include/hashtab.h

   1 /* An expandable hash tables datatype.
   2    Copyright (C) 1999 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 #include <ansidecl.h>
  40
  41 /* Callback function pointer types.  */
  42
  43 /* Calculate hash of a table entry.  */
  44 typedef unsigned int (*htab_hash) PARAMS ((const void *));
  45
  46 /* Compare a table entry with a possible entry.  The entry already in
  47    the table always comes first, so the second element can be of a
  48    different type (but in this case htab_find and htab_find_slot
  49    cannot be used; instead the variants that accept a hash value
  50    must be used).  */
  51 typedef int (*htab_eq) PARAMS ((const void *, const void *));
  52
  53 /* Cleanup function called whenever a live element is removed from
  54    the hash table.  */
  55 typedef void (*htab_del) PARAMS ((void *));
  56
  57 /* Function called by htab_traverse for each live element.  The first
  58    arg is the slot of the element (which can be passed to htab_clear_slot
  59    if desired), the second arg is the auxiliary pointer handed to
  60    htab_traverse.  Return 1 to continue scan, 0 to stop.  */
  61 typedef int (*htab_trav) PARAMS ((void **, void *));
  62
  63 /* Hash tables are of the following type.  The structure
  64    (implementation) of this type is not needed for using the hash
  65    tables.  All work with hash table should be executed only through
  66    functions mentioned below. */
  67
  68 struct htab
  69 {
  70   /* Pointer to hash function.  */
  71   htab_hash hash_f;
  72
  73   /* Pointer to comparison function.  */
  74   htab_eq eq_f;
  75
  76   /* Pointer to cleanup function.  */
  77   htab_del del_f;
  78
  79   /* Table itself.  */
  80   void **entries;
  81
  82   /* Current size (in entries) of the hash table */
  83   size_t size;
  84
  85   /* Current number of elements including also deleted elements */
  86   size_t n_elements;
  87
  88   /* Current number of deleted elements in the table */
  89   size_t n_deleted;
  90
  91   /* The following member is used for debugging. Its value is number
  92      of all calls of `htab_find_slot' for the hash table. */
  93   unsigned int searches;
  94
  95   /* The following member is used for debugging.  Its value is number
  96      of collisions fixed for time of work with the hash table. */
  97   unsigned int collisions;
  98 };
  99
 100 typedef struct htab *htab_t;
 101
 102 /* The prototypes of the package functions. */
 103
 104 extern htab_t   htab_create     PARAMS ((size_t, htab_hash,
 105                                          htab_eq, htab_del));
 106 extern void     htab_delete     PARAMS ((htab_t));
 107 extern void     htab_empty      PARAMS ((htab_t));
 108
 109 extern void    *htab_find       PARAMS ((htab_t, const void *));
 110 extern void   **htab_find_slot  PARAMS ((htab_t, const void *, int));
 111 extern void    *htab_find_with_hash             PARAMS ((htab_t, const void *,
 112                                                          unsigned int));
 113 extern void   **htab_find_slot_with_hash        PARAMS ((htab_t, const void *,
 114                                                          unsigned int, int));
 115 extern void     htab_clear_slot PARAMS ((htab_t, void **));
 116 extern void     htab_remove_elt PARAMS ((htab_t, void *));
 117
 118 extern void     htab_traverse   PARAMS ((htab_t, htab_trav, void *));
 119
 120 extern size_t   htab_size       PARAMS ((htab_t));
 121 extern size_t   htab_elements   PARAMS ((htab_t));
 122 extern double   htab_collisions PARAMS ((htab_t));
 123
 124 #ifdef __cplusplus
 125 }
 126 #endif /* __cplusplus */
 127
 128 #endif /* __HASHTAB_H */