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| -rw-r--r-- | lib/hash.h | 261 |
1 files changed, 261 insertions, 0 deletions
diff --git a/lib/hash.h b/lib/hash.h new file mode 100644 index 0000000..e280adb --- /dev/null +++ b/lib/hash.h @@ -0,0 +1,261 @@ +/* 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 |