include/hashtab.h

   1 /* An expandable hash tables datatype.
   2    Copyright (C) 1999-2020 Free Software Foundation, Inc.
   3    Contributed by Vladimir Makarov (vmakarov@cygnus.com).
   4
   5 This program is free software; you can redistribute it and/or modify
   6 it under the terms of the GNU General Public License as published by
   7 the Free Software Foundation; either version 2 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 /* This package implements basic hash table functionality.  It is possible
  20    to search for an entry, create an entry and destroy an entry.
  21
  22    Elements in the table are generic pointers.
  23
  24    The size of the table is not fixed; if the occupancy of the table
  25    grows too high the hash table will be expanded.
  26
  27    The abstract data implementation is based on generalized Algorithm D
  28    from Knuth's book "The art of computer programming".  Hash table is
  29    expanded by creation of new hash table and transferring elements from
  30    the old table to the new table.  */
  31
  32 #ifndef __HASHTAB_H__
  33 #define __HASHTAB_H__
  34
  35 #ifdef __cplusplus
  36 extern "C" {
  37 #endif /* __cplusplus */
  38
  39 #include "ansidecl.h"
  40
  41 /* The type for a hash code.  */
  42 typedef unsigned int hashval_t;
  43
  44 /* Callback function pointer types.  */
  45
  46 /* Calculate hash of a table entry.  */
  47 typedef hashval_t (*htab_hash) (const void *);
  48
  49 /* Compare a table entry with a possible entry.  The entry already in
  50    the table always comes first, so the second element can be of a
  51    different type (but in this case htab_find and htab_find_slot
  52    cannot be used; instead the variants that accept a hash value
  53    must be used).  */
  54 typedef int (*htab_eq) (const void *, const void *);
  55
  56 /* Cleanup function called whenever a live element is removed from
  57    the hash table.  */
  58 typedef void (*htab_del) (void *);
  59
  60 /* Function called by htab_traverse for each live element.  The first
  61    arg is the slot of the element (which can be passed to htab_clear_slot
  62    if desired), the second arg is the auxiliary pointer handed to
  63    htab_traverse.  Return 1 to continue scan, 0 to stop.  */
  64 typedef int (*htab_trav) (void **, void *);
  65
  66 /* Memory-allocation function, with the same functionality as calloc().
  67    Iff it returns NULL, the hash table implementation will pass an error
  68    code back to the user, so if your code doesn't handle errors,
  69    best if you use xcalloc instead.  */
  70 typedef void *(*htab_alloc) (size_t, size_t);
  71
  72 /* We also need a free() routine.  */
  73 typedef void (*htab_free) (void *);
  74
  75 /* Memory allocation and deallocation; variants which take an extra
  76    argument.  */
  77 typedef void *(*htab_alloc_with_arg) (void *, size_t, size_t);
  78 typedef void (*htab_free_with_arg) (void *, void *);
  79
  80 /* This macro defines reserved value for empty table entry.  */
  81
  82 #define HTAB_EMPTY_ENTRY    ((PTR) 0)
  83
  84 /* This macro defines reserved value for table entry which contained
  85    a deleted element. */
  86
  87 #define HTAB_DELETED_ENTRY  ((PTR) 1)
  88
  89 /* Hash tables are of the following type.  The structure
  90    (implementation) of this type is not needed for using the hash
  91    tables.  All work with hash table should be executed only through
  92    functions mentioned below.  The size of this structure is subject to
  93    change.  */
  94
  95 struct htab {
  96   /* Pointer to hash function.  */
  97   htab_hash hash_f;
  98
  99   /* Pointer to comparison function.  */
 100   htab_eq eq_f;
 101
 102   /* Pointer to cleanup function.  */
 103   htab_del del_f;
 104
 105   /* Table itself.  */
 106   void **entries;
 107
 108   /* Current size (in entries) of the hash table.  */
 109   size_t size;
 110
 111   /* Current number of elements including also deleted elements.  */
 112   size_t n_elements;
 113
 114   /* Current number of deleted elements in the table.  */
 115   size_t n_deleted;
 116
 117   /* The following member is used for debugging. Its value is number
 118      of all calls of `htab_find_slot' for the hash table. */
 119   unsigned int searches;
 120
 121   /* The following member is used for debugging.  Its value is number
 122      of collisions fixed for time of work with the hash table. */
 123   unsigned int collisions;
 124
 125   /* Pointers to allocate/free functions.  */
 126   htab_alloc alloc_f;
 127   htab_free free_f;
 128
 129   /* Alternate allocate/free functions, which take an extra argument.  */
 130   void *alloc_arg;
 131   htab_alloc_with_arg alloc_with_arg_f;
 132   htab_free_with_arg free_with_arg_f;
 133
 134   /* Current size (in entries) of the hash table, as an index into the
 135      table of primes.  */
 136   unsigned int size_prime_index;
 137 };
 138
 139 typedef struct htab *htab_t;
 140
 141 /* An enum saying whether we insert into the hash table or not.  */
 142 enum insert_option {NO_INSERT, INSERT};
 143
 144 /* The prototypes of the package functions. */
 145
 146 extern htab_t   htab_create_alloc  (size_t, htab_hash,
 147                                     htab_eq, htab_del,
 148                                     htab_alloc, htab_free);
 149
 150 extern htab_t   htab_create_alloc_ex (size_t, htab_hash,
 151                                       htab_eq, htab_del,
 152                                       void *, htab_alloc_with_arg,
 153                                       htab_free_with_arg);
 154
 155 extern htab_t  htab_create_typed_alloc (size_t, htab_hash, htab_eq, htab_del,
 156                                         htab_alloc, htab_alloc, htab_free);
 157
 158 /* Backward-compatibility functions.  */
 159 extern htab_t htab_create (size_t, htab_hash, htab_eq, htab_del);
 160 extern htab_t htab_try_create (size_t, htab_hash, htab_eq, htab_del);
 161
 162 extern void     htab_set_functions_ex (htab_t, htab_hash,
 163                                        htab_eq, htab_del,
 164                                        void *, htab_alloc_with_arg,
 165                                        htab_free_with_arg);
 166
 167 extern void     htab_delete (htab_t);
 168 extern void     htab_empty (htab_t);
 169
 170 extern void *   htab_find (htab_t, const void *);
 171 extern void **  htab_find_slot (htab_t, const void *, enum insert_option);
 172 extern void *   htab_find_with_hash (htab_t, const void *, hashval_t);
 173 extern void **  htab_find_slot_with_hash (htab_t, const void *,
 174                                           hashval_t, enum insert_option);
 175 extern void     htab_clear_slot (htab_t, void **);
 176 extern void     htab_remove_elt (htab_t, const void *);
 177 extern void     htab_remove_elt_with_hash (htab_t, const void *, hashval_t);
 178
 179 extern void     htab_traverse (htab_t, htab_trav, void *);
 180 extern void     htab_traverse_noresize (htab_t, htab_trav, void *);
 181
 182 extern size_t   htab_size (htab_t);
 183 extern size_t   htab_elements (htab_t);
 184 extern double   htab_collisions (htab_t);
 185
 186 /* A hash function for pointers.  */
 187 extern htab_hash htab_hash_pointer;
 188
 189 /* An equality function for pointers.  */
 190 extern htab_eq htab_eq_pointer;
 191
 192 /* A hash function for null-terminated strings.  */
 193 extern hashval_t htab_hash_string (const void *);
 194
 195 /* An iterative hash function for arbitrary data.  */
 196 extern hashval_t iterative_hash (const void *, size_t, hashval_t);
 197 /* Shorthand for hashing something with an intrinsic size.  */
 198 #define iterative_hash_object(OB,INIT) iterative_hash (&OB, sizeof (OB), INIT)
 199
 200 #ifdef __cplusplus
 201 }
 202 #endif /* __cplusplus */
 203
 204 #endif /* __HASHTAB_H */