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., 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 fio_rb_node *node, struct rb_root *root)
  26 {
  27         struct fio_rb_node *right = node->rb_right;
  28         struct fio_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 fio_rb_node *node, struct rb_root *root)
  49 {
  50         struct fio_rb_node *left = node->rb_left;
  51         struct fio_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 fio_rb_node *node, struct rb_root *root)
  72 {
  73         struct fio_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 fio_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 fio_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 fio_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 fio_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 fio_rb_node *node,
 137                              struct fio_rb_node *parent,
 138                              struct rb_root *root)
 139 {
 140         struct fio_rb_node *other;
 141
 142         while ((!node || rb_is_black(node)) && node != root->rb_node)
 143         {
 144                 if (parent->rb_left == node)
 145                 {
 146                         other = parent->rb_right;
 147                         if (rb_is_red(other))
 148                         {
 149                                 rb_set_black(other);
 150                                 rb_set_red(parent);
 151                                 __rb_rotate_left(parent, root);
 152                                 other = parent->rb_right;
 153                         }
 154                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 155                             (!other->rb_right || rb_is_black(other->rb_right)))
 156                         {
 157                                 rb_set_red(other);
 158                                 node = parent;
 159                                 parent = rb_parent(node);
 160                         }
 161                         else
 162                         {
 163                                 if (!other->rb_right || rb_is_black(other->rb_right))
 164                                 {
 165                                         struct fio_rb_node *o_left;
 166                                         if ((o_left = other->rb_left))
 167                                                 rb_set_black(o_left);
 168                                         rb_set_red(other);
 169                                         __rb_rotate_right(other, root);
 170                                         other = parent->rb_right;
 171                                 }
 172                                 rb_set_color(other, rb_color(parent));
 173                                 rb_set_black(parent);
 174                                 if (other->rb_right)
 175                                         rb_set_black(other->rb_right);
 176                                 __rb_rotate_left(parent, root);
 177                                 node = root->rb_node;
 178                                 break;
 179                         }
 180                 }
 181                 else
 182                 {
 183                         other = parent->rb_left;
 184                         if (rb_is_red(other))
 185                         {
 186                                 rb_set_black(other);
 187                                 rb_set_red(parent);
 188                                 __rb_rotate_right(parent, root);
 189                                 other = parent->rb_left;
 190                         }
 191                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 192                             (!other->rb_right || rb_is_black(other->rb_right)))
 193                         {
 194                                 rb_set_red(other);
 195                                 node = parent;
 196                                 parent = rb_parent(node);
 197                         }
 198                         else
 199                         {
 200                                 if (!other->rb_left || rb_is_black(other->rb_left))
 201                                 {
 202                                         register struct fio_rb_node *o_right;
 203                                         if ((o_right = other->rb_right))
 204                                                 rb_set_black(o_right);
 205                                         rb_set_red(other);
 206                                         __rb_rotate_left(other, root);
 207                                         other = parent->rb_left;
 208                                 }
 209                                 rb_set_color(other, rb_color(parent));
 210                                 rb_set_black(parent);
 211                                 if (other->rb_left)
 212                                         rb_set_black(other->rb_left);
 213                                 __rb_rotate_right(parent, root);
 214                                 node = root->rb_node;
 215                                 break;
 216                         }
 217                 }
 218         }
 219         if (node)
 220                 rb_set_black(node);
 221 }
 222
 223 void rb_erase(struct fio_rb_node *node, struct rb_root *root)
 224 {
 225         struct fio_rb_node *child, *parent;
 226         int color;
 227
 228         if (!node->rb_left)
 229                 child = node->rb_right;
 230         else if (!node->rb_right)
 231                 child = node->rb_left;
 232         else
 233         {
 234                 struct fio_rb_node *old = node, *left;
 235
 236                 node = node->rb_right;
 237                 while ((left = node->rb_left) != NULL)
 238                         node = left;
 239                 child = node->rb_right;
 240                 parent = rb_parent(node);
 241                 color = rb_color(node);
 242
 243                 if (child)
 244                         rb_set_parent(child, parent);
 245                 if (parent == old) {
 246                         parent->rb_right = child;
 247                         parent = node;
 248                 } else
 249                         parent->rb_left = child;
 250
 251                 node->rb_parent_color = old->rb_parent_color;
 252                 node->rb_right = old->rb_right;
 253                 node->rb_left = old->rb_left;
 254
 255                 if (rb_parent(old))
 256                 {
 257                         if (rb_parent(old)->rb_left == old)
 258                                 rb_parent(old)->rb_left = node;
 259                         else
 260                                 rb_parent(old)->rb_right = node;
 261                 } else
 262                         root->rb_node = node;
 263
 264                 rb_set_parent(old->rb_left, node);
 265                 if (old->rb_right)
 266                         rb_set_parent(old->rb_right, node);
 267                 goto color;
 268         }
 269
 270         parent = rb_parent(node);
 271         color = rb_color(node);
 272
 273         if (child)
 274                 rb_set_parent(child, parent);
 275         if (parent)
 276         {
 277                 if (parent->rb_left == node)
 278                         parent->rb_left = child;
 279                 else
 280                         parent->rb_right = child;
 281         }
 282         else
 283                 root->rb_node = child;
 284
 285  color:
 286         if (color == RB_BLACK)
 287                 __rb_erase_color(child, parent, root);
 288 }
 289
 290 /*
 291  * This function returns the first node (in sort order) of the tree.
 292  */
 293 struct fio_rb_node *rb_first(struct rb_root *root)
 294 {
 295         struct fio_rb_node      *n;
 296
 297         n = root->rb_node;
 298         if (!n)
 299                 return NULL;
 300         while (n->rb_left)
 301                 n = n->rb_left;
 302         return n;
 303 }
 304
 305 struct fio_rb_node *rb_next(const struct fio_rb_node *node)
 306 {
 307         struct fio_rb_node *parent;
 308
 309         if (RB_EMPTY_NODE(node))
 310                 return NULL;
 311
 312         /*
 313          * If we have a right-hand child, go down and then left as far
 314          * as we can.
 315          */
 316         if (node->rb_right) {
 317                 node = node->rb_right;
 318                 while (node->rb_left)
 319                         node=node->rb_left;
 320                 return (struct fio_rb_node *)node;
 321         }
 322
 323         /*
 324          * No right-hand children. Everything down and left is smaller than us,
 325          * so any 'next' node must be in the general direction of our parent.
 326          * Go up the tree; any time the ancestor is a right-hand child of its
 327          * parent, keep going up. First time it's a left-hand child of its
 328          * parent, said parent is our 'next' node.
 329          */
 330         while ((parent = rb_parent(node)) && node == parent->rb_right)
 331                 node = parent;
 332
 333         return parent;
 334 }