include/hashtab.h

   1 /* An expandable hash tables datatype.
   2    Copyright (C) 1999, 2000, 2002, 2003, 2004, 2005, 2009, 2010
   3    Free Software Foundation, Inc.
   4    Contributed by Vladimir Makarov (vmakarov@cygnus.com).
   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 2 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, write to the Free Software
  18 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 /* This package implements basic hash table functionality.  It is possible
  21    to search for an entry, create an entry and destroy an entry.
  22
  23    Elements in the table are generic pointers.
  24
  25    The size of the table is not fixed; if the occupancy of the table
  26    grows too high the hash table will be expanded.
  27
  28    The abstract data implementation is based on generalized Algorithm D
  29    from Knuth's book "The art of computer programming".  Hash table is
  30    expanded by creation of new hash table and transferring elements from
  31    the old table to the new table.  */
  32
  33 #ifndef __HASHTAB_H__
  34 #define __HASHTAB_H__
  35
  36 #ifdef __cplusplus
  37 extern "C" {
  38 #endif /* __cplusplus */
  39
  40 #include "ansidecl.h"
  41
  42 /* The type for a hash code.  */
  43 typedef unsigned int hashval_t;
  44
  45 /* Callback function pointer types.  */
  46
  47 /* Calculate hash of a table entry.  */
  48 typedef hashval_t (*htab_hash) (const void *);
  49
  50 /* Compare a table entry with a possible entry.  The entry already in
  51    the table always comes first, so the second element can be of a
  52    different type (but in this case htab_find and htab_find_slot
  53    cannot be used; instead the variants that accept a hash value
  54    must be used).  */
  55 typedef int (*htab_eq) (const void *, const void *);
  56
  57 /* Cleanup function called whenever a live element is removed from
  58    the hash table.  */
  59 typedef void (*htab_del) (void *);
  60
  61 /* Function called by htab_traverse for each live element.  The first
  62    arg is the slot of the element (which can be passed to htab_clear_slot
  63    if desired), the second arg is the auxiliary pointer handed to
  64    htab_traverse.  Return 1 to continue scan, 0 to stop.  */
  65 typedef int (*htab_trav) (void **, void *);
  66
  67 /* Memory-allocation function, with the same functionality as calloc().
  68    Iff it returns NULL, the hash table implementation will pass an error
  69    code back to the user, so if your code doesn't handle errors,
  70    best if you use xcalloc instead.  */
  71 typedef void *(*htab_alloc) (size_t, size_t);
  72
  73 /* We also need a free() routine.  */
  74 typedef void (*htab_free) (void *);
  75
  76 /* Memory allocation and deallocation; variants which take an extra
  77    argument.  */
  78 typedef void *(*htab_alloc_with_arg) (void *, size_t, size_t);
  79 typedef void (*htab_free_with_arg) (void *, void *);
  80
  81 /* This macro defines reserved value for empty table entry.  */
  82
  83 #define HTAB_EMPTY_ENTRY    ((PTR) 0)
  84
  85 /* This macro defines reserved value for table entry which contained
  86    a deleted element. */
  87
  88 #define HTAB_DELETED_ENTRY  ((PTR) 1)
  89
  90 /* Hash tables are of the following type.  The structure
  91    (implementation) of this type is not needed for using the hash
  92    tables.  All work with hash table should be executed only through
  93    functions mentioned below.  The size of this structure is subject to
  94    change.  */
  95
  96 struct htab {
  97   /* Pointer to hash function.  */
  98   htab_hash hash_f;
  99
 100   /* Pointer to comparison function.  */
 101   htab_eq eq_f;
 102
 103   /* Pointer to cleanup function.  */
 104   htab_del del_f;
 105
 106   /* Table itself.  */
 107   void **entries;
 108
 109   /* Current size (in entries) of the hash table.  */
 110   size_t size;
 111
 112   /* Current number of elements including also deleted elements.  */
 113   size_t n_elements;
 114
 115   /* Current number of deleted elements in the table.  */
 116   size_t n_deleted;
 117
 118   /* The following member is used for debugging. Its value is number
 119      of all calls of `htab_find_slot' for the hash table. */
 120   unsigned int searches;
 121
 122   /* The following member is used for debugging.  Its value is number
 123      of collisions fixed for time of work with the hash table. */
 124   unsigned int collisions;
 125
 126   /* Pointers to allocate/free functions.  */
 127   htab_alloc alloc_f;
 128   htab_free free_f;
 129
 130   /* Alternate allocate/free functions, which take an extra argument.  */
 131   void *alloc_arg;
 132   htab_alloc_with_arg alloc_with_arg_f;
 133   htab_free_with_arg free_with_arg_f;
 134
 135   /* Current size (in entries) of the hash table, as an index into the
 136      table of primes.  */
 137   unsigned int size_prime_index;
 138 };
 139
 140 typedef struct htab *htab_t;
 141
 142 /* An enum saying whether we insert into the hash table or not.  */
 143 enum insert_option {NO_INSERT, INSERT};
 144
 145 /* The prototypes of the package functions. */
 146
 147 extern htab_t   htab_create_alloc  (size_t, htab_hash,
 148                                     htab_eq, htab_del,
 149                                     htab_alloc, htab_free);
 150
 151 extern htab_t   htab_create_alloc_ex (size_t, htab_hash,
 152                                       htab_eq, htab_del,
 153                                       void *, htab_alloc_with_arg,
 154                                       htab_free_with_arg);
 155
 156 extern htab_t  htab_create_typed_alloc (size_t, htab_hash, htab_eq, htab_del,
 157                                         htab_alloc, htab_alloc, htab_free);
 158
 159 /* Backward-compatibility functions.  */
 160 extern htab_t htab_create (size_t, htab_hash, htab_eq, htab_del);
 161 extern htab_t htab_try_create (size_t, htab_hash, htab_eq, htab_del);
 162
 163 extern void     htab_set_functions_ex (htab_t, htab_hash,
 164                                        htab_eq, htab_del,
 165                                        void *, htab_alloc_with_arg,
 166                                        htab_free_with_arg);
 167
 168 extern void     htab_delete (htab_t);
 169 extern void     htab_empty (htab_t);
 170
 171 extern void *   htab_find (htab_t, const void *);
 172 extern void **  htab_find_slot (htab_t, const void *, enum insert_option);
 173 extern void *   htab_find_with_hash (htab_t, const void *, hashval_t);
 174 extern void **  htab_find_slot_with_hash (htab_t, const void *,
 175                                           hashval_t, enum insert_option);
 176 extern void     htab_clear_slot (htab_t, void **);
 177 extern void     htab_remove_elt (htab_t, void *);
 178 extern void     htab_remove_elt_with_hash (htab_t, void *, hashval_t);
 179
 180 extern void     htab_traverse (htab_t, htab_trav, void *);
 181 extern void     htab_traverse_noresize (htab_t, htab_trav, void *);
 182
 183 extern size_t   htab_size (htab_t);
 184 extern size_t   htab_elements (htab_t);
 185 extern double   htab_collisions (htab_t);
 186
 187 /* A hash function for pointers.  */
 188 extern htab_hash htab_hash_pointer;
 189
 190 /* An equality function for pointers.  */
 191 extern htab_eq htab_eq_pointer;
 192
 193 /* A hash function for null-terminated strings.  */
 194 extern hashval_t htab_hash_string (const void *);
 195
 196 /* An iterative hash function for arbitrary data.  */
 197 extern hashval_t iterative_hash (const void *, size_t, hashval_t);
 198 /* Shorthand for hashing something with an intrinsic size.  */
 199 #define iterative_hash_object(OB,INIT) iterative_hash (&OB, sizeof (OB), INIT)
 200
 201 #ifdef __cplusplus
 202 }
 203 #endif /* __cplusplus */
 204
 205 #endif /* __HASHTAB_H */