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