tools/hashtab.h

   1 /* An expandable hash tables datatype.
   2    Copyright (C) 1999, 2000 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 /* The type for a hash code.  */
  40 typedef unsigned int hashval_t;
  41
  42 /* Callback function pointer types.  */
  43
  44 /* Calculate hash of a table entry.  */
  45 typedef hashval_t (*htab_hash) (const void *);
  46
  47 /* Compare a table entry with a possible entry.  The entry already in
  48    the table always comes first, so the second element can be of a
  49    different type (but in this case htab_find and htab_find_slot
  50    cannot be used; instead the variants that accept a hash value
  51    must be used).  */
  52 typedef int (*htab_eq) (const void *, const void *);
  53
  54 /* Cleanup function called whenever a live element is removed from
  55    the hash table.  */
  56 typedef void (*htab_del) (void *);
  57
  58 /* Function called by htab_traverse for each live element.  The first
  59    arg is the slot of the element (which can be passed to htab_clear_slot
  60    if desired), the second arg is the auxiliary pointer handed to
  61    htab_traverse.  Return 1 to continue scan, 0 to stop.  */
  62 typedef int (*htab_trav) (void **, void *);
  63
  64 /* Hash tables are of the following type.  The structure
  65    (implementation) of this type is not needed for using the hash
  66    tables.  All work with hash table should be executed only through
  67    functions mentioned below. */
  68
  69 struct htab
  70 {
  71   /* Pointer to hash function.  */
  72   htab_hash hash_f;
  73
  74   /* Pointer to comparison function.  */
  75   htab_eq eq_f;
  76
  77   /* Pointer to cleanup function.  */
  78   htab_del del_f;
  79
  80   /* Table itself.  */
  81   void **entries;
  82
  83   /* Current size (in entries) of the hash table */
  84   size_t size;
  85
  86   /* Current number of elements including also deleted elements */
  87   size_t n_elements;
  88
  89   /* Current number of deleted elements in the table */
  90   size_t n_deleted;
  91
  92   /* The following member is used for debugging. Its value is number
  93      of all calls of `htab_find_slot' for the hash table. */
  94   unsigned int searches;
  95
  96   /* The following member is used for debugging.  Its value is number
  97      of collisions fixed for time of work with the hash table. */
  98   unsigned int collisions;
  99
 100   /* This is non-zero if we are allowed to return NULL for function calls
 101      that allocate memory.  */
 102   int return_allocation_failure;
 103 };
 104
 105 typedef struct htab *htab_t;
 106
 107 /* An enum saying whether we insert into the hash table or not.  */
 108 enum insert_option {NO_INSERT, INSERT};
 109
 110 /* The prototypes of the package functions. */
 111
 112 /* This function is like htab_create, but may return NULL if memory
 113    allocation fails, and also signals that htab_find_slot_with_hash and
 114    htab_find_slot are allowed to return NULL when inserting.  */
 115 extern htab_t   htab_try_create (size_t, htab_hash, htab_eq, htab_del);
 116 extern void     htab_delete     (htab_t);
 117 extern void     htab_empty      (htab_t);
 118
 119 extern void    *htab_find       (htab_t, const void *);
 120 extern void    **htab_find_slot (htab_t, const void *, enum insert_option);
 121 extern void    *htab_find_with_hash (htab_t, const void *, hashval_t);
 122 extern void    **htab_find_slot_with_hash (htab_t, const void *, hashval_t,
 123                                           enum insert_option);
 124 extern void     htab_clear_slot (htab_t, void **);
 125 extern void     htab_remove_elt (htab_t, void *);
 126
 127 extern void     htab_traverse   (htab_t, htab_trav, void *);
 128
 129 extern size_t   htab_size       (htab_t);
 130 extern size_t   htab_elements   (htab_t);
 131 extern double   htab_collisions (htab_t);
 132
 133 /* A hash function for pointers.  */
 134 extern htab_hash htab_hash_pointer;
 135
 136 /* An equality function for pointers.  */
 137 extern htab_eq htab_eq_pointer;
 138
 139 #ifdef __cplusplus
 140 }
 141 #endif /* __cplusplus */
 142
 143 #endif /* __HASHTAB_H */