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[binutils.git] / gas / hash.c
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1 /* hash.c -- gas hash table code
2 Copyright 1987, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999,
3 2000, 2001, 2002, 2003, 2005, 2007
4 Free Software Foundation, Inc.
6 This file is part of GAS, the GNU Assembler.
8 GAS is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
11 any later version.
13 GAS is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GAS; see the file COPYING. If not, write to the Free
20 Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
21 02110-1301, USA. */
23 /* This version of the hash table code is a wholescale replacement of
24 the old hash table code, which was fairly bad. This is based on
25 the hash table code in BFD, but optimized slightly for the
26 assembler. The assembler does not need to derive structures that
27 are stored in the hash table. Instead, it always stores a pointer.
28 The assembler uses the hash table mostly to store symbols, and we
29 don't need to confuse the symbol structure with a hash table
30 structure. */
32 #include "as.h"
33 #include "safe-ctype.h"
34 #include "obstack.h"
36 /* An entry in a hash table. */
38 struct hash_entry {
39 /* Next entry for this hash code. */
40 struct hash_entry *next;
41 /* String being hashed. */
42 const char *string;
43 /* Hash code. This is the full hash code, not the index into the
44 table. */
45 unsigned long hash;
46 /* Pointer being stored in the hash table. */
47 PTR data;
50 /* A hash table. */
52 struct hash_control {
53 /* The hash array. */
54 struct hash_entry **table;
55 /* The number of slots in the hash table. */
56 unsigned int size;
57 /* An obstack for this hash table. */
58 struct obstack memory;
60 #ifdef HASH_STATISTICS
61 /* Statistics. */
62 unsigned long lookups;
63 unsigned long hash_compares;
64 unsigned long string_compares;
65 unsigned long insertions;
66 unsigned long replacements;
67 unsigned long deletions;
68 #endif /* HASH_STATISTICS */
71 /* The default number of entries to use when creating a hash table.
72 Note this value can be reduced to 4051 by using the command line
73 switch --reduce-memory-overheads, or set to other values by using
74 the --hash-size=<NUMBER> switch. */
76 static unsigned long gas_hash_table_size = 65537;
78 void
79 set_gas_hash_table_size (unsigned long size)
81 gas_hash_table_size = size;
84 /* FIXME: This function should be amalgmated with bfd/hash.c:bfd_hash_set_default_size(). */
85 static unsigned long
86 get_gas_hash_table_size (void)
88 /* Extend this prime list if you want more granularity of hash table size. */
89 static const unsigned long hash_size_primes[] =
91 1021, 4051, 8599, 16699, 65537
93 unsigned int index;
95 /* Work out the best prime number near the hash_size.
96 FIXME: This could be a more sophisticated algorithm,
97 but is it really worth implementing it ? */
98 for (index = 0; index < ARRAY_SIZE (hash_size_primes) - 1; ++index)
99 if (gas_hash_table_size <= hash_size_primes[index])
100 break;
102 return hash_size_primes[index];
105 /* Create a hash table. This return a control block. */
107 struct hash_control *
108 hash_new (void)
110 unsigned long size;
111 unsigned long alloc;
112 struct hash_control *ret;
114 size = get_gas_hash_table_size ();
116 ret = xmalloc (sizeof *ret);
117 obstack_begin (&ret->memory, chunksize);
118 alloc = size * sizeof (struct hash_entry *);
119 ret->table = obstack_alloc (&ret->memory, alloc);
120 memset (ret->table, 0, alloc);
121 ret->size = size;
123 #ifdef HASH_STATISTICS
124 ret->lookups = 0;
125 ret->hash_compares = 0;
126 ret->string_compares = 0;
127 ret->insertions = 0;
128 ret->replacements = 0;
129 ret->deletions = 0;
130 #endif
132 return ret;
135 /* Delete a hash table, freeing all allocated memory. */
137 void
138 hash_die (struct hash_control *table)
140 obstack_free (&table->memory, 0);
141 free (table);
144 /* Look up a string in a hash table. This returns a pointer to the
145 hash_entry, or NULL if the string is not in the table. If PLIST is
146 not NULL, this sets *PLIST to point to the start of the list which
147 would hold this hash entry. If PHASH is not NULL, this sets *PHASH
148 to the hash code for KEY.
150 Each time we look up a string, we move it to the start of the list
151 for its hash code, to take advantage of referential locality. */
153 static struct hash_entry *
154 hash_lookup (struct hash_control *table, const char *key, size_t len,
155 struct hash_entry ***plist, unsigned long *phash)
157 unsigned long hash;
158 size_t n;
159 unsigned int c;
160 unsigned int index;
161 struct hash_entry **list;
162 struct hash_entry *p;
163 struct hash_entry *prev;
165 #ifdef HASH_STATISTICS
166 ++table->lookups;
167 #endif
169 hash = 0;
170 for (n = 0; n < len; n++)
172 c = key[n];
173 hash += c + (c << 17);
174 hash ^= hash >> 2;
176 hash += len + (len << 17);
177 hash ^= hash >> 2;
179 if (phash != NULL)
180 *phash = hash;
182 index = hash % table->size;
183 list = table->table + index;
185 if (plist != NULL)
186 *plist = list;
188 prev = NULL;
189 for (p = *list; p != NULL; p = p->next)
191 #ifdef HASH_STATISTICS
192 ++table->hash_compares;
193 #endif
195 if (p->hash == hash)
197 #ifdef HASH_STATISTICS
198 ++table->string_compares;
199 #endif
201 if (strncmp (p->string, key, len) == 0 && p->string[len] == '\0')
203 if (prev != NULL)
205 prev->next = p->next;
206 p->next = *list;
207 *list = p;
210 return p;
214 prev = p;
217 return NULL;
220 /* Insert an entry into a hash table. This returns NULL on success.
221 On error, it returns a printable string indicating the error. It
222 is considered to be an error if the entry already exists in the
223 hash table. */
225 const char *
226 hash_insert (struct hash_control *table, const char *key, PTR value)
228 struct hash_entry *p;
229 struct hash_entry **list;
230 unsigned long hash;
232 p = hash_lookup (table, key, strlen (key), &list, &hash);
233 if (p != NULL)
234 return "exists";
236 #ifdef HASH_STATISTICS
237 ++table->insertions;
238 #endif
240 p = (struct hash_entry *) obstack_alloc (&table->memory, sizeof (*p));
241 p->string = key;
242 p->hash = hash;
243 p->data = value;
245 p->next = *list;
246 *list = p;
248 return NULL;
251 /* Insert or replace an entry in a hash table. This returns NULL on
252 success. On error, it returns a printable string indicating the
253 error. If an entry already exists, its value is replaced. */
255 const char *
256 hash_jam (struct hash_control *table, const char *key, PTR value)
258 struct hash_entry *p;
259 struct hash_entry **list;
260 unsigned long hash;
262 p = hash_lookup (table, key, strlen (key), &list, &hash);
263 if (p != NULL)
265 #ifdef HASH_STATISTICS
266 ++table->replacements;
267 #endif
269 p->data = value;
271 else
273 #ifdef HASH_STATISTICS
274 ++table->insertions;
275 #endif
277 p = (struct hash_entry *) obstack_alloc (&table->memory, sizeof (*p));
278 p->string = key;
279 p->hash = hash;
280 p->data = value;
282 p->next = *list;
283 *list = p;
286 return NULL;
289 /* Replace an existing entry in a hash table. This returns the old
290 value stored for the entry. If the entry is not found in the hash
291 table, this does nothing and returns NULL. */
294 hash_replace (struct hash_control *table, const char *key, PTR value)
296 struct hash_entry *p;
297 PTR ret;
299 p = hash_lookup (table, key, strlen (key), NULL, NULL);
300 if (p == NULL)
301 return NULL;
303 #ifdef HASH_STATISTICS
304 ++table->replacements;
305 #endif
307 ret = p->data;
309 p->data = value;
311 return ret;
314 /* Find an entry in a hash table, returning its value. Returns NULL
315 if the entry is not found. */
318 hash_find (struct hash_control *table, const char *key)
320 struct hash_entry *p;
322 p = hash_lookup (table, key, strlen (key), NULL, NULL);
323 if (p == NULL)
324 return NULL;
326 return p->data;
329 /* As hash_find, but KEY is of length LEN and is not guaranteed to be
330 NUL-terminated. */
333 hash_find_n (struct hash_control *table, const char *key, size_t len)
335 struct hash_entry *p;
337 p = hash_lookup (table, key, len, NULL, NULL);
338 if (p == NULL)
339 return NULL;
341 return p->data;
344 /* Delete an entry from a hash table. This returns the value stored
345 for that entry, or NULL if there is no such entry. */
348 hash_delete (struct hash_control *table, const char *key)
350 struct hash_entry *p;
351 struct hash_entry **list;
353 p = hash_lookup (table, key, strlen (key), &list, NULL);
354 if (p == NULL)
355 return NULL;
357 if (p != *list)
358 abort ();
360 #ifdef HASH_STATISTICS
361 ++table->deletions;
362 #endif
364 *list = p->next;
366 /* Note that we never reclaim the memory for this entry. If gas
367 ever starts deleting hash table entries in a big way, this will
368 have to change. */
370 return p->data;
373 /* Traverse a hash table. Call the function on every entry in the
374 hash table. */
376 void
377 hash_traverse (struct hash_control *table,
378 void (*pfn) (const char *key, PTR value))
380 unsigned int i;
382 for (i = 0; i < table->size; ++i)
384 struct hash_entry *p;
386 for (p = table->table[i]; p != NULL; p = p->next)
387 (*pfn) (p->string, p->data);
391 /* Print hash table statistics on the specified file. NAME is the
392 name of the hash table, used for printing a header. */
394 void
395 hash_print_statistics (FILE *f ATTRIBUTE_UNUSED,
396 const char *name ATTRIBUTE_UNUSED,
397 struct hash_control *table ATTRIBUTE_UNUSED)
399 #ifdef HASH_STATISTICS
400 unsigned int i;
401 unsigned long total;
402 unsigned long empty;
404 fprintf (f, "%s hash statistics:\n", name);
405 fprintf (f, "\t%lu lookups\n", table->lookups);
406 fprintf (f, "\t%lu hash comparisons\n", table->hash_compares);
407 fprintf (f, "\t%lu string comparisons\n", table->string_compares);
408 fprintf (f, "\t%lu insertions\n", table->insertions);
409 fprintf (f, "\t%lu replacements\n", table->replacements);
410 fprintf (f, "\t%lu deletions\n", table->deletions);
412 total = 0;
413 empty = 0;
414 for (i = 0; i < table->size; ++i)
416 struct hash_entry *p;
418 if (table->table[i] == NULL)
419 ++empty;
420 else
422 for (p = table->table[i]; p != NULL; p = p->next)
423 ++total;
427 fprintf (f, "\t%g average chain length\n", (double) total / table->size);
428 fprintf (f, "\t%lu empty slots\n", empty);
429 #endif
432 #ifdef TEST
434 /* This test program is left over from the old hash table code. */
436 /* Number of hash tables to maintain (at once) in any testing. */
437 #define TABLES (6)
439 /* We can have 12 statistics. */
440 #define STATBUFSIZE (12)
442 /* Display statistics here. */
443 int statbuf[STATBUFSIZE];
445 /* Human farts here. */
446 char answer[100];
448 /* We test many hash tables at once. */
449 char *hashtable[TABLES];
451 /* Points to current hash_control. */
452 char *h;
453 char **pp;
454 char *p;
455 char *name;
456 char *value;
457 int size;
458 int used;
459 char command;
461 /* Number 0:TABLES-1 of current hashed symbol table. */
462 int number;
465 main ()
467 void applicatee ();
468 void destroy ();
469 char *what ();
470 int *ip;
472 number = 0;
473 h = 0;
474 printf ("type h <RETURN> for help\n");
475 for (;;)
477 printf ("hash_test command: ");
478 gets (answer);
479 command = answer[0];
480 command = TOLOWER (command); /* Ecch! */
481 switch (command)
483 case '#':
484 printf ("old hash table #=%d.\n", number);
485 whattable ();
486 break;
487 case '?':
488 for (pp = hashtable; pp < hashtable + TABLES; pp++)
490 printf ("address of hash table #%d control block is %xx\n",
491 pp - hashtable, *pp);
493 break;
494 case 'a':
495 hash_traverse (h, applicatee);
496 break;
497 case 'd':
498 hash_traverse (h, destroy);
499 hash_die (h);
500 break;
501 case 'f':
502 p = hash_find (h, name = what ("symbol"));
503 printf ("value of \"%s\" is \"%s\"\n", name, p ? p : "NOT-PRESENT");
504 break;
505 case 'h':
506 printf ("# show old, select new default hash table number\n");
507 printf ("? display all hashtable control block addresses\n");
508 printf ("a apply a simple display-er to each symbol in table\n");
509 printf ("d die: destroy hashtable\n");
510 printf ("f find value of nominated symbol\n");
511 printf ("h this help\n");
512 printf ("i insert value into symbol\n");
513 printf ("j jam value into symbol\n");
514 printf ("n new hashtable\n");
515 printf ("r replace a value with another\n");
516 printf ("s say what %% of table is used\n");
517 printf ("q exit this program\n");
518 printf ("x delete a symbol from table, report its value\n");
519 break;
520 case 'i':
521 p = hash_insert (h, name = what ("symbol"), value = what ("value"));
522 if (p)
524 printf ("symbol=\"%s\" value=\"%s\" error=%s\n", name, value,
527 break;
528 case 'j':
529 p = hash_jam (h, name = what ("symbol"), value = what ("value"));
530 if (p)
532 printf ("symbol=\"%s\" value=\"%s\" error=%s\n", name, value, p);
534 break;
535 case 'n':
536 h = hashtable[number] = (char *) hash_new ();
537 break;
538 case 'q':
539 exit (EXIT_SUCCESS);
540 case 'r':
541 p = hash_replace (h, name = what ("symbol"), value = what ("value"));
542 printf ("old value was \"%s\"\n", p ? p : "{}");
543 break;
544 case 's':
545 hash_say (h, statbuf, STATBUFSIZE);
546 for (ip = statbuf; ip < statbuf + STATBUFSIZE; ip++)
548 printf ("%d ", *ip);
550 printf ("\n");
551 break;
552 case 'x':
553 p = hash_delete (h, name = what ("symbol"));
554 printf ("old value was \"%s\"\n", p ? p : "{}");
555 break;
556 default:
557 printf ("I can't understand command \"%c\"\n", command);
558 break;
563 char *
564 what (description)
565 char *description;
567 printf (" %s : ", description);
568 gets (answer);
569 return xstrdup (answer);
572 void
573 destroy (string, value)
574 char *string;
575 char *value;
577 free (string);
578 free (value);
581 void
582 applicatee (string, value)
583 char *string;
584 char *value;
586 printf ("%.20s-%.20s\n", string, value);
589 /* Determine number: what hash table to use.
590 Also determine h: points to hash_control. */
592 void
593 whattable ()
595 for (;;)
597 printf (" what hash table (%d:%d) ? ", 0, TABLES - 1);
598 gets (answer);
599 sscanf (answer, "%d", &number);
600 if (number >= 0 && number < TABLES)
602 h = hashtable[number];
603 if (!h)
605 printf ("warning: current hash-table-#%d. has no hash-control\n", number);
607 return;
609 else
611 printf ("invalid hash table number: %d\n", number);
616 #endif /* TEST */