623 lines
15 KiB
C
623 lines
15 KiB
C
/* An expandable hash tables datatype.
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Copyright (C) 1999, 2000, 2001, 2002 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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#ifdef HAVE_STRING_H
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#include <string.h>
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#endif
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#ifdef HAVE_MALLOC_H
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#include <malloc.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 ((PTR) 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 ((PTR) 1)
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static unsigned long higher_prime_number PARAMS ((unsigned long));
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static hashval_t hash_pointer PARAMS ((const void *));
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static int eq_pointer PARAMS ((const void *, const void *));
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static int htab_expand PARAMS ((htab_t));
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static PTR *find_empty_slot_for_expand PARAMS ((htab_t, hashval_t));
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/* At some point, we could make these be NULL, and modify the
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hash-table routines to handle NULL specially; that would avoid
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function-call overhead for the common case of hashing pointers. */
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htab_hash htab_hash_pointer = hash_pointer;
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htab_eq htab_eq_pointer = eq_pointer;
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/* The following function returns a nearest prime number which is
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greater than N, and near a power of two. */
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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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/* These are primes that are near, but slightly smaller than, a
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power of two. */
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static const unsigned long primes[] = {
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(unsigned long) 7,
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(unsigned long) 13,
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(unsigned long) 31,
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(unsigned long) 61,
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(unsigned long) 127,
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(unsigned long) 251,
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(unsigned long) 509,
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(unsigned long) 1021,
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(unsigned long) 2039,
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(unsigned long) 4093,
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(unsigned long) 8191,
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(unsigned long) 16381,
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(unsigned long) 32749,
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(unsigned long) 65521,
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(unsigned long) 131071,
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(unsigned long) 262139,
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(unsigned long) 524287,
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(unsigned long) 1048573,
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(unsigned long) 2097143,
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(unsigned long) 4194301,
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(unsigned long) 8388593,
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(unsigned long) 16777213,
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(unsigned long) 33554393,
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(unsigned long) 67108859,
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(unsigned long) 134217689,
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(unsigned long) 268435399,
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(unsigned long) 536870909,
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(unsigned long) 1073741789,
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(unsigned long) 2147483647,
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/* 4294967291L */
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((unsigned long) 2147483647) + ((unsigned long) 2147483644),
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};
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const unsigned long *low = &primes[0];
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const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
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while (low != high)
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{
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const unsigned long *mid = low + (high - low) / 2;
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if (n > *mid)
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low = mid + 1;
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else
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high = mid;
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}
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/* If we've run out of primes, abort. */
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if (n > *low)
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{
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fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
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abort ();
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}
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return *low;
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}
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/* Returns a hash code for P. */
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static hashval_t
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hash_pointer (p)
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const PTR p;
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{
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return (hashval_t) ((long)p >> 3);
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}
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/* Returns non-zero if P1 and P2 are equal. */
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static int
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eq_pointer (p1, p2)
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const PTR p1;
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const PTR p2;
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{
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return p1 == p2;
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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, or NULL if memory allocation fails. */
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htab_t
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htab_create_alloc (size, hash_f, eq_f, del_f, alloc_f, free_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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htab_alloc alloc_f;
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htab_free free_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) (*alloc_f) (1, sizeof (struct htab));
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if (result == NULL)
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return NULL;
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result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR));
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if (result->entries == NULL)
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{
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if (free_f != NULL)
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(*free_f) (result);
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return NULL;
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}
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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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result->alloc_f = alloc_f;
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result->free_f = free_f;
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return result;
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}
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/* These functions exist solely for backward compatibility. */
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#undef htab_create
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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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return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
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}
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htab_t
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htab_try_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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return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free);
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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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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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if (htab->free_f != NULL)
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{
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(*htab->free_f) (htab->entries);
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(*htab->free_f) (htab);
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}
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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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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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memset (htab->entries, 0, htab->size * sizeof (PTR));
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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 PTR *
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find_empty_slot_for_expand (htab, hash)
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htab_t htab;
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hashval_t hash;
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{
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size_t size = htab->size;
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unsigned int index = hash % size;
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PTR *slot = htab->entries + index;
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hashval_t hash2;
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if (*slot == EMPTY_ENTRY)
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return slot;
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else if (*slot == DELETED_ENTRY)
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abort ();
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hash2 = 1 + hash % (size - 2);
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for (;;)
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{
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index += hash2;
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if (index >= size)
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index -= size;
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slot = htab->entries + index;
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if (*slot == EMPTY_ENTRY)
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return slot;
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else if (*slot == DELETED_ENTRY)
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abort ();
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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. If memory allocation failures are allowed,
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this function will return zero, indicating that the table could not be
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expanded. If all goes well, it will return a non-zero value. */
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static int
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htab_expand (htab)
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htab_t htab;
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{
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PTR *oentries;
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PTR *olimit;
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PTR *p;
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PTR *nentries;
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size_t nsize;
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oentries = htab->entries;
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olimit = oentries + htab->size;
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nsize = higher_prime_number (htab->size * 2);
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nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR));
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if (nentries == NULL)
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return 0;
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htab->entries = nentries;
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htab->size = nsize;
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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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PTR x = *p;
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if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
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{
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PTR *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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if (htab->free_f != NULL)
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(*htab->free_f) (oentries);
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return 1;
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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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PTR
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htab_find_with_hash (htab, element, hash)
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htab_t htab;
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const PTR element;
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hashval_t hash;
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{
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unsigned int index;
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hashval_t hash2;
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size_t size;
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PTR entry;
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htab->searches++;
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size = htab->size;
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index = hash % size;
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entry = htab->entries[index];
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if (entry == EMPTY_ENTRY
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|| (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
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return entry;
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hash2 = 1 + hash % (size - 2);
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for (;;)
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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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entry = htab->entries[index];
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if (entry == EMPTY_ENTRY
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|| (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
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return entry;
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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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PTR
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htab_find (htab, element)
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htab_t htab;
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const PTR 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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When inserting an entry, NULL may be returned if memory allocation
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fails. */
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PTR *
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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 PTR element;
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hashval_t hash;
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enum insert_option insert;
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{
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PTR *first_deleted_slot;
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unsigned int index;
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hashval_t hash2;
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size_t size;
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PTR entry;
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if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4
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&& htab_expand (htab) == 0)
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return NULL;
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size = htab->size;
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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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entry = htab->entries[index];
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if (entry == EMPTY_ENTRY)
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goto empty_entry;
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else if (entry == DELETED_ENTRY)
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first_deleted_slot = &htab->entries[index];
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else if ((*htab->eq_f) (entry, element))
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return &htab->entries[index];
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hash2 = 1 + hash % (size - 2);
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for (;;)
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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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entry = htab->entries[index];
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if (entry == EMPTY_ENTRY)
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goto empty_entry;
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else 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 if ((*htab->eq_f) (entry, element))
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return &htab->entries[index];
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}
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empty_entry:
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if (insert == NO_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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/* Like htab_find_slot_with_hash, but compute the hash value from the
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element. */
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PTR *
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htab_find_slot (htab, element, insert)
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htab_t htab;
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const PTR element;
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enum insert_option 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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PTR element;
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{
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PTR *slot;
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slot = htab_find_slot (htab, element, NO_INSERT);
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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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PTR *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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|
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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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PTR info;
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{
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PTR *slot = htab->entries;
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PTR *limit = slot + htab->size;
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do
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{
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PTR 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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|
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/* Return the current size of given hash table. */
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|
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size_t
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htab_size (htab)
|
|
htab_t htab;
|
|
{
|
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return htab->size;
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}
|
|
|
|
/* Return the current number of elements in given hash table. */
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|
|
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size_t
|
|
htab_elements (htab)
|
|
htab_t htab;
|
|
{
|
|
return htab->n_elements - htab->n_deleted;
|
|
}
|
|
|
|
/* Return the fraction of fixed collisions during all work with given
|
|
hash table. */
|
|
|
|
double
|
|
htab_collisions (htab)
|
|
htab_t htab;
|
|
{
|
|
if (htab->searches == 0)
|
|
return 0.0;
|
|
|
|
return (double) htab->collisions / (double) htab->searches;
|
|
}
|
|
|
|
/* Hash P as a null-terminated string.
|
|
|
|
Copied from gcc/hashtable.c. Zack had the following to say with respect
|
|
to applicability, though note that unlike hashtable.c, this hash table
|
|
implementation re-hashes rather than chain buckets.
|
|
|
|
http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
|
|
From: Zack Weinberg <zackw@panix.com>
|
|
Date: Fri, 17 Aug 2001 02:15:56 -0400
|
|
|
|
I got it by extracting all the identifiers from all the source code
|
|
I had lying around in mid-1999, and testing many recurrences of
|
|
the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either
|
|
prime numbers or the appropriate identity. This was the best one.
|
|
I don't remember exactly what constituted "best", except I was
|
|
looking at bucket-length distributions mostly.
|
|
|
|
So it should be very good at hashing identifiers, but might not be
|
|
as good at arbitrary strings.
|
|
|
|
I'll add that it thoroughly trounces the hash functions recommended
|
|
for this use at http://burtleburtle.net/bob/hash/index.html, both
|
|
on speed and bucket distribution. I haven't tried it against the
|
|
function they just started using for Perl's hashes. */
|
|
|
|
hashval_t
|
|
htab_hash_string (p)
|
|
const PTR p;
|
|
{
|
|
const unsigned char *str = (const unsigned char *) p;
|
|
hashval_t r = 0;
|
|
unsigned char c;
|
|
|
|
while ((c = *str++) != 0)
|
|
r = r * 67 + c - 113;
|
|
|
|
return r;
|
|
}
|