include/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 #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) PARAMS ((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) PARAMS ((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) PARAMS ((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) PARAMS ((void **, void *));
  65
  66 /* Hash tables are of the following type.  The structure
  67    (implementation) of this type is not needed for using the hash
  68    tables.  All work with hash table should be executed only through
  69    functions mentioned below. */
  70
  71 struct htab
  72 {
  73   /* Pointer to hash function.  */
  74   htab_hash hash_f;
  75
  76   /* Pointer to comparison function.  */
  77   htab_eq eq_f;
  78
  79   /* Pointer to cleanup function.  */
  80   htab_del del_f;
  81
  82   /* Table itself.  */
  83   PTR *entries;
  84
  85   /* Current size (in entries) of the hash table */
  86   size_t size;
  87
  88   /* Current number of elements including also deleted elements */
  89   size_t n_elements;
  90
  91   /* Current number of deleted elements in the table */
  92   size_t n_deleted;
  93
  94   /* The following member is used for debugging. Its value is number
  95      of all calls of `htab_find_slot' for the hash table. */
  96   unsigned int searches;
  97
  98   /* The following member is used for debugging.  Its value is number
  99      of collisions fixed for time of work with the hash table. */
 100   unsigned int collisions;
 101
 102   /* This is non-zero if we are allowed to return NULL for function calls
 103      that allocate memory.  */
 104   int return_allocation_failure;
 105 };
 106
 107 typedef struct htab *htab_t;
 108
 109 /* An enum saying whether we insert into the hash table or not.  */
 110 enum insert_option {NO_INSERT, INSERT};
 111
 112 /* The prototypes of the package functions. */
 113
 114 extern htab_t   htab_create     PARAMS ((size_t, htab_hash,
 115                                          htab_eq, htab_del));
 116
 117 /* This function is like htab_create, but may return NULL if memory
 118    allocation fails, and also signals that htab_find_slot_with_hash and
 119    htab_find_slot are allowed to return NULL when inserting.  */
 120 extern htab_t   htab_try_create PARAMS ((size_t, htab_hash,
 121                                          htab_eq, htab_del));
 122 extern void     htab_delete     PARAMS ((htab_t));
 123 extern void     htab_empty      PARAMS ((htab_t));
 124
 125 extern PTR      htab_find       PARAMS ((htab_t, const void *));
 126 extern PTR     *htab_find_slot  PARAMS ((htab_t, const void *,
 127                                          enum insert_option));
 128 extern PTR      htab_find_with_hash       PARAMS ((htab_t, const void *,
 129                                                    hashval_t));
 130 extern PTR     *htab_find_slot_with_hash  PARAMS ((htab_t, const void *,
 131                                                    hashval_t,
 132                                                    enum insert_option));
 133 extern void     htab_clear_slot PARAMS ((htab_t, void **));
 134 extern void     htab_remove_elt PARAMS ((htab_t, void *));
 135
 136 extern void     htab_traverse   PARAMS ((htab_t, htab_trav, void *));
 137
 138 extern size_t   htab_size       PARAMS ((htab_t));
 139 extern size_t   htab_elements   PARAMS ((htab_t));
 140 extern double   htab_collisions PARAMS ((htab_t));
 141
 142 /* A hash function for pointers.  */
 143 extern htab_hash htab_hash_pointer;
 144
 145 /* An equality function for pointers.  */
 146 extern htab_eq htab_eq_pointer;
 147
 148 /* A hash function for null-terminated strings.  */
 149 extern hashval_t htab_hash_string PARAMS ((const PTR));
 150
 151 #ifdef __cplusplus
 152 }
 153 #endif /* __cplusplus */
 154
 155 #endif /* __HASHTAB_H */