-/* Global assumptions:
- - ANSI C
- - a certain amount of library support, at least <stdlib.h>
- - C ints are at least 32-bits long
- */
+/* hash - hashing table processing.
-/* Things to do:
- - add a sample do_all function for listing the hash table.
- */
+ Copyright (C) 1998-2004, 2006-2007, 2009-2014 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
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ 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, see <http://www.gnu.org/licenses/>. */
+
+/* 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>
+
+#include "hash.h"
+
+#include "bitrotate.h"
+#include "xalloc-oversized.h"
+
+#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
-#include <assert.h>
-#include "near-prime.h"
-#include "hash.h"
+#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
-#ifdef USE_OBSTACK
-/* This macro assumes that there is an HT with an initialized
- HT_OBSTACK in scope. */
-# define ZALLOC(n) obstack_alloc (&(ht->ht_obstack), (n))
-#else
-# define ZALLOC(n) malloc ((n))
+struct hash_entry
+ {
+ void *data;
+ struct hash_entry *next;
+ };
+
+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 const *bucket_limit;
+ size_t n_buckets;
+ size_t n_buckets_used;
+ size_t n_entries;
+
+ /* Tuning arguments, kept in a physically separate structure. */
+ const Hash_tuning *tuning;
+
+ /* 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;
+
+ /* A linked list of freed struct hash_entry structs. */
+ struct hash_entry *free_entry_list;
+
+#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 0.8f
+#define DEFAULT_GROWTH_FACTOR 1.414f
+
+/* 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 0.0f
+#define DEFAULT_SHRINK_FACTOR 1.0f
+
+/* 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
+ };
-#define BUCKET_HEAD(ht, idx) ((ht)->hash_table[(idx)])
+/* Information and lookup. */
-static void hash_free_0 (HT *, int);
+/* The following few functions provide information about the overall hash
+ table organization: the number of entries, number of buckets and maximum
+ length of buckets. */
-static void
-hash_free_entry (HT *ht, HASH_ENT *e)
-{
- e->key = NULL;
- e->next = ht->hash_free_entry_list;
- ht->hash_free_entry_list = e;
-}
+/* 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. */
-static HASH_ENT *
-hash_allocate_entry (HT *ht)
+size_t
+hash_get_n_buckets (const Hash_table *table)
{
- HASH_ENT *new;
- if (ht->hash_free_entry_list)
- {
- new = ht->hash_free_entry_list;
- ht->hash_free_entry_list = new->next;
- }
- else
- {
- new = (HASH_ENT *) ZALLOC (sizeof (HASH_ENT));
- }
- return new;
+ return table->n_buckets;
}
-unsigned int
-hash_get_n_slots_used (const HT *ht)
+/* Return the number of slots in use (non-empty buckets). */
+
+size_t
+hash_get_n_buckets_used (const Hash_table *table)
{
- return ht->hash_n_slots_used;
+ return table->n_buckets_used;
}
-/* FIXME-comment */
+/* Return the number of active entries. */
-int
-hash_rehash (HT *ht, unsigned int new_table_size)
+size_t
+hash_get_n_entries (const Hash_table *table)
{
- HT *ht_new;
- unsigned int i;
-
- if (ht->hash_table_size <= 0 || new_table_size == 0)
- return 1;
+ return table->n_entries;
+}
- ht_new = hash_initialize (new_table_size, ht->hash_key_freer,
- ht->hash_hash, ht->hash_key_comparator);
+/* Return the length of the longest chain (bucket). */
- if (ht_new == NULL)
- return 1;
+size_t
+hash_get_max_bucket_length (const Hash_table *table)
+{
+ struct hash_entry const *bucket;
+ size_t max_bucket_length = 0;
- for (i = 0; i < ht->hash_table_size; i++)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- HASH_ENT *p = BUCKET_HEAD (ht, i);
- for ( /* empty */ ; p; p = p->next)
- {
- int failed;
- const void *already_in_table;
- already_in_table = hash_insert_if_absent (ht_new, p->key, &failed);
- assert (failed == 0 && already_in_table == 0);
- }
- }
-
- hash_free_0 (ht, 0);
+ if (bucket->data)
+ {
+ struct hash_entry const *cursor = bucket;
+ size_t bucket_length = 1;
-#ifdef TESTING
- assert (hash_table_ok (ht_new));
-#endif
- *ht = *ht_new;
- free (ht_new);
+ while (cursor = cursor->next, cursor)
+ bucket_length++;
- /* FIXME: fill in ht_new->n_slots_used and other statistics fields. */
+ if (bucket_length > max_bucket_length)
+ max_bucket_length = bucket_length;
+ }
+ }
- return 0;
+ return max_bucket_length;
}
-/* FIXME-comment */
+/* Do a mild validation of a hash table, by traversing it and checking two
+ statistics. */
-unsigned int
-hash_get_max_chain_length (HT *ht)
+bool
+hash_table_ok (const Hash_table *table)
{
- unsigned int i;
- unsigned int max_chain_length = 0;
-
- if (!ht->hash_dirty_max_chain_length)
- return ht->hash_max_chain_length;
+ struct hash_entry const *bucket;
+ size_t n_buckets_used = 0;
+ size_t n_entries = 0;
- for (i = 0; i < ht->hash_table_size; i++)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- unsigned int chain_length = 0;
- HASH_ENT *p = BUCKET_HEAD (ht, i);
- for ( /* empty */ ; p; p = p->next)
- ++chain_length;
- if (chain_length > max_chain_length)
- max_chain_length = chain_length;
+ if (bucket->data)
+ {
+ struct hash_entry const *cursor = bucket;
+
+ /* Count bucket head. */
+ n_buckets_used++;
+ n_entries++;
+
+ /* Count bucket overflow. */
+ while (cursor = cursor->next, cursor)
+ n_entries++;
+ }
}
- ht->hash_max_chain_length = max_chain_length;
- ht->hash_dirty_max_chain_length = 0;
- return ht->hash_max_chain_length;
+ if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
+ return true;
+
+ return false;
}
-unsigned int
-hash_get_n_keys (const HT *ht)
+void
+hash_print_statistics (const Hash_table *table, FILE *stream)
{
- return ht->hash_n_keys;
+ size_t n_entries = hash_get_n_entries (table);
+ size_t n_buckets = hash_get_n_buckets (table);
+ size_t n_buckets_used = hash_get_n_buckets_used (table);
+ size_t max_bucket_length = hash_get_max_bucket_length (table);
+
+ fprintf (stream, "# entries: %lu\n", (unsigned long int) n_entries);
+ fprintf (stream, "# buckets: %lu\n", (unsigned long int) n_buckets);
+ fprintf (stream, "# buckets used: %lu (%.2f%%)\n",
+ (unsigned long int) n_buckets_used,
+ (100.0 * n_buckets_used) / n_buckets);
+ fprintf (stream, "max bucket length: %lu\n",
+ (unsigned long int) max_bucket_length);
}
-unsigned int
-hash_get_table_size (const HT *ht)
+/* Hash KEY and return a pointer to the selected bucket.
+ If TABLE->hasher misbehaves, abort. */
+static struct hash_entry *
+safe_hasher (const Hash_table *table, const void *key)
{
- return ht->hash_table_size;
+ size_t n = table->hasher (key, table->n_buckets);
+ if (! (n < table->n_buckets))
+ abort ();
+ return table->bucket + n;
}
-/* TABLE_SIZE should be prime. If WHEN_TO_REHASH is positive, when
- that percentage of table entries have been used, the table is
- deemed too small; then a new, larger table (GROW_FACTOR times
- larger than the previous size) is allocated and all entries in
- the old table are rehashed into the new, larger one. The old
- table is freed. If WHEN_TO_REHASH is zero or negative, the
- table is never resized.
+/* If ENTRY matches an entry already in the hash table, return the
+ entry from the table. Otherwise, return NULL. */
- The function returns non-zero
- - if TABLE_SIZE is zero or negative
- - if EQUALITY_TESTER or HASH is null
- - if it was unable to allocate sufficient storage for the hash table
- - if WHEN_TO_REHASH is zero or negative
- Otherwise it returns zero.
+void *
+hash_lookup (const Hash_table *table, const void *entry)
+{
+ struct hash_entry const *bucket = safe_hasher (table, entry);
+ struct hash_entry const *cursor;
- FIXME: tell what happens to any existing hash table when this
- function is called (e.g. a second time). */
+ if (bucket->data == NULL)
+ return NULL;
-HT *
-hash_initialize (unsigned int table_size,
- Hash_key_freer_type key_freer,
- unsigned int (*hash) (const void *, unsigned int),
- int (*key_comparator) (const void *, const void *))
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ if (entry == cursor->data || 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, and an entry
+ may be removed only if there is no shrink threshold and the entry being
+ removed has already been passed to hash_get_next. */
+
+/* Return the first data in the table, or NULL if the table is empty. */
+
+void *
+hash_get_first (const Hash_table *table)
{
- HT *ht;
- unsigned int i;
+ struct hash_entry const *bucket;
- if (table_size <= 0)
+ if (table->n_entries == 0)
return NULL;
- if (hash == NULL || key_comparator == NULL)
- return NULL;
+ for (bucket = table->bucket; ; bucket++)
+ if (! (bucket < table->bucket_limit))
+ abort ();
+ else if (bucket->data)
+ return bucket->data;
+}
- ht = (HT *) malloc (sizeof (HT));
- if (ht == NULL)
- return NULL;
+/* 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. */
- ht->hash_table = (HASH_ENT **) malloc (table_size * sizeof (HASH_ENT *));
- if (ht->hash_table == NULL)
- return NULL;
+void *
+hash_get_next (const Hash_table *table, const void *entry)
+{
+ struct hash_entry const *bucket = safe_hasher (table, entry);
+ struct hash_entry const *cursor;
- for (i = 0; i < table_size; i++)
+ /* Find next entry in the same bucket. */
+ cursor = bucket;
+ do
{
- BUCKET_HEAD (ht, i) = NULL;
+ if (cursor->data == entry && cursor->next)
+ return cursor->next->data;
+ cursor = cursor->next;
}
+ while (cursor != NULL);
- ht->hash_free_entry_list = NULL;
- ht->hash_table_size = table_size;
- ht->hash_hash = hash;
- ht->hash_key_comparator = key_comparator;
- ht->hash_key_freer = key_freer;
- ht->hash_n_slots_used = 0;
- ht->hash_max_chain_length = 0;
- ht->hash_n_keys = 0;
- ht->hash_dirty_max_chain_length = 0;
-#ifdef USE_OBSTACK
- obstack_init (&(ht->ht_obstack));
-#endif
+ /* Find first entry in any subsequent bucket. */
+ while (++bucket < table->bucket_limit)
+ if (bucket->data)
+ return bucket->data;
- return ht;
+ /* None found. */
+ return NULL;
}
-/* This private function is used to help with insertion and deletion.
- If E does *not* compare equal to the key of any entry in the table,
- return NULL.
- When E matches an entry in the table, return a pointer to the matching
- entry. When DELETE is non-zero and E matches an entry in the table,
- unlink the matching entry. Set *CHAIN_LENGTH to the number of keys
- that have hashed to the bucket E hashed to. */
+/* 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. */
-static HASH_ENT *
-hash_find_entry (HT *ht, const void *e, unsigned int *table_idx,
- unsigned int *chain_length, int delete)
+size_t
+hash_get_entries (const Hash_table *table, void **buffer,
+ size_t buffer_size)
{
- unsigned int idx;
- int found;
- HASH_ENT *p, *prev;
-
- idx = ht->hash_hash (e, ht->hash_table_size);
- assert (idx < ht->hash_table_size);
+ size_t counter = 0;
+ struct hash_entry const *bucket;
+ struct hash_entry const *cursor;
- *table_idx = idx;
- *chain_length = 0;
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ {
+ if (bucket->data)
+ {
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ if (counter >= buffer_size)
+ return counter;
+ buffer[counter++] = cursor->data;
+ }
+ }
+ }
- prev = ht->hash_table[idx];
+ return counter;
+}
- if (prev == NULL)
- return NULL;
+/* 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. */
+
+size_t
+hash_do_for_each (const Hash_table *table, Hash_processor processor,
+ void *processor_data)
+{
+ size_t counter = 0;
+ struct hash_entry const *bucket;
+ struct hash_entry const *cursor;
- *chain_length = 1;
- if (ht->hash_key_comparator (e, prev->key) == 0)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (delete)
- ht->hash_table[idx] = prev->next;
- return prev;
+ if (bucket->data)
+ {
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ if (! processor (cursor->data, processor_data))
+ return counter;
+ counter++;
+ }
+ }
}
- p = prev->next;
- found = 0;
- while (p)
- {
- ++(*chain_length);
- if (ht->hash_key_comparator (e, p->key) == 0)
- {
- found = 1;
- break;
- }
- prev = p;
- p = p->next;
- }
+ return counter;
+}
- if (!found)
- return NULL;
+/* Allocation and clean-up. */
- assert (p != NULL);
- if (delete)
- prev->next = p->next;
+/* 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. */
- return p;
-}
+#if USE_DIFF_HASH
-/* Return non-zero if E is already in the table, zero otherwise. */
+/* 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." */
-int
-hash_query_in_table (const HT *ht, const void *e)
+size_t
+hash_string (const char *string, size_t n_buckets)
{
- unsigned int idx;
- HASH_ENT *p;
+# define HASH_ONE_CHAR(Value, Byte) \
+ ((Byte) + rotl_sz (Value, 7))
- idx = ht->hash_hash (e, ht->hash_table_size);
- assert (idx < ht->hash_table_size);
- for (p = BUCKET_HEAD (ht, idx); p != NULL; p = p->next)
- if (ht->hash_key_comparator (e, p->key) == 0)
- return 1;
- return 0;
-}
+ size_t value = 0;
+ unsigned char ch;
-void *
-hash_lookup (const HT *ht, const void *e)
-{
- unsigned int idx;
- HASH_ENT *p;
+ for (; (ch = *string); string++)
+ value = HASH_ONE_CHAR (value, ch);
+ return value % n_buckets;
- idx = ht->hash_hash (e, ht->hash_table_size);
- assert (idx < ht->hash_table_size);
- for (p = BUCKET_HEAD (ht, idx); p != NULL; p = p->next)
- if (ht->hash_key_comparator (e, p->key) == 0)
- return p->key;
- return NULL;
+# undef HASH_ONE_CHAR
}
-/* If E matches an entry already in the hash table, don't modify the
- table and return a pointer to the matched entry. If E does not
- match any item in the table, insert E and return NULL.
- If the storage required for insertion cannot be allocated
- set *FAILED to non-zero and return NULL. */
+#else /* not USE_DIFF_HASH */
-void *
-hash_insert_if_absent (HT *ht, const void *e, int *failed)
-{
- const HASH_ENT *ent;
- HASH_ENT *new;
- unsigned int idx;
- unsigned int chain_length;
-
- assert (e != NULL); /* Can't insert a NULL key. */
-
- *failed = 0;
- ent = hash_find_entry (ht, e, &idx, &chain_length, 0);
- if (ent != NULL)
- {
- /* E matches a key from an entry already in the table. */
- return ent->key;
- }
+/* 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?) */
- new = hash_allocate_entry (ht);
- if (new == NULL)
- {
- *failed = 1;
- return NULL;
- }
+size_t
+hash_string (const char *string, size_t n_buckets)
+{
+ size_t value = 0;
+ unsigned char ch;
- new->key = (void *) e;
- new->next = BUCKET_HEAD (ht, idx);
- BUCKET_HEAD (ht, idx) = new;
+ for (; (ch = *string); string++)
+ value = (value * 31 + ch) % n_buckets;
+ return value;
+}
- if (chain_length == 0)
- ++(ht->hash_n_slots_used);
+#endif /* not USE_DIFF_HASH */
- /* The insertion has just increased chain_length by 1. */
- ++chain_length;
+/* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
+ number at least equal to 11. */
- if (chain_length > ht->hash_max_chain_length)
- ht->hash_max_chain_length = chain_length;
+static bool _GL_ATTRIBUTE_CONST
+is_prime (size_t candidate)
+{
+ size_t divisor = 3;
+ size_t square = divisor * divisor;
- ++(ht->hash_n_keys);
- if ((double) ht->hash_n_keys / ht->hash_table_size > 0.80)
+ while (square < candidate && (candidate % divisor))
{
- unsigned int new_size;
- new_size = near_prime (2 * ht->hash_table_size);
- *failed = hash_rehash (ht, new_size);
+ divisor++;
+ square += 4 * divisor;
+ divisor++;
}
-#ifdef TESTING
- assert (hash_table_ok (ht));
-#endif
-
- return NULL;
+ return (candidate % divisor ? true : false);
}
-/* If E is already in the table, remove it and return a pointer to
- the just-deleted key (the user may want to deallocate its storage).
- If E is not in the table, don't modify the table and return NULL. */
+/* Round a given CANDIDATE number up to the nearest prime, and return that
+ prime. Primes lower than 10 are merely skipped. */
-void *
-hash_delete_if_present (HT *ht, const void *e)
+static size_t _GL_ATTRIBUTE_CONST
+next_prime (size_t candidate)
{
- HASH_ENT *ent;
- void *key;
- unsigned int idx;
- unsigned int chain_length;
-
- ent = hash_find_entry (ht, e, &idx, &chain_length, 1);
- if (ent == NULL)
- return NULL;
+ /* Skip small primes. */
+ if (candidate < 10)
+ candidate = 10;
- if (ent->next == NULL && chain_length == 1)
- --(ht->hash_n_slots_used);
+ /* Make it definitely odd. */
+ candidate |= 1;
- key = ent->key;
+ while (SIZE_MAX != candidate && !is_prime (candidate))
+ candidate += 2;
- --(ht->hash_n_keys);
- ht->hash_dirty_max_chain_length = 1;
- if (ent->next == NULL && chain_length < ht->hash_max_chain_length)
- ht->hash_dirty_max_chain_length = 0;
-
- hash_free_entry (ht, ent);
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
-#endif
- return key;
+ return candidate;
}
void
-hash_print_statistics (const HT *ht, FILE *stream)
+hash_reset_tuning (Hash_tuning *tuning)
{
- unsigned int n_slots_used;
- unsigned int n_keys;
- unsigned int max_chain_length;
- int err;
-
- err = hash_get_statistics (ht, &n_slots_used, &n_keys, &max_chain_length);
- assert (err == 0);
- fprintf (stream, "table size: %d\n", ht->hash_table_size);
- fprintf (stream, "# slots used: %u (%.2f%%)\n", n_slots_used,
- (100.0 * n_slots_used) / ht->hash_table_size);
- fprintf (stream, "# keys: %u\n", n_keys);
- fprintf (stream, "max chain length: %u\n", max_chain_length);
+ *tuning = default_tuning;
}
-/* If there is *NO* table (so, no meaningful stats) return non-zero
- and don't reference the argument pointers. Otherwise compute the
- performance statistics and return non-zero. */
-
-int
-hash_get_statistics (const HT *ht,
- unsigned int *n_slots_used,
- unsigned int *n_keys,
- unsigned int *max_chain_length)
+/* If the user passes a NULL hasher, we hash the raw pointer. */
+static size_t
+raw_hasher (const void *data, size_t n)
{
- unsigned int i;
+ /* When hashing unique pointers, it is often the case that they were
+ generated by malloc and thus have the property that the low-order
+ bits are 0. As this tends to give poorer performance with small
+ tables, we rotate the pointer value before performing division,
+ in an attempt to improve hash quality. */
+ size_t val = rotr_sz ((size_t) data, 3);
+ return val % n;
+}
- if (ht == NULL || ht->hash_table == NULL)
- return 1;
+/* If the user passes a NULL comparator, we use pointer comparison. */
+static bool
+raw_comparator (const void *a, const void *b)
+{
+ return a == b;
+}
- *max_chain_length = 0;
- *n_slots_used = 0;
- *n_keys = 0;
- for (i = 0; i < ht->hash_table_size; i++)
- {
- unsigned int chain_length = 0;
- HASH_ENT *p;
+/* 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. */
- p = BUCKET_HEAD (ht, i);
- if (p != NULL)
- ++(*n_slots_used);
+static bool
+check_tuning (Hash_table *table)
+{
+ const Hash_tuning *tuning = table->tuning;
+ float epsilon;
+ if (tuning == &default_tuning)
+ return true;
+
+ /* Be a bit stricter than mathematics would require, so that
+ rounding errors in size calculations do not cause allocations to
+ fail to grow or shrink as they should. The smallest allocation
+ is 11 (due to next_prime's algorithm), so an epsilon of 0.1
+ should be good enough. */
+ epsilon = 0.1f;
+
+ if (epsilon < tuning->growth_threshold
+ && tuning->growth_threshold < 1 - epsilon
+ && 1 + epsilon < tuning->growth_factor
+ && 0 <= tuning->shrink_threshold
+ && tuning->shrink_threshold + epsilon < tuning->shrink_factor
+ && tuning->shrink_factor <= 1
+ && tuning->shrink_threshold + epsilon < tuning->growth_threshold)
+ return true;
+
+ table->tuning = &default_tuning;
+ return false;
+}
- for (; p; p = p->next)
- ++chain_length;
+/* Compute the size of the bucket array for the given CANDIDATE and
+ TUNING, or return 0 if there is no possible way to allocate that
+ many entries. */
- *n_keys += chain_length;
- if (chain_length > *max_chain_length)
- *max_chain_length = chain_length;
+static size_t _GL_ATTRIBUTE_PURE
+compute_bucket_size (size_t candidate, const Hash_tuning *tuning)
+{
+ if (!tuning->is_n_buckets)
+ {
+ float new_candidate = candidate / tuning->growth_threshold;
+ if (SIZE_MAX <= new_candidate)
+ return 0;
+ candidate = new_candidate;
}
- return 0;
+ candidate = next_prime (candidate);
+ if (xalloc_oversized (candidate, sizeof (struct hash_entry *)))
+ return 0;
+ return candidate;
}
-int
-hash_table_ok (HT *ht)
+/* 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. If TUNING is
+ provided but the values requested are out of bounds or might cause
+ rounding errors, return NULL.
+
+ The user-supplied HASHER function, when not NULL, 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, when not NULL, 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,
+ but which are distinct pointers.
+
+ 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 (size_t candidate, const Hash_tuning *tuning,
+ Hash_hasher hasher, Hash_comparator comparator,
+ Hash_data_freer data_freer)
{
- int code;
- unsigned int n_slots_used;
- unsigned int n_keys;
- unsigned int max_chain_length;
+ Hash_table *table;
- if (ht == NULL || ht->hash_table == NULL)
- return 1;
+ if (hasher == NULL)
+ hasher = raw_hasher;
+ if (comparator == NULL)
+ comparator = raw_comparator;
- code = hash_get_statistics (ht, &n_slots_used, &n_keys,
- &max_chain_length);
+ table = malloc (sizeof *table);
+ if (table == NULL)
+ return NULL;
- if (code != 0
- || n_slots_used != ht->hash_n_slots_used
- || n_keys != ht->hash_n_keys
- || max_chain_length != hash_get_max_chain_length (ht))
- return 0;
+ 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. */
+ goto fail;
+ }
- return 1;
-}
+ table->n_buckets = compute_bucket_size (candidate, tuning);
+ if (!table->n_buckets)
+ goto fail;
-/* See hash_do_for_each_2 (below) for a variant. */
+ table->bucket = calloc (table->n_buckets, sizeof *table->bucket);
+ if (table->bucket == NULL)
+ goto fail;
+ table->bucket_limit = table->bucket + table->n_buckets;
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
-void
-hash_do_for_each (HT *ht, void (*f) (void *e, void *aux), void *aux)
-{
- unsigned int i;
+ table->hasher = hasher;
+ table->comparator = comparator;
+ table->data_freer = data_freer;
-#ifdef TESTING
- assert (hash_table_ok (ht));
+ table->free_entry_list = NULL;
+#if USE_OBSTACK
+ obstack_init (&table->entry_stack);
#endif
+ return table;
- if (ht->hash_table == NULL)
- return;
-
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *p;
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- (*f) (p->key, aux);
- }
- }
+ fail:
+ free (table);
+ return NULL;
}
-/* Just like hash_do_for_each, except that function F returns an int
- that can signal (when non-zero) we should return early. */
+/* 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. */
-int
-hash_do_for_each_2 (HT *ht, int (*f) (void *e, void *aux), void *aux)
+void
+hash_clear (Hash_table *table)
{
- unsigned int i;
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
-#endif
+ struct hash_entry *bucket;
- if (ht->hash_table == NULL)
- return 0;
-
- for (i = 0; i < ht->hash_table_size; i++)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- HASH_ENT *p;
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- int return_code;
-
- return_code = (*f) (p->key, aux);
- if (return_code != 0)
- return return_code;
- }
+ 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;
+ }
}
- return 0;
+
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
}
-/* For each entry in the bucket addressed by BUCKET_KEY of the hash
- table HT, invoke the function F. If F returns non-zero, stop
- iterating and return that value. Otherwise, apply F to all entries
- in the selected bucket and return zero. The AUX argument to this
- function is passed as the last argument in each invocation of F.
- The first argument to F is BUCKET_KEY, and the second is the key of
- an entry in the selected bucket. */
+/* 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. */
-int
-hash_do_for_each_in_selected_bucket (HT *ht, const void *bucket_key,
- int (*f) (const void *bucket_key,
- void *e, void *aux),
- void *aux)
+void
+hash_free (Hash_table *table)
{
- int idx;
- HASH_ENT *p;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
-#ifdef TESTING
- assert (hash_table_ok (ht));
-#endif
+ /* 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 (ht->hash_table == NULL)
- return 0;
+#if USE_OBSTACK
+
+ obstack_free (&table->entry_stack, NULL);
- idx = ht->hash_hash (bucket_key, ht->hash_table_size);
+#else
- for (p = BUCKET_HEAD (ht, idx); p != NULL; p = p->next)
+ /* Free all bucket overflowed entries. */
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- int return_code;
+ for (cursor = bucket->next; cursor; cursor = next)
+ {
+ next = cursor->next;
+ free (cursor);
+ }
+ }
- return_code = (*f) (bucket_key, p->key, aux);
- if (return_code != 0)
- return return_code;
+ /* Also reclaim the internal list of previously freed entries. */
+ for (cursor = table->free_entry_list; cursor; cursor = next)
+ {
+ next = cursor->next;
+ free (cursor);
}
- return 0;
+#endif
+
+ /* Free the remainder of the hash table structure. */
+ free (table->bucket);
+ free (table);
}
-/* Make all buckets empty, placing any chained entries on the free list.
- As with hash_free, apply the user-specified function key_freer
- (if it's not NULL) to the keys of any affected entries. */
+/* Insertion and deletion. */
-void
-hash_clear (HT *ht)
+/* Get a new hash entry for a bucket overflow, possibly by recycling a
+ previously freed one. If this is not possible, allocate a new one. */
+
+static struct hash_entry *
+allocate_entry (Hash_table *table)
{
- unsigned int i;
- HASH_ENT *p;
+ struct hash_entry *new;
- for (i = 0; i < ht->hash_table_size; i++)
+ if (table->free_entry_list)
{
- HASH_ENT *tail = NULL;
- HASH_ENT *head = BUCKET_HEAD (ht, i);
-
- /* Free any keys and get tail pointer to last entry in chain. */
- for (p = head; p; p = p->next)
- {
- if (ht->hash_key_freer != NULL)
- ht->hash_key_freer (p->key);
- p->key = NULL; /* Make sure no one tries to use this key later. */
- tail = p;
- }
- BUCKET_HEAD (ht, i) = NULL;
-
- /* If there's a chain in this bucket, tack it onto the
- beginning of the free list. */
- if (head != NULL)
- {
- assert (tail != NULL && tail->next == NULL);
- tail->next = ht->hash_free_entry_list;
- ht->hash_free_entry_list = head;
- }
+ new = table->free_entry_list;
+ table->free_entry_list = new->next;
}
- ht->hash_n_slots_used = 0;
- ht->hash_max_chain_length = 0;
- ht->hash_n_keys = 0;
- ht->hash_dirty_max_chain_length = 0;
+ else
+ {
+#if USE_OBSTACK
+ new = obstack_alloc (&table->entry_stack, sizeof *new);
+#else
+ new = malloc (sizeof *new);
+#endif
+ }
+
+ return new;
}
-/* Free all storage associated with HT that functions in this package
- have allocated. If a key_freer function has been supplied (when HT
- was created), this function applies it to the key of each entry before
- freeing that entry. */
+/* Free a hash entry which was part of some bucket overflow,
+ saving it for later recycling. */
static void
-hash_free_0 (HT *ht, int free_user_data)
+free_entry (Hash_table *table, struct hash_entry *entry)
{
- if (free_user_data && ht->hash_key_freer != NULL)
+ entry->data = NULL;
+ entry->next = table->free_entry_list;
+ table->free_entry_list = entry;
+}
+
+/* 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. */
+
+static void *
+hash_find_entry (Hash_table *table, const void *entry,
+ struct hash_entry **bucket_head, bool delete)
+{
+ struct hash_entry *bucket = safe_hasher (table, entry);
+ struct hash_entry *cursor;
+
+ *bucket_head = bucket;
+
+ /* Test for empty bucket. */
+ if (bucket->data == NULL)
+ return NULL;
+
+ /* See if the entry is the first in the bucket. */
+ if (entry == bucket->data || table->comparator (entry, bucket->data))
{
- unsigned int i;
-
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *p;
- HASH_ENT *next;
-
- for (p = BUCKET_HEAD (ht, i); p; p = next)
- {
- next = p->next;
- ht->hash_key_freer (p->key);
- }
- }
+ 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;
}
-#ifdef USE_OBSTACK
- obstack_free (&(ht->ht_obstack), NULL);
-#else
- {
- unsigned int i;
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *p;
- HASH_ENT *next;
-
- for (p = BUCKET_HEAD (ht, i); p; p = next)
- {
- next = p->next;
- free (p);
- }
- }
- }
-#endif
- ht->hash_free_entry_list = NULL;
- free (ht->hash_table);
+ /* Scan the bucket overflow. */
+ for (cursor = bucket; cursor->next; cursor = cursor->next)
+ {
+ if (entry == cursor->next->data
+ || 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_free (HT *ht)
+/* Internal helper, to move entries from SRC to DST. Both tables must
+ share the same free entry list. If SAFE, only move overflow
+ entries, saving bucket heads for later, so that no allocations will
+ occur. Return false if the free entry list is exhausted and an
+ allocation fails. */
+
+static bool
+transfer_entries (Hash_table *dst, Hash_table *src, bool safe)
{
- hash_free_0 (ht, 1);
- free (ht);
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
+ for (bucket = src->bucket; bucket < src->bucket_limit; bucket++)
+ if (bucket->data)
+ {
+ void *data;
+ struct hash_entry *new_bucket;
+
+ /* Within each bucket, transfer overflow entries first and
+ then the bucket head, to minimize memory pressure. After
+ all, the only time we might allocate is when moving the
+ bucket head, but moving overflow entries first may create
+ free entries that can be recycled by the time we finally
+ get to the bucket head. */
+ for (cursor = bucket->next; cursor; cursor = next)
+ {
+ data = cursor->data;
+ new_bucket = safe_hasher (dst, data);
+
+ next = cursor->next;
+
+ if (new_bucket->data)
+ {
+ /* 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. */
+ new_bucket->data = data;
+ dst->n_buckets_used++;
+ free_entry (dst, cursor);
+ }
+ }
+ /* Now move the bucket head. Be sure that if we fail due to
+ allocation failure that the src table is in a consistent
+ state. */
+ data = bucket->data;
+ bucket->next = NULL;
+ if (safe)
+ continue;
+ new_bucket = safe_hasher (dst, data);
+
+ if (new_bucket->data)
+ {
+ /* Allocate or recycle an entry, when moving from a bucket
+ header into a bucket overflow. */
+ struct hash_entry *new_entry = allocate_entry (dst);
+
+ if (new_entry == NULL)
+ return false;
+
+ new_entry->data = data;
+ new_entry->next = new_bucket->next;
+ new_bucket->next = new_entry;
+ }
+ else
+ {
+ /* Move from one bucket header to another. */
+ new_bucket->data = data;
+ dst->n_buckets_used++;
+ }
+ bucket->data = NULL;
+ src->n_buckets_used--;
+ }
+ return true;
}
-#ifdef TESTING
+/* 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. Return true iff the rehash succeeded. */
-void
-hash_print (const HT *ht)
+bool
+hash_rehash (Hash_table *table, size_t candidate)
{
- int i;
+ Hash_table storage;
+ Hash_table *new_table;
+ size_t new_size = compute_bucket_size (candidate, table->tuning);
+
+ if (!new_size)
+ return false;
+ if (new_size == table->n_buckets)
+ return true;
+ new_table = &storage;
+ new_table->bucket = calloc (new_size, sizeof *new_table->bucket);
+ if (new_table->bucket == NULL)
+ return false;
+ new_table->n_buckets = new_size;
+ new_table->bucket_limit = new_table->bucket + new_size;
+ new_table->n_buckets_used = 0;
+ new_table->n_entries = 0;
+ new_table->tuning = table->tuning;
+ new_table->hasher = table->hasher;
+ new_table->comparator = table->comparator;
+ new_table->data_freer = table->data_freer;
+
+ /* In order for the transfer to successfully complete, we need
+ additional overflow entries when distinct buckets in the old
+ table collide into a common bucket in the new table. The worst
+ case possible is a hasher that gives a good spread with the old
+ size, but returns a constant with the new size; if we were to
+ guarantee table->n_buckets_used-1 free entries in advance, then
+ the transfer would be guaranteed to not allocate memory.
+ However, for large tables, a guarantee of no further allocation
+ introduces a lot of extra memory pressure, all for an unlikely
+ corner case (most rehashes reduce, rather than increase, the
+ number of overflow entries needed). So, we instead ensure that
+ the transfer process can be reversed if we hit a memory
+ allocation failure mid-transfer. */
+
+ /* Merely reuse the extra old space into the new table. */
+#if USE_OBSTACK
+ new_table->entry_stack = table->entry_stack;
+#endif
+ new_table->free_entry_list = table->free_entry_list;
- for (i = 0; i < ht->hash_table_size; i++)
+ if (transfer_entries (new_table, table, false))
{
- HASH_ENT *p;
+ /* Entries transferred successfully; tie up the loose ends. */
+ 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 and table->entry_stack already hold their value. */
+ return true;
+ }
- if (BUCKET_HEAD (ht, i) != NULL)
- printf ("%d:\n", i);
+ /* We've allocated new_table->bucket (and possibly some entries),
+ exhausted the free list, and moved some but not all entries into
+ new_table. We must undo the partial move before returning
+ failure. The only way to get into this situation is if new_table
+ uses fewer buckets than the old table, so we will reclaim some
+ free entries as overflows in the new table are put back into
+ distinct buckets in the old table.
+
+ There are some pathological cases where a single pass through the
+ table requires more intermediate overflow entries than using two
+ passes. Two passes give worse cache performance and takes
+ longer, but at this point, we're already out of memory, so slow
+ and safe is better than failure. */
+ table->free_entry_list = new_table->free_entry_list;
+ if (! (transfer_entries (table, new_table, true)
+ && transfer_entries (table, new_table, false)))
+ abort ();
+ /* table->n_entries already holds its value. */
+ free (new_table->bucket);
+ return false;
+}
+
+/* Insert ENTRY into hash TABLE if there is not already a matching entry.
+
+ Return -1 upon memory allocation failure.
+ Return 1 if insertion succeeded.
+ Return 0 if there is already a matching entry in the table,
+ and in that case, if MATCHED_ENT is non-NULL, set *MATCHED_ENT
+ to that entry.
+
+ This interface is easier to use than hash_insert when you must
+ distinguish between the latter two cases. More importantly,
+ hash_insert is unusable for some types of ENTRY values. When using
+ hash_insert, the only way to distinguish those cases is to compare
+ the return value and ENTRY. That works only when you can have two
+ different ENTRY values that point to data that compares "equal". Thus,
+ when the ENTRY value is a simple scalar, you must use
+ hash_insert_if_absent. ENTRY must not be NULL. */
+int
+hash_insert_if_absent (Hash_table *table, void const *entry,
+ void const **matched_ent)
+{
+ void *data;
+ struct hash_entry *bucket;
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- char *s = (char *) p->key;
- /* FIXME */
- printf (" %s\n", s);
- }
+ /* The caller cannot insert a NULL entry, since hash_lookup returns NULL
+ to indicate "not found", and hash_find_entry uses "bucket->data == NULL"
+ to indicate an empty bucket. */
+ 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)
+ {
+ if (matched_ent)
+ *matched_ent = data;
+ return 0;
}
-}
-#endif /* TESTING */
+ /* 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. */
-void
-hash_get_key_list (const HT *ht, unsigned int bufsize, void **buf)
-{
- unsigned int i;
- unsigned int c = 0;
+ 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;
+ float candidate =
+ (tuning->is_n_buckets
+ ? (table->n_buckets * tuning->growth_factor)
+ : (table->n_buckets * tuning->growth_factor
+ * tuning->growth_threshold));
+
+ if (SIZE_MAX <= candidate)
+ return -1;
+
+ /* If the rehash fails, arrange to return NULL. */
+ if (!hash_rehash (table, candidate))
+ return -1;
+
+ /* Update the bucket we are interested in. */
+ if (hash_find_entry (table, entry, &bucket, false) != NULL)
+ abort ();
+ }
+ }
+
+ /* ENTRY is not matched, it should be inserted. */
- for (i = 0; i < ht->hash_table_size; i++)
+ if (bucket->data)
{
- HASH_ENT *p;
-
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- if (c >= bufsize)
- return;
- buf[c++] = p->key;
- }
+ struct hash_entry *new_entry = allocate_entry (table);
+
+ if (new_entry == NULL)
+ return -1;
+
+ /* 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 1;
}
+
+ /* Add ENTRY right in the bucket head. */
+
+ bucket->data = (void *) entry;
+ table->n_entries++;
+ table->n_buckets_used++;
+
+ return 1;
+}
+
+/* hash_insert0 is the deprecated name for hash_insert_if_absent.
+ . */
+int
+hash_insert0 (Hash_table *table, void const *entry, void const **matched_ent)
+{
+ return hash_insert_if_absent (table, entry, matched_ent);
+}
+
+/* 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.
+ This implementation does not support duplicate entries or insertion of
+ NULL. */
+
+void *
+hash_insert (Hash_table *table, void const *entry)
+{
+ void const *matched_ent;
+ int err = hash_insert_if_absent (table, entry, &matched_ent);
+ return (err == -1
+ ? NULL
+ : (void *) (err == 0 ? matched_ent : entry));
}
-/* Return the first key in the table. If the table is empty, return NULL. */
+/* 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. */
void *
-hash_get_first (const HT *ht)
+hash_delete (Hash_table *table, const void *entry)
{
- unsigned int idx;
- HASH_ENT *p;
+ void *data;
+ struct hash_entry *bucket;
- if (ht->hash_n_keys == 0)
+ data = hash_find_entry (table, entry, &bucket, true);
+ if (!data)
return NULL;
- for (idx = 0; idx < ht->hash_table_size; idx++)
+ table->n_entries--;
+ if (!bucket->data)
{
- if ((p = BUCKET_HEAD (ht, idx)) != NULL)
- return p->key;
+ 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;
+ size_t candidate =
+ (tuning->is_n_buckets
+ ? table->n_buckets * tuning->shrink_factor
+ : (table->n_buckets * tuning->shrink_factor
+ * tuning->growth_threshold));
+
+ if (!hash_rehash (table, candidate))
+ {
+ /* Failure to allocate memory in an attempt to
+ shrink the table is not fatal. But since memory
+ is low, we can at least be kind and free any
+ spare entries, rather than keeping them tied up
+ in the free entry list. */
+#if ! USE_OBSTACK
+ struct hash_entry *cursor = table->free_entry_list;
+ struct hash_entry *next;
+ while (cursor)
+ {
+ next = cursor->next;
+ free (cursor);
+ cursor = next;
+ }
+ table->free_entry_list = NULL;
+#endif
+ }
+ }
+ }
}
- abort ();
+
+ return data;
}
-/* Return the key in the entry following the entry whose key matches E.
- If there is the only one key in the table and that key matches E,
- return the matching key. If E is not in the table, return NULL. */
+/* Testing. */
-void *
-hash_get_next (const HT *ht, const void *e)
+#if TESTING
+
+void
+hash_print (const Hash_table *table)
{
- unsigned int idx;
- HASH_ENT *p;
+ struct hash_entry *bucket = (struct hash_entry *) table->bucket;
- idx = ht->hash_hash (e, ht->hash_table_size);
- assert (idx < ht->hash_table_size);
- for (p = BUCKET_HEAD (ht, idx); p != NULL; p = p->next)
+ for ( ; bucket < table->bucket_limit; bucket++)
{
- if (ht->hash_key_comparator (e, p->key) == 0)
- {
- if (p->next != NULL)
- {
- return p->next->key;
- }
- else
- {
- unsigned int bucket;
-
- /* E is the last or only key in the bucket chain. */
- if (ht->hash_n_keys == 1)
- {
- /* There is only one key in the table, and it matches E. */
- return p->key;
- }
- bucket = idx;
- do
- {
- idx = (idx + 1) % ht->hash_table_size;
- if ((p = BUCKET_HEAD (ht, idx)) != NULL)
- return p->key;
- }
- while (idx != bucket);
- }
- }
+ struct hash_entry *cursor;
+
+ if (bucket)
+ printf ("%lu:\n", (unsigned long int) (bucket - table->bucket));
+
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ {
+ char const *s = cursor->data;
+ /* FIXME */
+ if (s)
+ printf (" %s\n", s);
+ }
}
-
- /* E is not in the table. */
- return NULL;
}
+
+#endif /* TESTING */
projects / gnulib.git / blobdiff