1 /* Sequential list data type implemented by a hash table with a binary tree.
2 Copyright (C) 2006-2007 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2006.
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.
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.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */
18 /* Common code of gl_avltreehash_list.c and gl_rbtreehash_list.c. */
20 /* Hash table entry representing the same value at more than one position. */
21 struct gl_multiple_nodes
23 struct gl_hash_entry h; /* hash table entry fields; must be first */
24 void *magic; /* used to distinguish from single node */
25 gl_oset_t nodes; /* set of nodes, sorted by position */
27 /* A value that cannot occur at the corresponding field (->left) in
29 #define MULTIPLE_NODES_MAGIC (void *) -1
31 /* Resize the hash table if needed, after list->count was incremented. */
33 hash_resize_after_add (gl_list_t list)
35 size_t count = (list->root != 0 ? list->root->branch_size : 0);
36 size_t estimate = xsum (count, count / 2); /* 1.5 * count */
37 if (estimate > list->table_size)
38 hash_resize (list, estimate);
41 /* Return the position of the given node in the tree. */
43 node_position (gl_list_node_t node)
47 if (node->left != NULL)
48 position += node->left->branch_size;
51 gl_list_node_t parent = node->parent;
55 /* position is now relative to the subtree of node. */
56 if (parent->right == node)
59 if (parent->left != NULL)
60 position += parent->left->branch_size;
62 /* position is now relative to the subtree of parent. */
67 /* Compares two nodes by their position in the tree. */
69 compare_by_position (const void *x1, const void *x2)
71 gl_list_node_t node1 = (gl_list_node_t) x1;
72 gl_list_node_t node2 = (gl_list_node_t) x2;
73 size_t position1 = node_position (node1);
74 size_t position2 = node_position (node2);
76 return (position1 > position2 ? 1 :
77 position1 < position2 ? -1 : 0);
80 /* Compares a node's position in the tree with a given threshold. */
82 compare_position_threshold (const void *x, const void *threshold)
84 gl_list_node_t node = (gl_list_node_t) x;
85 size_t position = node_position (node);
86 return (position >= (uintptr_t)threshold);
89 /* Return the first element of a non-empty ordered set of nodes. */
90 static inline gl_list_node_t
91 gl_oset_first (gl_oset_t set)
93 gl_oset_iterator_t iter = gl_oset_iterator (set);
96 if (!gl_oset_iterator_next (&iter, &first))
98 gl_oset_iterator_free (&iter);
99 return (gl_list_node_t) first;
102 /* Add a node to the hash table structure.
103 If duplicates are allowed, this function performs in average time
104 O((log n)^2): gl_oset_add may need to add an element to an ordered set of
105 size O(n), needing O(log n) comparison function calls. The comparison
106 function is compare_by_position, which is O(log n) worst-case.
107 If duplicates are forbidden, this function is O(1). */
109 add_to_bucket (gl_list_t list, gl_list_node_t new_node)
111 size_t bucket = new_node->h.hashcode % list->table_size;
113 /* If no duplicates are allowed, multiple nodes are not needed. */
114 if (list->base.allow_duplicates)
116 size_t hashcode = new_node->h.hashcode;
117 const void *value = new_node->value;
118 gl_listelement_equals_fn equals = list->base.equals_fn;
119 gl_hash_entry_t *entryp;
121 for (entryp = &list->table[bucket]; *entryp != NULL; entryp = &(*entryp)->hash_next)
123 gl_hash_entry_t entry = *entryp;
125 if (entry->hashcode == hashcode)
127 if (((struct gl_multiple_nodes *) entry)->magic == MULTIPLE_NODES_MAGIC)
129 /* An entry representing multiple nodes. */
130 gl_oset_t nodes = ((struct gl_multiple_nodes *) entry)->nodes;
131 /* Only the first node is interesting. */
132 gl_list_node_t node = gl_oset_first (nodes);
133 if (equals != NULL ? equals (value, node->value) : value == node->value)
135 /* Found already multiple nodes with the same value.
136 Add the new_node to it. */
137 gl_oset_add (nodes, new_node);
143 /* An entry representing a single node. */
144 gl_list_node_t node = (struct gl_list_node_impl *) entry;
145 if (equals != NULL ? equals (value, node->value) : value == node->value)
147 /* Found already a node with the same value. Turn it
148 into an ordered set, and add new_node to it. */
150 struct gl_multiple_nodes *multi_entry;
153 gl_oset_create_empty (OSET_TREE_FLAVOR,
154 compare_by_position, NULL);
156 gl_oset_add (nodes, node);
157 gl_oset_add (nodes, new_node);
159 multi_entry = XMALLOC (struct gl_multiple_nodes);
160 multi_entry->h.hash_next = entry->hash_next;
161 multi_entry->h.hashcode = entry->hashcode;
162 multi_entry->magic = MULTIPLE_NODES_MAGIC;
163 multi_entry->nodes = nodes;
164 *entryp = &multi_entry->h;
171 /* If no duplicates are allowed, multiple nodes are not needed. */
172 new_node->h.hash_next = list->table[bucket];
173 list->table[bucket] = &new_node->h;
176 /* Remove a node from the hash table structure.
177 If duplicates are allowed, this function performs in average time
178 O((log n)^2): gl_oset_remove may need to remove an element from an ordered
179 set of size O(n), needing O(log n) comparison function calls. The
180 comparison function is compare_by_position, which is O(log n) worst-case.
181 If duplicates are forbidden, this function is O(1) on average. */
183 remove_from_bucket (gl_list_t list, gl_list_node_t old_node)
185 size_t bucket = old_node->h.hashcode % list->table_size;
187 if (list->base.allow_duplicates)
189 size_t hashcode = old_node->h.hashcode;
190 const void *value = old_node->value;
191 gl_listelement_equals_fn equals = list->base.equals_fn;
192 gl_hash_entry_t *entryp;
194 for (entryp = &list->table[bucket]; ; entryp = &(*entryp)->hash_next)
196 gl_hash_entry_t entry = *entryp;
198 if (entry == &old_node->h)
200 /* Found old_node as a single node in the bucket. Remove it. */
201 *entryp = old_node->h.hash_next;
205 /* node is not in the right bucket. Did the hash codes
206 change inadvertently? */
208 if (((struct gl_multiple_nodes *) entry)->magic == MULTIPLE_NODES_MAGIC
209 && entry->hashcode == hashcode)
211 /* An entry representing multiple nodes. */
212 gl_oset_t nodes = ((struct gl_multiple_nodes *) entry)->nodes;
213 /* Only the first node is interesting. */
214 gl_list_node_t node = gl_oset_first (nodes);
215 if (equals != NULL ? equals (value, node->value) : value == node->value)
217 /* Found multiple nodes with the same value.
218 old_node must be one of them. Remove it. */
219 if (!gl_oset_remove (nodes, old_node))
221 if (gl_oset_size (nodes) == 1)
223 /* Replace a one-element set with a single node. */
224 node = gl_oset_first (nodes);
225 node->h.hash_next = entry->hash_next;
227 gl_oset_free (nodes);
237 /* If no duplicates are allowed, multiple nodes are not needed. */
238 gl_hash_entry_t *entryp;
240 for (entryp = &list->table[bucket]; ; entryp = &(*entryp)->hash_next)
242 if (*entryp == &old_node->h)
244 *entryp = old_node->h.hash_next;
248 /* node is not in the right bucket. Did the hash codes
249 change inadvertently? */
255 /* Build up the hash table during initialization: Store all the nodes of
256 list->root in the hash table. */
258 add_nodes_to_buckets (gl_list_t list)
260 /* Iterate across all nodes. */
261 gl_list_node_t node = list->root;
263 iterstack_item_t *stack_ptr = &stack[0];
267 /* Descend on left branch. */
272 stack_ptr->node = node;
273 stack_ptr->rightp = false;
277 /* Climb up again. */
280 if (stack_ptr == &stack[0])
283 if (!stack_ptr->rightp)
286 node = stack_ptr->node;
287 /* Add the current node to the hash table. */
289 (list->base.hashcode_fn != NULL
290 ? list->base.hashcode_fn (node->value)
291 : (size_t)(uintptr_t) node->value);
292 add_to_bucket (list, node);
293 /* Descend on right branch. */
294 stack_ptr->rightp = true;