lib/util/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 "includes.h"
  24 #include "rbtree.h"
  25
  26 #define RB_RED          0
  27 #define RB_BLACK        1
  28
  29 #define rb_parent(r)   ((struct rb_node *)((r)->rb_parent_color & ~3))
  30 #define rb_color(r)   ((r)->rb_parent_color & 1)
  31 #define rb_is_red(r)   (!rb_color(r))
  32 #define rb_is_black(r) rb_color(r)
  33 #define rb_set_red(r)  do { (r)->rb_parent_color &= ~1; } while (0)
  34 #define rb_set_black(r)  do { (r)->rb_parent_color |= 1; } while (0)
  35
  36 static void rb_set_parent(struct rb_node *rb, struct rb_node *p)
  37 {
  38         rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
  39 }
  40 static void rb_set_color(struct rb_node *rb, int color)
  41 {
  42         rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
  43 }
  44
  45 #define RB_EMPTY_ROOT(root)     ((root)->rb_node == NULL)
  46 #define RB_EMPTY_NODE(node)     (rb_parent(node) == node)
  47 #define RB_CLEAR_NODE(node)     (rb_set_parent(node, node))
  48
  49 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
  50 {
  51         struct rb_node *right = node->rb_right;
  52         struct rb_node *parent = rb_parent(node);
  53
  54         if ((node->rb_right = right->rb_left))
  55                 rb_set_parent(right->rb_left, node);
  56         right->rb_left = node;
  57
  58         rb_set_parent(right, parent);
  59
  60         if (parent)
  61         {
  62                 if (node == parent->rb_left)
  63                         parent->rb_left = right;
  64                 else
  65                         parent->rb_right = right;
  66         }
  67         else
  68                 root->rb_node = right;
  69         rb_set_parent(node, right);
  70 }
  71
  72 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  73 {
  74         struct rb_node *left = node->rb_left;
  75         struct rb_node *parent = rb_parent(node);
  76
  77         if ((node->rb_left = left->rb_right))
  78                 rb_set_parent(left->rb_right, node);
  79         left->rb_right = node;
  80
  81         rb_set_parent(left, parent);
  82
  83         if (parent)
  84         {
  85                 if (node == parent->rb_right)
  86                         parent->rb_right = left;
  87                 else
  88                         parent->rb_left = left;
  89         }
  90         else
  91                 root->rb_node = left;
  92         rb_set_parent(node, left);
  93 }
  94
  95 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  96 {
  97         struct rb_node *parent, *gparent;
  98
  99         while ((parent = rb_parent(node)) && rb_is_red(parent))
 100         {
 101                 gparent = rb_parent(parent);
 102
 103                 if (parent == gparent->rb_left)
 104                 {
 105                         {
 106                                 register struct rb_node *uncle = gparent->rb_right;
 107                                 if (uncle && rb_is_red(uncle))
 108                                 {
 109                                         rb_set_black(uncle);
 110                                         rb_set_black(parent);
 111                                         rb_set_red(gparent);
 112                                         node = gparent;
 113                                         continue;
 114                                 }
 115                         }
 116
 117                         if (parent->rb_right == node)
 118                         {
 119                                 register struct rb_node *tmp;
 120                                 __rb_rotate_left(parent, root);
 121                                 tmp = parent;
 122                                 parent = node;
 123                                 node = tmp;
 124                         }
 125
 126                         rb_set_black(parent);
 127                         rb_set_red(gparent);
 128                         __rb_rotate_right(gparent, root);
 129                 } else {
 130                         {
 131                                 register struct rb_node *uncle = gparent->rb_left;
 132                                 if (uncle && rb_is_red(uncle))
 133                                 {
 134                                         rb_set_black(uncle);
 135                                         rb_set_black(parent);
 136                                         rb_set_red(gparent);
 137                                         node = gparent;
 138                                         continue;
 139                                 }
 140                         }
 141
 142                         if (parent->rb_left == node)
 143                         {
 144                                 register struct rb_node *tmp;
 145                                 __rb_rotate_right(parent, root);
 146                                 tmp = parent;
 147                                 parent = node;
 148                                 node = tmp;
 149                         }
 150
 151                         rb_set_black(parent);
 152                         rb_set_red(gparent);
 153                         __rb_rotate_left(gparent, root);
 154                 }
 155         }
 156
 157         rb_set_black(root->rb_node);
 158 }
 159
 160 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 161                              struct rb_root *root)
 162 {
 163         struct rb_node *other;
 164
 165         while ((!node || rb_is_black(node)) && node != root->rb_node)
 166         {
 167                 if (parent->rb_left == node)
 168                 {
 169                         other = parent->rb_right;
 170                         if (rb_is_red(other))
 171                         {
 172                                 rb_set_black(other);
 173                                 rb_set_red(parent);
 174                                 __rb_rotate_left(parent, root);
 175                                 other = parent->rb_right;
 176                         }
 177                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 178                             (!other->rb_right || rb_is_black(other->rb_right)))
 179                         {
 180                                 rb_set_red(other);
 181                                 node = parent;
 182                                 parent = rb_parent(node);
 183                         }
 184                         else
 185                         {
 186                                 if (!other->rb_right || rb_is_black(other->rb_right))
 187                                 {
 188                                         struct rb_node *o_left;
 189                                         if ((o_left = other->rb_left))
 190                                                 rb_set_black(o_left);
 191                                         rb_set_red(other);
 192                                         __rb_rotate_right(other, root);
 193                                         other = parent->rb_right;
 194                                 }
 195                                 rb_set_color(other, rb_color(parent));
 196                                 rb_set_black(parent);
 197                                 if (other->rb_right)
 198                                         rb_set_black(other->rb_right);
 199                                 __rb_rotate_left(parent, root);
 200                                 node = root->rb_node;
 201                                 break;
 202                         }
 203                 }
 204                 else
 205                 {
 206                         other = parent->rb_left;
 207                         if (rb_is_red(other))
 208                         {
 209                                 rb_set_black(other);
 210                                 rb_set_red(parent);
 211                                 __rb_rotate_right(parent, root);
 212                                 other = parent->rb_left;
 213                         }
 214                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 215                             (!other->rb_right || rb_is_black(other->rb_right)))
 216                         {
 217                                 rb_set_red(other);
 218                                 node = parent;
 219                                 parent = rb_parent(node);
 220                         }
 221                         else
 222                         {
 223                                 if (!other->rb_left || rb_is_black(other->rb_left))
 224                                 {
 225                                         register struct rb_node *o_right;
 226                                         if ((o_right = other->rb_right))
 227                                                 rb_set_black(o_right);
 228                                         rb_set_red(other);
 229                                         __rb_rotate_left(other, root);
 230                                         other = parent->rb_left;
 231                                 }
 232                                 rb_set_color(other, rb_color(parent));
 233                                 rb_set_black(parent);
 234                                 if (other->rb_left)
 235                                         rb_set_black(other->rb_left);
 236                                 __rb_rotate_right(parent, root);
 237                                 node = root->rb_node;
 238                                 break;
 239                         }
 240                 }
 241         }
 242         if (node)
 243                 rb_set_black(node);
 244 }
 245
 246 void rb_erase(struct rb_node *node, struct rb_root *root)
 247 {
 248         struct rb_node *child, *parent;
 249         int color;
 250
 251         if (!node->rb_left)
 252                 child = node->rb_right;
 253         else if (!node->rb_right)
 254                 child = node->rb_left;
 255         else
 256         {
 257                 struct rb_node *old = node, *left;
 258
 259                 node = node->rb_right;
 260                 while ((left = node->rb_left) != NULL)
 261                         node = left;
 262                 child = node->rb_right;
 263                 parent = rb_parent(node);
 264                 color = rb_color(node);
 265
 266                 if (child)
 267                         rb_set_parent(child, parent);
 268                 if (parent == old) {
 269                         parent->rb_right = child;
 270                         parent = node;
 271                 } else
 272                         parent->rb_left = child;
 273
 274                 node->rb_parent_color = old->rb_parent_color;
 275                 node->rb_right = old->rb_right;
 276                 node->rb_left = old->rb_left;
 277
 278                 if (rb_parent(old))
 279                 {
 280                         if (rb_parent(old)->rb_left == old)
 281                                 rb_parent(old)->rb_left = node;
 282                         else
 283                                 rb_parent(old)->rb_right = node;
 284                 } else
 285                         root->rb_node = node;
 286
 287                 rb_set_parent(old->rb_left, node);
 288                 if (old->rb_right)
 289                         rb_set_parent(old->rb_right, node);
 290                 goto color;
 291         }
 292
 293         parent = rb_parent(node);
 294         color = rb_color(node);
 295
 296         if (child)
 297                 rb_set_parent(child, parent);
 298         if (parent)
 299         {
 300                 if (parent->rb_left == node)
 301                         parent->rb_left = child;
 302                 else
 303                         parent->rb_right = child;
 304         }
 305         else
 306                 root->rb_node = child;
 307
 308  color:
 309         if (color == RB_BLACK)
 310                 __rb_erase_color(child, parent, root);
 311 }
 312
 313 /*
 314  * This function returns the first node (in sort order) of the tree.
 315  */
 316 struct rb_node *rb_first(struct rb_root *root)
 317 {
 318         struct rb_node  *n;
 319
 320         n = root->rb_node;
 321         if (!n)
 322                 return NULL;
 323         while (n->rb_left)
 324                 n = n->rb_left;
 325         return n;
 326 }
 327
 328 struct rb_node *rb_last(struct rb_root *root)
 329 {
 330         struct rb_node  *n;
 331
 332         n = root->rb_node;
 333         if (!n)
 334                 return NULL;
 335         while (n->rb_right)
 336                 n = n->rb_right;
 337         return n;
 338 }
 339
 340 struct rb_node *rb_next(struct rb_node *node)
 341 {
 342         struct rb_node *parent;
 343
 344         if (rb_parent(node) == node)
 345                 return NULL;
 346
 347         /* If we have a right-hand child, go down and then left as far
 348            as we can. */
 349         if (node->rb_right) {
 350                 node = node->rb_right;
 351                 while (node->rb_left)
 352                         node=node->rb_left;
 353                 return node;
 354         }
 355
 356         /* No right-hand children.  Everything down and left is
 357            smaller than us, so any 'next' node must be in the general
 358            direction of our parent. Go up the tree; any time the
 359            ancestor is a right-hand child of its parent, keep going
 360            up. First time it's a left-hand child of its parent, said
 361            parent is our 'next' node. */
 362         while ((parent = rb_parent(node)) && node == parent->rb_right)
 363                 node = parent;
 364
 365         return parent;
 366 }
 367
 368 struct rb_node *rb_prev(struct rb_node *node)
 369 {
 370         struct rb_node *parent;
 371
 372         if (rb_parent(node) == node)
 373                 return NULL;
 374
 375         /* If we have a left-hand child, go down and then right as far
 376            as we can. */
 377         if (node->rb_left) {
 378                 node = node->rb_left;
 379                 while (node->rb_right)
 380                         node=node->rb_right;
 381                 return node;
 382         }
 383
 384         /* No left-hand children. Go up till we find an ancestor which
 385            is a right-hand child of its parent */
 386         while ((parent = rb_parent(node)) && node == parent->rb_left)
 387                 node = parent;
 388
 389         return parent;
 390 }
 391
 392 void rb_replace_node(struct rb_node *victim, struct rb_node *new_node,
 393                      struct rb_root *root)
 394 {
 395         struct rb_node *parent = rb_parent(victim);
 396
 397         /* Set the surrounding nodes to point to the replacement */
 398         if (parent) {
 399                 if (victim == parent->rb_left)
 400                         parent->rb_left = new_node;
 401                 else
 402                         parent->rb_right = new_node;
 403         } else {
 404                 root->rb_node = new_node;
 405         }
 406         if (victim->rb_left)
 407                 rb_set_parent(victim->rb_left, new_node);
 408         if (victim->rb_right)
 409                 rb_set_parent(victim->rb_right, new_node);
 410
 411         /* Copy the pointers/colour from the victim to the replacement */
 412         *new_node = *victim;
 413 }
 414
 415 void rb_link_node(struct rb_node * node, struct rb_node * parent,
 416                   struct rb_node ** rb_link)
 417 {
 418         node->rb_parent_color = (unsigned long )parent;
 419         node->rb_left = node->rb_right = NULL;
 420
 421         *rb_link = node;
 422 }