lib/rbtree.c

   1 /*
   2   Red Black Trees
   3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   4   (C) 2002  David Woodhouse <dwmw2@infradead.org>
   5
   6   This program is free software; you can redistribute it and/or modify
   7   it under the terms of the GNU General Public License as published by
   8   the Free Software Foundation; either version 2 of the License, or
   9   (at your option) any later version.
  10
  11   This program is distributed in the hope that it will be useful,
  12   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14   GNU General Public License for more details.
  15
  16   You should have received a copy of the GNU General Public License
  17   along with this program; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19
  20   linux/lib/rbtree.c
  21 */
  22
  23 #include <linux/rbtree.h>
  24 #include <linux/module.h>
  25
  26 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
  27 {
  28         struct rb_node *right = node->rb_right;
  29         struct rb_node *parent = rb_parent(node);
  30
  31         if ((node->rb_right = right->rb_left))
  32                 rb_set_parent(right->rb_left, node);
  33         right->rb_left = node;
  34
  35         rb_set_parent(right, parent);
  36
  37         if (parent)
  38         {
  39                 if (node == parent->rb_left)
  40                         parent->rb_left = right;
  41                 else
  42                         parent->rb_right = right;
  43         }
  44         else
  45                 root->rb_node = right;
  46         rb_set_parent(node, right);
  47 }
  48
  49 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  50 {
  51         struct rb_node *left = node->rb_left;
  52         struct rb_node *parent = rb_parent(node);
  53
  54         if ((node->rb_left = left->rb_right))
  55                 rb_set_parent(left->rb_right, node);
  56         left->rb_right = node;
  57
  58         rb_set_parent(left, parent);
  59
  60         if (parent)
  61         {
  62                 if (node == parent->rb_right)
  63                         parent->rb_right = left;
  64                 else
  65                         parent->rb_left = left;
  66         }
  67         else
  68                 root->rb_node = left;
  69         rb_set_parent(node, left);
  70 }
  71
  72 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  73 {
  74         struct rb_node *parent, *gparent;
  75
  76         while ((parent = rb_parent(node)) && rb_is_red(parent))
  77         {
  78                 gparent = rb_parent(parent);
  79
  80                 if (parent == gparent->rb_left)
  81                 {
  82                         {
  83                                 register struct rb_node *uncle = gparent->rb_right;
  84                                 if (uncle && rb_is_red(uncle))
  85                                 {
  86                                         rb_set_black(uncle);
  87                                         rb_set_black(parent);
  88                                         rb_set_red(gparent);
  89                                         node = gparent;
  90                                         continue;
  91                                 }
  92                         }
  93
  94                         if (parent->rb_right == node)
  95                         {
  96                                 register struct rb_node *tmp;
  97                                 __rb_rotate_left(parent, root);
  98                                 tmp = parent;
  99                                 parent = node;
 100                                 node = tmp;
 101                         }
 102
 103                         rb_set_black(parent);
 104                         rb_set_red(gparent);
 105                         __rb_rotate_right(gparent, root);
 106                 } else {
 107                         {
 108                                 register struct rb_node *uncle = gparent->rb_left;
 109                                 if (uncle && rb_is_red(uncle))
 110                                 {
 111                                         rb_set_black(uncle);
 112                                         rb_set_black(parent);
 113                                         rb_set_red(gparent);
 114                                         node = gparent;
 115                                         continue;
 116                                 }
 117                         }
 118
 119                         if (parent->rb_left == node)
 120                         {
 121                                 register struct rb_node *tmp;
 122                                 __rb_rotate_right(parent, root);
 123                                 tmp = parent;
 124                                 parent = node;
 125                                 node = tmp;
 126                         }
 127
 128                         rb_set_black(parent);
 129                         rb_set_red(gparent);
 130                         __rb_rotate_left(gparent, root);
 131                 }
 132         }
 133
 134         rb_set_black(root->rb_node);
 135 }
 136 EXPORT_SYMBOL(rb_insert_color);
 137
 138 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 139                              struct rb_root *root)
 140 {
 141         struct rb_node *other;
 142
 143         while ((!node || rb_is_black(node)) && node != root->rb_node)
 144         {
 145                 if (parent->rb_left == node)
 146                 {
 147                         other = parent->rb_right;
 148                         if (rb_is_red(other))
 149                         {
 150                                 rb_set_black(other);
 151                                 rb_set_red(parent);
 152                                 __rb_rotate_left(parent, root);
 153                                 other = parent->rb_right;
 154                         }
 155                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 156                             (!other->rb_right || rb_is_black(other->rb_right)))
 157                         {
 158                                 rb_set_red(other);
 159                                 node = parent;
 160                                 parent = rb_parent(node);
 161                         }
 162                         else
 163                         {
 164                                 if (!other->rb_right || rb_is_black(other->rb_right))
 165                                 {
 166                                         struct rb_node *o_left;
 167                                         if ((o_left = other->rb_left))
 168                                                 rb_set_black(o_left);
 169                                         rb_set_red(other);
 170                                         __rb_rotate_right(other, root);
 171                                         other = parent->rb_right;
 172                                 }
 173                                 rb_set_color(other, rb_color(parent));
 174                                 rb_set_black(parent);
 175                                 if (other->rb_right)
 176                                         rb_set_black(other->rb_right);
 177                                 __rb_rotate_left(parent, root);
 178                                 node = root->rb_node;
 179                                 break;
 180                         }
 181                 }
 182                 else
 183                 {
 184                         other = parent->rb_left;
 185                         if (rb_is_red(other))
 186                         {
 187                                 rb_set_black(other);
 188                                 rb_set_red(parent);
 189                                 __rb_rotate_right(parent, root);
 190                                 other = parent->rb_left;
 191                         }
 192                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 193                             (!other->rb_right || rb_is_black(other->rb_right)))
 194                         {
 195                                 rb_set_red(other);
 196                                 node = parent;
 197                                 parent = rb_parent(node);
 198                         }
 199                         else
 200                         {
 201                                 if (!other->rb_left || rb_is_black(other->rb_left))
 202                                 {
 203                                         register struct rb_node *o_right;
 204                                         if ((o_right = other->rb_right))
 205                                                 rb_set_black(o_right);
 206                                         rb_set_red(other);
 207                                         __rb_rotate_left(other, root);
 208                                         other = parent->rb_left;
 209                                 }
 210                                 rb_set_color(other, rb_color(parent));
 211                                 rb_set_black(parent);
 212                                 if (other->rb_left)
 213                                         rb_set_black(other->rb_left);
 214                                 __rb_rotate_right(parent, root);
 215                                 node = root->rb_node;
 216                                 break;
 217                         }
 218                 }
 219         }
 220         if (node)
 221                 rb_set_black(node);
 222 }
 223
 224 void rb_erase(struct rb_node *node, struct rb_root *root)
 225 {
 226         struct rb_node *child, *parent;
 227         int color;
 228
 229         if (!node->rb_left)
 230                 child = node->rb_right;
 231         else if (!node->rb_right)
 232                 child = node->rb_left;
 233         else
 234         {
 235                 struct rb_node *old = node, *left;
 236
 237                 node = node->rb_right;
 238                 while ((left = node->rb_left) != NULL)
 239                         node = left;
 240                 child = node->rb_right;
 241                 parent = rb_parent(node);
 242                 color = rb_color(node);
 243
 244                 if (child)
 245                         rb_set_parent(child, parent);
 246                 if (parent == old) {
 247                         parent->rb_right = child;
 248                         parent = node;
 249                 } else
 250                         parent->rb_left = child;
 251
 252                 node->rb_parent_color = old->rb_parent_color;
 253                 node->rb_right = old->rb_right;
 254                 node->rb_left = old->rb_left;
 255
 256                 if (rb_parent(old))
 257                 {
 258                         if (rb_parent(old)->rb_left == old)
 259                                 rb_parent(old)->rb_left = node;
 260                         else
 261                                 rb_parent(old)->rb_right = node;
 262                 } else
 263                         root->rb_node = node;
 264
 265                 rb_set_parent(old->rb_left, node);
 266                 if (old->rb_right)
 267                         rb_set_parent(old->rb_right, node);
 268                 goto color;
 269         }
 270
 271         parent = rb_parent(node);
 272         color = rb_color(node);
 273
 274         if (child)
 275                 rb_set_parent(child, parent);
 276         if (parent)
 277         {
 278                 if (parent->rb_left == node)
 279                         parent->rb_left = child;
 280                 else
 281                         parent->rb_right = child;
 282         }
 283         else
 284                 root->rb_node = child;
 285
 286  color:
 287         if (color == RB_BLACK)
 288                 __rb_erase_color(child, parent, root);
 289 }
 290 EXPORT_SYMBOL(rb_erase);
 291
 292 /*
 293  * This function returns the first node (in sort order) of the tree.
 294  */
 295 struct rb_node *rb_first(struct rb_root *root)
 296 {
 297         struct rb_node  *n;
 298
 299         n = root->rb_node;
 300         if (!n)
 301                 return NULL;
 302         while (n->rb_left)
 303                 n = n->rb_left;
 304         return n;
 305 }
 306 EXPORT_SYMBOL(rb_first);
 307
 308 struct rb_node *rb_last(struct rb_root *root)
 309 {
 310         struct rb_node  *n;
 311
 312         n = root->rb_node;
 313         if (!n)
 314                 return NULL;
 315         while (n->rb_right)
 316                 n = n->rb_right;
 317         return n;
 318 }
 319 EXPORT_SYMBOL(rb_last);
 320
 321 struct rb_node *rb_next(struct rb_node *node)
 322 {
 323         struct rb_node *parent;
 324
 325         if (rb_parent(node) == node)
 326                 return NULL;
 327
 328         /* If we have a right-hand child, go down and then left as far
 329            as we can. */
 330         if (node->rb_right) {
 331                 node = node->rb_right;
 332                 while (node->rb_left)
 333                         node=node->rb_left;
 334                 return node;
 335         }
 336
 337         /* No right-hand children.  Everything down and left is
 338            smaller than us, so any 'next' node must be in the general
 339            direction of our parent. Go up the tree; any time the
 340            ancestor is a right-hand child of its parent, keep going
 341            up. First time it's a left-hand child of its parent, said
 342            parent is our 'next' node. */
 343         while ((parent = rb_parent(node)) && node == parent->rb_right)
 344                 node = parent;
 345
 346         return parent;
 347 }
 348 EXPORT_SYMBOL(rb_next);
 349
 350 struct rb_node *rb_prev(struct rb_node *node)
 351 {
 352         struct rb_node *parent;
 353
 354         if (rb_parent(node) == node)
 355                 return NULL;
 356
 357         /* If we have a left-hand child, go down and then right as far
 358            as we can. */
 359         if (node->rb_left) {
 360                 node = node->rb_left;
 361                 while (node->rb_right)
 362                         node=node->rb_right;
 363                 return node;
 364         }
 365
 366         /* No left-hand children. Go up till we find an ancestor which
 367            is a right-hand child of its parent */
 368         while ((parent = rb_parent(node)) && node == parent->rb_left)
 369                 node = parent;
 370
 371         return parent;
 372 }
 373 EXPORT_SYMBOL(rb_prev);
 374
 375 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 376                      struct rb_root *root)
 377 {
 378         struct rb_node *parent = rb_parent(victim);
 379
 380         /* Set the surrounding nodes to point to the replacement */
 381         if (parent) {
 382                 if (victim == parent->rb_left)
 383                         parent->rb_left = new;
 384                 else
 385                         parent->rb_right = new;
 386         } else {
 387                 root->rb_node = new;
 388         }
 389         if (victim->rb_left)
 390                 rb_set_parent(victim->rb_left, new);
 391         if (victim->rb_right)
 392                 rb_set_parent(victim->rb_right, new);
 393
 394         /* Copy the pointers/colour from the victim to the replacement */
 395         *new = *victim;
 396 }
 397 EXPORT_SYMBOL(rb_replace_node);