lib/gl_set.h

   1 /* Abstract set data type.
   2    Copyright (C) 2006-2007, 2009-2019 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2018.
   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 3 of the License, or
   8    (at your option) 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, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _GL_SET_H
  19 #define _GL_SET_H
  20
  21 #include <stdbool.h>
  22 #include <stddef.h>
  23
  24 #ifndef _GL_INLINE_HEADER_BEGIN
  25  #error "Please include config.h first."
  26 #endif
  27 _GL_INLINE_HEADER_BEGIN
  28 #ifndef GL_SET_INLINE
  29 # define GL_SET_INLINE _GL_INLINE
  30 #endif
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36
  37 /* gl_set is an abstract set data type.  It can contain any number of objects
  38    ('void *' or 'const void *' pointers); the order does not matter.
  39    Duplicates (in the sense of the comparator) are forbidden.
  40
  41    There are several implementations of this set datatype, optimized for
  42    different operations or for memory.  You can start using the simplest set
  43    implementation, GL_ARRAY_SET, and switch to a different implementation
  44    later, when you realize which operations are performed the most frequently.
  45    The API of the different implementations is exactly the same; when switching
  46    to a different implementation, you only have to change the gl_set_create
  47    call.
  48
  49    The implementations are:
  50      GL_ARRAY_SET         a growable array
  51      GL_LINKEDHASH_SET    a hash table with a linked list
  52      GL_HASH_SET          a hash table
  53
  54    The memory consumption is asymptotically the same: O(1) for every object
  55    in the set.  When looking more closely at the average memory consumed
  56    for an object, GL_ARRAY_SET is the most compact representation, then comes
  57    GL_HASH_SET, and GL_LINKEDHASH_SET needs the most memory.
  58
  59    The guaranteed average performance of the operations is, for a set of
  60    n elements:
  61
  62    Operation                  ARRAY   LINKEDHASH
  63                                       HASH
  64
  65    gl_set_size                 O(1)   O(1)
  66    gl_set_add                  O(n)   O(1)
  67    gl_set_remove               O(n)   O(1)
  68    gl_set_search               O(n)   O(1)
  69    gl_set_iterator             O(1)   O(1)
  70    gl_set_iterator_next        O(1)   O(1)
  71  */
  72
  73 /* --------------------------- gl_set_t Data Type --------------------------- */
  74
  75 /* Type of function used to compare two elements.
  76    NULL denotes pointer comparison.  */
  77 typedef bool (*gl_setelement_equals_fn) (const void *elt1, const void *elt2);
  78
  79 /* Type of function used to compute a hash code.
  80    NULL denotes a function that depends only on the pointer itself.  */
  81 typedef size_t (*gl_setelement_hashcode_fn) (const void *elt);
  82
  83 #ifndef _GL_SETELEMENT_DISPOSE_FN_DEFINED
  84 /* Type of function used to dispose an element once it's removed from a set.
  85    NULL denotes a no-op.  */
  86 typedef void (*gl_setelement_dispose_fn) (const void *elt);
  87 # define _GL_SETELEMENT_DISPOSE_FN_DEFINED 1
  88 #endif
  89
  90 struct gl_set_impl;
  91 /* Type representing an entire set.  */
  92 typedef struct gl_set_impl * gl_set_t;
  93
  94 struct gl_set_implementation;
  95 /* Type representing a set datatype implementation.  */
  96 typedef const struct gl_set_implementation * gl_set_implementation_t;
  97
  98 #if 0 /* Unless otherwise specified, these are defined inline below.  */
  99
 100 /* Create an empty set.
 101    IMPLEMENTATION is one of GL_ARRAY_SET, GL_LINKEDHASH_SET, GL_HASH_SET.
 102    EQUALS_FN is an element comparison function or NULL.
 103    HASHCODE_FN is an element hash code function or NULL.
 104    DISPOSE_FN is an element disposal function or NULL.  */
 105 /* declared in gl_xset.h */
 106 extern gl_set_t gl_set_create_empty (gl_set_implementation_t implementation,
 107                                      gl_setelement_equals_fn equals_fn,
 108                                      gl_setelement_hashcode_fn hashcode_fn,
 109                                      gl_setelement_dispose_fn dispose_fn);
 110 /* Likewise.  Return NULL upon out-of-memory.  */
 111 extern gl_set_t gl_set_nx_create_empty (gl_set_implementation_t implementation,
 112                                         gl_setelement_equals_fn equals_fn,
 113                                         gl_setelement_hashcode_fn hashcode_fn,
 114                                         gl_setelement_dispose_fn dispose_fn);
 115
 116 /* Return the current number of elements in a set.  */
 117 extern size_t gl_set_size (gl_set_t set);
 118
 119 /* Search whether an element is already in the set.
 120    Return true if found, or false if not present in the set.  */
 121 extern bool gl_set_search (gl_set_t set, const void *elt);
 122
 123 /* Add an element to a set.
 124    Return true if it was not already in the set and added, false otherwise.  */
 125 /* declared in gl_xset.h */
 126 extern bool gl_set_add (gl_set_t set, const void *elt);
 127 /* Likewise.  Return -1 upon out-of-memory.  */
 128 extern int gl_set_nx_add (gl_set_t set, const void *elt)
 129 #if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
 130   __attribute__ ((__warn_unused_result__))
 131 #endif
 132   ;
 133
 134 /* Remove an element from a set.
 135    Return true if it was found and removed.  */
 136 extern bool gl_set_remove (gl_set_t set, const void *elt);
 137
 138 /* Free an entire set.
 139    (But this call does not free the elements of the set.  It only invokes
 140    the DISPOSE_FN on each of the elements of the set.)  */
 141 extern void gl_set_free (gl_set_t set);
 142
 143 #endif /* End of inline and gl_xset.h-defined functions.  */
 144
 145 /* ---------------------- gl_set_iterator_t Data Type ---------------------- */
 146
 147 /* Functions for iterating through a set.
 148    Note: Iterating through a set of type GL_HASH_SET returns the elements in an
 149    unpredictable order.  If you need a predictable order, use GL_LINKEDHASH_SET
 150    instead of GL_HASH_SET.  */
 151
 152 /* Type of an iterator that traverses a set.
 153    This is a fixed-size struct, so that creation of an iterator doesn't need
 154    memory allocation on the heap.  */
 155 typedef struct
 156 {
 157   /* For fast dispatch of gl_set_iterator_next.  */
 158   const struct gl_set_implementation *vtable;
 159   /* For detecting whether the last returned element was removed.  */
 160   gl_set_t set;
 161   size_t count;
 162   /* Other, implementation-private fields.  */
 163   void *p; void *q;
 164   size_t i; size_t j;
 165 } gl_set_iterator_t;
 166
 167 #if 0 /* These are defined inline below.  */
 168
 169 /* Create an iterator traversing a set.
 170    The set's contents must not be modified while the iterator is in use,
 171    except for removing the last returned element.  */
 172 extern gl_set_iterator_t gl_set_iterator (gl_set_t set);
 173
 174 /* If there is a next element, store the next element in *ELTP, advance the
 175    iterator and return true.  Otherwise, return false.  */
 176 extern bool gl_set_iterator_next (gl_set_iterator_t *iterator,
 177                                   const void **eltp);
 178
 179 /* Free an iterator.  */
 180 extern void gl_set_iterator_free (gl_set_iterator_t *iterator);
 181
 182 #endif /* End of inline functions.  */
 183
 184 /* ------------------------ Implementation Details ------------------------ */
 185
 186 struct gl_set_implementation
 187 {
 188   /* gl_set_t functions.  */
 189   gl_set_t (*nx_create_empty) (gl_set_implementation_t implementation,
 190                                gl_setelement_equals_fn equals_fn,
 191                                gl_setelement_hashcode_fn hashcode_fn,
 192                                gl_setelement_dispose_fn dispose_fn);
 193   size_t (*size) (gl_set_t set);
 194   bool (*search) (gl_set_t set, const void *elt);
 195   int (*nx_add) (gl_set_t set, const void *elt);
 196   bool (*remove_elt) (gl_set_t set, const void *elt);
 197   void (*set_free) (gl_set_t set);
 198   /* gl_set_iterator_t functions.  */
 199   gl_set_iterator_t (*iterator) (gl_set_t set);
 200   bool (*iterator_next) (gl_set_iterator_t *iterator, const void **eltp);
 201   void (*iterator_free) (gl_set_iterator_t *iterator);
 202 };
 203
 204 struct gl_set_impl_base
 205 {
 206   const struct gl_set_implementation *vtable;
 207   gl_setelement_equals_fn equals_fn;
 208   gl_setelement_dispose_fn dispose_fn;
 209 };
 210
 211 /* Define all functions of this file as accesses to the
 212    struct gl_set_implementation.  */
 213
 214 GL_SET_INLINE gl_set_t
 215 gl_set_nx_create_empty (gl_set_implementation_t implementation,
 216                         gl_setelement_equals_fn equals_fn,
 217                         gl_setelement_hashcode_fn hashcode_fn,
 218                         gl_setelement_dispose_fn dispose_fn)
 219 {
 220   return implementation->nx_create_empty (implementation, equals_fn,
 221                                           hashcode_fn, dispose_fn);
 222 }
 223
 224 GL_SET_INLINE size_t
 225 gl_set_size (gl_set_t set)
 226 {
 227   return ((const struct gl_set_impl_base *) set)->vtable->size (set);
 228 }
 229
 230 GL_SET_INLINE bool
 231 gl_set_search (gl_set_t set, const void *elt)
 232 {
 233   return ((const struct gl_set_impl_base *) set)->vtable->search (set, elt);
 234 }
 235
 236 GL_SET_INLINE int
 237 #if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
 238   __attribute__ ((__warn_unused_result__))
 239 #endif
 240 gl_set_nx_add (gl_set_t set, const void *elt)
 241 {
 242   return ((const struct gl_set_impl_base *) set)->vtable->nx_add (set, elt);
 243 }
 244
 245 GL_SET_INLINE bool
 246 gl_set_remove (gl_set_t set, const void *elt)
 247 {
 248   return ((const struct gl_set_impl_base *) set)->vtable->remove_elt (set, elt);
 249 }
 250
 251 GL_SET_INLINE void
 252 gl_set_free (gl_set_t set)
 253 {
 254   ((const struct gl_set_impl_base *) set)->vtable->set_free (set);
 255 }
 256
 257 GL_SET_INLINE gl_set_iterator_t
 258 gl_set_iterator (gl_set_t set)
 259 {
 260   return ((const struct gl_set_impl_base *) set)->vtable->iterator (set);
 261 }
 262
 263 GL_SET_INLINE bool
 264 gl_set_iterator_next (gl_set_iterator_t *iterator, const void **eltp)
 265 {
 266   return iterator->vtable->iterator_next (iterator, eltp);
 267 }
 268
 269 GL_SET_INLINE void
 270 gl_set_iterator_free (gl_set_iterator_t *iterator)
 271 {
 272   iterator->vtable->iterator_free (iterator);
 273 }
 274
 275 #ifdef __cplusplus
 276 }
 277 #endif
 278
 279 _GL_INLINE_HEADER_END
 280
 281 #endif /* _GL_SET_H */