X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=lib%2Fhash.c;fp=lib%2Fhash.c;h=0000000000000000000000000000000000000000;hb=22f1eb8bc17e5be72dd23d42d6aaa60196ac22e6;hp=7d76d45f71250c5d6b92a816fc69b1e23c4ce5a3;hpb=00fa13ff3f2d5b6e2a94c5e948c38616ff7ad37a;p=debian%2Ftar
diff --git a/lib/hash.c b/lib/hash.c
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--- a/lib/hash.c
+++ /dev/null
@@ -1,1049 +0,0 @@
-/* hash - hashing table processing.
-
- Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006, 2007 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 . */
-
-/* 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
-
-#include "hash.h"
-#include "xalloc.h"
-
-#include
-#include
-#include
-
-#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
-
-#ifndef SIZE_MAX
-# define SIZE_MAX ((size_t) -1)
-#endif
-
-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 physicaly 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 0.8
-#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. */
-
-size_t
-hash_get_n_buckets (const Hash_table *table)
-{
- return table->n_buckets;
-}
-
-/* Return the number of slots in use (non-empty buckets). */
-
-size_t
-hash_get_n_buckets_used (const Hash_table *table)
-{
- return table->n_buckets_used;
-}
-
-/* Return the number of active entries. */
-
-size_t
-hash_get_n_entries (const Hash_table *table)
-{
- return table->n_entries;
-}
-
-/* Return the length of the longest chain (bucket). */
-
-size_t
-hash_get_max_bucket_length (const Hash_table *table)
-{
- struct hash_entry const *bucket;
- size_t max_bucket_length = 0;
-
- for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
- {
- if (bucket->data)
- {
- struct hash_entry const *cursor = bucket;
- size_t 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;
-}
-
-/* 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 const *bucket;
- size_t n_buckets_used = 0;
- size_t n_entries = 0;
-
- for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
- {
- 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++;
- }
- }
-
- 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)
-{
- 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);
-}
-
-/* If ENTRY matches an entry already in the hash table, return the
- entry from the table. Otherwise, return NULL. */
-
-void *
-hash_lookup (const Hash_table *table, const void *entry)
-{
- struct hash_entry const *bucket
- = table->bucket + table->hasher (entry, table->n_buckets);
- struct hash_entry const *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_get_first (const Hash_table *table)
-{
- struct hash_entry const *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_get_next (const Hash_table *table, const void *entry)
-{
- struct hash_entry const *bucket
- = table->bucket + table->hasher (entry, table->n_buckets);
- struct hash_entry const *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. */
-
-size_t
-hash_get_entries (const Hash_table *table, void **buffer,
- size_t buffer_size)
-{
- size_t counter = 0;
- struct hash_entry const *bucket;
- struct hash_entry const *cursor;
-
- 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;
- }
- }
- }
-
- return counter;
-}
-
-/* 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;
-
- 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;
-}
-
-/* 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." */
-
-size_t
-hash_string (const char *string, size_t n_buckets)
-{
-# define ROTATE_LEFT(Value, Shift) \
- ((Value) << (Shift) | (Value) >> ((sizeof (size_t) * CHAR_BIT) - (Shift)))
-# define HASH_ONE_CHAR(Value, Byte) \
- ((Byte) + ROTATE_LEFT (Value, 7))
-
- size_t value = 0;
- unsigned char ch;
-
- for (; (ch = *string); string++)
- value = HASH_ONE_CHAR (value, ch);
- 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?) */
-
-size_t
-hash_string (const char *string, size_t n_buckets)
-{
- size_t value = 0;
- unsigned char ch;
-
- for (; (ch = *string); string++)
- value = (value * 31 + ch) % 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 (size_t candidate)
-{
- size_t divisor = 3;
- size_t square = divisor * divisor;
-
- while (square < candidate && (candidate % divisor))
- {
- divisor++;
- square += 4 * divisor;
- divisor++;
- }
-
- 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 size_t
-next_prime (size_t 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_reset_tuning (Hash_tuning *tuning)
-{
- *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;
-
- /* 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. */
- float 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;
-}
-
-/* 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 (size_t candidate, const Hash_tuning *tuning,
- Hash_hasher hasher, Hash_comparator comparator,
- Hash_data_freer data_freer)
-{
- Hash_table *table;
-
- if (hasher == NULL || comparator == NULL)
- return NULL;
-
- table = malloc (sizeof *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. */
- goto fail;
- }
-
- if (!tuning->is_n_buckets)
- {
- float new_candidate = candidate / tuning->growth_threshold;
- if (SIZE_MAX <= new_candidate)
- goto fail;
- candidate = new_candidate;
- }
-
- if (xalloc_oversized (candidate, sizeof *table->bucket))
- goto fail;
- table->n_buckets = next_prime (candidate);
- if (xalloc_oversized (table->n_buckets, sizeof *table->bucket))
- goto fail;
-
- 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;
-
- 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;
-
- fail:
- free (table);
- return NULL;
-}
-
-/* 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_clear (Hash_table *table)
-{
- 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 (Hash_table *table)
-{
- 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);
-}
-
-/* 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)
-{
- struct hash_entry *new;
-
- if (table->free_entry_list)
- {
- new = table->free_entry_list;
- table->free_entry_list = new->next;
- }
- else
- {
-#if USE_OBSTACK
- new = obstack_alloc (&table->entry_stack, sizeof *new);
-#else
- new = malloc (sizeof *new);
-#endif
- }
-
- return new;
-}
-
-/* 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)
-{
- 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
- = 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))
- {
- 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;
- }
-
- /* 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;
-}
-
-/* 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, size_t candidate)
-{
- 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;
-}
-
-/* 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_insert (Hash_table *table, const void *entry)
-{
- 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;
- 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 NULL;
-
- /* If the rehash fails, arrange to return NULL. */
- if (!hash_rehash (table, candidate))
- entry = NULL;
- }
- }
-
- return (void *) entry;
-}
-
-/* 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_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;
- size_t candidate =
- (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)
-{
- struct hash_entry const *bucket;
-
- for (bucket = table->bucket; bucket < table->bucket_limit; 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);
- }
- }
-}
-
-#endif /* TESTING */