+/* hash - hashing table processing.
+ Copyright (C) 1998 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 2, 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, 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! */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+#if HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#if HAVE_STDBOOL_H
+# include <stdbool.h>
+#else
+typedef enum {false = 0, true = 1} bool;
+#endif
#include <stdio.h>
-#include <stdlib.h>
#include <assert.h>
-#include "hash.h"
+#if !HAVE_DECL_FREE
+void free ();
+#endif
+#if !HAVE_DECL_MALLOC
+char *malloc ();
+#endif
-#ifdef USE_OBSTACK
-# define ZALLOC(Ht, N) obstack_alloc (&(ht->ht_obstack), (N))
-#else
-# define ZALLOC(Ht, N) malloc ((N))
+#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
-#define BUCKET_HEAD(ht, idx) ((ht)->hash_table[(idx)])
+#include "hash.h"
-static int
-is_prime (candidate)
- unsigned long candidate;
-{
- /* No even number and none less than 10 will be passed here. */
- unsigned long divn = 3;
- unsigned long sq = divn * divn;
+/* An 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 randomisation 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 at constant speed by the `hasher', and the later finding of a precise
+ entry is linear in time with the size of the bucket. Consequently, a
+ bigger hash table size (that is, a bigger number of buckets) is prone to
+ yielding shorter buckets, *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 at
+ least bigger than the actual number of entries.
+
+ Currently, whenever the addition of an entry gets 80% of buckets to be
+ non-empty, this package automatically doubles the number of buckets. */
+\f
+/* Information and lookup. */
+
+/* The following few functions provide information about the overall hash
+ table organisation: 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. */
- while (sq < candidate && (candidate % divn))
- {
- divn++;
- sq += 4 * divn;
- divn++;
- }
-
- return (candidate % divn);
+unsigned int
+hash_get_n_buckets (const Hash_table *table)
+{
+ return table->n_buckets;
}
-/* Round a given number up to the nearest prime. */
+/* Return the number of slots in use (non-empty buckets). */
-static unsigned long
-next_prime (candidate)
- unsigned long candidate;
+unsigned int
+hash_get_n_buckets_used (const Hash_table *table)
{
- /* Make it definitely odd. */
- candidate |= 1;
+ return table->n_buckets_used;
+}
- while (!is_prime (candidate))
- candidate += 2;
+/* Return the number of active entries. */
- return candidate;
+unsigned int
+hash_get_n_entries (const Hash_table *table)
+{
+ return table->n_entries;
}
-static void
-hash_free_entry (HT *ht, HASH_ENT *e)
+/* Return the length of the most lenghty chain (bucket). */
+
+unsigned int
+hash_get_max_bucket_length (const Hash_table *table)
{
- e->key = NULL;
- e->next = ht->hash_free_entry_list;
- ht->hash_free_entry_list = e;
+ struct hash_entry *bucket;
+ unsigned int max_bucket_length = 0;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ {
+ struct hash_entry *cursor = bucket;
+ unsigned int bucket_length = 1;
+
+ while (cursor = cursor->next, cursor)
+ bucket_length++;
+
+ if (bucket_length > max_bucket_length)
+ max_bucket_length = bucket_length;
+ }
+
+ return max_bucket_length;
}
-static HASH_ENT *
-hash_allocate_entry (HT *ht)
+/* Do a mild validation of an hash table, by traversing it and checking two
+ statistics. */
+
+bool
+hash_table_ok (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 (ht, sizeof (HASH_ENT));
- }
- return new;
+ struct hash_entry *bucket;
+ unsigned int n_buckets_used = 0;
+ unsigned int n_entries = 0;
+
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ {
+ struct hash_entry *cursor = bucket;
+
+ /* Count bucket head. */
+ n_buckets_used++;
+ n_entries++;
+
+ /* Count bucket overflow. */
+ while (cursor = cursor->next, cursor)
+ n_entries++;
+ }
+
+ if (n_buckets_used == table->n_buckets_used && n_entries == table->n_entries)
+ return true;
+
+ return false;
}
-unsigned int
-hash_get_n_slots_used (const HT *ht)
+void
+hash_print_statistics (const Hash_table *table, FILE *stream)
{
- return ht->hash_n_slots_used;
+ unsigned int n_entries = hash_get_n_entries (table);
+ unsigned int n_buckets = hash_get_n_buckets (table);
+ unsigned int n_buckets_used = hash_get_n_buckets_used (table);
+ unsigned int 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);
}
-/* 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. */
+/* Return the user entry from the hash table, if some entry in the hash table
+ compares equally with ENTRY, or NULL otherwise. */
-static void
-hash_free_0 (HT *ht, int free_user_data)
+void *
+hash_lookup (const Hash_table *table, const void *entry)
{
- if (free_user_data && ht->hash_key_freer != NULL)
- {
- unsigned int i;
+ struct hash_entry *bucket
+ = table->bucket + table->hasher (entry, table->n_buckets);
+ struct hash_entry *cursor;
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *p;
- HASH_ENT *next;
+ assert (bucket < table->bucket_limit);
- for (p = BUCKET_HEAD (ht, i); p; p = next)
- {
- next = p->next;
- ht->hash_key_freer (p->key);
- }
- }
- }
+ if (bucket->data == NULL)
+ return NULL;
-#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 (cursor = bucket; cursor; cursor = cursor->next)
+ if (table->comparator (entry, cursor->data))
+ return cursor->data;
- 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);
+ return NULL;
}
+\f
+/* 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. */
-/* FIXME-comment */
+/* Return the first data in the table, or NULL if the table is empty. */
-int
-hash_rehash (HT *ht, unsigned int new_table_size)
+void *
+hash_get_first (const Hash_table *table)
{
- HT *ht_new;
- unsigned int i;
+ struct hash_entry *bucket;
- if (ht->hash_table_size <= 0 || new_table_size == 0)
- return 1;
+ if (table->n_entries == 0)
+ return NULL;
- ht_new = hash_initialize (new_table_size, ht->hash_key_freer,
- ht->hash_hash, ht->hash_key_comparator);
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ return bucket->data;
- if (ht_new == NULL)
- return 1;
+ abort ();
+}
- for (i = 0; i < ht->hash_table_size; i++)
- {
- 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);
- }
- }
+/* 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 is no more entries. */
+
+void *
+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;
- hash_free_0 (ht, 0);
+ assert (bucket < table->bucket_limit);
-#ifdef TESTING
- assert (hash_table_ok (ht_new));
-#endif
- *ht = *ht_new;
- free (ht_new);
+ /* Find next entry in the same bucket. */
+ for (cursor = bucket; cursor; cursor = cursor->next)
+ if (cursor->data == entry && cursor->next)
+ return cursor->next->data;
- /* FIXME: fill in ht_new->n_slots_used and other statistics fields. */
+ /* Find first entry in any subsequent bucket. */
+ for (; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ return bucket->data;
- return 0;
+ /* None found. */
+ return NULL;
}
-/* FIXME-comment */
+/* 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 int
-hash_get_max_chain_length (HT *ht)
+hash_get_entries (const Hash_table *table, void **buffer, unsigned int buffer_size)
{
- unsigned int i;
- unsigned int max_chain_length = 0;
+ unsigned int counter = 0;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
- if (!ht->hash_dirty_max_chain_length)
- return ht->hash_max_chain_length;
-
- for (i = 0; i < ht->hash_table_size; i++)
- {
- 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;
- }
+ 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;
+ }
- ht->hash_max_chain_length = max_chain_length;
- ht->hash_dirty_max_chain_length = 0;
- return ht->hash_max_chain_length;
+ return counter;
}
+/* Call a PROCESSOR function for each entry of an 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 int
-hash_get_n_keys (const HT *ht)
+hash_do_for_each (const Hash_table *table, Hash_processor processor,
+ void *processor_data)
{
- return ht->hash_n_keys;
+ unsigned int 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;
}
+\f
+/* 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 int
-hash_get_table_size (const HT *ht)
+hash_string (const char *string, unsigned int n_buckets)
{
- return ht->hash_table_size;
+# ifndef CHAR_BIT
+# define CHAR_BIT 8
+# endif
+# 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
}
-/* CANDIDATE_TABLE_SIZE need not be prime. If WHEN_TO_REHASH (FIXME: add
- this parameter) is positive, when that percentage of table entries have
- been used, the table size is increased; then a new, larger table
- (GROW_FACTOR (FIXME: maybe add this parameter) 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.
-
- The function returns non-zero
- - if CANDIDATE_TABLE_SIZE is zero or negative
- - if KEY_COMPARATOR 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. */
-
-HT *
-hash_initialize (unsigned int candidate_table_size,
- Hash_key_freer_type key_freer,
- unsigned int (*hash) (const void *, unsigned int),
- int (*key_comparator) (const void *, const void *))
+#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 int
+hash_string (const char *string, unsigned int n_buckets)
{
- HT *ht;
- unsigned int i;
- unsigned int table_size;
+ unsigned value = 0;
- if (candidate_table_size <= 0)
- return NULL;
+ while (*string)
+ value = ((value * 31 + (int) *(const unsigned char *) string++)
+ % n_buckets);
+ return value;
+}
- if (hash == NULL || key_comparator == NULL)
- return NULL;
+#endif /* not USE_DIFF_HASH */
- ht = (HT *) malloc (sizeof (HT));
- if (ht == NULL)
- return NULL;
+/* Return true if CANDIDATE is a prime number. CANDIDATE should be an odd
+ number at least equal to 11. */
- table_size = next_prime (candidate_table_size);
- ht->hash_table = (HASH_ENT **) malloc (table_size * sizeof (HASH_ENT *));
- if (ht->hash_table == NULL)
- return NULL;
+static bool
+is_prime (candidate)
+ unsigned long candidate;
+{
+ unsigned long divisor = 3;
+ unsigned long square = divisor * divisor;
- for (i = 0; i < table_size; i++)
+ while (square < candidate && (candidate % divisor))
{
- BUCKET_HEAD (ht, i) = NULL;
+ divisor++;
+ square += 4 * divisor;
+ divisor++;
}
- 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
-
- return ht;
+ return candidate % divisor != 0;
}
-/* 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. */
-
-static HASH_ENT *
-hash_find_entry (HT *ht, const void *e, unsigned int *table_idx,
- unsigned int *chain_length, int delete)
+/* Round a given CANDIDATE number up to the nearest prime, and return that
+ prime. CANDIDATE should be at least equal to 10. */
+
+static unsigned long
+next_prime (candidate)
+ unsigned long candidate;
{
- unsigned int idx;
- int found;
- HASH_ENT *p, *prev;
+ /* Make it definitely odd. */
+ candidate |= 1;
+
+ while (!is_prime (candidate))
+ candidate += 2;
+
+ return candidate;
+}
+
+/* Allocate and return a new hash table, or NULL if an error is met. The
+ initial number of buckets would be at least CANDIDATE (which need not be prime).
+
+ If DATA_FREER is not NULL, this function may be later called with the data as
+ an argument, just before they entry containing the data gets freed. The
+ HASHER function should be supplied, and FIXME. The COMPARATOR function
+ should also be supplied, and FIXME. */
- idx = ht->hash_hash (e, ht->hash_table_size);
- assert (idx < ht->hash_table_size);
+ /* User-supplied function for freeing datas. It is specified in
+ hash_initialize. If non-null, it is used by hash_free and hash_clear.
+ You should specify `free' here only if you want these functions to free
+ all of your `data' data. This is typically the case when your data is
+ simply an auxilliary struct that you have malloc'd to aggregate several
+ values. */
- *table_idx = idx;
- *chain_length = 0;
+ /* User-supplied hash function that hashes entry ENTRY to an integer in
+ the range 0..TABLE_SIZE-1. */
- prev = ht->hash_table[idx];
+ /* User-supplied function that determines whether a new entry is unique by
+ comparing the new entry to entries that hashed to the same bucket
+ index. It should return zero for a pair of entries that compare equal,
+ non-zero otherwise. */
- if (prev == NULL)
+Hash_table *
+hash_initialize (unsigned int candidate, 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;
- *chain_length = 1;
- if (ht->hash_key_comparator (e, prev->key) == 0)
+ table->n_buckets = next_prime (candidate < 10 ? 10 : candidate);
+ table->bucket = (struct hash_entry *)
+ malloc (table->n_buckets * sizeof (struct hash_entry));
+ if (table->bucket == NULL)
{
- if (delete)
- ht->hash_table[idx] = prev->next;
- return prev;
+ free (table);
+ return NULL;
}
+ table->bucket_limit = table->bucket + table->n_buckets;
- p = prev->next;
- found = 0;
- while (p)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- ++(*chain_length);
- if (ht->hash_key_comparator (e, p->key) == 0)
- {
- found = 1;
- break;
- }
- prev = p;
- p = p->next;
+ bucket->data = NULL;
+ bucket->next = NULL;
}
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
- if (!found)
- return NULL;
-
- assert (p != NULL);
- if (delete)
- prev->next = p->next;
+ table->hasher = hasher;
+ table->comparator = comparator;
+ table->data_freer = data_freer;
- return p;
+ table->free_entry_list = NULL;
+#if USE_OBSTACK
+ obstack_init (&table->entry_stack);
+#endif
+ return table;
}
-/* Return non-zero if E is already in the table, zero otherwise. */
+/* 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_query_in_table (const HT *ht, const void *e)
+void
+hash_clear (Hash_table *table)
{
- unsigned int idx;
- HASH_ENT *p;
-
- 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;
-}
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
-void *
-hash_lookup (const HT *ht, const void *e)
-{
- unsigned int idx;
- HASH_ENT *p;
-
- 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;
-}
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ {
+ /* Free the bucket overflow. */
+ for (cursor = bucket->next; cursor; cursor = cursor->next)
+ {
+ if (table->data_freer)
+ (*table->data_freer) (cursor->data);
+ cursor->data = NULL;
+
+ /* 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;
+ }
-/* 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. */
+ /* Free the bucket head. */
+ if (table->data_freer)
+ (*table->data_freer) (bucket->data);
+ bucket->data = NULL;
+ bucket->next = NULL;
+ }
-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;
+ table->n_buckets_used = 0;
+ table->n_entries = 0;
+}
- assert (e != NULL); /* Can't insert a NULL key. */
+/* Reclaim all storage associated with an 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. */
- *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;
- }
+void
+hash_free (Hash_table *table)
+{
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
- new = hash_allocate_entry (ht);
- if (new == NULL)
- {
- *failed = 1;
- return NULL;
- }
+ /* 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);
- new->key = (void *) e;
- new->next = BUCKET_HEAD (ht, idx);
- BUCKET_HEAD (ht, idx) = new;
+#if USE_OBSTACK
- if (chain_length == 0)
- ++(ht->hash_n_slots_used);
+ obstack_free (&table->entry_stack, NULL);
- /* The insertion has just increased chain_length by 1. */
- ++chain_length;
+#else
- if (chain_length > ht->hash_max_chain_length)
- ht->hash_max_chain_length = chain_length;
+ /* 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);
+ }
- ++(ht->hash_n_keys);
- if ((double) ht->hash_n_keys / ht->hash_table_size > 0.80)
+ /* Also reclaim the internal list of previously freed entries. */
+ for (cursor = table->free_entry_list; cursor; cursor = next)
{
- unsigned int new_size;
- new_size = next_prime (2 * ht->hash_table_size + 1);
- *failed = hash_rehash (ht, new_size);
+ next = cursor->next;
+ free (cursor);
}
-#ifdef TESTING
- assert (hash_table_ok (ht));
#endif
- return NULL;
+ /* Free the remainder of the hash table structure. */
+ free (table->bucket);
+ free (table);
}
+\f
+/* Insertion and deletion. */
-/* 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. */
+/* 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. */
-void *
-hash_delete_if_present (HT *ht, const void *e)
+static struct hash_entry *
+allocate_entry (Hash_table *table)
{
- 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;
-
- if (ent->next == NULL && chain_length == 1)
- --(ht->hash_n_slots_used);
-
- key = ent->key;
-
- --(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;
+ struct hash_entry *new;
- hash_free_entry (ht, ent);
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
+ if (table->free_entry_list)
+ {
+ new = table->free_entry_list;
+ table->free_entry_list = new->next;
+ }
+ else
+ {
+#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 key;
+ }
+
+ return new;
}
-void
-hash_print_statistics (const HT *ht, FILE *stream)
+/* Free a hash entry which was part of some bucket overflow,
+ saving it for later recycling. */
+
+static void
+free_entry (Hash_table *table, struct hash_entry *entry)
{
- 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);
+ entry->data = NULL;
+ entry->next = table->free_entry_list;
+ table->free_entry_list = entry;
}
-/* 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. */
+/* 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. */
-int
-hash_get_statistics (const HT *ht,
- unsigned int *n_slots_used,
- unsigned int *n_keys,
- unsigned int *max_chain_length)
+static void *
+hash_find_entry (Hash_table *table, const void *entry,
+ struct hash_entry **bucket_head, bool delete)
{
- unsigned int i;
+ struct hash_entry *bucket
+ = table->bucket + table->hasher (entry, table->n_buckets);
+ struct hash_entry *cursor;
- if (ht == NULL || ht->hash_table == NULL)
- return 1;
+ assert (bucket < table->bucket_limit);
+ *bucket_head = bucket;
- *max_chain_length = 0;
- *n_slots_used = 0;
- *n_keys = 0;
+ /* Test for empty bucket. */
+ if (bucket->data == NULL)
+ return NULL;
- for (i = 0; i < ht->hash_table_size; i++)
+ /* Check if then entry is found as the bucket head. */
+ if ((*table->comparator) (entry, bucket->data))
{
- unsigned int chain_length = 0;
- HASH_ENT *p;
+ void *data = bucket->data;
- p = BUCKET_HEAD (ht, i);
- if (p != NULL)
- ++(*n_slots_used);
+ if (delete)
+ if (bucket->next)
+ {
+ struct hash_entry *next = bucket->next;
- for (; p; p = p->next)
- ++chain_length;
+ /* 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;
- *n_keys += chain_length;
- if (chain_length > *max_chain_length)
- *max_chain_length = chain_length;
+ return data;
}
- return 0;
-}
-int
-hash_table_ok (HT *ht)
-{
- int code;
- unsigned int n_slots_used;
- unsigned int n_keys;
- unsigned int max_chain_length;
+ /* 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 (ht == NULL || ht->hash_table == NULL)
- return 1;
+ if (delete)
+ {
+ struct hash_entry *next = cursor->next;
- code = hash_get_statistics (ht, &n_slots_used, &n_keys,
- &max_chain_length);
+ /* Unlink the entry to delete, then save the freed entry for later
+ recycling. */
+ cursor->next = next->next;
+ free_entry (table, next);
+ }
- 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;
+ return data;
+ }
- return 1;
+ /* No entry found. */
+ return NULL;
}
-/* See hash_do_for_each_2 (below) for a variant. */
+/* For an already existing hash table, change the number of buckets and make
+ it NEW_TABLE_SIZE. The contents of the hash table are preserved. */
-void
-hash_do_for_each (HT *ht, void (*f) (void *e, void *aux), void *aux)
+bool
+hash_rehash (Hash_table *table, unsigned int new_n_buckets)
{
- unsigned int i;
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
+ Hash_table *new_table;
+ struct hash_entry *bucket;
+ struct hash_entry *cursor;
+ struct hash_entry *next;
+
+ if (table->n_buckets <= 0 || new_n_buckets == 0)
+ return false;
+
+ new_table = hash_initialize (new_n_buckets, 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;
- 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)
+ for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
+ if (bucket->data)
+ for (cursor = bucket; cursor; cursor = next)
{
- (*f) (p->key, aux);
- }
- }
-}
+ void *data = cursor->data;
+ struct hash_entry *new_bucket
+ = new_table->bucket + new_table->hasher (data, new_n_buckets);
-/* Just like hash_do_for_each, except that function F returns an int
- that can signal (when non-zero) we should return early. */
+ assert (new_bucket < new_table->bucket_limit);
-int
-hash_do_for_each_2 (HT *ht, int (*f) (void *e, void *aux), void *aux)
-{
- unsigned int i;
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
-#endif
+ /* Free overflow entries as soon as possible, moving them from the
+ old hash table into the new one, as they may be needed now. */
+ next = cursor->next;
+ if (cursor != bucket)
+ free_entry (new_table, cursor);
- if (ht->hash_table == NULL)
- return 0;
+ /* Insert the entry into the new hash table. */
+ if (new_bucket->data)
+ {
+ struct hash_entry *new_entry = allocate_entry (new_table);
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *p;
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- int return_code;
+ if (new_entry == NULL)
+ return false;
- return_code = (*f) (p->key, aux);
- if (return_code != 0)
- return return_code;
+ new_entry->data = data;
+ new_entry->next = new_bucket->next;
+ new_bucket->next = new_entry;
+ }
+ else
+ {
+ new_bucket->data = data;
+ new_table->n_buckets_used++;
+ }
}
- }
- return 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. */
-
-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)
-{
- int idx;
- HASH_ENT *p;
-
-#ifdef TESTING
- assert (hash_table_ok (ht));
+ 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->n_entries already holds its value. */
+#if USE_OBSTACK
+ table->entry_stack = new_table->entry_stack;
#endif
+ free (new_table);
- if (ht->hash_table == NULL)
- return 0;
-
- idx = ht->hash_hash (bucket_key, ht->hash_table_size);
-
- for (p = BUCKET_HEAD (ht, idx); p != NULL; p = p->next)
- {
- int return_code;
-
- return_code = (*f) (bucket_key, p->key, aux);
- if (return_code != 0)
- return return_code;
- }
-
- return 0;
+ return true;
}
-/* 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. */
+/* If ENTRY matches an entry already in the hash table, don't modify the table
+ and return the matched entry. Otherwise, insert ENTRY and return NULL.
+ *DONE is set to true in all cases, unless the storage required for
+ insertion cannot be allocated. */
-void
-hash_clear (HT *ht)
+void *
+hash_insert (Hash_table *table, const void *entry, bool *done)
{
- unsigned int i;
- HASH_ENT *p;
+ void *data;
+ struct hash_entry *bucket;
- for (i = 0; i < ht->hash_table_size; i++)
- {
- HASH_ENT *tail = NULL;
- HASH_ENT *head = BUCKET_HEAD (ht, i);
+ assert (entry); /* cannot insert a NULL data */
- /* 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;
- }
+ if (data = hash_find_entry (table, entry, &bucket, false), data)
+ {
+ *done = true;
+ return data;
}
- ht->hash_n_slots_used = 0;
- ht->hash_max_chain_length = 0;
- ht->hash_n_keys = 0;
- ht->hash_dirty_max_chain_length = 0;
-}
-
-void
-hash_free (HT *ht)
-{
- hash_free_0 (ht, 1);
- free (ht);
-}
-#ifdef TESTING
+ /* ENTRY is not matched, it should be inserted. */
-void
-hash_print (const HT *ht)
-{
- int i;
+ table->n_entries++;
- for (i = 0; i < ht->hash_table_size; i++)
+ if (bucket->data)
{
- HASH_ENT *p;
-
- if (BUCKET_HEAD (ht, i) != NULL)
- printf ("%d:\n", i);
+ struct hash_entry *new_entry = allocate_entry (table);
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
+ if (new_entry == NULL)
{
- char *s = (char *) p->key;
- /* FIXME */
- printf (" %s\n", s);
+ *done = false;
+ return NULL;
}
+
+ /* Add ENTRY in the overflow of the bucket. */
+
+ new_entry->data = (void *) entry;
+ new_entry->next = bucket->next;
+ bucket->next = new_entry;
+ *done = true;
+ return NULL;
}
-}
-#endif /* TESTING */
+ /* Add ENTRY right in the bucket head. */
-void
-hash_get_key_list (const HT *ht, unsigned int bufsize, void **buf)
-{
- unsigned int i;
- unsigned int c = 0;
+ bucket->data = (void *) entry;
+ table->n_buckets_used++;
- for (i = 0; i < ht->hash_table_size; i++)
+ /* If more than 80% of the buckets are in use, rehash the table two
+ times bigger. It's no real use checking the number of entries, as if
+ the hashing function is ill-conditioned, rehashing is not likely to
+ improve it. */
+
+ if (5 * table->n_buckets_used > 4 * table->n_buckets)
{
- HASH_ENT *p;
+ unsigned int new_n_buckets = next_prime (2 * table->n_buckets + 1);
- for (p = BUCKET_HEAD (ht, i); p; p = p->next)
- {
- if (c >= bufsize)
- return;
- buf[c++] = p->key;
- }
+ *done = hash_rehash (table, new_n_buckets);
+ return NULL;
}
+
+ *done = true;
+ return NULL;
}
-/* 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)
+ if (data = hash_find_entry (table, entry, &bucket, true), !data)
return NULL;
- for (idx = 0; idx < ht->hash_table_size; idx++)
- {
- if ((p = BUCKET_HEAD (ht, idx)) != NULL)
- return p->key;
- }
- abort ();
+ if (!bucket->data)
+ table->n_buckets_used--;
+ table->n_entries--;
+
+ return data;
}
+\f
+/* Testing. */
-/* 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. */
+#if TESTING
-void *
-hash_get_next (const HT *ht, const void *e)
+void
+hash_print (const Hash_table *table)
{
- unsigned int idx;
- HASH_ENT *p;
+ struct hash_entry *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; bucket < table->bucket_limit; bucket++)
{
- if (ht->hash_key_comparator (e, p->key) == 0)
+ struct hash_entry *cursor;
+
+ if (bucket)
+ printf ("%d:\n", slot);
+
+ for (cursor = bucket; cursor; cursor = cursor->next)
{
- 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);
- }
+ char *s = (char *) cursor->data;
+ /* FIXME */
+ printf (" %s\n", s);
}
}
-
- /* E is not in the table. */
- return NULL;
}
+
+#endif /* TESTING */
projects / gnulib.git / commitdiff