430 lines
9.9 KiB
C
430 lines
9.9 KiB
C
/* An expandable hash tables datatype.
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Copyright (C) 1999 Free Software Foundation, Inc.
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Contributed by Vladimir Makarov (vmakarov@cygnus.com).
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This file is part of the libiberty library.
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Libiberty is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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Libiberty 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 GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with libiberty; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <sys/types.h>
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#ifdef HAVE_STDLIB_H
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#include <stdlib.h>
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#endif
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#include <stdio.h>
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#include "libiberty.h"
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#include "hashtab.h"
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/* This macro defines reserved value for empty table entry. */
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#define EMPTY_ENTRY ((void *) 0)
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/* This macro defines reserved value for table entry which contained
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a deleted element. */
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#define DELETED_ENTRY ((void *) 1)
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/* The following function returns the nearest prime number which is
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greater than given source number. */
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static unsigned long
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higher_prime_number (n)
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unsigned long n;
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{
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unsigned long i;
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n |= 0x01; /* Force N to be odd. */
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if (n < 9)
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return n; /* All odd numbers < 9 are prime. */
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next:
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n += 2;
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i = 3;
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do
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{
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if (n % i == 0)
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goto next;
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i += 2;
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}
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while ((i * i) <= n);
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return n;
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}
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/* This function creates table with length slightly longer than given
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source length. Created hash table is initiated as empty (all the
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hash table entries are EMPTY_ENTRY). The function returns the
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created hash table. */
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htab_t
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htab_create (size, hash_f, eq_f, del_f)
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size_t size;
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htab_hash hash_f;
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htab_eq eq_f;
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htab_del del_f;
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{
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htab_t result;
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size = higher_prime_number (size);
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result = (htab_t) xcalloc (1, sizeof (struct htab));
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result->entries = (void **) xcalloc (size, sizeof (void *));
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result->size = size;
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result->hash_f = hash_f;
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result->eq_f = eq_f;
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result->del_f = del_f;
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return result;
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}
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/* This function frees all memory allocated for given hash table.
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Naturally the hash table must already exist. */
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void
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htab_delete (htab)
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htab_t htab;
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{
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int i;
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if (htab->del_f)
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for (i = htab->size - 1; i >= 0; i--)
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{
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if (htab->entries[i] != EMPTY_ENTRY
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&& htab->entries[i] != DELETED_ENTRY)
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(*htab->del_f) (htab->entries[i]);
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}
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free (htab->entries);
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free (htab);
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}
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/* This function clears all entries in the given hash table. */
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void
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htab_empty (htab)
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htab_t htab;
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{
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int i;
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if (htab->del_f)
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for (i = htab->size - 1; i >= 0; i--)
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{
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if (htab->entries[i] != EMPTY_ENTRY
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&& htab->entries[i] != DELETED_ENTRY)
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(*htab->del_f) (htab->entries[i]);
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}
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memset (htab->entries, 0, htab->size * sizeof (void *));
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}
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/* Similar to htab_find_slot, but without several unwanted side effects:
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- Does not call htab->eq_f when it finds an existing entry.
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- Does not change the count of elements/searches/collisions in the
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hash table.
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This function also assumes there are no deleted entries in the table.
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HASH is the hash value for the element to be inserted. */
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static void **
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find_empty_slot_for_expand (htab, hash)
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htab_t htab;
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unsigned int hash;
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{
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size_t size = htab->size;
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unsigned int hash2 = 1 + hash % (size - 2);
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unsigned int index = hash % size;
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for (;;)
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{
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void **slot = htab->entries + index;
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if (*slot == EMPTY_ENTRY)
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return slot;
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if (*slot == DELETED_ENTRY)
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abort ();
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index += hash2;
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if (index >= size)
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index -= size;
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}
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}
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/* The following function changes size of memory allocated for the
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entries and repeatedly inserts the table elements. The occupancy
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of the table after the call will be about 50%. Naturally the hash
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table must already exist. Remember also that the place of the
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table entries is changed. */
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static void
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htab_expand (htab)
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htab_t htab;
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{
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void **oentries;
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void **olimit;
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void **p;
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oentries = htab->entries;
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olimit = oentries + htab->size;
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htab->size = higher_prime_number (htab->size * 2);
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htab->entries = xcalloc (htab->size, sizeof (void **));
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htab->n_elements -= htab->n_deleted;
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htab->n_deleted = 0;
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p = oentries;
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do
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{
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void *x = *p;
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if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
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{
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void **q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
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*q = x;
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}
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p++;
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}
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while (p < olimit);
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free (oentries);
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}
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/* This function searches for a hash table entry equal to the given
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element. It cannot be used to insert or delete an element. */
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void *
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htab_find_with_hash (htab, element, hash)
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htab_t htab;
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const void *element;
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unsigned int hash;
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{
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unsigned int index, hash2;
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size_t size;
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htab->searches++;
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size = htab->size;
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hash2 = 1 + hash % (size - 2);
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index = hash % size;
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for (;;)
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{
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void *entry = htab->entries[index];
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if (entry == EMPTY_ENTRY)
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return NULL;
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else if (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element))
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return entry;
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htab->collisions++;
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index += hash2;
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if (index >= size)
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index -= size;
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}
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}
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/* Like htab_find_slot_with_hash, but compute the hash value from the
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element. */
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void *
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htab_find (htab, element)
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htab_t htab;
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const void *element;
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{
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return htab_find_with_hash (htab, element, (*htab->hash_f) (element));
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}
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/* This function searches for a hash table slot containing an entry
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equal to the given element. To delete an entry, call this with
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INSERT = 0, then call htab_clear_slot on the slot returned (possibly
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after doing some checks). To insert an entry, call this with
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INSERT = 1, then write the value you want into the returned slot. */
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void **
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htab_find_slot_with_hash (htab, element, hash, insert)
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htab_t htab;
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const void *element;
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unsigned int hash;
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int insert;
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{
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void **first_deleted_slot;
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unsigned int index, hash2;
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size_t size;
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if (insert && htab->size * 3 <= htab->n_elements * 4)
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htab_expand (htab);
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size = htab->size;
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hash2 = 1 + hash % (size - 2);
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index = hash % size;
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htab->searches++;
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first_deleted_slot = NULL;
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for (;;)
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{
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void *entry = htab->entries[index];
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if (entry == EMPTY_ENTRY)
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{
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if (!insert)
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return NULL;
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htab->n_elements++;
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if (first_deleted_slot)
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{
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*first_deleted_slot = EMPTY_ENTRY;
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return first_deleted_slot;
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}
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return &htab->entries[index];
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}
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if (entry == DELETED_ENTRY)
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{
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if (!first_deleted_slot)
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first_deleted_slot = &htab->entries[index];
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}
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else
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{
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if ((*htab->eq_f) (entry, element))
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return &htab->entries[index];
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}
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htab->collisions++;
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index += hash2;
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if (index >= size)
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index -= size;
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}
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}
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/* Like htab_find_slot_with_hash, but compute the hash value from the
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element. */
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void **
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htab_find_slot (htab, element, insert)
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htab_t htab;
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const void *element;
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int insert;
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{
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return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element),
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insert);
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}
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/* This function deletes an element with the given value from hash
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table. If there is no matching element in the hash table, this
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function does nothing. */
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void
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htab_remove_elt (htab, element)
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htab_t htab;
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void *element;
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{
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void **slot;
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slot = htab_find_slot (htab, element, 0);
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if (*slot == EMPTY_ENTRY)
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return;
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if (htab->del_f)
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(*htab->del_f) (*slot);
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*slot = DELETED_ENTRY;
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htab->n_deleted++;
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}
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/* This function clears a specified slot in a hash table. It is
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useful when you've already done the lookup and don't want to do it
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again. */
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void
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htab_clear_slot (htab, slot)
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htab_t htab;
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void **slot;
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{
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if (slot < htab->entries || slot >= htab->entries + htab->size
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|| *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY)
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abort ();
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if (htab->del_f)
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(*htab->del_f) (*slot);
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*slot = DELETED_ENTRY;
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htab->n_deleted++;
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}
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/* This function scans over the entire hash table calling
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CALLBACK for each live entry. If CALLBACK returns false,
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the iteration stops. INFO is passed as CALLBACK's second
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argument. */
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void
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htab_traverse (htab, callback, info)
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htab_t htab;
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htab_trav callback;
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void *info;
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{
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void **slot, **limit;
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slot = htab->entries;
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limit = slot + htab->size;
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do
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{
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void *x = *slot;
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if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
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if (!(*callback) (slot, info))
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break;
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}
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while (++slot < limit);
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}
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/* The following function returns current size of given hash table. */
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size_t
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htab_size (htab)
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htab_t htab;
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{
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return htab->size;
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}
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/* The following function returns current number of elements in given
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hash table. */
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size_t
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htab_elements (htab)
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htab_t htab;
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{
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return htab->n_elements - htab->n_deleted;
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}
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/* The following function returns number of percents of fixed
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collisions during all work with given hash table. */
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double
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htab_collisions (htab)
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htab_t htab;
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{
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int searches;
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searches = htab->searches;
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if (searches == 0)
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return 0.0;
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return (double)htab->collisions / (double)searches;
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}
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