lib/gl_set.h

   1 /* Abstract set data type.
   2    Copyright (C) 2006-2007, 2009-2021 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 /* Creates 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.  Returns 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 /* Returns the current number of elements in a set.  */
 117 extern size_t gl_set_size (gl_set_t set);
 118
 119 /* Searches whether an element is already in the set.
 120    Returns 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 /* Adds an element to a set.
 124    Returns 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.  Returns -1 upon out-of-memory.  */
 128 extern int gl_set_nx_add (gl_set_t set, const void *elt)
 129   _GL_ATTRIBUTE_NODISCARD;
 130
 131 /* Removes an element from a set.
 132    Returns true if it was found and removed.  */
 133 extern bool gl_set_remove (gl_set_t set, const void *elt);
 134
 135 /* Frees an entire set.
 136    (But this call does not free the elements of the set.  It only invokes
 137    the DISPOSE_FN on each of the elements of the set.)  */
 138 extern void gl_set_free (gl_set_t set);
 139
 140 #endif /* End of inline and gl_xset.h-defined functions.  */
 141
 142 /* ---------------------- gl_set_iterator_t Data Type ---------------------- */
 143
 144 /* Functions for iterating through a set.
 145    Note: Iterating through a set of type GL_HASH_SET returns the elements in an
 146    unpredictable order.  If you need a predictable order, use GL_LINKEDHASH_SET
 147    instead of GL_HASH_SET.  */
 148
 149 /* Type of an iterator that traverses a set.
 150    This is a fixed-size struct, so that creation of an iterator doesn't need
 151    memory allocation on the heap.  */
 152 typedef struct
 153 {
 154   /* For fast dispatch of gl_set_iterator_next.  */
 155   const struct gl_set_implementation *vtable;
 156   /* For detecting whether the last returned element was removed.  */
 157   gl_set_t set;
 158   size_t count;
 159   /* Other, implementation-private fields.  */
 160   void *p; void *q;
 161   size_t i; size_t j;
 162 } gl_set_iterator_t;
 163
 164 #if 0 /* These are defined inline below.  */
 165
 166 /* Creates an iterator traversing a set.
 167    The set's contents must not be modified while the iterator is in use,
 168    except for removing the last returned element.  */
 169 extern gl_set_iterator_t gl_set_iterator (gl_set_t set);
 170
 171 /* If there is a next element, stores the next element in *ELTP, advances the
 172    iterator and returns true.  Otherwise, returns false.  */
 173 extern bool gl_set_iterator_next (gl_set_iterator_t *iterator,
 174                                   const void **eltp);
 175
 176 /* Frees an iterator.  */
 177 extern void gl_set_iterator_free (gl_set_iterator_t *iterator);
 178
 179 #endif /* End of inline functions.  */
 180
 181 /* ------------------------ Implementation Details ------------------------ */
 182
 183 struct gl_set_implementation
 184 {
 185   /* gl_set_t functions.  */
 186   gl_set_t (*nx_create_empty) (gl_set_implementation_t implementation,
 187                                gl_setelement_equals_fn equals_fn,
 188                                gl_setelement_hashcode_fn hashcode_fn,
 189                                gl_setelement_dispose_fn dispose_fn);
 190   size_t (*size) (gl_set_t set);
 191   bool (*search) (gl_set_t set, const void *elt);
 192   int (*nx_add) (gl_set_t set, const void *elt);
 193   bool (*remove_elt) (gl_set_t set, const void *elt);
 194   void (*set_free) (gl_set_t set);
 195   /* gl_set_iterator_t functions.  */
 196   gl_set_iterator_t (*iterator) (gl_set_t set);
 197   bool (*iterator_next) (gl_set_iterator_t *iterator, const void **eltp);
 198   void (*iterator_free) (gl_set_iterator_t *iterator);
 199 };
 200
 201 struct gl_set_impl_base
 202 {
 203   const struct gl_set_implementation *vtable;
 204   gl_setelement_equals_fn equals_fn;
 205   gl_setelement_dispose_fn dispose_fn;
 206 };
 207
 208 /* Define all functions of this file as accesses to the
 209    struct gl_set_implementation.  */
 210
 211 GL_SET_INLINE gl_set_t
 212 gl_set_nx_create_empty (gl_set_implementation_t implementation,
 213                         gl_setelement_equals_fn equals_fn,
 214                         gl_setelement_hashcode_fn hashcode_fn,
 215                         gl_setelement_dispose_fn dispose_fn)
 216 {
 217   return implementation->nx_create_empty (implementation, equals_fn,
 218                                           hashcode_fn, dispose_fn);
 219 }
 220
 221 GL_SET_INLINE size_t
 222 gl_set_size (gl_set_t set)
 223 {
 224   return ((const struct gl_set_impl_base *) set)->vtable->size (set);
 225 }
 226
 227 GL_SET_INLINE bool
 228 gl_set_search (gl_set_t set, const void *elt)
 229 {
 230   return ((const struct gl_set_impl_base *) set)->vtable->search (set, elt);
 231 }
 232
 233 GL_SET_INLINE _GL_ATTRIBUTE_NODISCARD int
 234 gl_set_nx_add (gl_set_t set, const void *elt)
 235 {
 236   return ((const struct gl_set_impl_base *) set)->vtable->nx_add (set, elt);
 237 }
 238
 239 GL_SET_INLINE bool
 240 gl_set_remove (gl_set_t set, const void *elt)
 241 {
 242   return ((const struct gl_set_impl_base *) set)->vtable->remove_elt (set, elt);
 243 }
 244
 245 GL_SET_INLINE void
 246 gl_set_free (gl_set_t set)
 247 {
 248   ((const struct gl_set_impl_base *) set)->vtable->set_free (set);
 249 }
 250
 251 GL_SET_INLINE gl_set_iterator_t
 252 gl_set_iterator (gl_set_t set)
 253 {
 254   return ((const struct gl_set_impl_base *) set)->vtable->iterator (set);
 255 }
 256
 257 GL_SET_INLINE bool
 258 gl_set_iterator_next (gl_set_iterator_t *iterator, const void **eltp)
 259 {
 260   return iterator->vtable->iterator_next (iterator, eltp);
 261 }
 262
 263 GL_SET_INLINE void
 264 gl_set_iterator_free (gl_set_iterator_t *iterator)
 265 {
 266   iterator->vtable->iterator_free (iterator);
 267 }
 268
 269 #ifdef __cplusplus
 270 }
 271 #endif
 272
 273 _GL_INLINE_HEADER_END
 274
 275 #endif /* _GL_SET_H */