contrib/tar/lib/hash.h

   1 /* hash - hashing table processing.
   2    Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   3    Written by Jim Meyering <meyering@ascend.com>, 1998.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 /* A generic hash table package.  */
  20
  21 /* Make sure USE_OBSTACK is defined to 1 if you want the allocator to use
  22    obstacks instead of malloc, and recompile `hash.c' with same setting.  */
  23
  24 #ifndef PARAMS
  25 # if PROTOTYPES || __STDC__
  26 #  define PARAMS(Args) Args
  27 # else
  28 #  define PARAMS(Args) ()
  29 # endif
  30 #endif
  31
  32 typedef unsigned (*Hash_hasher) PARAMS ((const void *, unsigned));
  33 typedef bool (*Hash_comparator) PARAMS ((const void *, const void *));
  34 typedef void (*Hash_data_freer) PARAMS ((void *));
  35 typedef bool (*Hash_processor) PARAMS ((void *, void *));
  36
  37 struct hash_entry
  38   {
  39     void *data;
  40     struct hash_entry *next;
  41   };
  42
  43 struct hash_tuning
  44   {
  45     /* This structure is mainly used for `hash_initialize', see the block
  46        documentation of `hash_reset_tuning' for more complete comments.  */
  47
  48     float shrink_threshold;     /* ratio of used buckets to trigger a shrink */
  49     float shrink_factor;        /* ratio of new smaller size to original size */
  50     float growth_threshold;     /* ratio of used buckets to trigger a growth */
  51     float growth_factor;        /* ratio of new bigger size to original size */
  52     bool is_n_buckets;          /* if CANDIDATE really means table size */
  53   };
  54
  55 typedef struct hash_tuning Hash_tuning;
  56
  57 struct hash_table
  58   {
  59     /* The array of buckets starts at BUCKET and extends to BUCKET_LIMIT-1,
  60        for a possibility of N_BUCKETS.  Among those, N_BUCKETS_USED buckets
  61        are not empty, there are N_ENTRIES active entries in the table.  */
  62     struct hash_entry *bucket;
  63     struct hash_entry *bucket_limit;
  64     unsigned n_buckets;
  65     unsigned n_buckets_used;
  66     unsigned n_entries;
  67
  68     /* Tuning arguments, kept in a physicaly separate structure.  */
  69     const Hash_tuning *tuning;
  70
  71     /* Three functions are given to `hash_initialize', see the documentation
  72        block for this function.  In a word, HASHER randomizes a user entry
  73        into a number up from 0 up to some maximum minus 1; COMPARATOR returns
  74        true if two user entries compare equally; and DATA_FREER is the cleanup
  75        function for a user entry.  */
  76     Hash_hasher hasher;
  77     Hash_comparator comparator;
  78     Hash_data_freer data_freer;
  79
  80     /* A linked list of freed struct hash_entry structs.  */
  81     struct hash_entry *free_entry_list;
  82
  83 #if USE_OBSTACK
  84     /* Whenever obstacks are used, it is possible to allocate all overflowed
  85        entries into a single stack, so they all can be freed in a single
  86        operation.  It is not clear if the speedup is worth the trouble.  */
  87     struct obstack entry_stack;
  88 #endif
  89   };
  90
  91 typedef struct hash_table Hash_table;
  92
  93 /* Information and lookup.  */
  94 unsigned hash_get_n_buckets PARAMS ((const Hash_table *));
  95 unsigned hash_get_n_buckets_used PARAMS ((const Hash_table *));
  96 unsigned hash_get_n_entries PARAMS ((const Hash_table *));
  97 unsigned hash_get_max_bucket_length PARAMS ((const Hash_table *));
  98 bool hash_table_ok PARAMS ((const Hash_table *));
  99 void hash_print_statistics PARAMS ((const Hash_table *, FILE *));
 100 void *hash_lookup PARAMS ((const Hash_table *, const void *));
 101
 102 /* Walking.  */
 103 void *hash_get_first PARAMS ((const Hash_table *));
 104 void *hash_get_next PARAMS ((const Hash_table *, const void *));
 105 unsigned hash_get_entries PARAMS ((const Hash_table *, void **, unsigned));
 106 unsigned hash_do_for_each PARAMS ((const Hash_table *, Hash_processor, void *));
 107
 108 /* Allocation and clean-up.  */
 109 unsigned hash_string PARAMS ((const char *, unsigned));
 110 void hash_reset_tuning PARAMS ((Hash_tuning *));
 111 Hash_table *hash_initialize PARAMS ((unsigned, const Hash_tuning *,
 112                                      Hash_hasher, Hash_comparator,
 113                                      Hash_data_freer));
 114 void hash_clear PARAMS ((Hash_table *));
 115 void hash_free PARAMS ((Hash_table *));
 116
 117 /* Insertion and deletion.  */
 118 bool hash_rehash PARAMS ((Hash_table *, unsigned));
 119 void *hash_insert PARAMS ((Hash_table *, const void *));
 120 void *hash_delete PARAMS ((Hash_table *, const void *));