/* An expandable hash tables datatype.
- Copyright (C) 1999, 2000 Free Software Foundation, Inc.
+ Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
Contributed by Vladimir Makarov (vmakarov@cygnus.com).
This file is part of the libiberty library.
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 void htab_expand PARAMS ((htab_t));
+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
htab_hash htab_hash_pointer = hash_pointer;
htab_eq htab_eq_pointer = eq_pointer;
-/* The following function returns the nearest prime number which is
- greater than a given source number, N. */
+/* 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 (n)
unsigned long n;
{
- unsigned long i;
-
- /* Ensure we have a larger number and then force to odd. */
- n++;
- n |= 0x01;
-
- /* All odd numbers < 9 are prime. */
- if (n < 9)
- return n;
-
- /* Otherwise find the next prime using a sieve. */
-
- next:
+ /* These are primes that are near, but slightly smaller than, a
+ power of two. */
+ static const unsigned long primes[] = {
+ (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),
+ };
+
+ const unsigned long *low = &primes[0];
+ const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
+
+ while (low != high)
+ {
+ const unsigned long *mid = low + (high - low) / 2;
+ if (n > *mid)
+ low = mid + 1;
+ else
+ high = mid;
+ }
- for (i = 3; i * i <= n; i += 2)
- if (n % i == 0)
- {
- n += 2;
- goto next;
- }
+ /* If we've run out of primes, abort. */
+ if (n > *low)
+ {
+ fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
+ abort ();
+ }
- return n;
+ return *low;
}
/* Returns a hash code for P. */
/* 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, 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->alloc_f = alloc_f;
+ result->free_f = free_f;
return result;
}
+/* As above, but use the variants of alloc_f and free_f which accept
+ an extra argument. */
+
+htab_t
+htab_create_alloc_ex (size, hash_f, eq_f, del_f, alloc_arg, alloc_f,
+ free_f)
+ size_t size;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+ PTR alloc_arg;
+ htab_alloc_with_arg alloc_f;
+ htab_free_with_arg free_f;
+{
+ htab_t result;
+
+ size = higher_prime_number (size);
+ result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab));
+ if (result == NULL)
+ return NULL;
+ result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR));
+ if (result->entries == NULL)
+ {
+ if (free_f != NULL)
+ (*free_f) (alloc_arg, result);
+ return NULL;
+ }
+ result->size = size;
+ result->hash_f = hash_f;
+ result->eq_f = eq_f;
+ result->del_f = del_f;
+ result->alloc_arg = alloc_arg;
+ result->alloc_with_arg_f = alloc_f;
+ result->free_with_arg_f = free_f;
+ return result;
+}
+
+/* Update the function pointers and allocation parameter in the htab_t. */
+
+void
+htab_set_functions_ex (htab, hash_f, eq_f, del_f, alloc_arg, alloc_f, free_f)
+ htab_t htab;
+ htab_hash hash_f;
+ htab_eq eq_f;
+ htab_del del_f;
+ PTR alloc_arg;
+ htab_alloc_with_arg alloc_f;
+ htab_free_with_arg free_f;
+{
+ htab->hash_f = hash_f;
+ htab->eq_f = eq_f;
+ htab->del_f = del_f;
+ htab->alloc_arg = alloc_arg;
+ htab->alloc_with_arg_f = alloc_f;
+ htab->free_with_arg_f = free_f;
+}
+
+/* These functions exist solely for backward compatibility. */
+
+#undef htab_create
+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;
+{
+ return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
+}
+
+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.
Naturally the hash table must already exist. */
&& 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);
+ }
+ else if (htab->free_with_arg_f != NULL)
+ {
+ (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries);
+ (*htab->free_with_arg_f) (htab->alloc_arg, 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;
}
}
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
+static int
htab_expand (htab)
htab_t htab;
{
PTR *oentries;
PTR *olimit;
PTR *p;
+ PTR *nentries;
+ size_t nsize;
oentries = htab->entries;
olimit = oentries + htab->size;
- htab->size = higher_prime_number (htab->size * 2);
- htab->entries = (PTR *) xcalloc (htab->size, sizeof (PTR *));
+ /* Resize only when table after removal of unused elements is either
+ too full or too empty. */
+ if ((htab->n_elements - htab->n_deleted) * 2 > htab->size
+ || ((htab->n_elements - htab->n_deleted) * 8 < htab->size
+ && htab->size > 32))
+ nsize = higher_prime_number ((htab->n_elements - htab->n_deleted) * 2);
+ else
+ nsize = htab->size;
+
+ if (htab->alloc_with_arg_f != NULL)
+ nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
+ sizeof (PTR *));
+ else
+ nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
+ if (nentries == NULL)
+ return 0;
+ htab->entries = nentries;
+ htab->size = nsize;
htab->n_elements -= htab->n_deleted;
htab->n_deleted = 0;
}
while (p < olimit);
- free (oentries);
+ if (htab->free_f != NULL)
+ (*htab->free_f) (oentries);
+ else if (htab->free_with_arg_f != NULL)
+ (*htab->free_with_arg_f) (htab->alloc_arg, oentries);
+ return 1;
}
/* This function searches for a hash table entry equal to the given
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. */
+ 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)
unsigned int index;
hashval_t hash2;
size_t size;
+ PTR entry;
- if (insert == INSERT && htab->size * 3 <= htab->n_elements * 4)
- htab_expand (htab);
+ 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
argument. */
void
-htab_traverse (htab, callback, info)
+htab_traverse_noresize (htab, callback, info)
htab_t htab;
htab_trav callback;
PTR info;
{
- PTR *slot = htab->entries;
- PTR *limit = slot + htab->size;
+ PTR *slot;
+ PTR *limit;
+
+ slot = htab->entries;
+ limit = slot + htab->size;
do
{
while (++slot < limit);
}
+/* Like htab_traverse_noresize, but does resize the table when it is
+ too empty to improve effectivity of subsequent calls. */
+
+void
+htab_traverse (htab, callback, info)
+ htab_t htab;
+ htab_trav callback;
+ PTR info;
+{
+ if ((htab->n_elements - htab->n_deleted) * 8 < htab->size)
+ htab_expand (htab);
+
+ htab_traverse_noresize (htab, callback, info);
+}
+
/* Return the current size of given hash table. */
size_t
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;
+}
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