/* An expandable hash tables datatype.
- Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
Contributed by Vladimir Makarov (vmakarov@cygnus.com).
This file is part of the libiberty library.
{
/* These are primes that are near, but slightly smaller than, a
power of two. */
- static unsigned long primes[] = {
- (unsigned long) 2,
+ static const unsigned long primes[] = {
(unsigned long) 7,
(unsigned long) 13,
(unsigned long) 31,
(unsigned long) 1073741789,
(unsigned long) 2147483647,
/* 4294967291L */
- ((unsigned long) 2147483647) + ((unsigned long) 2147483642),
+ ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
};
- unsigned long* low = &primes[0];
- unsigned long* high = &primes[sizeof(primes) / sizeof(primes[0])];
+ const unsigned long *low = &primes[0];
+ const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
while (low != high)
{
- unsigned long* mid = low + (high - low) / 2;
+ const unsigned long *mid = low + (high - low) / 2;
if (n > *mid)
low = mid + 1;
else
/* 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. Memory allocation must not fail. */
+ created hash table, or NULL if memory allocation fails. */
htab_t
-htab_create (size, hash_f, eq_f, del_f)
+htab_create_alloc (size, hash_f, eq_f, del_f, alloc_f, free_f)
size_t size;
htab_hash hash_f;
htab_eq eq_f;
htab_del del_f;
+ htab_alloc alloc_f;
+ htab_free free_f;
{
htab_t result;
size = higher_prime_number (size);
- result = (htab_t) xcalloc (1, sizeof (struct htab));
- result->entries = (PTR *) xcalloc (size, sizeof (PTR));
+ result = (htab_t) (*alloc_f) (1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+ result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ if (free_f != NULL)
+ (*free_f) (result);
+ return NULL;
+ }
result->size = size;
result->hash_f = hash_f;
result->eq_f = eq_f;
result->del_f = del_f;
- result->return_allocation_failure = 0;
+ result->alloc_f = alloc_f;
+ result->free_f = free_f;
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. */
+/* These functions exist solely for backward compatibility. */
+#undef htab_create
htab_t
-htab_try_create (size, hash_f, eq_f, del_f)
+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) 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;
- }
+ return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
+}
- result->size = size;
- result->hash_f = hash_f;
- result->eq_f = eq_f;
- result->del_f = del_f;
- result->return_allocation_failure = 1;
- return result;
+htab_t
+htab_try_create (size, hash_f, eq_f, del_f)
+ size_t size;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+{
+ return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free);
}
/* This function frees all memory allocated for given hash table.
&& htab->entries[i] != DELETED_ENTRY)
(*htab->del_f) (htab->entries[i]);
- free (htab->entries);
- free (htab);
+ if (htab->free_f != NULL)
+ {
+ (*htab->free_f) (htab->entries);
+ (*htab->free_f) (htab);
+ }
}
/* This function clears all entries in the given hash table. */
hashval_t hash;
{
size_t size = htab->size;
- hashval_t hash2 = 1 + hash % (size - 2);
unsigned int index = hash % size;
+ PTR *slot = htab->entries + index;
+ hashval_t hash2;
+
+ if (*slot == EMPTY_ENTRY)
+ return slot;
+ else if (*slot == DELETED_ENTRY)
+ abort ();
+ hash2 = 1 + hash % (size - 2);
for (;;)
{
- PTR *slot = htab->entries + index;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+ slot = htab->entries + index;
if (*slot == EMPTY_ENTRY)
return slot;
else if (*slot == DELETED_ENTRY)
abort ();
-
- index += hash2;
- if (index >= size)
- index -= size;
}
}
PTR *oentries;
PTR *olimit;
PTR *p;
+ PTR *nentries;
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 *));
+ nentries = (PTR *) (*htab->alloc_f) (htab->size, sizeof (PTR *));
+ if (nentries == NULL)
+ return 0;
+ htab->entries = nentries;
htab->n_elements -= htab->n_deleted;
htab->n_deleted = 0;
}
while (p < olimit);
- free (oentries);
+ if (htab->free_f != NULL)
+ (*htab->free_f) (oentries);
return 1;
}
unsigned int index;
hashval_t hash2;
size_t size;
+ PTR entry;
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++;
first_deleted_slot = NULL;
+ entry = htab->entries[index];
+ if (entry == EMPTY_ENTRY)
+ goto empty_entry;
+ else if (entry == DELETED_ENTRY)
+ first_deleted_slot = &htab->entries[index];
+ else if ((*htab->eq_f) (entry, element))
+ return &htab->entries[index];
+
+ hash2 = 1 + hash % (size - 2);
for (;;)
{
- PTR entry = htab->entries[index];
+ htab->collisions++;
+ index += hash2;
+ if (index >= size)
+ index -= size;
+
+ entry = htab->entries[index];
if (entry == EMPTY_ENTRY)
- {
- if (insert == NO_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)
+ goto empty_entry;
+ else if (entry == DELETED_ENTRY)
{
if (!first_deleted_slot)
first_deleted_slot = &htab->entries[index];
}
- else if ((*htab->eq_f) (entry, element))
+ else if ((*htab->eq_f) (entry, element))
return &htab->entries[index];
-
- htab->collisions++;
- index += hash2;
- if (index >= size)
- index -= size;
}
+
+ empty_entry:
+ if (insert == NO_INSERT)
+ return NULL;
+
+ htab->n_elements++;
+
+ if (first_deleted_slot)
+ {
+ *first_deleted_slot = EMPTY_ENTRY;
+ return first_deleted_slot;
+ }
+
+ return &htab->entries[index];
}
/* Like htab_find_slot_with_hash, but compute the hash value from the
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;
+}