--- /dev/null
+/* An expandable hash tables datatype.
+ Copyright (C) 1999 Free Software Foundation, Inc.
+ Contributed by Vladimir Makarov (vmakarov@cygnus.com).
+
+This file is part of the libiberty library.
+Libiberty is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public
+License as published by the Free Software Foundation; either
+version 2 of the License, or (at your option) any later version.
+
+Libiberty is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with libiberty; see the file COPYING.LIB. If
+not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
+
+/* This package implements basic hash table functionality. It is possible
+ to search for an entry, create an entry and destroy an entry.
+
+ Elements in the table are generic pointers.
+
+ The size of the table is not fixed; if the occupancy of the table
+ grows too high the hash table will be expanded.
+
+ The abstract data implementation is based on generalized Algorithm D
+ from Knuth's book "The art of computer programming". Hash table is
+ expanded by creation of new hash table and transferring elements from
+ the old table to the new table. */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
+
+#include "libiberty.h"
+#include "hashtab.h"
+
+/* The following variable is used for debugging. Its value is number
+ of all calls of `find_hash_table_entry' for all hash tables. */
+
+static int all_searches = 0;
+
+/* The following variable is used for debugging. Its value is number
+ of collisions fixed for time of work with all hash tables. */
+
+static int all_collisions = 0;
+
+/* The following variable is used for debugging. Its value is number
+ of all table expansions fixed for time of work with all hash
+ tables. */
+
+static int all_expansions = 0;
+
+/* This macro defines reserved value for empty table entry. */
+
+#define EMPTY_ENTRY NULL
+
+/* This macro defines reserved value for table entry which contained
+ a deleted element. */
+
+#define DELETED_ENTRY ((void *) 1)
+
+/* The following function returns the nearest prime number which is
+ greater than given source number. */
+
+static unsigned long
+higher_prime_number (number)
+ unsigned long number;
+{
+ unsigned long i;
+
+ for (number = (number / 2) * 2 + 3;; number += 2)
+ {
+ for (i = 3; i * i <= number; i += 2)
+ if (number % i == 0)
+ break;
+ if (i * i > number)
+ return number;
+ }
+}
+
+/* This function creates table with length slightly longer than given
+ source length. Created hash table is initiated as empty (all the
+ hash table entries are EMPTY_ENTRY). The function returns the
+ created hash table. */
+
+hash_table_t
+create_hash_table (size, hash_function, eq_function)
+ size_t size;
+ unsigned (*hash_function) PARAMS ((hash_table_entry_t));
+ int (*eq_function) PARAMS ((hash_table_entry_t, hash_table_entry_t));
+{
+ hash_table_t result;
+
+ size = higher_prime_number (size);
+ result = (hash_table_t) xmalloc (sizeof (*result));
+ result->entries
+ = (hash_table_entry_t *) xmalloc (size * sizeof (hash_table_entry_t));
+ result->size = size;
+ result->hash_function = hash_function;
+ result->eq_function = eq_function;
+ result->number_of_elements = 0;
+ result->number_of_deleted_elements = 0;
+ result->searches = 0;
+ result->collisions = 0;
+ memset (result->entries, 0, size * sizeof (hash_table_entry_t));
+ return result;
+}
+
+/* This function frees all memory allocated for given hash table.
+ Naturally the hash table must already exist. */
+
+void
+delete_hash_table (htab)
+ hash_table_t htab;
+{
+ free (htab->entries);
+ free (htab);
+}
+
+/* This function clears all entries in the given hash table. */
+
+void
+empty_hash_table (htab)
+ hash_table_t htab;
+{
+ memset (htab->entries, 0, htab->size * sizeof (hash_table_entry_t));
+}
+
+/* The following function changes size of memory allocated for the
+ entries and repeatedly inserts the table elements. The occupancy
+ of the table after the call will be about 50%. Naturally the hash
+ table must already exist. Remember also that the place of the
+ table entries is changed. */
+
+static void
+expand_hash_table (htab)
+ hash_table_t htab;
+{
+ hash_table_t new_htab;
+ hash_table_entry_t *entry_ptr;
+ hash_table_entry_t *new_entry_ptr;
+
+ new_htab = create_hash_table (htab->number_of_elements * 2,
+ htab->hash_function, htab->eq_function);
+ for (entry_ptr = htab->entries; entry_ptr < htab->entries + htab->size;
+ entry_ptr++)
+ if (*entry_ptr != EMPTY_ENTRY && *entry_ptr != DELETED_ENTRY)
+ {
+ new_entry_ptr = find_hash_table_entry (new_htab, *entry_ptr, 1);
+ *new_entry_ptr = (*entry_ptr);
+ }
+ free (htab->entries);
+ *htab = (*new_htab);
+ free (new_htab);
+}
+
+/* This function searches for hash table entry which contains element
+ equal to given value or empty entry in which given value can be
+ placed (if the element with given value does not exist in the
+ table). The function works in two regimes. The first regime is
+ used only for search. The second is used for search and
+ reservation empty entry for given value. The table is expanded if
+ occupancy (taking into accout also deleted elements) is more than
+ 75%. Naturally the hash table must already exist. If reservation
+ flag is TRUE then the element with given value should be inserted
+ into the table entry before another call of
+ `find_hash_table_entry'. */
+
+hash_table_entry_t *
+find_hash_table_entry (htab, element, reserve)
+ hash_table_t htab;
+ hash_table_entry_t element;
+ int reserve;
+{
+ hash_table_entry_t *entry_ptr;
+ hash_table_entry_t *first_deleted_entry_ptr;
+ unsigned index, hash_value, secondary_hash_value;
+
+ if (htab->size * 3 <= htab->number_of_elements * 4)
+ {
+ all_expansions++;
+ expand_hash_table (htab);
+ }
+ hash_value = (*htab->hash_function) (element);
+ secondary_hash_value = 1 + hash_value % (htab->size - 2);
+ index = hash_value % htab->size;
+ htab->searches++;
+ all_searches++;
+ first_deleted_entry_ptr = NULL;
+ for (;;htab->collisions++, all_collisions++)
+ {
+ entry_ptr = htab->entries + index;
+ if (*entry_ptr == EMPTY_ENTRY)
+ {
+ if (reserve)
+ {
+ htab->number_of_elements++;
+ if (first_deleted_entry_ptr != NULL)
+ {
+ entry_ptr = first_deleted_entry_ptr;
+ *entry_ptr = DELETED_ENTRY;
+ }
+ }
+ break;
+ }
+ else if (*entry_ptr != DELETED_ENTRY)
+ {
+ if ((*htab->eq_function) (*entry_ptr, element))
+ break;
+ }
+ else if (first_deleted_entry_ptr == NULL)
+ first_deleted_entry_ptr = entry_ptr;
+ index += secondary_hash_value;
+ if (index >= htab->size)
+ index -= htab->size;
+ }
+ return entry_ptr;
+}
+
+/* This function deletes element with given value from hash table.
+ The hash table entry value will be `DELETED_ENTRY' after the
+ function call. Naturally the hash table must already exist. Hash
+ table entry for given value should be not empty (or deleted). */
+
+void
+remove_element_from_hash_table_entry (htab, element)
+ hash_table_t htab;
+ hash_table_entry_t element;
+{
+ hash_table_entry_t *entry_ptr;
+
+ entry_ptr = find_hash_table_entry (htab, element, 0);
+ *entry_ptr = DELETED_ENTRY;
+ htab->number_of_deleted_elements++;
+}
+
+/* The following function returns current size of given hash table. */
+
+size_t
+hash_table_size (htab)
+ hash_table_t htab;
+{
+ return htab->size;
+}
+
+/* The following function returns current number of elements in given
+ hash table. */
+
+size_t
+hash_table_elements_number (htab)
+ hash_table_t htab;
+{
+ return htab->number_of_elements - htab->number_of_deleted_elements;
+}
+
+/* The following function returns number of percents of fixed
+ collisions during all work with given hash table. */
+
+int
+hash_table_collisions (htab)
+ hash_table_t htab;
+{
+ int searches;
+
+ searches = htab->searches;
+ if (searches == 0)
+ searches++;
+ return htab->collisions * 100 / searches;
+}
+
+/* The following function returns number of percents of fixed
+ collisions during all work with all hash tables. */
+
+int
+all_hash_table_collisions ()
+{
+ int searches;
+
+ searches = all_searches;
+ if (searches == 0)
+ searches++;
+ return all_collisions * 100 / searches;
+}
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