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/* hash - hashing table processing.
Copyright (C) 1998-1999, 2001, 2003, 2009-2020 Free Software Foundation,
Inc.
Written by Jim Meyering <meyering@ascend.com>, 1998.
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 <https://www.gnu.org/licenses/>. */
/* A generic hash table package. */
/* Make sure USE_OBSTACK is defined to 1 if you want the allocator to use
obstacks instead of malloc, and recompile 'hash.c' with same setting. */
#ifndef HASH_H_
# define HASH_H_
# include <stdio.h>
# include <stdbool.h>
# ifdef __cplusplus
extern "C" {
# endif
struct hash_tuning
{
/* This structure is mainly used for 'hash_initialize', see the block
documentation of 'hash_reset_tuning' for more complete comments. */
float shrink_threshold; /* ratio of used buckets to trigger a shrink */
float shrink_factor; /* ratio of new smaller size to original size */
float growth_threshold; /* ratio of used buckets to trigger a growth */
float growth_factor; /* ratio of new bigger size to original size */
bool is_n_buckets; /* if CANDIDATE really means table size */
};
typedef struct hash_tuning Hash_tuning;
struct hash_table;
typedef struct hash_table Hash_table;
/*
* 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. */
extern size_t hash_get_n_buckets (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
/* Return the number of slots in use (non-empty buckets). */
extern size_t hash_get_n_buckets_used (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
/* Return the number of active entries. */
extern size_t hash_get_n_entries (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
/* Return the length of the longest chain (bucket). */
extern size_t hash_get_max_bucket_length (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
/* Do a mild validation of a hash table, by traversing it and checking two
statistics. */
extern bool hash_table_ok (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
extern void hash_print_statistics (const Hash_table *table, FILE *stream);
/* If ENTRY matches an entry already in the hash table, return the
entry from the table. Otherwise, return NULL. */
extern void *hash_lookup (const Hash_table *table, const void *entry);
/*
* 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. */
extern void *hash_get_first (const Hash_table *table)
_GL_ATTRIBUTE_PURE;
/* 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. */
extern void *hash_get_next (const Hash_table *table, const void *entry);
/* 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. */
extern size_t hash_get_entries (const Hash_table *table, void **buffer,
size_t buffer_size);
typedef bool (*Hash_processor) (void *entry, void *processor_data);
/* 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. */
extern size_t hash_do_for_each (const Hash_table *table,
Hash_processor processor, void *processor_data);
/*
* 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. */
extern size_t hash_string (const char *string, size_t n_buckets)
_GL_ATTRIBUTE_PURE;
extern void hash_reset_tuning (Hash_tuning *tuning);
typedef size_t (*Hash_hasher) (const void *entry, size_t table_size);
typedef bool (*Hash_comparator) (const void *entry1, const void *entry2);
typedef void (*Hash_data_freer) (void *entry);
/* 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. */
extern Hash_table *hash_initialize (size_t candidate,
const Hash_tuning *tuning,
Hash_hasher hasher,
Hash_comparator comparator,
Hash_data_freer data_freer)
_GL_ATTRIBUTE_NODISCARD;
/* Same as hash_initialize, but invokes xalloc_die on memory exhaustion. */
/* This function is defined by module 'xhash'. */
extern Hash_table *hash_xinitialize (size_t candidate,
const Hash_tuning *tuning,
Hash_hasher hasher,
Hash_comparator comparator,
Hash_data_freer data_freer)
_GL_ATTRIBUTE_NODISCARD;
/* 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. */
extern void hash_clear (Hash_table *table);
/* 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. */
extern void hash_free (Hash_table *table);
/*
* Insertion and deletion.
*/
/* 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. */
extern bool hash_rehash (Hash_table *table, size_t candidate)
_GL_ATTRIBUTE_NODISCARD;
/* 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. */
extern void *hash_insert (Hash_table *table, const void *entry)
_GL_ATTRIBUTE_NODISCARD;
/* Same as hash_insert, but invokes xalloc_die on memory exhaustion. */
/* This function is defined by module 'xhash'. */
extern void *hash_xinsert (Hash_table *table, const void *entry);
/* 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. */
extern int hash_insert_if_absent (Hash_table *table, const void *entry,
const void **matched_ent);
/* 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. */
extern void *hash_remove (Hash_table *table, const void *entry);
/* Same as hash_remove. This interface is deprecated.
FIXME: Remove in 2022. */
extern void *hash_delete (Hash_table *table, const void *entry)
_GL_ATTRIBUTE_DEPRECATED;
# ifdef __cplusplus
}
# endif
#endif
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