Mercurial > hg > CbC > CbC_gcc
annotate libiberty/hashtab.c @ 67:f6334be47118
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author | nobuyasu <dimolto@cr.ie.u-ryukyu.ac.jp> |
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date | Tue, 22 Mar 2011 17:18:12 +0900 |
parents | 77e2b8dfacca |
children | 04ced10e8804 |
rev | line source |
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0 | 1 /* An expandable hash tables datatype. |
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2 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2009, 2010 |
0 | 3 Free Software Foundation, Inc. |
4 Contributed by Vladimir Makarov (vmakarov@cygnus.com). | |
5 | |
6 This file is part of the libiberty library. | |
7 Libiberty is free software; you can redistribute it and/or | |
8 modify it under the terms of the GNU Library General Public | |
9 License as published by the Free Software Foundation; either | |
10 version 2 of the License, or (at your option) any later version. | |
11 | |
12 Libiberty is distributed in the hope that it will be useful, | |
13 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
15 Library General Public License for more details. | |
16 | |
17 You should have received a copy of the GNU Library General Public | |
18 License along with libiberty; see the file COPYING.LIB. If | |
19 not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor, | |
20 Boston, MA 02110-1301, USA. */ | |
21 | |
22 /* This package implements basic hash table functionality. It is possible | |
23 to search for an entry, create an entry and destroy an entry. | |
24 | |
25 Elements in the table are generic pointers. | |
26 | |
27 The size of the table is not fixed; if the occupancy of the table | |
28 grows too high the hash table will be expanded. | |
29 | |
30 The abstract data implementation is based on generalized Algorithm D | |
31 from Knuth's book "The art of computer programming". Hash table is | |
32 expanded by creation of new hash table and transferring elements from | |
33 the old table to the new table. */ | |
34 | |
35 #ifdef HAVE_CONFIG_H | |
36 #include "config.h" | |
37 #endif | |
38 | |
39 #include <sys/types.h> | |
40 | |
41 #ifdef HAVE_STDLIB_H | |
42 #include <stdlib.h> | |
43 #endif | |
44 #ifdef HAVE_STRING_H | |
45 #include <string.h> | |
46 #endif | |
47 #ifdef HAVE_MALLOC_H | |
48 #include <malloc.h> | |
49 #endif | |
50 #ifdef HAVE_LIMITS_H | |
51 #include <limits.h> | |
52 #endif | |
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53 #ifdef HAVE_INTTYPES_H |
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54 #include <inttypes.h> |
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55 #endif |
0 | 56 #ifdef HAVE_STDINT_H |
57 #include <stdint.h> | |
58 #endif | |
59 | |
60 #include <stdio.h> | |
61 | |
62 #include "libiberty.h" | |
63 #include "ansidecl.h" | |
64 #include "hashtab.h" | |
65 | |
66 #ifndef CHAR_BIT | |
67 #define CHAR_BIT 8 | |
68 #endif | |
69 | |
70 static unsigned int higher_prime_index (unsigned long); | |
71 static hashval_t htab_mod_1 (hashval_t, hashval_t, hashval_t, int); | |
72 static hashval_t htab_mod (hashval_t, htab_t); | |
73 static hashval_t htab_mod_m2 (hashval_t, htab_t); | |
74 static hashval_t hash_pointer (const void *); | |
75 static int eq_pointer (const void *, const void *); | |
76 static int htab_expand (htab_t); | |
77 static PTR *find_empty_slot_for_expand (htab_t, hashval_t); | |
78 | |
79 /* At some point, we could make these be NULL, and modify the | |
80 hash-table routines to handle NULL specially; that would avoid | |
81 function-call overhead for the common case of hashing pointers. */ | |
82 htab_hash htab_hash_pointer = hash_pointer; | |
83 htab_eq htab_eq_pointer = eq_pointer; | |
84 | |
85 /* Table of primes and multiplicative inverses. | |
86 | |
87 Note that these are not minimally reduced inverses. Unlike when generating | |
88 code to divide by a constant, we want to be able to use the same algorithm | |
89 all the time. All of these inverses (are implied to) have bit 32 set. | |
90 | |
91 For the record, here's the function that computed the table; it's a | |
92 vastly simplified version of the function of the same name from gcc. */ | |
93 | |
94 #if 0 | |
95 unsigned int | |
96 ceil_log2 (unsigned int x) | |
97 { | |
98 int i; | |
99 for (i = 31; i >= 0 ; --i) | |
100 if (x > (1u << i)) | |
101 return i+1; | |
102 abort (); | |
103 } | |
104 | |
105 unsigned int | |
106 choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp) | |
107 { | |
108 unsigned long long mhigh; | |
109 double nx; | |
110 int lgup, post_shift; | |
111 int pow, pow2; | |
112 int n = 32, precision = 32; | |
113 | |
114 lgup = ceil_log2 (d); | |
115 pow = n + lgup; | |
116 pow2 = n + lgup - precision; | |
117 | |
118 nx = ldexp (1.0, pow) + ldexp (1.0, pow2); | |
119 mhigh = nx / d; | |
120 | |
121 *shiftp = lgup - 1; | |
122 *mlp = mhigh; | |
123 return mhigh >> 32; | |
124 } | |
125 #endif | |
126 | |
127 struct prime_ent | |
128 { | |
129 hashval_t prime; | |
130 hashval_t inv; | |
131 hashval_t inv_m2; /* inverse of prime-2 */ | |
132 hashval_t shift; | |
133 }; | |
134 | |
135 static struct prime_ent const prime_tab[] = { | |
136 { 7, 0x24924925, 0x9999999b, 2 }, | |
137 { 13, 0x3b13b13c, 0x745d1747, 3 }, | |
138 { 31, 0x08421085, 0x1a7b9612, 4 }, | |
139 { 61, 0x0c9714fc, 0x15b1e5f8, 5 }, | |
140 { 127, 0x02040811, 0x0624dd30, 6 }, | |
141 { 251, 0x05197f7e, 0x073260a5, 7 }, | |
142 { 509, 0x01824366, 0x02864fc8, 8 }, | |
143 { 1021, 0x00c0906d, 0x014191f7, 9 }, | |
144 { 2039, 0x0121456f, 0x0161e69e, 10 }, | |
145 { 4093, 0x00300902, 0x00501908, 11 }, | |
146 { 8191, 0x00080041, 0x00180241, 12 }, | |
147 { 16381, 0x000c0091, 0x00140191, 13 }, | |
148 { 32749, 0x002605a5, 0x002a06e6, 14 }, | |
149 { 65521, 0x000f00e2, 0x00110122, 15 }, | |
150 { 131071, 0x00008001, 0x00018003, 16 }, | |
151 { 262139, 0x00014002, 0x0001c004, 17 }, | |
152 { 524287, 0x00002001, 0x00006001, 18 }, | |
153 { 1048573, 0x00003001, 0x00005001, 19 }, | |
154 { 2097143, 0x00004801, 0x00005801, 20 }, | |
155 { 4194301, 0x00000c01, 0x00001401, 21 }, | |
156 { 8388593, 0x00001e01, 0x00002201, 22 }, | |
157 { 16777213, 0x00000301, 0x00000501, 23 }, | |
158 { 33554393, 0x00001381, 0x00001481, 24 }, | |
159 { 67108859, 0x00000141, 0x000001c1, 25 }, | |
160 { 134217689, 0x000004e1, 0x00000521, 26 }, | |
161 { 268435399, 0x00000391, 0x000003b1, 27 }, | |
162 { 536870909, 0x00000019, 0x00000029, 28 }, | |
163 { 1073741789, 0x0000008d, 0x00000095, 29 }, | |
164 { 2147483647, 0x00000003, 0x00000007, 30 }, | |
165 /* Avoid "decimal constant so large it is unsigned" for 4294967291. */ | |
166 { 0xfffffffb, 0x00000006, 0x00000008, 31 } | |
167 }; | |
168 | |
169 /* The following function returns an index into the above table of the | |
170 nearest prime number which is greater than N, and near a power of two. */ | |
171 | |
172 static unsigned int | |
173 higher_prime_index (unsigned long n) | |
174 { | |
175 unsigned int low = 0; | |
176 unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]); | |
177 | |
178 while (low != high) | |
179 { | |
180 unsigned int mid = low + (high - low) / 2; | |
181 if (n > prime_tab[mid].prime) | |
182 low = mid + 1; | |
183 else | |
184 high = mid; | |
185 } | |
186 | |
187 /* If we've run out of primes, abort. */ | |
188 if (n > prime_tab[low].prime) | |
189 { | |
190 fprintf (stderr, "Cannot find prime bigger than %lu\n", n); | |
191 abort (); | |
192 } | |
193 | |
194 return low; | |
195 } | |
196 | |
197 /* Returns a hash code for P. */ | |
198 | |
199 static hashval_t | |
200 hash_pointer (const PTR p) | |
201 { | |
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202 return (hashval_t) ((intptr_t)p >> 3); |
0 | 203 } |
204 | |
205 /* Returns non-zero if P1 and P2 are equal. */ | |
206 | |
207 static int | |
208 eq_pointer (const PTR p1, const PTR p2) | |
209 { | |
210 return p1 == p2; | |
211 } | |
212 | |
213 | |
214 /* The parens around the function names in the next two definitions | |
215 are essential in order to prevent macro expansions of the name. | |
216 The bodies, however, are expanded as expected, so they are not | |
217 recursive definitions. */ | |
218 | |
219 /* Return the current size of given hash table. */ | |
220 | |
221 #define htab_size(htab) ((htab)->size) | |
222 | |
223 size_t | |
224 (htab_size) (htab_t htab) | |
225 { | |
226 return htab_size (htab); | |
227 } | |
228 | |
229 /* Return the current number of elements in given hash table. */ | |
230 | |
231 #define htab_elements(htab) ((htab)->n_elements - (htab)->n_deleted) | |
232 | |
233 size_t | |
234 (htab_elements) (htab_t htab) | |
235 { | |
236 return htab_elements (htab); | |
237 } | |
238 | |
239 /* Return X % Y. */ | |
240 | |
241 static inline hashval_t | |
242 htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift) | |
243 { | |
244 /* The multiplicative inverses computed above are for 32-bit types, and | |
245 requires that we be able to compute a highpart multiply. */ | |
246 #ifdef UNSIGNED_64BIT_TYPE | |
247 __extension__ typedef UNSIGNED_64BIT_TYPE ull; | |
248 if (sizeof (hashval_t) * CHAR_BIT <= 32) | |
249 { | |
250 hashval_t t1, t2, t3, t4, q, r; | |
251 | |
252 t1 = ((ull)x * inv) >> 32; | |
253 t2 = x - t1; | |
254 t3 = t2 >> 1; | |
255 t4 = t1 + t3; | |
256 q = t4 >> shift; | |
257 r = x - (q * y); | |
258 | |
259 return r; | |
260 } | |
261 #endif | |
262 | |
263 /* Otherwise just use the native division routines. */ | |
264 return x % y; | |
265 } | |
266 | |
267 /* Compute the primary hash for HASH given HTAB's current size. */ | |
268 | |
269 static inline hashval_t | |
270 htab_mod (hashval_t hash, htab_t htab) | |
271 { | |
272 const struct prime_ent *p = &prime_tab[htab->size_prime_index]; | |
273 return htab_mod_1 (hash, p->prime, p->inv, p->shift); | |
274 } | |
275 | |
276 /* Compute the secondary hash for HASH given HTAB's current size. */ | |
277 | |
278 static inline hashval_t | |
279 htab_mod_m2 (hashval_t hash, htab_t htab) | |
280 { | |
281 const struct prime_ent *p = &prime_tab[htab->size_prime_index]; | |
282 return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift); | |
283 } | |
284 | |
285 /* This function creates table with length slightly longer than given | |
286 source length. Created hash table is initiated as empty (all the | |
287 hash table entries are HTAB_EMPTY_ENTRY). The function returns the | |
288 created hash table, or NULL if memory allocation fails. */ | |
289 | |
290 htab_t | |
291 htab_create_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, | |
292 htab_del del_f, htab_alloc alloc_f, htab_free free_f) | |
293 { | |
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294 return htab_create_typed_alloc (size, hash_f, eq_f, del_f, alloc_f, alloc_f, |
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295 free_f); |
0 | 296 } |
297 | |
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298 /* As above, but uses the variants of ALLOC_F and FREE_F which accept |
0 | 299 an extra argument. */ |
300 | |
301 htab_t | |
302 htab_create_alloc_ex (size_t size, htab_hash hash_f, htab_eq eq_f, | |
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303 htab_del del_f, void *alloc_arg, |
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304 htab_alloc_with_arg alloc_f, |
0 | 305 htab_free_with_arg free_f) |
306 { | |
307 htab_t result; | |
308 unsigned int size_prime_index; | |
309 | |
310 size_prime_index = higher_prime_index (size); | |
311 size = prime_tab[size_prime_index].prime; | |
312 | |
313 result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab)); | |
314 if (result == NULL) | |
315 return NULL; | |
316 result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR)); | |
317 if (result->entries == NULL) | |
318 { | |
319 if (free_f != NULL) | |
320 (*free_f) (alloc_arg, result); | |
321 return NULL; | |
322 } | |
323 result->size = size; | |
324 result->size_prime_index = size_prime_index; | |
325 result->hash_f = hash_f; | |
326 result->eq_f = eq_f; | |
327 result->del_f = del_f; | |
328 result->alloc_arg = alloc_arg; | |
329 result->alloc_with_arg_f = alloc_f; | |
330 result->free_with_arg_f = free_f; | |
331 return result; | |
332 } | |
333 | |
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334 /* |
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335 |
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336 @deftypefn Supplemental htab_t htab_create_typed_alloc (size_t @var{size}, @ |
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337 htab_hash @var{hash_f}, htab_eq @var{eq_f}, htab_del @var{del_f}, @ |
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338 htab_alloc @var{alloc_tab_f}, htab_alloc @var{alloc_f}, @ |
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339 htab_free @var{free_f}) |
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340 |
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341 This function creates a hash table that uses two different allocators |
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342 @var{alloc_tab_f} and @var{alloc_f} to use for allocating the table itself |
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343 and its entries respectively. This is useful when variables of different |
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344 types need to be allocated with different allocators. |
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345 |
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346 The created hash table is slightly larger than @var{size} and it is |
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347 initially empty (all the hash table entries are @code{HTAB_EMPTY_ENTRY}). |
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348 The function returns the created hash table, or @code{NULL} if memory |
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349 allocation fails. |
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350 |
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351 @end deftypefn |
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352 |
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353 */ |
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354 |
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355 htab_t |
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356 htab_create_typed_alloc (size_t size, htab_hash hash_f, htab_eq eq_f, |
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357 htab_del del_f, htab_alloc alloc_tab_f, |
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358 htab_alloc alloc_f, htab_free free_f) |
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359 { |
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360 htab_t result; |
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361 unsigned int size_prime_index; |
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362 |
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363 size_prime_index = higher_prime_index (size); |
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364 size = prime_tab[size_prime_index].prime; |
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365 |
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366 result = (htab_t) (*alloc_tab_f) (1, sizeof (struct htab)); |
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367 if (result == NULL) |
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368 return NULL; |
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369 result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR)); |
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370 if (result->entries == NULL) |
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371 { |
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372 if (free_f != NULL) |
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373 (*free_f) (result); |
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374 return NULL; |
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375 } |
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376 result->size = size; |
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377 result->size_prime_index = size_prime_index; |
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378 result->hash_f = hash_f; |
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379 result->eq_f = eq_f; |
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380 result->del_f = del_f; |
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381 result->alloc_f = alloc_f; |
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382 result->free_f = free_f; |
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383 return result; |
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384 } |
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385 |
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386 |
0 | 387 /* Update the function pointers and allocation parameter in the htab_t. */ |
388 | |
389 void | |
390 htab_set_functions_ex (htab_t htab, htab_hash hash_f, htab_eq eq_f, | |
391 htab_del del_f, PTR alloc_arg, | |
392 htab_alloc_with_arg alloc_f, htab_free_with_arg free_f) | |
393 { | |
394 htab->hash_f = hash_f; | |
395 htab->eq_f = eq_f; | |
396 htab->del_f = del_f; | |
397 htab->alloc_arg = alloc_arg; | |
398 htab->alloc_with_arg_f = alloc_f; | |
399 htab->free_with_arg_f = free_f; | |
400 } | |
401 | |
402 /* These functions exist solely for backward compatibility. */ | |
403 | |
404 #undef htab_create | |
405 htab_t | |
406 htab_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) | |
407 { | |
408 return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free); | |
409 } | |
410 | |
411 htab_t | |
412 htab_try_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f) | |
413 { | |
414 return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free); | |
415 } | |
416 | |
417 /* This function frees all memory allocated for given hash table. | |
418 Naturally the hash table must already exist. */ | |
419 | |
420 void | |
421 htab_delete (htab_t htab) | |
422 { | |
423 size_t size = htab_size (htab); | |
424 PTR *entries = htab->entries; | |
425 int i; | |
426 | |
427 if (htab->del_f) | |
428 for (i = size - 1; i >= 0; i--) | |
429 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) | |
430 (*htab->del_f) (entries[i]); | |
431 | |
432 if (htab->free_f != NULL) | |
433 { | |
434 (*htab->free_f) (entries); | |
435 (*htab->free_f) (htab); | |
436 } | |
437 else if (htab->free_with_arg_f != NULL) | |
438 { | |
439 (*htab->free_with_arg_f) (htab->alloc_arg, entries); | |
440 (*htab->free_with_arg_f) (htab->alloc_arg, htab); | |
441 } | |
442 } | |
443 | |
444 /* This function clears all entries in the given hash table. */ | |
445 | |
446 void | |
447 htab_empty (htab_t htab) | |
448 { | |
449 size_t size = htab_size (htab); | |
450 PTR *entries = htab->entries; | |
451 int i; | |
452 | |
453 if (htab->del_f) | |
454 for (i = size - 1; i >= 0; i--) | |
455 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY) | |
456 (*htab->del_f) (entries[i]); | |
457 | |
458 /* Instead of clearing megabyte, downsize the table. */ | |
459 if (size > 1024*1024 / sizeof (PTR)) | |
460 { | |
461 int nindex = higher_prime_index (1024 / sizeof (PTR)); | |
462 int nsize = prime_tab[nindex].prime; | |
463 | |
464 if (htab->free_f != NULL) | |
465 (*htab->free_f) (htab->entries); | |
466 else if (htab->free_with_arg_f != NULL) | |
467 (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries); | |
468 if (htab->alloc_with_arg_f != NULL) | |
469 htab->entries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, | |
470 sizeof (PTR *)); | |
471 else | |
472 htab->entries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); | |
473 htab->size = nsize; | |
474 htab->size_prime_index = nindex; | |
475 } | |
476 else | |
477 memset (entries, 0, size * sizeof (PTR)); | |
478 htab->n_deleted = 0; | |
479 htab->n_elements = 0; | |
480 } | |
481 | |
482 /* Similar to htab_find_slot, but without several unwanted side effects: | |
483 - Does not call htab->eq_f when it finds an existing entry. | |
484 - Does not change the count of elements/searches/collisions in the | |
485 hash table. | |
486 This function also assumes there are no deleted entries in the table. | |
487 HASH is the hash value for the element to be inserted. */ | |
488 | |
489 static PTR * | |
490 find_empty_slot_for_expand (htab_t htab, hashval_t hash) | |
491 { | |
492 hashval_t index = htab_mod (hash, htab); | |
493 size_t size = htab_size (htab); | |
494 PTR *slot = htab->entries + index; | |
495 hashval_t hash2; | |
496 | |
497 if (*slot == HTAB_EMPTY_ENTRY) | |
498 return slot; | |
499 else if (*slot == HTAB_DELETED_ENTRY) | |
500 abort (); | |
501 | |
502 hash2 = htab_mod_m2 (hash, htab); | |
503 for (;;) | |
504 { | |
505 index += hash2; | |
506 if (index >= size) | |
507 index -= size; | |
508 | |
509 slot = htab->entries + index; | |
510 if (*slot == HTAB_EMPTY_ENTRY) | |
511 return slot; | |
512 else if (*slot == HTAB_DELETED_ENTRY) | |
513 abort (); | |
514 } | |
515 } | |
516 | |
517 /* The following function changes size of memory allocated for the | |
518 entries and repeatedly inserts the table elements. The occupancy | |
519 of the table after the call will be about 50%. Naturally the hash | |
520 table must already exist. Remember also that the place of the | |
521 table entries is changed. If memory allocation failures are allowed, | |
522 this function will return zero, indicating that the table could not be | |
523 expanded. If all goes well, it will return a non-zero value. */ | |
524 | |
525 static int | |
526 htab_expand (htab_t htab) | |
527 { | |
528 PTR *oentries; | |
529 PTR *olimit; | |
530 PTR *p; | |
531 PTR *nentries; | |
532 size_t nsize, osize, elts; | |
533 unsigned int oindex, nindex; | |
534 | |
535 oentries = htab->entries; | |
536 oindex = htab->size_prime_index; | |
537 osize = htab->size; | |
538 olimit = oentries + osize; | |
539 elts = htab_elements (htab); | |
540 | |
541 /* Resize only when table after removal of unused elements is either | |
542 too full or too empty. */ | |
543 if (elts * 2 > osize || (elts * 8 < osize && osize > 32)) | |
544 { | |
545 nindex = higher_prime_index (elts * 2); | |
546 nsize = prime_tab[nindex].prime; | |
547 } | |
548 else | |
549 { | |
550 nindex = oindex; | |
551 nsize = osize; | |
552 } | |
553 | |
554 if (htab->alloc_with_arg_f != NULL) | |
555 nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize, | |
556 sizeof (PTR *)); | |
557 else | |
558 nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *)); | |
559 if (nentries == NULL) | |
560 return 0; | |
561 htab->entries = nentries; | |
562 htab->size = nsize; | |
563 htab->size_prime_index = nindex; | |
564 htab->n_elements -= htab->n_deleted; | |
565 htab->n_deleted = 0; | |
566 | |
567 p = oentries; | |
568 do | |
569 { | |
570 PTR x = *p; | |
571 | |
572 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) | |
573 { | |
574 PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); | |
575 | |
576 *q = x; | |
577 } | |
578 | |
579 p++; | |
580 } | |
581 while (p < olimit); | |
582 | |
583 if (htab->free_f != NULL) | |
584 (*htab->free_f) (oentries); | |
585 else if (htab->free_with_arg_f != NULL) | |
586 (*htab->free_with_arg_f) (htab->alloc_arg, oentries); | |
587 return 1; | |
588 } | |
589 | |
590 /* This function searches for a hash table entry equal to the given | |
591 element. It cannot be used to insert or delete an element. */ | |
592 | |
593 PTR | |
594 htab_find_with_hash (htab_t htab, const PTR element, hashval_t hash) | |
595 { | |
596 hashval_t index, hash2; | |
597 size_t size; | |
598 PTR entry; | |
599 | |
600 htab->searches++; | |
601 size = htab_size (htab); | |
602 index = htab_mod (hash, htab); | |
603 | |
604 entry = htab->entries[index]; | |
605 if (entry == HTAB_EMPTY_ENTRY | |
606 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
607 return entry; | |
608 | |
609 hash2 = htab_mod_m2 (hash, htab); | |
610 for (;;) | |
611 { | |
612 htab->collisions++; | |
613 index += hash2; | |
614 if (index >= size) | |
615 index -= size; | |
616 | |
617 entry = htab->entries[index]; | |
618 if (entry == HTAB_EMPTY_ENTRY | |
619 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element))) | |
620 return entry; | |
621 } | |
622 } | |
623 | |
624 /* Like htab_find_slot_with_hash, but compute the hash value from the | |
625 element. */ | |
626 | |
627 PTR | |
628 htab_find (htab_t htab, const PTR element) | |
629 { | |
630 return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); | |
631 } | |
632 | |
633 /* This function searches for a hash table slot containing an entry | |
634 equal to the given element. To delete an entry, call this with | |
635 insert=NO_INSERT, then call htab_clear_slot on the slot returned | |
636 (possibly after doing some checks). To insert an entry, call this | |
637 with insert=INSERT, then write the value you want into the returned | |
638 slot. When inserting an entry, NULL may be returned if memory | |
639 allocation fails. */ | |
640 | |
641 PTR * | |
642 htab_find_slot_with_hash (htab_t htab, const PTR element, | |
643 hashval_t hash, enum insert_option insert) | |
644 { | |
645 PTR *first_deleted_slot; | |
646 hashval_t index, hash2; | |
647 size_t size; | |
648 PTR entry; | |
649 | |
650 size = htab_size (htab); | |
651 if (insert == INSERT && size * 3 <= htab->n_elements * 4) | |
652 { | |
653 if (htab_expand (htab) == 0) | |
654 return NULL; | |
655 size = htab_size (htab); | |
656 } | |
657 | |
658 index = htab_mod (hash, htab); | |
659 | |
660 htab->searches++; | |
661 first_deleted_slot = NULL; | |
662 | |
663 entry = htab->entries[index]; | |
664 if (entry == HTAB_EMPTY_ENTRY) | |
665 goto empty_entry; | |
666 else if (entry == HTAB_DELETED_ENTRY) | |
667 first_deleted_slot = &htab->entries[index]; | |
668 else if ((*htab->eq_f) (entry, element)) | |
669 return &htab->entries[index]; | |
670 | |
671 hash2 = htab_mod_m2 (hash, htab); | |
672 for (;;) | |
673 { | |
674 htab->collisions++; | |
675 index += hash2; | |
676 if (index >= size) | |
677 index -= size; | |
678 | |
679 entry = htab->entries[index]; | |
680 if (entry == HTAB_EMPTY_ENTRY) | |
681 goto empty_entry; | |
682 else if (entry == HTAB_DELETED_ENTRY) | |
683 { | |
684 if (!first_deleted_slot) | |
685 first_deleted_slot = &htab->entries[index]; | |
686 } | |
687 else if ((*htab->eq_f) (entry, element)) | |
688 return &htab->entries[index]; | |
689 } | |
690 | |
691 empty_entry: | |
692 if (insert == NO_INSERT) | |
693 return NULL; | |
694 | |
695 if (first_deleted_slot) | |
696 { | |
697 htab->n_deleted--; | |
698 *first_deleted_slot = HTAB_EMPTY_ENTRY; | |
699 return first_deleted_slot; | |
700 } | |
701 | |
702 htab->n_elements++; | |
703 return &htab->entries[index]; | |
704 } | |
705 | |
706 /* Like htab_find_slot_with_hash, but compute the hash value from the | |
707 element. */ | |
708 | |
709 PTR * | |
710 htab_find_slot (htab_t htab, const PTR element, enum insert_option insert) | |
711 { | |
712 return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), | |
713 insert); | |
714 } | |
715 | |
716 /* This function deletes an element with the given value from hash | |
717 table (the hash is computed from the element). If there is no matching | |
718 element in the hash table, this function does nothing. */ | |
719 | |
720 void | |
721 htab_remove_elt (htab_t htab, PTR element) | |
722 { | |
723 htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element)); | |
724 } | |
725 | |
726 | |
727 /* This function deletes an element with the given value from hash | |
728 table. If there is no matching element in the hash table, this | |
729 function does nothing. */ | |
730 | |
731 void | |
732 htab_remove_elt_with_hash (htab_t htab, PTR element, hashval_t hash) | |
733 { | |
734 PTR *slot; | |
735 | |
736 slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT); | |
737 if (*slot == HTAB_EMPTY_ENTRY) | |
738 return; | |
739 | |
740 if (htab->del_f) | |
741 (*htab->del_f) (*slot); | |
742 | |
743 *slot = HTAB_DELETED_ENTRY; | |
744 htab->n_deleted++; | |
745 } | |
746 | |
747 /* This function clears a specified slot in a hash table. It is | |
748 useful when you've already done the lookup and don't want to do it | |
749 again. */ | |
750 | |
751 void | |
752 htab_clear_slot (htab_t htab, PTR *slot) | |
753 { | |
754 if (slot < htab->entries || slot >= htab->entries + htab_size (htab) | |
755 || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY) | |
756 abort (); | |
757 | |
758 if (htab->del_f) | |
759 (*htab->del_f) (*slot); | |
760 | |
761 *slot = HTAB_DELETED_ENTRY; | |
762 htab->n_deleted++; | |
763 } | |
764 | |
765 /* This function scans over the entire hash table calling | |
766 CALLBACK for each live entry. If CALLBACK returns false, | |
767 the iteration stops. INFO is passed as CALLBACK's second | |
768 argument. */ | |
769 | |
770 void | |
771 htab_traverse_noresize (htab_t htab, htab_trav callback, PTR info) | |
772 { | |
773 PTR *slot; | |
774 PTR *limit; | |
775 | |
776 slot = htab->entries; | |
777 limit = slot + htab_size (htab); | |
778 | |
779 do | |
780 { | |
781 PTR x = *slot; | |
782 | |
783 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY) | |
784 if (!(*callback) (slot, info)) | |
785 break; | |
786 } | |
787 while (++slot < limit); | |
788 } | |
789 | |
790 /* Like htab_traverse_noresize, but does resize the table when it is | |
791 too empty to improve effectivity of subsequent calls. */ | |
792 | |
793 void | |
794 htab_traverse (htab_t htab, htab_trav callback, PTR info) | |
795 { | |
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796 size_t size = htab_size (htab); |
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797 if (htab_elements (htab) * 8 < size && size > 32) |
0 | 798 htab_expand (htab); |
799 | |
800 htab_traverse_noresize (htab, callback, info); | |
801 } | |
802 | |
803 /* Return the fraction of fixed collisions during all work with given | |
804 hash table. */ | |
805 | |
806 double | |
807 htab_collisions (htab_t htab) | |
808 { | |
809 if (htab->searches == 0) | |
810 return 0.0; | |
811 | |
812 return (double) htab->collisions / (double) htab->searches; | |
813 } | |
814 | |
815 /* Hash P as a null-terminated string. | |
816 | |
817 Copied from gcc/hashtable.c. Zack had the following to say with respect | |
818 to applicability, though note that unlike hashtable.c, this hash table | |
819 implementation re-hashes rather than chain buckets. | |
820 | |
821 http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html | |
822 From: Zack Weinberg <zackw@panix.com> | |
823 Date: Fri, 17 Aug 2001 02:15:56 -0400 | |
824 | |
825 I got it by extracting all the identifiers from all the source code | |
826 I had lying around in mid-1999, and testing many recurrences of | |
827 the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either | |
828 prime numbers or the appropriate identity. This was the best one. | |
829 I don't remember exactly what constituted "best", except I was | |
830 looking at bucket-length distributions mostly. | |
831 | |
832 So it should be very good at hashing identifiers, but might not be | |
833 as good at arbitrary strings. | |
834 | |
835 I'll add that it thoroughly trounces the hash functions recommended | |
836 for this use at http://burtleburtle.net/bob/hash/index.html, both | |
837 on speed and bucket distribution. I haven't tried it against the | |
838 function they just started using for Perl's hashes. */ | |
839 | |
840 hashval_t | |
841 htab_hash_string (const PTR p) | |
842 { | |
843 const unsigned char *str = (const unsigned char *) p; | |
844 hashval_t r = 0; | |
845 unsigned char c; | |
846 | |
847 while ((c = *str++) != 0) | |
848 r = r * 67 + c - 113; | |
849 | |
850 return r; | |
851 } | |
852 | |
853 /* DERIVED FROM: | |
854 -------------------------------------------------------------------- | |
855 lookup2.c, by Bob Jenkins, December 1996, Public Domain. | |
856 hash(), hash2(), hash3, and mix() are externally useful functions. | |
857 Routines to test the hash are included if SELF_TEST is defined. | |
858 You can use this free for any purpose. It has no warranty. | |
859 -------------------------------------------------------------------- | |
860 */ | |
861 | |
862 /* | |
863 -------------------------------------------------------------------- | |
864 mix -- mix 3 32-bit values reversibly. | |
865 For every delta with one or two bit set, and the deltas of all three | |
866 high bits or all three low bits, whether the original value of a,b,c | |
867 is almost all zero or is uniformly distributed, | |
868 * If mix() is run forward or backward, at least 32 bits in a,b,c | |
869 have at least 1/4 probability of changing. | |
870 * If mix() is run forward, every bit of c will change between 1/3 and | |
871 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.) | |
872 mix() was built out of 36 single-cycle latency instructions in a | |
873 structure that could supported 2x parallelism, like so: | |
874 a -= b; | |
875 a -= c; x = (c>>13); | |
876 b -= c; a ^= x; | |
877 b -= a; x = (a<<8); | |
878 c -= a; b ^= x; | |
879 c -= b; x = (b>>13); | |
880 ... | |
881 Unfortunately, superscalar Pentiums and Sparcs can't take advantage | |
882 of that parallelism. They've also turned some of those single-cycle | |
883 latency instructions into multi-cycle latency instructions. Still, | |
884 this is the fastest good hash I could find. There were about 2^^68 | |
885 to choose from. I only looked at a billion or so. | |
886 -------------------------------------------------------------------- | |
887 */ | |
888 /* same, but slower, works on systems that might have 8 byte hashval_t's */ | |
889 #define mix(a,b,c) \ | |
890 { \ | |
891 a -= b; a -= c; a ^= (c>>13); \ | |
892 b -= c; b -= a; b ^= (a<< 8); \ | |
893 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \ | |
894 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \ | |
895 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \ | |
896 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \ | |
897 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \ | |
898 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \ | |
899 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \ | |
900 } | |
901 | |
902 /* | |
903 -------------------------------------------------------------------- | |
904 hash() -- hash a variable-length key into a 32-bit value | |
905 k : the key (the unaligned variable-length array of bytes) | |
906 len : the length of the key, counting by bytes | |
907 level : can be any 4-byte value | |
908 Returns a 32-bit value. Every bit of the key affects every bit of | |
909 the return value. Every 1-bit and 2-bit delta achieves avalanche. | |
910 About 36+6len instructions. | |
911 | |
912 The best hash table sizes are powers of 2. There is no need to do | |
913 mod a prime (mod is sooo slow!). If you need less than 32 bits, | |
914 use a bitmask. For example, if you need only 10 bits, do | |
915 h = (h & hashmask(10)); | |
916 In which case, the hash table should have hashsize(10) elements. | |
917 | |
918 If you are hashing n strings (ub1 **)k, do it like this: | |
919 for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h); | |
920 | |
921 By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this | |
922 code any way you wish, private, educational, or commercial. It's free. | |
923 | |
924 See http://burtleburtle.net/bob/hash/evahash.html | |
925 Use for hash table lookup, or anything where one collision in 2^32 is | |
926 acceptable. Do NOT use for cryptographic purposes. | |
927 -------------------------------------------------------------------- | |
928 */ | |
929 | |
930 hashval_t | |
931 iterative_hash (const PTR k_in /* the key */, | |
932 register size_t length /* the length of the key */, | |
933 register hashval_t initval /* the previous hash, or | |
934 an arbitrary value */) | |
935 { | |
936 register const unsigned char *k = (const unsigned char *)k_in; | |
937 register hashval_t a,b,c,len; | |
938 | |
939 /* Set up the internal state */ | |
940 len = length; | |
941 a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */ | |
942 c = initval; /* the previous hash value */ | |
943 | |
944 /*---------------------------------------- handle most of the key */ | |
945 #ifndef WORDS_BIGENDIAN | |
946 /* On a little-endian machine, if the data is 4-byte aligned we can hash | |
947 by word for better speed. This gives nondeterministic results on | |
948 big-endian machines. */ | |
949 if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0) | |
950 while (len >= 12) /* aligned */ | |
951 { | |
952 a += *(hashval_t *)(k+0); | |
953 b += *(hashval_t *)(k+4); | |
954 c += *(hashval_t *)(k+8); | |
955 mix(a,b,c); | |
956 k += 12; len -= 12; | |
957 } | |
958 else /* unaligned */ | |
959 #endif | |
960 while (len >= 12) | |
961 { | |
962 a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24)); | |
963 b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24)); | |
964 c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24)); | |
965 mix(a,b,c); | |
966 k += 12; len -= 12; | |
967 } | |
968 | |
969 /*------------------------------------- handle the last 11 bytes */ | |
970 c += length; | |
971 switch(len) /* all the case statements fall through */ | |
972 { | |
973 case 11: c+=((hashval_t)k[10]<<24); | |
974 case 10: c+=((hashval_t)k[9]<<16); | |
975 case 9 : c+=((hashval_t)k[8]<<8); | |
976 /* the first byte of c is reserved for the length */ | |
977 case 8 : b+=((hashval_t)k[7]<<24); | |
978 case 7 : b+=((hashval_t)k[6]<<16); | |
979 case 6 : b+=((hashval_t)k[5]<<8); | |
980 case 5 : b+=k[4]; | |
981 case 4 : a+=((hashval_t)k[3]<<24); | |
982 case 3 : a+=((hashval_t)k[2]<<16); | |
983 case 2 : a+=((hashval_t)k[1]<<8); | |
984 case 1 : a+=k[0]; | |
985 /* case 0: nothing left to add */ | |
986 } | |
987 mix(a,b,c); | |
988 /*-------------------------------------------- report the result */ | |
989 return c; | |
990 } |