156 lines
5.2 KiB
C
156 lines
5.2 KiB
C
/* An expandable hash tables datatype.
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Copyright (C) 1999, 2000 Free Software Foundation, Inc.
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Contributed by Vladimir Makarov (vmakarov@cygnus.com).
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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/* This package implements basic hash table functionality. It is possible
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to search for an entry, create an entry and destroy an entry.
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Elements in the table are generic pointers.
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The size of the table is not fixed; if the occupancy of the table
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grows too high the hash table will be expanded.
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The abstract data implementation is based on generalized Algorithm D
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from Knuth's book "The art of computer programming". Hash table is
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expanded by creation of new hash table and transferring elements from
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the old table to the new table. */
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#ifndef __HASHTAB_H__
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#define __HASHTAB_H__
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#ifdef __cplusplus
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extern "C" {
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#endif /* __cplusplus */
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#include <ansidecl.h>
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/* The type for a hash code. */
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typedef unsigned int hashval_t;
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/* Callback function pointer types. */
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/* Calculate hash of a table entry. */
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typedef hashval_t (*htab_hash) PARAMS ((const void *));
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/* Compare a table entry with a possible entry. The entry already in
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the table always comes first, so the second element can be of a
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different type (but in this case htab_find and htab_find_slot
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cannot be used; instead the variants that accept a hash value
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must be used). */
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typedef int (*htab_eq) PARAMS ((const void *, const void *));
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/* Cleanup function called whenever a live element is removed from
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the hash table. */
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typedef void (*htab_del) PARAMS ((void *));
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/* Function called by htab_traverse for each live element. The first
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arg is the slot of the element (which can be passed to htab_clear_slot
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if desired), the second arg is the auxiliary pointer handed to
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htab_traverse. Return 1 to continue scan, 0 to stop. */
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typedef int (*htab_trav) PARAMS ((void **, void *));
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/* Hash tables are of the following type. The structure
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(implementation) of this type is not needed for using the hash
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tables. All work with hash table should be executed only through
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functions mentioned below. */
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struct htab
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{
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/* Pointer to hash function. */
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htab_hash hash_f;
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/* Pointer to comparison function. */
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htab_eq eq_f;
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/* Pointer to cleanup function. */
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htab_del del_f;
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/* Table itself. */
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PTR *entries;
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/* Current size (in entries) of the hash table */
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size_t size;
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/* Current number of elements including also deleted elements */
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size_t n_elements;
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/* Current number of deleted elements in the table */
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size_t n_deleted;
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/* The following member is used for debugging. Its value is number
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of all calls of `htab_find_slot' for the hash table. */
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unsigned int searches;
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/* The following member is used for debugging. Its value is number
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of collisions fixed for time of work with the hash table. */
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unsigned int collisions;
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/* This is non-zero if we are allowed to return NULL for function calls
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that allocate memory. */
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int return_allocation_failure;
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};
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typedef struct htab *htab_t;
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/* An enum saying whether we insert into the hash table or not. */
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enum insert_option {NO_INSERT, INSERT};
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/* The prototypes of the package functions. */
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extern htab_t htab_create PARAMS ((size_t, htab_hash,
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htab_eq, htab_del));
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/* This function is like htab_create, but may return NULL if memory
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allocation fails, and also signals that htab_find_slot_with_hash and
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htab_find_slot are allowed to return NULL when inserting. */
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extern htab_t htab_try_create PARAMS ((size_t, htab_hash,
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htab_eq, htab_del));
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extern void htab_delete PARAMS ((htab_t));
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extern void htab_empty PARAMS ((htab_t));
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extern PTR htab_find PARAMS ((htab_t, const void *));
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extern PTR *htab_find_slot PARAMS ((htab_t, const void *,
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enum insert_option));
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extern PTR htab_find_with_hash PARAMS ((htab_t, const void *,
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hashval_t));
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extern PTR *htab_find_slot_with_hash PARAMS ((htab_t, const void *,
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hashval_t,
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enum insert_option));
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extern void htab_clear_slot PARAMS ((htab_t, void **));
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extern void htab_remove_elt PARAMS ((htab_t, void *));
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extern void htab_traverse PARAMS ((htab_t, htab_trav, void *));
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extern size_t htab_size PARAMS ((htab_t));
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extern size_t htab_elements PARAMS ((htab_t));
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extern double htab_collisions PARAMS ((htab_t));
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/* A hash function for pointers. */
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extern htab_hash htab_hash_pointer;
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/* An equality function for pointers. */
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extern htab_eq htab_eq_pointer;
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/* A hash function for null-terminated strings. */
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extern hashval_t htab_hash_string PARAMS ((const PTR));
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#ifdef __cplusplus
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}
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#endif /* __cplusplus */
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#endif /* __HASHTAB_H */
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