| /* 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 |
| |
| #include <sys/types.h> |
| |
| #ifdef HAVE_STDLIB_H |
| #include <stdlib.h> |
| #endif |
| |
| #ifdef HAVE_STRING_H |
| #include <string.h> |
| #endif |
| |
| #include <stdio.h> |
| |
| #include "libiberty.h" |
| #include "hashtab.h" |
| |
| /* This macro defines reserved value for empty table entry. */ |
| |
| #define EMPTY_ENTRY ((void *) 0) |
| |
| /* 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 (n) |
| unsigned long n; |
| { |
| unsigned long i; |
| |
| n |= 0x01; /* Force N to be odd. */ |
| if (n < 9) |
| return n; /* All odd numbers < 9 are prime. */ |
| |
| next: |
| n += 2; |
| i = 3; |
| do |
| { |
| if (n % i == 0) |
| goto next; |
| i += 2; |
| } |
| while ((i * i) <= n); |
| |
| return n; |
| } |
| |
| /* 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. */ |
| |
| htab_t |
| htab_create (size, hash_f, eq_f, del_f) |
| size_t size; |
| htab_hash hash_f; |
| htab_eq eq_f; |
| htab_del del_f; |
| { |
| htab_t result; |
| |
| size = higher_prime_number (size); |
| result = (htab_t) xcalloc (1, sizeof (struct htab)); |
| result->entries = (void **) xcalloc (size, sizeof (void *)); |
| result->size = size; |
| result->hash_f = hash_f; |
| result->eq_f = eq_f; |
| result->del_f = del_f; |
| return result; |
| } |
| |
| /* This function frees all memory allocated for given hash table. |
| Naturally the hash table must already exist. */ |
| |
| void |
| htab_delete (htab) |
| htab_t htab; |
| { |
| int i; |
| if (htab->del_f) |
| for (i = htab->size - 1; i >= 0; i--) |
| { |
| if (htab->entries[i] != EMPTY_ENTRY |
| && htab->entries[i] != DELETED_ENTRY) |
| (*htab->del_f) (htab->entries[i]); |
| } |
| |
| free (htab->entries); |
| free (htab); |
| } |
| |
| /* This function clears all entries in the given hash table. */ |
| |
| void |
| htab_empty (htab) |
| htab_t htab; |
| { |
| int i; |
| if (htab->del_f) |
| for (i = htab->size - 1; i >= 0; i--) |
| { |
| if (htab->entries[i] != EMPTY_ENTRY |
| && htab->entries[i] != DELETED_ENTRY) |
| (*htab->del_f) (htab->entries[i]); |
| } |
| |
| memset (htab->entries, 0, htab->size * sizeof (void *)); |
| } |
| |
| /* Similar to htab_find_slot, but without several unwanted side effects: |
| - Does not call htab->eq_f when it finds an existing entry. |
| - Does not change the count of elements/searches/collisions in the |
| hash table. |
| This function also assumes there are no deleted entries in the table. |
| HASH is the hash value for the element to be inserted. */ |
| static void ** |
| find_empty_slot_for_expand (htab, hash) |
| htab_t htab; |
| unsigned int hash; |
| { |
| size_t size = htab->size; |
| unsigned int hash2 = 1 + hash % (size - 2); |
| unsigned int index = hash % size; |
| |
| for (;;) |
| { |
| void **slot = htab->entries + index; |
| if (*slot == EMPTY_ENTRY) |
| return slot; |
| |
| if (*slot == DELETED_ENTRY) |
| abort (); |
| |
| index += hash2; |
| if (index >= size) |
| index -= size; |
| } |
| } |
| |
| /* 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 |
| htab_expand (htab) |
| htab_t htab; |
| { |
| void **oentries; |
| void **olimit; |
| void **p; |
| |
| oentries = htab->entries; |
| olimit = oentries + htab->size; |
| |
| htab->size = higher_prime_number (htab->size * 2); |
| htab->entries = xcalloc (htab->size, sizeof (void **)); |
| |
| htab->n_elements -= htab->n_deleted; |
| htab->n_deleted = 0; |
| |
| p = oentries; |
| do |
| { |
| void *x = *p; |
| if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
| { |
| void **q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x)); |
| *q = x; |
| } |
| p++; |
| } |
| while (p < olimit); |
| free (oentries); |
| } |
| |
| /* This function searches for a hash table entry equal to the given |
| element. It cannot be used to insert or delete an element. */ |
| |
| void * |
| htab_find_with_hash (htab, element, hash) |
| htab_t htab; |
| const void *element; |
| unsigned int hash; |
| { |
| unsigned int index, hash2; |
| size_t size; |
| |
| htab->searches++; |
| size = htab->size; |
| hash2 = 1 + hash % (size - 2); |
| index = hash % size; |
| |
| for (;;) |
| { |
| void *entry = htab->entries[index]; |
| if (entry == EMPTY_ENTRY) |
| return NULL; |
| else if (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)) |
| return entry; |
| |
| htab->collisions++; |
| index += hash2; |
| if (index >= size) |
| index -= size; |
| } |
| } |
| |
| /* Like htab_find_slot_with_hash, but compute the hash value from the |
| element. */ |
| void * |
| htab_find (htab, element) |
| htab_t htab; |
| const void *element; |
| { |
| return htab_find_with_hash (htab, element, (*htab->hash_f) (element)); |
| } |
| |
| /* This function searches for a hash table slot containing an entry |
| equal to the given element. To delete an entry, call this with |
| INSERT = 0, then call htab_clear_slot on the slot returned (possibly |
| after doing some checks). To insert an entry, call this with |
| INSERT = 1, then write the value you want into the returned slot. */ |
| |
| void ** |
| htab_find_slot_with_hash (htab, element, hash, insert) |
| htab_t htab; |
| const void *element; |
| unsigned int hash; |
| int insert; |
| { |
| void **first_deleted_slot; |
| unsigned int index, hash2; |
| size_t size; |
| |
| if (insert && htab->size * 3 <= htab->n_elements * 4) |
| htab_expand (htab); |
| |
| size = htab->size; |
| hash2 = 1 + hash % (size - 2); |
| index = hash % size; |
| |
| htab->searches++; |
| first_deleted_slot = NULL; |
| |
| for (;;) |
| { |
| void *entry = htab->entries[index]; |
| if (entry == EMPTY_ENTRY) |
| { |
| if (!insert) |
| return NULL; |
| |
| htab->n_elements++; |
| |
| if (first_deleted_slot) |
| { |
| *first_deleted_slot = EMPTY_ENTRY; |
| return first_deleted_slot; |
| } |
| |
| return &htab->entries[index]; |
| } |
| |
| if (entry == DELETED_ENTRY) |
| { |
| if (!first_deleted_slot) |
| first_deleted_slot = &htab->entries[index]; |
| } |
| else |
| { |
| if ((*htab->eq_f) (entry, element)) |
| return &htab->entries[index]; |
| } |
| |
| htab->collisions++; |
| index += hash2; |
| if (index >= size) |
| index -= size; |
| } |
| } |
| |
| /* Like htab_find_slot_with_hash, but compute the hash value from the |
| element. */ |
| void ** |
| htab_find_slot (htab, element, insert) |
| htab_t htab; |
| const void *element; |
| int insert; |
| { |
| return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element), |
| insert); |
| } |
| |
| /* This function deletes an element with the given value from hash |
| table. If there is no matching element in the hash table, this |
| function does nothing. */ |
| |
| void |
| htab_remove_elt (htab, element) |
| htab_t htab; |
| void *element; |
| { |
| void **slot; |
| |
| slot = htab_find_slot (htab, element, 0); |
| if (*slot == EMPTY_ENTRY) |
| return; |
| |
| if (htab->del_f) |
| (*htab->del_f) (*slot); |
| |
| *slot = DELETED_ENTRY; |
| htab->n_deleted++; |
| } |
| |
| /* This function clears a specified slot in a hash table. It is |
| useful when you've already done the lookup and don't want to do it |
| again. */ |
| |
| void |
| htab_clear_slot (htab, slot) |
| htab_t htab; |
| void **slot; |
| { |
| if (slot < htab->entries || slot >= htab->entries + htab->size |
| || *slot == EMPTY_ENTRY || *slot == DELETED_ENTRY) |
| abort (); |
| if (htab->del_f) |
| (*htab->del_f) (*slot); |
| *slot = DELETED_ENTRY; |
| htab->n_deleted++; |
| } |
| |
| /* This function scans over the entire hash table calling |
| CALLBACK for each live entry. If CALLBACK returns false, |
| the iteration stops. INFO is passed as CALLBACK's second |
| argument. */ |
| |
| void |
| htab_traverse (htab, callback, info) |
| htab_t htab; |
| htab_trav callback; |
| void *info; |
| { |
| void **slot, **limit; |
| slot = htab->entries; |
| limit = slot + htab->size; |
| do |
| { |
| void *x = *slot; |
| if (x != EMPTY_ENTRY && x != DELETED_ENTRY) |
| if (!(*callback) (slot, info)) |
| break; |
| } |
| while (++slot < limit); |
| } |
| |
| /* The following function returns current size of given hash table. */ |
| |
| size_t |
| htab_size (htab) |
| htab_t htab; |
| { |
| return htab->size; |
| } |
| |
| /* The following function returns current number of elements in given |
| hash table. */ |
| |
| size_t |
| htab_elements (htab) |
| htab_t htab; |
| { |
| return htab->n_elements - htab->n_deleted; |
| } |
| |
| /* The following function returns number of percents of fixed |
| collisions during all work with given hash table. */ |
| |
| double |
| htab_collisions (htab) |
| htab_t htab; |
| { |
| int searches; |
| |
| searches = htab->searches; |
| if (searches == 0) |
| return 0.0; |
| return (double)htab->collisions / (double)searches; |
| } |