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 "replace.h"
  24 #include "rbtree.h"
  25 #include "fault.h"
  26
  27 #define RB_RED          0
  28 #define RB_BLACK        1
  29
  30 #define rb_parent(r)   ((struct rb_node *)((r)->rb_parent_color & ~3))
  31 #define rb_color(r)   ((r)->rb_parent_color & 1)
  32 #define rb_is_red(r)   (!rb_color(r))
  33 #define rb_is_black(r) rb_color(r)
  34 #define rb_set_red(r)  do { (r)->rb_parent_color &= ~1; } while (0)
  35 #define rb_set_black(r)  do { (r)->rb_parent_color |= 1; } while (0)
  36
  37 static void rb_set_parent(struct rb_node *rb, struct rb_node *p)
  38 {
  39         rb->rb_parent_color = (rb->rb_parent_color & 3) | (unsigned long)p;
  40 }
  41 static void rb_set_color(struct rb_node *rb, int color)
  42 {
  43         rb->rb_parent_color = (rb->rb_parent_color & ~1) | color;
  44 }
  45
  46 #define RB_EMPTY_ROOT(root)     ((root)->rb_node == NULL)
  47 #define RB_EMPTY_NODE(node)     (rb_parent(node) == node)
  48 #define RB_CLEAR_NODE(node)     (rb_set_parent(node, node))
  49
  50 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
  51 {
  52         struct rb_node *right = node->rb_right;
  53         struct rb_node *parent = rb_parent(node);
  54
  55         if ((node->rb_right = right->rb_left))
  56                 rb_set_parent(right->rb_left, node);
  57         right->rb_left = node;
  58
  59         rb_set_parent(right, parent);
  60
  61         if (parent)
  62         {
  63                 if (node == parent->rb_left)
  64                         parent->rb_left = right;
  65                 else
  66                         parent->rb_right = right;
  67         }
  68         else
  69                 root->rb_node = right;
  70         rb_set_parent(node, right);
  71 }
  72
  73 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  74 {
  75         struct rb_node *left = node->rb_left;
  76         struct rb_node *parent = rb_parent(node);
  77
  78         if ((node->rb_left = left->rb_right))
  79                 rb_set_parent(left->rb_right, node);
  80         left->rb_right = node;
  81
  82         rb_set_parent(left, parent);
  83
  84         if (parent)
  85         {
  86                 if (node == parent->rb_right)
  87                         parent->rb_right = left;
  88                 else
  89                         parent->rb_left = left;
  90         }
  91         else
  92                 root->rb_node = left;
  93         rb_set_parent(node, left);
  94 }
  95
  96 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  97 {
  98         struct rb_node *parent, *gparent;
  99
 100         while ((parent = rb_parent(node)) && rb_is_red(parent))
 101         {
 102                 gparent = rb_parent(parent);
 103
 104                 if (parent == gparent->rb_left)
 105                 {
 106                         {
 107                                 register struct rb_node *uncle = gparent->rb_right;
 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_right == node)
 119                         {
 120                                 register struct rb_node *tmp;
 121                                 __rb_rotate_left(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_right(gparent, root);
 130                 } else {
 131                         {
 132                                 register struct rb_node *uncle = gparent->rb_left;
 133                                 if (uncle && rb_is_red(uncle))
 134                                 {
 135                                         rb_set_black(uncle);
 136                                         rb_set_black(parent);
 137                                         rb_set_red(gparent);
 138                                         node = gparent;
 139                                         continue;
 140                                 }
 141                         }
 142
 143                         if (parent->rb_left == node)
 144                         {
 145                                 register struct rb_node *tmp;
 146                                 __rb_rotate_right(parent, root);
 147                                 tmp = parent;
 148                                 parent = node;
 149                                 node = tmp;
 150                         }
 151
 152                         rb_set_black(parent);
 153                         rb_set_red(gparent);
 154                         __rb_rotate_left(gparent, root);
 155                 }
 156         }
 157
 158         rb_set_black(root->rb_node);
 159 }
 160
 161 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 162                              struct rb_root *root)
 163 {
 164         struct rb_node *other;
 165
 166         while ((!node || rb_is_black(node)) && node != root->rb_node)
 167         {
 168                 if (parent->rb_left == node)
 169                 {
 170                         other = parent->rb_right;
 171                         if (other == NULL) {
 172                                 /* we should never get here */
 173                                 smb_panic("corrupted rb tree");
 174                                 /* satisfy static checkers */
 175                                 return;
 176                         }
 177                         if (rb_is_red(other))
 178                         {
 179                                 rb_set_black(other);
 180                                 rb_set_red(parent);
 181                                 __rb_rotate_left(parent, root);
 182                                 other = parent->rb_right;
 183                         }
 184                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 185                             (!other->rb_right || rb_is_black(other->rb_right)))
 186                         {
 187                                 rb_set_red(other);
 188                                 node = parent;
 189                                 parent = rb_parent(node);
 190                         }
 191                         else
 192                         {
 193                                 if (!other->rb_right || rb_is_black(other->rb_right))
 194                                 {
 195                                         struct rb_node *o_left;
 196                                         if ((o_left = other->rb_left))
 197                                                 rb_set_black(o_left);
 198                                         rb_set_red(other);
 199                                         __rb_rotate_right(other, root);
 200                                         other = parent->rb_right;
 201                                 }
 202                                 rb_set_color(other, rb_color(parent));
 203                                 rb_set_black(parent);
 204                                 if (other->rb_right)
 205                                         rb_set_black(other->rb_right);
 206                                 __rb_rotate_left(parent, root);
 207                                 node = root->rb_node;
 208                                 break;
 209                         }
 210                 }
 211                 else
 212                 {
 213                         other = parent->rb_left;
 214                         if (rb_is_red(other))
 215                         {
 216                                 rb_set_black(other);
 217                                 rb_set_red(parent);
 218                                 __rb_rotate_right(parent, root);
 219                                 other = parent->rb_left;
 220                         }
 221                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 222                             (!other->rb_right || rb_is_black(other->rb_right)))
 223                         {
 224                                 rb_set_red(other);
 225                                 node = parent;
 226                                 parent = rb_parent(node);
 227                         }
 228                         else
 229                         {
 230                                 if (!other->rb_left || rb_is_black(other->rb_left))
 231                                 {
 232                                         register struct rb_node *o_right;
 233                                         if ((o_right = other->rb_right))
 234                                                 rb_set_black(o_right);
 235                                         rb_set_red(other);
 236                                         __rb_rotate_left(other, root);
 237                                         other = parent->rb_left;
 238                                 }
 239                                 rb_set_color(other, rb_color(parent));
 240                                 rb_set_black(parent);
 241                                 if (other->rb_left)
 242                                         rb_set_black(other->rb_left);
 243                                 __rb_rotate_right(parent, root);
 244                                 node = root->rb_node;
 245                                 break;
 246                         }
 247                 }
 248         }
 249         if (node)
 250                 rb_set_black(node);
 251 }
 252
 253 void rb_erase(struct rb_node *node, struct rb_root *root)
 254 {
 255         struct rb_node *child, *parent;
 256         int color;
 257
 258         if (!node->rb_left)
 259                 child = node->rb_right;
 260         else if (!node->rb_right)
 261                 child = node->rb_left;
 262         else
 263         {
 264                 struct rb_node *old = node, *left;
 265
 266                 node = node->rb_right;
 267                 while ((left = node->rb_left) != NULL)
 268                         node = left;
 269                 child = node->rb_right;
 270                 parent = rb_parent(node);
 271                 color = rb_color(node);
 272
 273                 if (child)
 274                         rb_set_parent(child, parent);
 275                 if (parent == old) {
 276                         parent->rb_right = child;
 277                         parent = node;
 278                 } else
 279                         parent->rb_left = child;
 280
 281                 node->rb_parent_color = old->rb_parent_color;
 282                 node->rb_right = old->rb_right;
 283                 node->rb_left = old->rb_left;
 284
 285                 if (rb_parent(old))
 286                 {
 287                         if (rb_parent(old)->rb_left == old)
 288                                 rb_parent(old)->rb_left = node;
 289                         else
 290                                 rb_parent(old)->rb_right = node;
 291                 } else
 292                         root->rb_node = node;
 293
 294                 rb_set_parent(old->rb_left, node);
 295                 if (old->rb_right)
 296                         rb_set_parent(old->rb_right, node);
 297                 goto color;
 298         }
 299
 300         parent = rb_parent(node);
 301         color = rb_color(node);
 302
 303         if (child)
 304                 rb_set_parent(child, parent);
 305         if (parent)
 306         {
 307                 if (parent->rb_left == node)
 308                         parent->rb_left = child;
 309                 else
 310                         parent->rb_right = child;
 311         }
 312         else
 313                 root->rb_node = child;
 314
 315  color:
 316         if (color == RB_BLACK)
 317                 __rb_erase_color(child, parent, root);
 318 }
 319
 320 /*
 321  * This function returns the first node (in sort order) of the tree.
 322  */
 323 struct rb_node *rb_first(struct rb_root *root)
 324 {
 325         struct rb_node  *n;
 326
 327         n = root->rb_node;
 328         if (!n)
 329                 return NULL;
 330         while (n->rb_left)
 331                 n = n->rb_left;
 332         return n;
 333 }
 334
 335 struct rb_node *rb_last(struct rb_root *root)
 336 {
 337         struct rb_node  *n;
 338
 339         n = root->rb_node;
 340         if (!n)
 341                 return NULL;
 342         while (n->rb_right)
 343                 n = n->rb_right;
 344         return n;
 345 }
 346
 347 struct rb_node *rb_next(struct rb_node *node)
 348 {
 349         struct rb_node *parent;
 350
 351         if (rb_parent(node) == node)
 352                 return NULL;
 353
 354         /* If we have a right-hand child, go down and then left as far
 355            as we can. */
 356         if (node->rb_right) {
 357                 node = node->rb_right;
 358                 while (node->rb_left)
 359                         node=node->rb_left;
 360                 return node;
 361         }
 362
 363         /* No right-hand children.  Everything down and left is
 364            smaller than us, so any 'next' node must be in the general
 365            direction of our parent. Go up the tree; any time the
 366            ancestor is a right-hand child of its parent, keep going
 367            up. First time it's a left-hand child of its parent, said
 368            parent is our 'next' node. */
 369         while ((parent = rb_parent(node)) && node == parent->rb_right)
 370                 node = parent;
 371
 372         return parent;
 373 }
 374
 375 struct rb_node *rb_prev(struct rb_node *node)
 376 {
 377         struct rb_node *parent;
 378
 379         if (rb_parent(node) == node)
 380                 return NULL;
 381
 382         /* If we have a left-hand child, go down and then right as far
 383            as we can. */
 384         if (node->rb_left) {
 385                 node = node->rb_left;
 386                 while (node->rb_right)
 387                         node=node->rb_right;
 388                 return node;
 389         }
 390
 391         /* No left-hand children. Go up till we find an ancestor which
 392            is a right-hand child of its parent */
 393         while ((parent = rb_parent(node)) && node == parent->rb_left)
 394                 node = parent;
 395
 396         return parent;
 397 }
 398
 399 void rb_replace_node(struct rb_node *victim, struct rb_node *new_node,
 400                      struct rb_root *root)
 401 {
 402         struct rb_node *parent = rb_parent(victim);
 403
 404         /* Set the surrounding nodes to point to the replacement */
 405         if (parent) {
 406                 if (victim == parent->rb_left)
 407                         parent->rb_left = new_node;
 408                 else
 409                         parent->rb_right = new_node;
 410         } else {
 411                 root->rb_node = new_node;
 412         }
 413         if (victim->rb_left)
 414                 rb_set_parent(victim->rb_left, new_node);
 415         if (victim->rb_right)
 416                 rb_set_parent(victim->rb_right, new_node);
 417
 418         /* Copy the pointers/colour from the victim to the replacement */
 419         *new_node = *victim;
 420 }
 421
 422 void rb_link_node(struct rb_node * node, struct rb_node * parent,
 423                   struct rb_node ** rb_link)
 424 {
 425         node->rb_parent_color = (unsigned long )parent;
 426         node->rb_left = node->rb_right = NULL;
 427
 428         *rb_link = node;
 429 }