-/* hash.c -- hash table maintenance
- Copyright (C) 1995 Free Software Foundation, Inc.
- Written by Greg McGary <gkm@gnu.ai.mit.edu>
+/* hash - hashing table processing.
+
+ Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 Free Software
+ Foundation, Inc.
+
+ Written by Jim Meyering, 1992.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
-*/
+ along with this program; if not, write to the Free Software Foundation,
+ Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+/* A generic hash table package. */
+
+/* Define USE_OBSTACK to 1 if you want the allocator to use obstacks instead
+ of malloc. If you change USE_OBSTACK, you have to recompile! */
-#include <config.h>
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+#if HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+
+#include <limits.h>
+#include <stdbool.h>
#include <stdio.h>
+
+#ifndef HAVE_DECL_FREE
+"this configure-time declaration test was not run"
+#endif
+#if !HAVE_DECL_FREE
+void free ();
+#endif
+
+#ifndef HAVE_DECL_MALLOC
+"this configure-time declaration test was not run"
+#endif
+#if !HAVE_DECL_MALLOC
+char *malloc ();
+#endif
+
+#if USE_OBSTACK
+# include "obstack.h"
+# ifndef obstack_chunk_alloc
+# define obstack_chunk_alloc malloc
+# endif
+# ifndef obstack_chunk_free
+# define obstack_chunk_free free
+# endif
+#endif
+
#include "hash.h"
-#include "error.h"
-#include "system.h"
-#include "xalloc.h"
-static void hash_rehash __P((struct hash_table* ht));
-static unsigned long round_up_2 __P((unsigned long rough));
+struct hash_table
+ {
+ /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
+ for a possibility of N_BUCKETS. Among those, N_BUCKETS_USED buckets
+ are not empty, there are N_ENTRIES active entries in the table. */
+ struct hash_entry *bucket;
+ struct hash_entry *bucket_limit;
+ unsigned n_buckets;
+ unsigned n_buckets_used;
+ unsigned n_entries;
-/* Implement double hashing with open addressing. The table size is
- always a power of two. The secondary (`increment') hash function
- is forced to return an odd-value, in order to be relatively prime
- to the table size. This guarantees that the increment can
- potentially hit every slot in the table during collision
- resolution. */
+ /* Tuning arguments, kept in a physicaly separate structure. */
+ const Hash_tuning *tuning;
-void *hash_deleted_item = &hash_deleted_item;
+ /* Three functions are given to `hash_initialize', see the documentation
+ block for this function. In a word, HASHER randomizes a user entry
+ into a number up from 0 up to some maximum minus 1; COMPARATOR returns
+ true if two user entries compare equally; and DATA_FREER is the cleanup
+ function for a user entry. */
+ Hash_hasher hasher;
+ Hash_comparator comparator;
+ Hash_data_freer data_freer;
-/* Force the table size to be a power of two, possibly rounding up the
- given size. */
+ /* A linked list of freed struct hash_entry structs. */
+ struct hash_entry *free_entry_list;
-void
-hash_init (struct hash_table* ht, unsigned long size,
- hash_func_t hash_1, hash_func_t hash_2, hash_cmp_func_t hash_cmp)
+#if USE_OBSTACK
+ /* Whenever obstacks are used, it is possible to allocate all overflowed
+ entries into a single stack, so they all can be freed in a single
+ operation. It is not clear if the speedup is worth the trouble. */
+ struct obstack entry_stack;
+#endif
+ };
+
+/* A hash table contains many internal entries, each holding a pointer to
+ some user provided data (also called a user entry). An entry indistinctly
+ refers to both the internal entry and its associated user entry. A user
+ entry contents may be hashed by a randomization function (the hashing
+ function, or just `hasher' for short) into a number (or `slot') between 0
+ and the current table size. At each slot position in the hash table,
+ starts a linked chain of entries for which the user data all hash to this
+ slot. A bucket is the collection of all entries hashing to the same slot.
+
+ A good `hasher' function will distribute entries rather evenly in buckets.
+ In the ideal case, the length of each bucket is roughly the number of
+ entries divided by the table size. Finding the slot for a data is usually
+ done in constant time by the `hasher', and the later finding of a precise
+ entry is linear in time with the size of the bucket. Consequently, a
+ larger hash table size (that is, a larger number of buckets) is prone to
+ yielding shorter chains, *given* the `hasher' function behaves properly.
+
+ Long buckets slow down the lookup algorithm. One might use big hash table
+ sizes in hope to reduce the average length of buckets, but this might
+ become inordinate, as unused slots in the hash table take some space. The
+ best bet is to make sure you are using a good `hasher' function (beware
+ that those are not that easy to write! :-), and to use a table size
+ larger than the actual number of entries. */
+
+/* If an insertion makes the ratio of nonempty buckets to table size larger
+ than the growth threshold (a number between 0.0 and 1.0), then increase
+ the table size by multiplying by the growth factor (a number greater than
+ 1.0). The growth threshold defaults to 0.8, and the growth factor
+ defaults to 1.414, meaning that the table will have doubled its size
+ every second time 80% of the buckets get used. */
+#define DEFAULT_GROWTH_THRESHOLD 0.8
+#define DEFAULT_GROWTH_FACTOR 1.414
+
+/* If a deletion empties a bucket and causes the ratio of used buckets to
+ table size to become smaller than the shrink threshold (a number between
+ 0.0 and 1.0), then shrink the table by multiplying by the shrink factor (a
+ number greater than the shrink threshold but smaller than 1.0). The shrink
+ threshold and factor default to 0.0 and 1.0, meaning that the table never
+ shrinks. */
+#define DEFAULT_SHRINK_THRESHOLD 0.0
+#define DEFAULT_SHRINK_FACTOR 1.0
+
+/* Use this to initialize or reset a TUNING structure to
+ some sensible values. */
+static const Hash_tuning default_tuning =
+ {
+ DEFAULT_SHRINK_THRESHOLD,
+ DEFAULT_SHRINK_FACTOR,
+ DEFAULT_GROWTH_THRESHOLD,
+ DEFAULT_GROWTH_FACTOR,
+ false
+ };
+
+/* Information and lookup. */
+
+/* The following few functions provide information about the overall hash
+ table organization: the number of entries, number of buckets and maximum
+ length of buckets. */
+
+/* Return the number of buckets in the hash table. The table size, the total
+ number of buckets (used plus unused), or the maximum number of slots, are
+ the same quantity. */
+
+unsigned
+hash_get_n_buckets (const Hash_table *table)
{
- ht->ht_size = round_up_2 (size);
- if (ht->ht_size > (128 * 1024)) /* prevent size from getting out of hand */
- ht->ht_size /= 2;
- ht->ht_vec = (void**) XCALLOC (struct token *, ht->ht_size);
- if (ht->ht_vec == 0)
- error (1, 0, _("can't allocate %ld bytes for hash table: memory exhausted"),
- ht->ht_size * sizeof(struct token *));
- ht->ht_capacity = ht->ht_size * 15 / 16; /* 93.75% loading factor */
- ht->ht_fill = 0;
- ht->ht_collisions = 0;
- ht->ht_lookups = 0;
- ht->ht_rehashes = 0;
- ht->ht_hash_1 = hash_1;
- ht->ht_hash_2 = hash_2;
- ht->ht_compare = hash_cmp;
+ return table->n_buckets;
}
-/* Load an array of items into `ht'. */
+/* Return the number of slots in use (non-empty buckets). */
-void
-hash_load (struct hash_table* ht, void *item_table, unsigned long cardinality, unsigned long size)
+unsigned
+hash_get_n_buckets_used (const Hash_table *table)
{
- char *items = (char *) item_table;
- while (cardinality--)
- {
- hash_insert (ht, items);
- items += size;
- }
+ return table->n_buckets_used;
}
-/* Returns the address of the table slot matching `key'. If `key' is
- not found, return the address of an empty slot suitable for
- inserting `key'. The caller is responsible for incrementing
- ht_fill on insertion. */
+/* Return the number of active entries. */
-void **
-hash_find_slot (struct hash_table* ht, void const *key)
+unsigned
+hash_get_n_entries (const Hash_table *table)
{
- void **slot;
- void **deleted_slot = 0;
- unsigned int hash_2 = 0;
- unsigned int hash_1 = (*ht->ht_hash_1) (key);
+ return table->n_entries;
+}
- ht->ht_lookups++;
- for (;;)
- {
- hash_1 %= ht->ht_size;
- slot = &ht->ht_vec[hash_1];
+/* Return the length of the longest chain (bucket). */
+
+unsigned
+hash_get_max_bucket_length (const Hash_table *table)
+{
+ struct hash_entry *bucket;
+ unsigned max_bucket_length = 0;
- if (*slot == 0)
- return slot;
- if (*slot == hash_deleted_item)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
{
- if (deleted_slot == 0)
- deleted_slot = slot;
+ struct hash_entry *cursor = bucket;
+ unsigned bucket_length = 1;
+
+ while (cursor = cursor->next, cursor)
+ bucket_length++;
+
+ if (bucket_length > max_bucket_length)
+ max_bucket_length = bucket_length;
}
- else
+ }
+
+ return max_bucket_length;
+}
+
+/* Do a mild validation of a hash table, by traversing it and checking two
+ statistics. */
+
+bool
+hash_table_ok (const Hash_table *table)
+{
+ struct hash_entry *bucket;
+ unsigned n_buckets_used = 0;
+ unsigned n_entries = 0;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
{
- if (key == *slot)
- return slot;
- if ((*ht->ht_compare) (key, *slot) == 0)
- return slot;
- ht->ht_collisions++;
+ struct hash_entry *cursor = bucket;
+
+ /* Count bucket head. */
+ n_buckets_used++;
+ n_entries++;
+
+ /* Count bucket overflow. */
+ while (cursor = cursor->next, cursor)
+ n_entries++;
}
- if (!hash_2)
- hash_2 = (*ht->ht_hash_2) (key) | 1;
- hash_1 += hash_2;
}
+
+ if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
+ return true;
+
+ return false;
+}
+
+void
+hash_print_statistics (const Hash_table *table, FILE *stream)
+{
+ unsigned n_entries = hash_get_n_entries (table);
+ unsigned n_buckets = hash_get_n_buckets (table);
+ unsigned n_buckets_used = hash_get_n_buckets_used (table);
+ unsigned max_bucket_length = hash_get_max_bucket_length (table);
+
+ fprintf (stream, "# entries: %u\n", n_entries);
+ fprintf (stream, "# buckets: %u\n", n_buckets);
+ fprintf (stream, "# buckets used: %u (%.2f%%)\n", n_buckets_used,
+ (100.0 * n_buckets_used) / n_buckets);
+ fprintf (stream, "max bucket length: %u\n", max_bucket_length);
}
+/* If ENTRY matches an entry already in the hash table, return the
+ entry from the table. Otherwise, return NULL. */
+
void *
-hash_find_item (struct hash_table* ht, void const *key)
+hash_lookup (const Hash_table *table, const void *entry)
{
- void **slot = hash_find_slot (ht, key);
- return ((HASH_VACANT (*slot)) ? 0 : *slot);
+ struct hash_entry *bucket
+ = table->bucket + table->hasher (entry, table->n_buckets);
+ struct hash_entry *cursor;
+
+ if (! (bucket < table->bucket_limit))
+ abort ();
+
+ if (bucket->data == NULL)
+ return NULL;
+
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ if (table->comparator (entry, cursor->data))
+ return cursor->data;
+
+ return NULL;
}
+/* Walking. */
+
+/* The functions in this page traverse the hash table and process the
+ contained entries. For the traversal to work properly, the hash table
+ should not be resized nor modified while any particular entry is being
+ processed. In particular, entries should not be added or removed. */
+
+/* Return the first data in the table, or NULL if the table is empty. */
+
void *
-hash_insert (struct hash_table* ht, void *item)
+hash_get_first (const Hash_table *table)
{
- void **slot = hash_find_slot (ht, item);
- return hash_insert_at (ht, item, slot);
+ struct hash_entry *bucket;
+
+ if (table->n_entries == 0)
+ return NULL;
+
+ for (bucket = table->bucket; ; bucket++)
+ if (! (bucket < table->bucket_limit))
+ abort ();
+ else if (bucket->data)
+ return bucket->data;
}
+/* Return the user data for the entry following ENTRY, where ENTRY has been
+ returned by a previous call to either `hash_get_first' or `hash_get_next'.
+ Return NULL if there are no more entries. */
+
void *
-hash_insert_at (struct hash_table* ht, void *item, void const *slot)
+hash_get_next (const Hash_table *table, const void *entry)
+{
+ struct hash_entry *bucket
+ = table->bucket + table->hasher (entry, table->n_buckets);
+ struct hash_entry *cursor;
+
+ if (! (bucket < table->bucket_limit))
+ abort ();
+
+ /* Find next entry in the same bucket. */
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ if (cursor->data == entry && cursor->next)
+ return cursor->next->data;
+
+ /* Find first entry in any subsequent bucket. */
+ while (++bucket < table->bucket_limit)
+ if (bucket->data)
+ return bucket->data;
+
+ /* None found. */
+ return NULL;
+}
+
+/* Fill BUFFER with pointers to active user entries in the hash table, then
+ return the number of pointers copied. Do not copy more than BUFFER_SIZE
+ pointers. */
+
+unsigned
+hash_get_entries (const Hash_table *table, void **buffer,
+ unsigned buffer_size)
{
- void *old_item = *(void **) slot;
- if (HASH_VACANT (old_item))
+ unsigned counter = 0;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- ht->ht_fill++;
- old_item = item;
+ if (bucket->data)
+ {
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ if (counter >= buffer_size)
+ return counter;
+ buffer[counter++] = cursor->data;
+ }
+ }
}
- *(void const **) slot = item;
- if (ht->ht_fill >= ht->ht_capacity)
- hash_rehash (ht);
- return old_item;
+
+ return counter;
}
-void *
-hash_delete (struct hash_table* ht, void const *item)
+/* Call a PROCESSOR function for each entry of a hash table, and return the
+ number of entries for which the processor function returned success. A
+ pointer to some PROCESSOR_DATA which will be made available to each call to
+ the processor function. The PROCESSOR accepts two arguments: the first is
+ the user entry being walked into, the second is the value of PROCESSOR_DATA
+ as received. The walking continue for as long as the PROCESSOR function
+ returns nonzero. When it returns zero, the walking is interrupted. */
+
+unsigned
+hash_do_for_each (const Hash_table *table, Hash_processor processor,
+ void *processor_data)
{
- void **slot = hash_find_slot (ht, item);
- return hash_delete_at (ht, slot);
+ unsigned counter = 0;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
+ {
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ if (!(*processor) (cursor->data, processor_data))
+ return counter;
+ counter++;
+ }
+ }
+ }
+
+ return counter;
}
-void *
-hash_delete_at (struct hash_table* ht, void const *slot)
+/* Allocation and clean-up. */
+
+/* Return a hash index for a NUL-terminated STRING between 0 and N_BUCKETS-1.
+ This is a convenience routine for constructing other hashing functions. */
+
+#if USE_DIFF_HASH
+
+/* About hashings, Paul Eggert writes to me (FP), on 1994-01-01: "Please see
+ B. J. McKenzie, R. Harries & T. Bell, Selecting a hashing algorithm,
+ Software--practice & experience 20, 2 (Feb 1990), 209-224. Good hash
+ algorithms tend to be domain-specific, so what's good for [diffutils'] io.c
+ may not be good for your application." */
+
+unsigned
+hash_string (const char *string, unsigned n_buckets)
+{
+# define ROTATE_LEFT(Value, Shift) \
+ ((Value) << (Shift) | (Value) >> ((sizeof (unsigned) * CHAR_BIT) - (Shift)))
+# define HASH_ONE_CHAR(Value, Byte) \
+ ((Byte) + ROTATE_LEFT (Value, 7))
+
+ unsigned value = 0;
+
+ for (; *string; string++)
+ value = HASH_ONE_CHAR (value, *(const unsigned char *) string);
+ return value % n_buckets;
+
+# undef ROTATE_LEFT
+# undef HASH_ONE_CHAR
+}
+
+#else /* not USE_DIFF_HASH */
+
+/* This one comes from `recode', and performs a bit better than the above as
+ per a few experiments. It is inspired from a hashing routine found in the
+ very old Cyber `snoop', itself written in typical Greg Mansfield style.
+ (By the way, what happened to this excellent man? Is he still alive?) */
+
+unsigned
+hash_string (const char *string, unsigned n_buckets)
+{
+ unsigned value = 0;
+
+ while (*string)
+ value = ((value * 31 + (int) *(const unsigned char *) string++)
+ % n_buckets);
+ return value;
+}
+
+#endif /* not USE_DIFF_HASH */
+
+/* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
+ number at least equal to 11. */
+
+static bool
+is_prime (unsigned long candidate)
{
- void *item = *(void **) slot;
- if (!HASH_VACANT (item))
+ unsigned long divisor = 3;
+ unsigned long square = divisor * divisor;
+
+ while (square < candidate && (candidate % divisor))
{
- *(void const **) slot = hash_deleted_item;
- ht->ht_fill--;
- return item;
+ divisor++;
+ square += 4 * divisor;
+ divisor++;
}
- else
- return 0;
+
+ return (candidate % divisor ? true : false);
+}
+
+/* Round a given CANDIDATE number up to the nearest prime, and return that
+ prime. Primes lower than 10 are merely skipped. */
+
+static unsigned long
+next_prime (unsigned long candidate)
+{
+ /* Skip small primes. */
+ if (candidate < 10)
+ candidate = 10;
+
+ /* Make it definitely odd. */
+ candidate |= 1;
+
+ while (!is_prime (candidate))
+ candidate += 2;
+
+ return candidate;
}
void
-hash_free_items (struct hash_table* ht)
+hash_reset_tuning (Hash_tuning *tuning)
{
- void **vec = ht->ht_vec;
- void **end = &vec[ht->ht_size];
- for (; vec < end; vec++)
+ *tuning = default_tuning;
+}
+
+/* For the given hash TABLE, check the user supplied tuning structure for
+ reasonable values, and return true if there is no gross error with it.
+ Otherwise, definitively reset the TUNING field to some acceptable default
+ in the hash table (that is, the user loses the right of further modifying
+ tuning arguments), and return false. */
+
+static bool
+check_tuning (Hash_table *table)
+{
+ const Hash_tuning *tuning = table->tuning;
+
+ if (tuning->growth_threshold > 0.0
+ && tuning->growth_threshold < 1.0
+ && tuning->growth_factor > 1.0
+ && tuning->shrink_threshold >= 0.0
+ && tuning->shrink_threshold < 1.0
+ && tuning->shrink_factor > tuning->shrink_threshold
+ && tuning->shrink_factor <= 1.0
+ && tuning->shrink_threshold < tuning->growth_threshold)
+ return true;
+
+ table->tuning = &default_tuning;
+ return false;
+}
+
+/* Allocate and return a new hash table, or NULL upon failure. The initial
+ number of buckets is automatically selected so as to _guarantee_ that you
+ may insert at least CANDIDATE different user entries before any growth of
+ the hash table size occurs. So, if have a reasonably tight a-priori upper
+ bound on the number of entries you intend to insert in the hash table, you
+ may save some table memory and insertion time, by specifying it here. If
+ the IS_N_BUCKETS field of the TUNING structure is true, the CANDIDATE
+ argument has its meaning changed to the wanted number of buckets.
+
+ TUNING points to a structure of user-supplied values, in case some fine
+ tuning is wanted over the default behavior of the hasher. If TUNING is
+ NULL, the default tuning parameters are used instead.
+
+ The user-supplied HASHER function should be provided. It accepts two
+ arguments ENTRY and TABLE_SIZE. It computes, by hashing ENTRY contents, a
+ slot number for that entry which should be in the range 0..TABLE_SIZE-1.
+ This slot number is then returned.
+
+ The user-supplied COMPARATOR function should be provided. It accepts two
+ arguments pointing to user data, it then returns true for a pair of entries
+ that compare equal, or false otherwise. This function is internally called
+ on entries which are already known to hash to the same bucket index.
+
+ The user-supplied DATA_FREER function, when not NULL, may be later called
+ with the user data as an argument, just before the entry containing the
+ data gets freed. This happens from within `hash_free' or `hash_clear'.
+ You should specify this function only if you want these functions to free
+ all of your `data' data. This is typically the case when your data is
+ simply an auxiliary struct that you have malloc'd to aggregate several
+ values. */
+
+Hash_table *
+hash_initialize (unsigned candidate, const Hash_tuning *tuning,
+ Hash_hasher hasher, Hash_comparator comparator,
+ Hash_data_freer data_freer)
+{
+ Hash_table *table;
+ struct hash_entry *bucket;
+
+ if (hasher == NULL || comparator == NULL)
+ return NULL;
+
+ table = (Hash_table *) malloc (sizeof (Hash_table));
+ if (table == NULL)
+ return NULL;
+
+ if (!tuning)
+ tuning = &default_tuning;
+ table->tuning = tuning;
+ if (!check_tuning (table))
+ {
+ /* Fail if the tuning options are invalid. This is the only occasion
+ when the user gets some feedback about it. Once the table is created,
+ if the user provides invalid tuning options, we silently revert to
+ using the defaults, and ignore further request to change the tuning
+ options. */
+ free (table);
+ return NULL;
+ }
+
+ table->n_buckets
+ = next_prime (tuning->is_n_buckets ? candidate
+ : (unsigned) (candidate / tuning->growth_threshold));
+
+ table->bucket = (struct hash_entry *)
+ malloc (table->n_buckets * sizeof (struct hash_entry));
+ if (table->bucket == NULL)
+ {
+ free (table);
+ return NULL;
+ }
+ table->bucket_limit = table->bucket + table->n_buckets;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- void *item = *vec;
- if (!HASH_VACANT (item))
- free (item);
- *vec = 0;
+ bucket->data = NULL;
+ bucket->next = NULL;
}
- ht->ht_fill = 0;
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
+
+ table->hasher = hasher;
+ table->comparator = comparator;
+ table->data_freer = data_freer;
+
+ table->free_entry_list = NULL;
+#if USE_OBSTACK
+ obstack_init (&table->entry_stack);
+#endif
+ return table;
}
+/* Make all buckets empty, placing any chained entries on the free list.
+ Apply the user-specified function data_freer (if any) to the datas of any
+ affected entries. */
+
void
-hash_delete_items (struct hash_table* ht)
+hash_clear (Hash_table *table)
{
- void **vec = ht->ht_vec;
- void **end = &vec[ht->ht_size];
- for (; vec < end; vec++)
- *vec = 0;
- ht->ht_fill = 0;
- ht->ht_collisions = 0;
- ht->ht_lookups = 0;
- ht->ht_rehashes = 0;
+ struct hash_entry *bucket;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
+ {
+ struct hash_entry *cursor;
+ struct hash_entry *next;
+
+ /* Free the bucket overflow. */
+ for (cursor = bucket->next; cursor; cursor = next)
+ {
+ if (table->data_freer)
+ (*table->data_freer) (cursor->data);
+ cursor->data = NULL;
+
+ next = cursor->next;
+ /* Relinking is done one entry at a time, as it is to be expected
+ that overflows are either rare or short. */
+ cursor->next = table->free_entry_list;
+ table->free_entry_list = cursor;
+ }
+
+ /* Free the bucket head. */
+ if (table->data_freer)
+ (*table->data_freer) (bucket->data);
+ bucket->data = NULL;
+ bucket->next = NULL;
+ }
+ }
+
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
}
+/* Reclaim all storage associated with a hash table. If a data_freer
+ function has been supplied by the user when the hash table was created,
+ this function applies it to the data of each entry before freeing that
+ entry. */
+
void
-hash_free (struct hash_table* ht, int free_items)
+hash_free (Hash_table *table)
{
- if (free_items)
- hash_free_items (ht);
- free (ht->ht_vec);
- ht->ht_vec = 0;
- ht->ht_fill = 0;
- ht->ht_capacity = 0;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
+
+ /* Call the user data_freer function. */
+ if (table->data_freer && table->n_entries)
+ {
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
+ {
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ (*table->data_freer) (cursor->data);
+ }
+ }
+ }
+ }
+
+#if USE_OBSTACK
+
+ obstack_free (&table->entry_stack, NULL);
+
+#else
+
+ /* Free all bucket overflowed entries. */
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ for (cursor = bucket->next; cursor; cursor = next)
+ {
+ next = cursor->next;
+ free (cursor);
+ }
+ }
+
+ /* Also reclaim the internal list of previously freed entries. */
+ for (cursor = table->free_entry_list; cursor; cursor = next)
+ {
+ next = cursor->next;
+ free (cursor);
+ }
+
+#endif
+
+ /* Free the remainder of the hash table structure. */
+ free (table->bucket);
+ free (table);
}
-void
-hash_map (struct hash_table *ht, hash_map_func_t map)
+/* Insertion and deletion. */
+
+/* Get a new hash entry for a bucket overflow, possibly by reclying a
+ previously freed one. If this is not possible, allocate a new one. */
+
+static struct hash_entry *
+allocate_entry (Hash_table *table)
{
- void **slot;
- void **end = &ht->ht_vec[ht->ht_size];
+ struct hash_entry *new;
- for (slot = ht->ht_vec; slot < end; slot++)
+ if (table->free_entry_list)
+ {
+ new = table->free_entry_list;
+ table->free_entry_list = new->next;
+ }
+ else
{
- if (!HASH_VACANT (*slot))
- (*map) (*slot);
+#if USE_OBSTACK
+ new = (struct hash_entry *)
+ obstack_alloc (&table->entry_stack, sizeof (struct hash_entry));
+#else
+ new = (struct hash_entry *) malloc (sizeof (struct hash_entry));
+#endif
}
+
+ return new;
}
-/* Double the size of the hash table in the event of overflow... */
+/* Free a hash entry which was part of some bucket overflow,
+ saving it for later recycling. */
static void
-hash_rehash (struct hash_table* ht)
+free_entry (Hash_table *table, struct hash_entry *entry)
{
- unsigned long old_ht_size = ht->ht_size;
- void **old_vec = ht->ht_vec;
- void **ovp;
- void **slot;
+ entry->data = NULL;
+ entry->next = table->free_entry_list;
+ table->free_entry_list = entry;
+}
- ht->ht_size *= 2;
- ht->ht_rehashes++;
- ht->ht_capacity = ht->ht_size - (ht->ht_size >> 4);
- ht->ht_vec = (void **) XCALLOC (struct token *, ht->ht_size);
+/* This private function is used to help with insertion and deletion. When
+ ENTRY matches an entry in the table, return a pointer to the corresponding
+ user data and set *BUCKET_HEAD to the head of the selected bucket.
+ Otherwise, return NULL. When DELETE is true and ENTRY matches an entry in
+ the table, unlink the matching entry. */
- for (ovp = old_vec; ovp < &old_vec[old_ht_size]; ovp++)
+static void *
+hash_find_entry (Hash_table *table, const void *entry,
+ struct hash_entry **bucket_head, bool delete)
+{
+ struct hash_entry *bucket
+ = table->bucket + table->hasher (entry, table->n_buckets);
+ struct hash_entry *cursor;
+
+ if (! (bucket < table->bucket_limit))
+ abort ();
+
+ *bucket_head = bucket;
+
+ /* Test for empty bucket. */
+ if (bucket->data == NULL)
+ return NULL;
+
+ /* See if the entry is the first in the bucket. */
+ if ((*table->comparator) (entry, bucket->data))
{
- if (*ovp == 0)
- continue;
- slot = hash_find_slot (ht, *ovp);
- *slot = *ovp;
+ void *data = bucket->data;
+
+ if (delete)
+ {
+ if (bucket->next)
+ {
+ struct hash_entry *next = bucket->next;
+
+ /* Bump the first overflow entry into the bucket head, then save
+ the previous first overflow entry for later recycling. */
+ *bucket = *next;
+ free_entry (table, next);
+ }
+ else
+ {
+ bucket->data = NULL;
+ }
+ }
+
+ return data;
}
- free (old_vec);
+
+ /* Scan the bucket overflow. */
+ for (cursor = bucket; cursor->next; cursor = cursor->next)
+ {
+ if ((*table->comparator) (entry, cursor->next->data))
+ {
+ void *data = cursor->next->data;
+
+ if (delete)
+ {
+ struct hash_entry *next = cursor->next;
+
+ /* Unlink the entry to delete, then save the freed entry for later
+ recycling. */
+ cursor->next = next->next;
+ free_entry (table, next);
+ }
+
+ return data;
+ }
+ }
+
+ /* No entry found. */
+ return NULL;
}
-void
-hash_print_stats (struct hash_table *ht, FILE *out_FILE)
+/* For an already existing hash table, change the number of buckets through
+ specifying CANDIDATE. The contents of the hash table are preserved. The
+ new number of buckets is automatically selected so as to _guarantee_ that
+ the table may receive at least CANDIDATE different user entries, including
+ those already in the table, before any other growth of the hash table size
+ occurs. If TUNING->IS_N_BUCKETS is true, then CANDIDATE specifies the
+ exact number of buckets desired. */
+
+bool
+hash_rehash (Hash_table *table, unsigned candidate)
{
- fprintf (out_FILE, _("Load=%ld/%ld=%.0f%%, "), ht->ht_fill, ht->ht_size,
- 100.0 * (double) ht->ht_fill / (double) ht->ht_size);
- fprintf (out_FILE, _("Rehash=%d, "), ht->ht_rehashes);
- fprintf (out_FILE, _("Collisions=%ld/%ld=%.0f%%"), ht->ht_collisions, ht->ht_lookups,
- (ht->ht_lookups
- ? (100.0 * (double) ht->ht_collisions / (double) ht->ht_lookups)
- : 0));
+ Hash_table *new_table;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
+
+ new_table = hash_initialize (candidate, table->tuning, table->hasher,
+ table->comparator, table->data_freer);
+ if (new_table == NULL)
+ return false;
+
+ /* Merely reuse the extra old space into the new table. */
+#if USE_OBSTACK
+ obstack_free (&new_table->entry_stack, NULL);
+ new_table->entry_stack = table->entry_stack;
+#endif
+ new_table->free_entry_list = table->free_entry_list;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ for (cursor = bucket; cursor; cursor = next)
+ {
+ void *data = cursor->data;
+ struct hash_entry *new_bucket
+ = (new_table->bucket
+ + new_table->hasher (data, new_table->n_buckets));
+
+ if (! (new_bucket < new_table->bucket_limit))
+ abort ();
+
+ next = cursor->next;
+
+ if (new_bucket->data)
+ {
+ if (cursor == bucket)
+ {
+ /* Allocate or recycle an entry, when moving from a bucket
+ header into a bucket overflow. */
+ struct hash_entry *new_entry = allocate_entry (new_table);
+
+ if (new_entry == NULL)
+ return false;
+
+ new_entry->data = data;
+ new_entry->next = new_bucket->next;
+ new_bucket->next = new_entry;
+ }
+ else
+ {
+ /* Merely relink an existing entry, when moving from a
+ bucket overflow into a bucket overflow. */
+ cursor->next = new_bucket->next;
+ new_bucket->next = cursor;
+ }
+ }
+ else
+ {
+ /* Free an existing entry, when moving from a bucket
+ overflow into a bucket header. Also take care of the
+ simple case of moving from a bucket header into a bucket
+ header. */
+ new_bucket->data = data;
+ new_table->n_buckets_used++;
+ if (cursor != bucket)
+ free_entry (new_table, cursor);
+ }
+ }
+
+ free (table->bucket);
+ table->bucket = new_table->bucket;
+ table->bucket_limit = new_table->bucket_limit;
+ table->n_buckets = new_table->n_buckets;
+ table->n_buckets_used = new_table->n_buckets_used;
+ table->free_entry_list = new_table->free_entry_list;
+ /* table->n_entries already holds its value. */
+#if USE_OBSTACK
+ table->entry_stack = new_table->entry_stack;
+#endif
+ free (new_table);
+
+ return true;
}
-/* Dump all items into a NULL-terminated vector. Use the
- user-supplied vector, or malloc one. */
+/* If ENTRY matches an entry already in the hash table, return the pointer
+ to the entry from the table. Otherwise, insert ENTRY and return ENTRY.
+ Return NULL if the storage required for insertion cannot be allocated. */
-void**
-hash_dump (struct hash_table *ht, void **vector_0, qsort_cmp_t compare)
+void *
+hash_insert (Hash_table *table, const void *entry)
{
- void **vector;
- void **slot;
- void **end = &ht->ht_vec[ht->ht_size];
-
- if (vector_0 == 0)
- vector_0 = XMALLOC (void *, ht->ht_fill + 1);
- vector = vector_0;
-
- for (slot = ht->ht_vec; slot < end; slot++)
- if (!HASH_VACANT (*slot))
- *vector++ = *slot;
- *vector = 0;
-
- if (compare)
- qsort (vector_0, ht->ht_fill, sizeof (void *), compare);
- return vector_0;
+ void *data;
+ struct hash_entry *bucket;
+
+ /* The caller cannot insert a NULL entry. */
+ if (! entry)
+ abort ();
+
+ /* If there's a matching entry already in the table, return that. */
+ if ((data = hash_find_entry (table, entry, &bucket, false)) != NULL)
+ return data;
+
+ /* ENTRY is not matched, it should be inserted. */
+
+ if (bucket->data)
+ {
+ struct hash_entry *new_entry = allocate_entry (table);
+
+ if (new_entry == NULL)
+ return NULL;
+
+ /* Add ENTRY in the overflow of the bucket. */
+
+ new_entry->data = (void *) entry;
+ new_entry->next = bucket->next;
+ bucket->next = new_entry;
+ table->n_entries++;
+ return (void *) entry;
+ }
+
+ /* Add ENTRY right in the bucket head. */
+
+ bucket->data = (void *) entry;
+ table->n_entries++;
+ table->n_buckets_used++;
+
+ /* If the growth threshold of the buckets in use has been reached, increase
+ the table size and rehash. There's no point in checking the number of
+ entries: if the hashing function is ill-conditioned, rehashing is not
+ likely to improve it. */
+
+ if (table->n_buckets_used
+ > table->tuning->growth_threshold * table->n_buckets)
+ {
+ /* Check more fully, before starting real work. If tuning arguments
+ became invalid, the second check will rely on proper defaults. */
+ check_tuning (table);
+ if (table->n_buckets_used
+ > table->tuning->growth_threshold * table->n_buckets)
+ {
+ const Hash_tuning *tuning = table->tuning;
+ unsigned candidate
+ = (unsigned) (tuning->is_n_buckets
+ ? (table->n_buckets * tuning->growth_factor)
+ : (table->n_buckets * tuning->growth_factor
+ * tuning->growth_threshold));
+
+ /* If the rehash fails, arrange to return NULL. */
+ if (!hash_rehash (table, candidate))
+ entry = NULL;
+ }
+ }
+
+ return (void *) entry;
}
-/* Round a given number up to the nearest power of 2. */
+/* If ENTRY is already in the table, remove it and return the just-deleted
+ data (the user may want to deallocate its storage). If ENTRY is not in the
+ table, don't modify the table and return NULL. */
-static unsigned long
-round_up_2 (unsigned long rough)
+void *
+hash_delete (Hash_table *table, const void *entry)
+{
+ void *data;
+ struct hash_entry *bucket;
+
+ data = hash_find_entry (table, entry, &bucket, true);
+ if (!data)
+ return NULL;
+
+ table->n_entries--;
+ if (!bucket->data)
+ {
+ table->n_buckets_used--;
+
+ /* If the shrink threshold of the buckets in use has been reached,
+ rehash into a smaller table. */
+
+ if (table->n_buckets_used
+ < table->tuning->shrink_threshold * table->n_buckets)
+ {
+ /* Check more fully, before starting real work. If tuning arguments
+ became invalid, the second check will rely on proper defaults. */
+ check_tuning (table);
+ if (table->n_buckets_used
+ < table->tuning->shrink_threshold * table->n_buckets)
+ {
+ const Hash_tuning *tuning = table->tuning;
+ unsigned candidate
+ = (unsigned) (tuning->is_n_buckets
+ ? table->n_buckets * tuning->shrink_factor
+ : (table->n_buckets * tuning->shrink_factor
+ * tuning->growth_threshold));
+
+ hash_rehash (table, candidate);
+ }
+ }
+ }
+
+ return data;
+}
+
+/* Testing. */
+
+#if TESTING
+
+void
+hash_print (const Hash_table *table)
{
- int round;
+ struct hash_entry *bucket;
- round = 1;
- while (rough)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- round <<= 1;
- rough >>= 1;
+ struct hash_entry *cursor;
+
+ if (bucket)
+ printf ("%d:\n", bucket - table->bucket);
+
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ char *s = (char *) cursor->data;
+ /* FIXME */
+ if (s)
+ printf (" %s\n", s);
+ }
}
- return round;
}
+
+#endif /* TESTING */
projects / bison.git / blobdiff