->len);
359 /* --- @sym_createIter@ --- *
361 * Arguments: @sym_iter *i@ = pointer to an iterator object
362 * @sym_table *t@ = pointer to a symbol table object
366 * Use: Creates a new symbol table iterator which may be used to
367 * iterate through a symbol table.
370 void sym_createIter(sym_iter *i, sym_table *t)
377 /* --- @sym_next@ --- *
379 * Arguments: @sym_iter *i@ = pointer to iterator object
381 * Returns: Pointer to the next symbol found, or null when finished.
383 * Use: Returns the next symbol from the table. Symbols are not
384 * returned in any particular order.
387 void *sym_next(sym_iter *i)
391 /* --- Find the next item --- */
394 if (i->i > i->t->mask)
396 i->n = i->t->a[i->i++];
399 /* --- Update the iterator block --- */
409 /*----- Symbol table test code --------------------------------------------*/
416 typedef struct sym_word {
422 /* --- What it does --- *
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
432 char *buff, *p, *lim;
441 /* --- Initialise for reading the file --- */
444 buff = xmalloc(sz + 1);
448 if ((fp = fopen("/usr/dict/words", "r")) == 0)
449 fprintf(stderr, "buggered ;-( (%s)\n", strerror(errno));
451 /* --- Read buffers of text --- *
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
459 i = fread(buff + done, 1, sz - done, fp);
464 buff = xrealloc(buff, sz + 1);
467 /* --- Count the lines --- */
472 for (p = buff; p < lim; p++)
473 if (*p == '\n') sz++;
475 /* --- Build a table of line starts --- */
477 line = xmalloc(sz * sizeof(char *));
480 for (p = buff; p < lim; p++)
481 if (*p == '\n') *p = 0, line[i++] = p + 1;
484 /* --- Build a table of lines --- *
486 * This reverses the mapping which the symbol table performs, so that its
487 * accuracy can be tested.
490 flag = xmalloc(sz * sizeof(sym_word *));
491 for (i = 0; i < sz; i++)
495 sym_createTable(&tbl);
498 i = (unsigned)rand() % sz;
505 printf("find `%s'\n", line[i]);
506 if ((rand() & 1023) == 0) {
507 putchar('.'); fflush(stdout);
510 w = sym_find(&tbl, line[i], -1, 0, 0);
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",
523 printf("create `%s'\n", line[i]);
524 if ((rand() & 1023) == 0) {
525 putchar('+'); fflush(stdout);
528 w = sym_find(&tbl, line[i], -1, sizeof(sym_word), &f);
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",
541 printf("*** error: create `%s' gave new block, should be %p\n",
542 line[i], (void *)flag[i]);
558 v = (rand() % entries) == 0;
561 printf("\niterated %i entries\n", entries);
566 ntbl = xmalloc(sz * sizeof(sym_word *));
567 memcpy(ntbl, flag, sz * sizeof(sym_word *));
568 sym_createIter(&it, &tbl);
570 while ((w = sym_next(&it)) != 0) {
572 printf("*** error: iterate returned duff item %i\n", w->i);
577 for (i = 0; i < sz; i++)
578 if (ntbl[i]) printf("*** error: iterate didn't return item %i\n",
585 int v = rand() & 255 ? 0 : 1;
590 for (i = 0; i <= tbl.mask; i++) {
591 if (!tbl.a[i]) continue;
592 if (v) printf(" %i: ", i);
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],
603 if (v) putchar('\n');
609 printf("remove `%s'\n", SYM_NAME(&flag[i]->base));
610 if ((rand() & 1023) == 0) {
611 putchar('-'); fflush(stdout);
613 sym_remove(&tbl, flag[i]);
627 /*----- That's all, folks -------------------------------------------------*/