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
  30         if ((node->rb_right = right->rb_left))
  31                 right->rb_left->rb_parent = node;
  32         right->rb_left = node;
  33
  34         if ((right->rb_parent = node->rb_parent))
  35         {
  36                 if (node == node->rb_parent->rb_left)
  37                         node->rb_parent->rb_left = right;
  38                 else
  39                         node->rb_parent->rb_right = right;
  40         }
  41         else
  42                 root->rb_node = right;
  43         node->rb_parent = right;
  44 }
  45
  46 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  47 {
  48         struct rb_node *left = node->rb_left;
  49
  50         if ((node->rb_left = left->rb_right))
  51                 left->rb_right->rb_parent = node;
  52         left->rb_right = node;
  53
  54         if ((left->rb_parent = node->rb_parent))
  55         {
  56                 if (node == node->rb_parent->rb_right)
  57                         node->rb_parent->rb_right = left;
  58                 else
  59                         node->rb_parent->rb_left = left;
  60         }
  61         else
  62                 root->rb_node = left;
  63         node->rb_parent = left;
  64 }
  65
  66 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  67 {
  68         struct rb_node *parent, *gparent;
  69
  70         while ((parent = node->rb_parent) && parent->rb_color == RB_RED)
  71         {
  72                 gparent = parent->rb_parent;
  73
  74                 if (parent == gparent->rb_left)
  75                 {
  76                         {
  77                                 register struct rb_node *uncle = gparent->rb_right;
  78                                 if (uncle && uncle->rb_color == RB_RED)
  79                                 {
  80                                         uncle->rb_color = RB_BLACK;
  81                                         parent->rb_color = RB_BLACK;
  82                                         gparent->rb_color = RB_RED;
  83                                         node = gparent;
  84                                         continue;
  85                                 }
  86                         }
  87
  88                         if (parent->rb_right == node)
  89                         {
  90                                 register struct rb_node *tmp;
  91                                 __rb_rotate_left(parent, root);
  92                                 tmp = parent;
  93                                 parent = node;
  94                                 node = tmp;
  95                         }
  96
  97                         parent->rb_color = RB_BLACK;
  98                         gparent->rb_color = RB_RED;
  99                         __rb_rotate_right(gparent, root);
 100                 } else {
 101                         {
 102                                 register struct rb_node *uncle = gparent->rb_left;
 103                                 if (uncle && uncle->rb_color == RB_RED)
 104                                 {
 105                                         uncle->rb_color = RB_BLACK;
 106                                         parent->rb_color = RB_BLACK;
 107                                         gparent->rb_color = RB_RED;
 108                                         node = gparent;
 109                                         continue;
 110                                 }
 111                         }
 112
 113                         if (parent->rb_left == node)
 114                         {
 115                                 register struct rb_node *tmp;
 116                                 __rb_rotate_right(parent, root);
 117                                 tmp = parent;
 118                                 parent = node;
 119                                 node = tmp;
 120                         }
 121
 122                         parent->rb_color = RB_BLACK;
 123                         gparent->rb_color = RB_RED;
 124                         __rb_rotate_left(gparent, root);
 125                 }
 126         }
 127
 128         root->rb_node->rb_color = RB_BLACK;
 129 }
 130 EXPORT_SYMBOL(rb_insert_color);
 131
 132 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 133                              struct rb_root *root)
 134 {
 135         struct rb_node *other;
 136
 137         while ((!node || node->rb_color == RB_BLACK) && node != root->rb_node)
 138         {
 139                 if (parent->rb_left == node)
 140                 {
 141                         other = parent->rb_right;
 142                         if (other->rb_color == RB_RED)
 143                         {
 144                                 other->rb_color = RB_BLACK;
 145                                 parent->rb_color = RB_RED;
 146                                 __rb_rotate_left(parent, root);
 147                                 other = parent->rb_right;
 148                         }
 149                         if ((!other->rb_left ||
 150                              other->rb_left->rb_color == RB_BLACK)
 151                             && (!other->rb_right ||
 152                                 other->rb_right->rb_color == RB_BLACK))
 153                         {
 154                                 other->rb_color = RB_RED;
 155                                 node = parent;
 156                                 parent = node->rb_parent;
 157                         }
 158                         else
 159                         {
 160                                 if (!other->rb_right ||
 161                                     other->rb_right->rb_color == RB_BLACK)
 162                                 {
 163                                         register struct rb_node *o_left;
 164                                         if ((o_left = other->rb_left))
 165                                                 o_left->rb_color = RB_BLACK;
 166                                         other->rb_color = RB_RED;
 167                                         __rb_rotate_right(other, root);
 168                                         other = parent->rb_right;
 169                                 }
 170                                 other->rb_color = parent->rb_color;
 171                                 parent->rb_color = RB_BLACK;
 172                                 if (other->rb_right)
 173                                         other->rb_right->rb_color = RB_BLACK;
 174                                 __rb_rotate_left(parent, root);
 175                                 node = root->rb_node;
 176                                 break;
 177                         }
 178                 }
 179                 else
 180                 {
 181                         other = parent->rb_left;
 182                         if (other->rb_color == RB_RED)
 183                         {
 184                                 other->rb_color = RB_BLACK;
 185                                 parent->rb_color = RB_RED;
 186                                 __rb_rotate_right(parent, root);
 187                                 other = parent->rb_left;
 188                         }
 189                         if ((!other->rb_left ||
 190                              other->rb_left->rb_color == RB_BLACK)
 191                             && (!other->rb_right ||
 192                                 other->rb_right->rb_color == RB_BLACK))
 193                         {
 194                                 other->rb_color = RB_RED;
 195                                 node = parent;
 196                                 parent = node->rb_parent;
 197                         }
 198                         else
 199                         {
 200                                 if (!other->rb_left ||
 201                                     other->rb_left->rb_color == RB_BLACK)
 202                                 {
 203                                         register struct rb_node *o_right;
 204                                         if ((o_right = other->rb_right))
 205                                                 o_right->rb_color = RB_BLACK;
 206                                         other->rb_color = RB_RED;
 207                                         __rb_rotate_left(other, root);
 208                                         other = parent->rb_left;
 209                                 }
 210                                 other->rb_color = parent->rb_color;
 211                                 parent->rb_color = RB_BLACK;
 212                                 if (other->rb_left)
 213                                         other->rb_left->rb_color = RB_BLACK;
 214                                 __rb_rotate_right(parent, root);
 215                                 node = root->rb_node;
 216                                 break;
 217                         }
 218                 }
 219         }
 220         if (node)
 221                 node->rb_color = RB_BLACK;
 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 = node->rb_parent;
 242                 color = node->rb_color;
 243
 244                 if (child)
 245                         child->rb_parent = parent;
 246                 if (parent)
 247                 {
 248                         if (parent->rb_left == node)
 249                                 parent->rb_left = child;
 250                         else
 251                                 parent->rb_right = child;
 252                 }
 253                 else
 254                         root->rb_node = child;
 255
 256                 if (node->rb_parent == old)
 257                         parent = node;
 258                 node->rb_parent = old->rb_parent;
 259                 node->rb_color = old->rb_color;
 260                 node->rb_right = old->rb_right;
 261                 node->rb_left = old->rb_left;
 262
 263                 if (old->rb_parent)
 264                 {
 265                         if (old->rb_parent->rb_left == old)
 266                                 old->rb_parent->rb_left = node;
 267                         else
 268                                 old->rb_parent->rb_right = node;
 269                 } else
 270                         root->rb_node = node;
 271
 272                 old->rb_left->rb_parent = node;
 273                 if (old->rb_right)
 274                         old->rb_right->rb_parent = node;
 275                 goto color;
 276         }
 277
 278         parent = node->rb_parent;
 279         color = node->rb_color;
 280
 281         if (child)
 282                 child->rb_parent = parent;
 283         if (parent)
 284         {
 285                 if (parent->rb_left == node)
 286                         parent->rb_left = child;
 287                 else
 288                         parent->rb_right = child;
 289         }
 290         else
 291                 root->rb_node = child;
 292
 293  color:
 294         if (color == RB_BLACK)
 295                 __rb_erase_color(child, parent, root);
 296 }
 297 EXPORT_SYMBOL(rb_erase);
 298
 299 /*
 300  * This function returns the first node (in sort order) of the tree.
 301  */
 302 struct rb_node *rb_first(struct rb_root *root)
 303 {
 304         struct rb_node  *n;
 305
 306         n = root->rb_node;
 307         if (!n)
 308                 return NULL;
 309         while (n->rb_left)
 310                 n = n->rb_left;
 311         return n;
 312 }
 313 EXPORT_SYMBOL(rb_first);
 314
 315 struct rb_node *rb_last(struct rb_root *root)
 316 {
 317         struct rb_node  *n;
 318
 319         n = root->rb_node;
 320         if (!n)
 321                 return NULL;
 322         while (n->rb_right)
 323                 n = n->rb_right;
 324         return n;
 325 }
 326 EXPORT_SYMBOL(rb_last);
 327
 328 struct rb_node *rb_next(struct rb_node *node)
 329 {
 330         /* If we have a right-hand child, go down and then left as far
 331            as we can. */
 332         if (node->rb_right) {
 333                 node = node->rb_right;
 334                 while (node->rb_left)
 335                         node=node->rb_left;
 336                 return node;
 337         }
 338
 339         /* No right-hand children.  Everything down and left is
 340            smaller than us, so any 'next' node must be in the general
 341            direction of our parent. Go up the tree; any time the
 342            ancestor is a right-hand child of its parent, keep going
 343            up. First time it's a left-hand child of its parent, said
 344            parent is our 'next' node. */
 345         while (node->rb_parent && node == node->rb_parent->rb_right)
 346                 node = node->rb_parent;
 347
 348         return node->rb_parent;
 349 }
 350 EXPORT_SYMBOL(rb_next);
 351
 352 struct rb_node *rb_prev(struct rb_node *node)
 353 {
 354         /* If we have a left-hand child, go down and then right as far
 355            as we can. */
 356         if (node->rb_left) {
 357                 node = node->rb_left;
 358                 while (node->rb_right)
 359                         node=node->rb_right;
 360                 return node;
 361         }
 362
 363         /* No left-hand children. Go up till we find an ancestor which
 364            is a right-hand child of its parent */
 365         while (node->rb_parent && node == node->rb_parent->rb_left)
 366                 node = node->rb_parent;
 367
 368         return node->rb_parent;
 369 }
 370 EXPORT_SYMBOL(rb_prev);
 371
 372 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 373                      struct rb_root *root)
 374 {
 375         struct rb_node *parent = victim->rb_parent;
 376
 377         /* Set the surrounding nodes to point to the replacement */
 378         if (parent) {
 379                 if (victim == parent->rb_left)
 380                         parent->rb_left = new;
 381                 else
 382                         parent->rb_right = new;
 383         } else {
 384                 root->rb_node = new;
 385         }
 386         if (victim->rb_left)
 387                 victim->rb_left->rb_parent = new;
 388         if (victim->rb_right)
 389                 victim->rb_right->rb_parent = new;
 390
 391         /* Copy the pointers/colour from the victim to the replacement */
 392         *new = *victim;
 393 }
 394 EXPORT_SYMBOL(rb_replace_node);