1 /* hash - hashing table processing. 2 Copyright (C) 1998-1999, 2001, 2003, 2009-2021 Free Software Foundation, 3 Inc. 4 Written by Jim Meyering <meyering@ascend.com>, 1998. 5 6 This program is free software: you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 3 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 18 19 /* A generic hash table package. */ 20 21 /* Make sure USE_OBSTACK is defined to 1 if you want the allocator to use 22 obstacks instead of malloc, and recompile 'hash.c' with same setting. */ 23 24 #ifndef HASH_H_ 25 # define HASH_H_ 26 27 # include <stdio.h> 28 # include <stdbool.h> 29 30 # ifdef __cplusplus 31 extern "C" { 32 # endif 33 34 struct hash_tuning 35 { 36 /* This structure is mainly used for 'hash_initialize', see the block 37 documentation of 'hash_reset_tuning' for more complete comments. */ 38 39 float shrink_threshold; /* ratio of used buckets to trigger a shrink */ 40 float shrink_factor; /* ratio of new smaller size to original size */ 41 float growth_threshold; /* ratio of used buckets to trigger a growth */ 42 float growth_factor; /* ratio of new bigger size to original size */ 43 bool is_n_buckets; /* if CANDIDATE really means table size */ 44 }; 45 46 typedef struct hash_tuning Hash_tuning; 47 48 struct hash_table; 49 50 typedef struct hash_table Hash_table; 51 52 /* 53 * Information and lookup. 54 */ 55 56 /* The following few functions provide information about the overall hash 57 table organization: the number of entries, number of buckets and maximum 58 length of buckets. */ 59 60 /* Return the number of buckets in the hash table. The table size, the total 61 number of buckets (used plus unused), or the maximum number of slots, are 62 the same quantity. */ 63 extern size_t hash_get_n_buckets (const Hash_table *table) 64 _GL_ATTRIBUTE_PURE; 65 66 /* Return the number of slots in use (non-empty buckets). */ 67 extern size_t hash_get_n_buckets_used (const Hash_table *table) 68 _GL_ATTRIBUTE_PURE; 69 70 /* Return the number of active entries. */ 71 extern size_t hash_get_n_entries (const Hash_table *table) 72 _GL_ATTRIBUTE_PURE; 73 74 /* Return the length of the longest chain (bucket). */ 75 extern size_t hash_get_max_bucket_length (const Hash_table *table) 76 _GL_ATTRIBUTE_PURE; 77 78 /* Do a mild validation of a hash table, by traversing it and checking two 79 statistics. */ 80 extern bool hash_table_ok (const Hash_table *table) 81 _GL_ATTRIBUTE_PURE; 82 83 extern void hash_print_statistics (const Hash_table *table, FILE *stream); 84 85 /* If ENTRY matches an entry already in the hash table, return the 86 entry from the table. Otherwise, return NULL. */ 87 extern void *hash_lookup (const Hash_table *table, const void *entry); 88 89 /* 90 * Walking. 91 */ 92 93 /* The functions in this page traverse the hash table and process the 94 contained entries. For the traversal to work properly, the hash table 95 should not be resized nor modified while any particular entry is being 96 processed. In particular, entries should not be added, and an entry 97 may be removed only if there is no shrink threshold and the entry being 98 removed has already been passed to hash_get_next. */ 99 100 /* Return the first data in the table, or NULL if the table is empty. */ 101 extern void *hash_get_first (const Hash_table *table) 102 _GL_ATTRIBUTE_PURE; 103 104 /* Return the user data for the entry following ENTRY, where ENTRY has been 105 returned by a previous call to either 'hash_get_first' or 'hash_get_next'. 106 Return NULL if there are no more entries. */ 107 extern void *hash_get_next (const Hash_table *table, const void *entry); 108 109 /* Fill BUFFER with pointers to active user entries in the hash table, then 110 return the number of pointers copied. Do not copy more than BUFFER_SIZE 111 pointers. */ 112 extern size_t hash_get_entries (const Hash_table *table, void **buffer, 113 size_t buffer_size); 114 115 typedef bool (*Hash_processor) (void *entry, void *processor_data); 116 117 /* Call a PROCESSOR function for each entry of a hash table, and return the 118 number of entries for which the processor function returned success. A 119 pointer to some PROCESSOR_DATA which will be made available to each call to 120 the processor function. The PROCESSOR accepts two arguments: the first is 121 the user entry being walked into, the second is the value of PROCESSOR_DATA 122 as received. The walking continue for as long as the PROCESSOR function 123 returns nonzero. When it returns zero, the walking is interrupted. */ 124 extern size_t hash_do_for_each (const Hash_table *table, 125 Hash_processor processor, void *processor_data); 126 127 /* 128 * Allocation and clean-up. 129 */ 130 131 /* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1. 132 This is a convenience routine for constructing other hashing functions. */ 133 extern size_t hash_string (const char *string, size_t n_buckets) 134 _GL_ATTRIBUTE_PURE; 135 136 extern void hash_reset_tuning (Hash_tuning *tuning); 137 138 typedef size_t (*Hash_hasher) (const void *entry, size_t table_size); 139 typedef bool (*Hash_comparator) (const void *entry1, const void *entry2); 140 typedef void (*Hash_data_freer) (void *entry); 141 142 /* Allocate and return a new hash table, or NULL upon failure. The initial 143 number of buckets is automatically selected so as to _guarantee_ that you 144 may insert at least CANDIDATE different user entries before any growth of 145 the hash table size occurs. So, if have a reasonably tight a-priori upper 146 bound on the number of entries you intend to insert in the hash table, you 147 may save some table memory and insertion time, by specifying it here. If 148 the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE 149 argument has its meaning changed to the wanted number of buckets. 150 151 TUNING points to a structure of user-supplied values, in case some fine 152 tuning is wanted over the default behavior of the hasher. If TUNING is 153 NULL, the default tuning parameters are used instead. If TUNING is 154 provided but the values requested are out of bounds or might cause 155 rounding errors, return NULL. 156 157 The user-supplied HASHER function, when not NULL, accepts two 158 arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a 159 slot number for that entry which should be in the range 0..TABLE_SIZE-1. 160 This slot number is then returned. 161 162 The user-supplied COMPARATOR function, when not NULL, accepts two 163 arguments pointing to user data, it then returns true for a pair of entries 164 that compare equal, or false otherwise. This function is internally called 165 on entries which are already known to hash to the same bucket index, 166 but which are distinct pointers. 167 168 The user-supplied DATA_FREER function, when not NULL, may be later called 169 with the user data as an argument, just before the entry containing the 170 data gets freed. This happens from within 'hash_free' or 'hash_clear'. 171 You should specify this function only if you want these functions to free 172 all of your 'data' data. This is typically the case when your data is 173 simply an auxiliary struct that you have malloc'd to aggregate several 174 values. */ 175 extern Hash_table *hash_initialize (size_t candidate, 176 const Hash_tuning *tuning, 177 Hash_hasher hasher, 178 Hash_comparator comparator, 179 Hash_data_freer data_freer) 180 _GL_ATTRIBUTE_NODISCARD; 181 182 /* Same as hash_initialize, but invokes xalloc_die on memory exhaustion. */ 183 /* This function is defined by module 'xhash'. */ 184 extern Hash_table *hash_xinitialize (size_t candidate, 185 const Hash_tuning *tuning, 186 Hash_hasher hasher, 187 Hash_comparator comparator, 188 Hash_data_freer data_freer) 189 _GL_ATTRIBUTE_NODISCARD; 190 191 /* Make all buckets empty, placing any chained entries on the free list. 192 Apply the user-specified function data_freer (if any) to the datas of any 193 affected entries. */ 194 extern void hash_clear (Hash_table *table); 195 196 /* Reclaim all storage associated with a hash table. If a data_freer 197 function has been supplied by the user when the hash table was created, 198 this function applies it to the data of each entry before freeing that 199 entry. */ 200 extern void hash_free (Hash_table *table); 201 202 /* 203 * Insertion and deletion. 204 */ 205 206 /* For an already existing hash table, change the number of buckets through 207 specifying CANDIDATE. The contents of the hash table are preserved. The 208 new number of buckets is automatically selected so as to _guarantee_ that 209 the table may receive at least CANDIDATE different user entries, including 210 those already in the table, before any other growth of the hash table size 211 occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the 212 exact number of buckets desired. Return true iff the rehash succeeded. */ 213 extern bool hash_rehash (Hash_table *table, size_t candidate) 214 _GL_ATTRIBUTE_NODISCARD; 215 216 /* If ENTRY matches an entry already in the hash table, return the pointer 217 to the entry from the table. Otherwise, insert ENTRY and return ENTRY. 218 Return NULL if the storage required for insertion cannot be allocated. 219 This implementation does not support duplicate entries or insertion of 220 NULL. */ 221 extern void *hash_insert (Hash_table *table, const void *entry) 222 _GL_ATTRIBUTE_NODISCARD; 223 224 /* Same as hash_insert, but invokes xalloc_die on memory exhaustion. */ 225 /* This function is defined by module 'xhash'. */ 226 extern void *hash_xinsert (Hash_table *table, const void *entry); 227 228 /* Insert ENTRY into hash TABLE if there is not already a matching entry. 229 230 Return -1 upon memory allocation failure. 231 Return 1 if insertion succeeded. 232 Return 0 if there is already a matching entry in the table, 233 and in that case, if MATCHED_ENT is non-NULL, set *MATCHED_ENT 234 to that entry. 235 236 This interface is easier to use than hash_insert when you must 237 distinguish between the latter two cases. More importantly, 238 hash_insert is unusable for some types of ENTRY values. When using 239 hash_insert, the only way to distinguish those cases is to compare 240 the return value and ENTRY. That works only when you can have two 241 different ENTRY values that point to data that compares "equal". Thus, 242 when the ENTRY value is a simple scalar, you must use 243 hash_insert_if_absent. ENTRY must not be NULL. */ 244 extern int hash_insert_if_absent (Hash_table *table, const void *entry, 245 const void **matched_ent); 246 247 /* If ENTRY is already in the table, remove it and return the just-deleted 248 data (the user may want to deallocate its storage). If ENTRY is not in the 249 table, don't modify the table and return NULL. */ 250 extern void *hash_remove (Hash_table *table, const void *entry); 251 252 /* Same as hash_remove. This interface is deprecated. 253 FIXME: Remove in 2022. */ 254 extern void *hash_delete (Hash_table *table, const void *entry) 255 _GL_ATTRIBUTE_DEPRECATED; 256 257 # ifdef __cplusplus 258 } 259 # endif 260 261 #endif 262