lib/ext2fs/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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  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 = ext2fs_rb_parent(node);
  29
  30         if ((node->rb_right = right->rb_left))
  31                 ext2fs_rb_set_parent(right->rb_left, node);
  32         right->rb_left = node;
  33
  34         ext2fs_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         ext2fs_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 = ext2fs_rb_parent(node);
  52
  53         if ((node->rb_left = left->rb_right))
  54                 ext2fs_rb_set_parent(left->rb_right, node);
  55         left->rb_right = node;
  56
  57         ext2fs_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         ext2fs_rb_set_parent(node, left);
  69 }
  70
  71 void ext2fs_rb_insert_color(struct rb_node *node, struct rb_root *root)
  72 {
  73         struct rb_node *parent, *gparent;
  74
  75         while ((parent = ext2fs_rb_parent(node)) && ext2fs_rb_is_red(parent))
  76         {
  77                 gparent = ext2fs_rb_parent(parent);
  78
  79                 if (parent == gparent->rb_left)
  80                 {
  81                         {
  82                                 register struct rb_node *uncle = gparent->rb_right;
  83                                 if (uncle && ext2fs_rb_is_red(uncle))
  84                                 {
  85                                         ext2fs_rb_set_black(uncle);
  86                                         ext2fs_rb_set_black(parent);
  87                                         ext2fs_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                         ext2fs_rb_set_black(parent);
 103                         ext2fs_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 && ext2fs_rb_is_red(uncle))
 109                                 {
 110                                         ext2fs_rb_set_black(uncle);
 111                                         ext2fs_rb_set_black(parent);
 112                                         ext2fs_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                         ext2fs_rb_set_black(parent);
 128                         ext2fs_rb_set_red(gparent);
 129                         __rb_rotate_left(gparent, root);
 130                 }
 131         }
 132
 133         ext2fs_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 || ext2fs_rb_is_black(node)) && node != root->rb_node)
 142         {
 143                 if (parent->rb_left == node)
 144                 {
 145                         other = parent->rb_right;
 146                         if (ext2fs_rb_is_red(other))
 147                         {
 148                                 ext2fs_rb_set_black(other);
 149                                 ext2fs_rb_set_red(parent);
 150                                 __rb_rotate_left(parent, root);
 151                                 other = parent->rb_right;
 152                         }
 153                         if ((!other->rb_left || ext2fs_rb_is_black(other->rb_left)) &&
 154                             (!other->rb_right || ext2fs_rb_is_black(other->rb_right)))
 155                         {
 156                                 ext2fs_rb_set_red(other);
 157                                 node = parent;
 158                                 parent = ext2fs_rb_parent(node);
 159                         }
 160                         else
 161                         {
 162                                 if (!other->rb_right || ext2fs_rb_is_black(other->rb_right))
 163                                 {
 164                                         ext2fs_rb_set_black(other->rb_left);
 165                                         ext2fs_rb_set_red(other);
 166                                         __rb_rotate_right(other, root);
 167                                         other = parent->rb_right;
 168                                 }
 169                                 ext2fs_rb_set_color(other, ext2fs_rb_color(parent));
 170                                 ext2fs_rb_set_black(parent);
 171                                 ext2fs_rb_set_black(other->rb_right);
 172                                 __rb_rotate_left(parent, root);
 173                                 node = root->rb_node;
 174                                 break;
 175                         }
 176                 }
 177                 else
 178                 {
 179                         other = parent->rb_left;
 180                         if (ext2fs_rb_is_red(other))
 181                         {
 182                                 ext2fs_rb_set_black(other);
 183                                 ext2fs_rb_set_red(parent);
 184                                 __rb_rotate_right(parent, root);
 185                                 other = parent->rb_left;
 186                         }
 187                         if ((!other->rb_left || ext2fs_rb_is_black(other->rb_left)) &&
 188                             (!other->rb_right || ext2fs_rb_is_black(other->rb_right)))
 189                         {
 190                                 ext2fs_rb_set_red(other);
 191                                 node = parent;
 192                                 parent = ext2fs_rb_parent(node);
 193                         }
 194                         else
 195                         {
 196                                 if (!other->rb_left || ext2fs_rb_is_black(other->rb_left))
 197                                 {
 198                                         ext2fs_rb_set_black(other->rb_right);
 199                                         ext2fs_rb_set_red(other);
 200                                         __rb_rotate_left(other, root);
 201                                         other = parent->rb_left;
 202                                 }
 203                                 ext2fs_rb_set_color(other, ext2fs_rb_color(parent));
 204                                 ext2fs_rb_set_black(parent);
 205                                 ext2fs_rb_set_black(other->rb_left);
 206                                 __rb_rotate_right(parent, root);
 207                                 node = root->rb_node;
 208                                 break;
 209                         }
 210                 }
 211         }
 212         if (node)
 213                 ext2fs_rb_set_black(node);
 214 }
 215
 216 void ext2fs_rb_erase(struct rb_node *node, struct rb_root *root)
 217 {
 218         struct rb_node *child, *parent;
 219         int color;
 220
 221         if (!node->rb_left)
 222                 child = node->rb_right;
 223         else if (!node->rb_right)
 224                 child = node->rb_left;
 225         else
 226         {
 227                 struct rb_node *old = node, *left;
 228
 229                 node = node->rb_right;
 230                 while ((left = node->rb_left) != NULL)
 231                         node = left;
 232
 233                 if (ext2fs_rb_parent(old)) {
 234                         if (ext2fs_rb_parent(old)->rb_left == old)
 235                                 ext2fs_rb_parent(old)->rb_left = node;
 236                         else
 237                                 ext2fs_rb_parent(old)->rb_right = node;
 238                 } else
 239                         root->rb_node = node;
 240
 241                 child = node->rb_right;
 242                 parent = ext2fs_rb_parent(node);
 243                 color = ext2fs_rb_color(node);
 244
 245                 if (parent == old) {
 246                         parent = node;
 247                 } else {
 248                         if (child)
 249                                 ext2fs_rb_set_parent(child, parent);
 250                         parent->rb_left = child;
 251
 252                         node->rb_right = old->rb_right;
 253                         ext2fs_rb_set_parent(old->rb_right, node);
 254                 }
 255
 256                 node->rb_parent_color = old->rb_parent_color;
 257                 node->rb_left = old->rb_left;
 258                 ext2fs_rb_set_parent(old->rb_left, node);
 259
 260                 goto color;
 261         }
 262
 263         parent = ext2fs_rb_parent(node);
 264         color = ext2fs_rb_color(node);
 265
 266         if (child)
 267                 ext2fs_rb_set_parent(child, parent);
 268         if (parent)
 269         {
 270                 if (parent->rb_left == node)
 271                         parent->rb_left = child;
 272                 else
 273                         parent->rb_right = child;
 274         }
 275         else
 276                 root->rb_node = child;
 277
 278  color:
 279         if (color == RB_BLACK)
 280                 __rb_erase_color(child, parent, root);
 281 }
 282
 283 static void ext2fs_rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
 284 {
 285         struct rb_node *parent;
 286
 287 up:
 288         func(node, data);
 289         parent = ext2fs_rb_parent(node);
 290         if (!parent)
 291                 return;
 292
 293         if (node == parent->rb_left && parent->rb_right)
 294                 func(parent->rb_right, data);
 295         else if (parent->rb_left)
 296                 func(parent->rb_left, data);
 297
 298         node = parent;
 299         goto up;
 300 }
 301
 302 /*
 303  * after inserting @node into the tree, update the tree to account for
 304  * both the new entry and any damage done by rebalance
 305  */
 306 void ext2fs_rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
 307 {
 308         if (node->rb_left)
 309                 node = node->rb_left;
 310         else if (node->rb_right)
 311                 node = node->rb_right;
 312
 313         ext2fs_rb_augment_path(node, func, data);
 314 }
 315
 316 /*
 317  * before removing the node, find the deepest node on the rebalance path
 318  * that will still be there after @node gets removed
 319  */
 320 struct rb_node *ext2fs_rb_augment_erase_begin(struct rb_node *node)
 321 {
 322         struct rb_node *deepest;
 323
 324         if (!node->rb_right && !node->rb_left)
 325                 deepest = ext2fs_rb_parent(node);
 326         else if (!node->rb_right)
 327                 deepest = node->rb_left;
 328         else if (!node->rb_left)
 329                 deepest = node->rb_right;
 330         else {
 331                 deepest = ext2fs_rb_next(node);
 332                 if (deepest->rb_right)
 333                         deepest = deepest->rb_right;
 334                 else if (ext2fs_rb_parent(deepest) != node)
 335                         deepest = ext2fs_rb_parent(deepest);
 336         }
 337
 338         return deepest;
 339 }
 340
 341 /*
 342  * after removal, update the tree to account for the removed entry
 343  * and any rebalance damage.
 344  */
 345 void ext2fs_rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
 346 {
 347         if (node)
 348                 ext2fs_rb_augment_path(node, func, data);
 349 }
 350
 351 /*
 352  * This function returns the first node (in sort order) of the tree.
 353  */
 354 struct rb_node *ext2fs_rb_first(const struct rb_root *root)
 355 {
 356         struct rb_node  *n;
 357
 358         n = root->rb_node;
 359         if (!n)
 360                 return NULL;
 361         while (n->rb_left)
 362                 n = n->rb_left;
 363         return n;
 364 }
 365
 366 struct rb_node *ext2fs_rb_last(const struct rb_root *root)
 367 {
 368         struct rb_node  *n;
 369
 370         n = root->rb_node;
 371         if (!n)
 372                 return NULL;
 373         while (n->rb_right)
 374                 n = n->rb_right;
 375         return n;
 376 }
 377
 378 struct rb_node *ext2fs_rb_next(struct rb_node *node)
 379 {
 380         struct rb_node *parent;
 381
 382         if (ext2fs_rb_parent(node) == node)
 383                 return NULL;
 384
 385         /* If we have a right-hand child, go down and then left as far
 386            as we can. */
 387         if (node->rb_right) {
 388                 node = node->rb_right;
 389                 while (node->rb_left)
 390                         node=node->rb_left;
 391                 return (struct rb_node *)node;
 392         }
 393
 394         /* No right-hand children.  Everything down and left is
 395            smaller than us, so any 'next' node must be in the general
 396            direction of our parent. Go up the tree; any time the
 397            ancestor is a right-hand child of its parent, keep going
 398            up. First time it's a left-hand child of its parent, said
 399            parent is our 'next' node. */
 400         while ((parent = ext2fs_rb_parent(node)) && node == parent->rb_right)
 401                 node = parent;
 402
 403         return parent;
 404 }
 405
 406 struct rb_node *ext2fs_rb_prev(struct rb_node *node)
 407 {
 408         struct rb_node *parent;
 409
 410         if (ext2fs_rb_parent(node) == node)
 411                 return NULL;
 412
 413         /* If we have a left-hand child, go down and then right as far
 414            as we can. */
 415         if (node->rb_left) {
 416                 node = node->rb_left;
 417                 while (node->rb_right)
 418                         node=node->rb_right;
 419                 return (struct rb_node *)node;
 420         }
 421
 422         /* No left-hand children. Go up till we find an ancestor which
 423            is a right-hand child of its parent */
 424         while ((parent = ext2fs_rb_parent(node)) && node == parent->rb_left)
 425                 node = parent;
 426
 427         return parent;
 428 }
 429
 430 void ext2fs_rb_replace_node(struct rb_node *victim, struct rb_node *new,
 431                           struct rb_root *root)
 432 {
 433         struct rb_node *parent = ext2fs_rb_parent(victim);
 434
 435         /* Set the surrounding nodes to point to the replacement */
 436         if (parent) {
 437                 if (victim == parent->rb_left)
 438                         parent->rb_left = new;
 439                 else
 440                         parent->rb_right = new;
 441         } else {
 442                 root->rb_node = new;
 443         }
 444         if (victim->rb_left)
 445                 ext2fs_rb_set_parent(victim->rb_left, new);
 446         if (victim->rb_right)
 447                 ext2fs_rb_set_parent(victim->rb_right, new);
 448
 449         /* Copy the pointers/colour from the victim to the replacement */
 450         *new = *victim;
 451 }