/* An expandable hash tables datatype.
- Copyright (C) 1999 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
Contributed by Vladimir Makarov (vmakarov@cygnus.com).
This file is part of the libiberty library.
#include "config.h"
#endif
+#include <sys/types.h>
+
#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;
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
-/* The following variable is used for debugging. Its value is number
- of all table expansions fixed for time of work with all hash
- tables. */
+#include <stdio.h>
-static int all_expansions = 0;
+#include "libiberty.h"
+#include "hashtab.h"
/* This macro defines reserved value for empty table entry. */
-#define EMPTY_ENTRY NULL
+#define EMPTY_ENTRY ((PTR) 0)
/* This macro defines reserved value for table entry which contained
a deleted element. */
-#define DELETED_ENTRY ((void *) 1)
+#define DELETED_ENTRY ((PTR) 1)
-/* The following function returns the nearest prime number which is
- greater than given source number. */
+static unsigned long higher_prime_number PARAMS ((unsigned long));
+static hashval_t hash_pointer PARAMS ((const void *));
+static int eq_pointer PARAMS ((const void *, const void *));
+static int htab_expand PARAMS ((htab_t));
+static PTR *find_empty_slot_for_expand PARAMS ((htab_t, hashval_t));
+
+/* At some point, we could make these be NULL, and modify the
+ hash-table routines to handle NULL specially; that would avoid
+ function-call overhead for the common case of hashing pointers. */
+htab_hash htab_hash_pointer = hash_pointer;
+htab_eq htab_eq_pointer = eq_pointer;
+
+/* The following function returns a nearest prime number which is
+ greater than N, and near a power of two. */
static unsigned long
-higher_prime_number (number)
- unsigned long number;
+higher_prime_number (n)
+ unsigned long n;
{
- unsigned long i;
+ /* These are primes that are near, but slightly smaller than, a
+ power of two. */
+ static unsigned long primes[] = {
+ (unsigned long) 2,
+ (unsigned long) 7,
+ (unsigned long) 13,
+ (unsigned long) 31,
+ (unsigned long) 61,
+ (unsigned long) 127,
+ (unsigned long) 251,
+ (unsigned long) 509,
+ (unsigned long) 1021,
+ (unsigned long) 2039,
+ (unsigned long) 4093,
+ (unsigned long) 8191,
+ (unsigned long) 16381,
+ (unsigned long) 32749,
+ (unsigned long) 65521,
+ (unsigned long) 131071,
+ (unsigned long) 262139,
+ (unsigned long) 524287,
+ (unsigned long) 1048573,
+ (unsigned long) 2097143,
+ (unsigned long) 4194301,
+ (unsigned long) 8388593,
+ (unsigned long) 16777213,
+ (unsigned long) 33554393,
+ (unsigned long) 67108859,
+ (unsigned long) 134217689,
+ (unsigned long) 268435399,
+ (unsigned long) 536870909,
+ (unsigned long) 1073741789,
+ (unsigned long) 2147483647,
+ /* 4294967291L */
+ ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
+ };
+
+ unsigned long* low = &primes[0];
+ unsigned long* high = &primes[sizeof(primes) / sizeof(primes[0])];
+
+ while (low != high)
+ {
+ unsigned long* mid = low + (high - low) / 2;
+ if (n > *mid)
+ low = mid + 1;
+ else
+ high = mid;
+ }
- for (number = (number / 2) * 2 + 3;; number += 2)
+ /* If we've run out of primes, abort. */
+ if (n > *low)
{
- for (i = 3; i * i <= number; i += 2)
- if (number % i == 0)
- break;
- if (i * i > number)
- return number;
+ fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
+ abort ();
}
+
+ return *low;
+}
+
+/* Returns a hash code for P. */
+
+static hashval_t
+hash_pointer (p)
+ const PTR p;
+{
+ return (hashval_t) ((long)p >> 3);
+}
+
+/* Returns non-zero if P1 and P2 are equal. */
+
+static int
+eq_pointer (p1, p2)
+ const PTR p1;
+ const PTR p2;
+{
+ return p1 == p2;
}
/* 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. */
+ created hash table. Memory allocation must not fail. */
+
+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;
-hash_table_t
-create_hash_table (size, hash_function, eq_function)
+ size = higher_prime_number (size);
+ result = (htab_t) xcalloc (1, sizeof (struct htab));
+ result->entries = (PTR *) xcalloc (size, sizeof (PTR));
+ result->size = size;
+ result->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->return_allocation_failure = 0;
+ return result;
+}
+
+/* This function creates table with length slightly longer than given
+ source length. The created hash table is initiated as empty (all the
+ hash table entries are EMPTY_ENTRY). The function returns the created
+ hash table. Memory allocation may fail; it may return NULL. */
+
+htab_t
+htab_try_create (size, hash_f, eq_f, del_f)
size_t size;
- unsigned (*hash_function) PARAMS ((hash_table_entry_t));
- int (*eq_function) PARAMS ((hash_table_entry_t, hash_table_entry_t));
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
{
- hash_table_t result;
+ htab_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 = (htab_t) calloc (1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+
+ result->entries = (PTR *) calloc (size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ free (result);
+ return NULL;
+ }
+
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));
+ result->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->return_allocation_failure = 1;
return result;
}
Naturally the hash table must already exist. */
void
-delete_hash_table (htab)
- hash_table_t htab;
+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
-empty_hash_table (htab)
- hash_table_t htab;
+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 (PTR));
+}
+
+/* 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 PTR *
+find_empty_slot_for_expand (htab, hash)
+ htab_t htab;
+ hashval_t hash;
{
- memset (htab->entries, 0, htab->size * sizeof (hash_table_entry_t));
+ size_t size = htab->size;
+ hashval_t hash2 = 1 + hash % (size - 2);
+ unsigned int index = hash % size;
+
+ for (;;)
+ {
+ PTR *slot = htab->entries + index;
+
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else 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. */
+ table entries is changed. If memory allocation failures are allowed,
+ this function will return zero, indicating that the table could not be
+ expanded. If all goes well, it will return a non-zero value. */
-static void
-expand_hash_table (htab)
- hash_table_t htab;
+static int
+htab_expand (htab)
+ htab_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);
+ PTR *oentries;
+ PTR *olimit;
+ PTR *p;
+
+ oentries = htab->entries;
+ olimit = oentries + htab->size;
+
+ htab->size = higher_prime_number (htab->size * 2);
+
+ if (htab->return_allocation_failure)
+ {
+ PTR *nentries = (PTR *) calloc (htab->size, sizeof (PTR *));
+ if (nentries == NULL)
+ return 0;
+ htab->entries = nentries;
+ }
+ else
+ htab->entries = (PTR *) xcalloc (htab->size, sizeof (PTR *));
+
+ htab->n_elements -= htab->n_deleted;
+ htab->n_deleted = 0;
+
+ p = oentries;
+ do
+ {
+ PTR x = *p;
+
+ if (x != EMPTY_ENTRY && x != DELETED_ENTRY)
+ {
+ PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
+
+ *q = x;
+ }
+
+ p++;
+ }
+ while (p < olimit);
+
+ free (oentries);
+ return 1;
}
-/* 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;
+/* This function searches for a hash table entry equal to the given
+ element. It cannot be used to insert or delete an element. */
+
+PTR
+htab_find_with_hash (htab, element, hash)
+ htab_t htab;
+ const PTR element;
+ hashval_t hash;
{
- hash_table_entry_t *entry_ptr;
- hash_table_entry_t *first_deleted_entry_ptr;
- unsigned index, hash_value, secondary_hash_value;
+ unsigned int index;
+ hashval_t hash2;
+ size_t size;
+ PTR entry;
+
+ htab->searches++;
+ size = htab->size;
+ index = hash % size;
- if (htab->size * 3 <= htab->number_of_elements * 4)
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
+
+ hash2 = 1 + hash % (size - 2);
+
+ for (;;)
{
- all_expansions++;
- expand_hash_table (htab);
+ htab->collisions++;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY
+ || (entry != DELETED_ENTRY && (*htab->eq_f) (entry, element)))
+ return entry;
}
- hash_value = (*htab->hash_function) (element);
- secondary_hash_value = 1 + hash_value % (htab->size - 2);
- index = hash_value % htab->size;
+}
+
+/* Like htab_find_slot_with_hash, but compute the hash value from the
+ element. */
+
+PTR
+htab_find (htab, element)
+ htab_t htab;
+ const PTR 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.
+ When inserting an entry, NULL may be returned if memory allocation
+ fails. */
+
+PTR *
+htab_find_slot_with_hash (htab, element, hash, insert)
+ htab_t htab;
+ const PTR element;
+ hashval_t hash;
+ enum insert_option insert;
+{
+ PTR *first_deleted_slot;
+ unsigned int index;
+ hashval_t hash2;
+ size_t size;
+
+ if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4
+ && htab_expand (htab) == 0)
+ return NULL;
+
+ size = htab->size;
+ hash2 = 1 + hash % (size - 2);
+ index = hash % size;
+
htab->searches++;
- all_searches++;
- first_deleted_entry_ptr = NULL;
- for (;;htab->collisions++, all_collisions++)
+ first_deleted_slot = NULL;
+
+ for (;;)
{
- entry_ptr = htab->entries + index;
- if (*entry_ptr == EMPTY_ENTRY)
- {
- if (reserve)
+ PTR entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY)
+ {
+ if (insert == NO_INSERT)
+ return NULL;
+
+ htab->n_elements++;
+
+ if (first_deleted_slot)
{
- htab->number_of_elements++;
- if (first_deleted_entry_ptr != NULL)
- {
- entry_ptr = first_deleted_entry_ptr;
- *entry_ptr = EMPTY_ENTRY;
- }
+ *first_deleted_slot = EMPTY_ENTRY;
+ return first_deleted_slot;
}
- 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 &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;
}
- 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). */
+/* Like htab_find_slot_with_hash, but compute the hash value from the
+ element. */
+
+PTR *
+htab_find_slot (htab, element, insert)
+ htab_t htab;
+ const PTR element;
+ enum insert_option 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
-remove_element_from_hash_table_entry (htab, element)
- hash_table_t htab;
- hash_table_entry_t element;
+htab_remove_elt (htab, element)
+ htab_t htab;
+ PTR element;
{
- hash_table_entry_t *entry_ptr;
+ PTR *slot;
+
+ slot = htab_find_slot (htab, element, NO_INSERT);
+ if (*slot == EMPTY_ENTRY)
+ return;
- entry_ptr = find_hash_table_entry (htab, element, 0);
- *entry_ptr = DELETED_ENTRY;
- htab->number_of_deleted_elements++;
+ 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. */
+/* 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
-clear_hash_table_slot (htab, slot)
- hash_table_t htab;
- hash_table_entry_t *slot;
+htab_clear_slot (htab, slot)
+ htab_t htab;
+ PTR *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->number_of_deleted_elements++;
+ htab->n_deleted++;
}
/* This function scans over the entire hash table calling
argument. */
void
-traverse_hash_table (htab, callback, info)
- hash_table_t htab;
- int (*callback) (hash_table_entry_t, void *);
- void *info;
+htab_traverse (htab, callback, info)
+ htab_t htab;
+ htab_trav callback;
+ PTR info;
{
- hash_table_entry_t *entry_ptr;
- for (entry_ptr = htab->entries; entry_ptr < htab->entries + htab->size;
- entry_ptr++)
- if (*entry_ptr != EMPTY_ENTRY && *entry_ptr != DELETED_ENTRY)
- if (!callback (*entry_ptr, info))
- break;
+ PTR *slot = htab->entries;
+ PTR *limit = slot + htab->size;
+
+ do
+ {
+ PTR 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. */
+/* Return the current size of given hash table. */
size_t
-hash_table_size (htab)
- hash_table_t htab;
+htab_size (htab)
+ htab_t htab;
{
return htab->size;
}
-/* The following function returns current number of elements in given
- hash table. */
+/* Return the current number of elements in given hash table. */
size_t
-hash_table_elements_number (htab)
- hash_table_t htab;
+htab_elements (htab)
+ htab_t htab;
{
- return htab->number_of_elements - htab->number_of_deleted_elements;
+ return htab->n_elements - htab->n_deleted;
}
-/* The following function returns number of percents of fixed
- collisions during all work with given hash table. */
+/* Return the fraction of fixed collisions during all work with given
+ hash table. */
-int
-hash_table_collisions (htab)
- hash_table_t htab;
+double
+htab_collisions (htab)
+ htab_t htab;
{
- int searches;
+ if (htab->searches == 0)
+ return 0.0;
- searches = htab->searches;
- if (searches == 0)
- searches++;
- return htab->collisions * 100 / searches;
+ return (double) htab->collisions / (double) htab->searches;
}
-/* The following function returns number of percents of fixed
- collisions during all work with all hash tables. */
-
-int
-all_hash_table_collisions ()
+/* 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;
{
- int searches;
+ const unsigned char *str = (const unsigned char *) p;
+ hashval_t r = 0;
+ unsigned char c;
+
+ while ((c = *str++) != 0)
+ r = r * 67 + c - 113;
- searches = all_searches;
- if (searches == 0)
- searches++;
- return all_collisions * 100 / searches;
+ return r;
}
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