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