You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING. If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA. */
+the Free Software Foundation, 51 Franklin Street - Fifth Floor,
+Boston, MA 02110-1301, USA. */
/* For an easily readable description of splay-trees, see:
#include "splay-tree.h"
static void splay_tree_delete_helper (splay_tree, splay_tree_node);
+static inline void rotate_left (splay_tree_node *,
+ splay_tree_node, splay_tree_node);
+static inline void rotate_right (splay_tree_node *,
+ splay_tree_node, splay_tree_node);
static void splay_tree_splay (splay_tree, splay_tree_key);
-static splay_tree_node splay_tree_splay_helper (splay_tree,
- splay_tree_key,
- splay_tree_node*,
- splay_tree_node*,
- splay_tree_node*);
static int splay_tree_foreach_helper (splay_tree, splay_tree_node,
splay_tree_foreach_fn, void*);
#undef VDEL
}
-/* Help splay SP around KEY. PARENT and GRANDPARENT are the parent
- and grandparent, respectively, of NODE. */
+/* Rotate the edge joining the left child N with its parent P. PP is the
+ grandparents' pointer to P. */
-static splay_tree_node
-splay_tree_splay_helper (splay_tree sp, splay_tree_key key,
- splay_tree_node *node, splay_tree_node *parent,
- splay_tree_node *grandparent)
+static inline void
+rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
{
- splay_tree_node *next;
- splay_tree_node n;
- int comparison;
-
- n = *node;
-
- if (!n)
- return *parent;
-
- comparison = (*sp->comp) (key, n->key);
-
- if (comparison == 0)
- /* We've found the target. */
- next = 0;
- else if (comparison < 0)
- /* The target is to the left. */
- next = &n->left;
- else
- /* The target is to the right. */
- next = &n->right;
-
- if (next)
- {
- /* Continue down the tree. */
- n = splay_tree_splay_helper (sp, key, next, node, parent);
-
- /* The recursive call will change the place to which NODE
- points. */
- if (*node != n)
- return n;
- }
-
- if (!parent)
- /* NODE is the root. We are done. */
- return n;
-
- /* First, handle the case where there is no grandparent (i.e.,
- *PARENT is the root of the tree.) */
- if (!grandparent)
- {
- if (n == (*parent)->left)
- {
- *node = n->right;
- n->right = *parent;
- }
- else
- {
- *node = n->left;
- n->left = *parent;
- }
- *parent = n;
- return n;
- }
+ splay_tree_node tmp;
+ tmp = n->right;
+ n->right = p;
+ p->left = tmp;
+ *pp = n;
+}
- /* Next handle the cases where both N and *PARENT are left children,
- or where both are right children. */
- if (n == (*parent)->left && *parent == (*grandparent)->left)
- {
- splay_tree_node p = *parent;
-
- (*grandparent)->left = p->right;
- p->right = *grandparent;
- p->left = n->right;
- n->right = p;
- *grandparent = n;
- return n;
- }
- else if (n == (*parent)->right && *parent == (*grandparent)->right)
- {
- splay_tree_node p = *parent;
-
- (*grandparent)->right = p->left;
- p->left = *grandparent;
- p->right = n->left;
- n->left = p;
- *grandparent = n;
- return n;
- }
+/* Rotate the edge joining the right child N with its parent P. PP is the
+ grandparents' pointer to P. */
- /* Finally, deal with the case where N is a left child, but *PARENT
- is a right child, or vice versa. */
- if (n == (*parent)->left)
- {
- (*parent)->left = n->right;
- n->right = *parent;
- (*grandparent)->right = n->left;
- n->left = *grandparent;
- *grandparent = n;
- return n;
- }
- else
- {
- (*parent)->right = n->left;
- n->left = *parent;
- (*grandparent)->left = n->right;
- n->right = *grandparent;
- *grandparent = n;
- return n;
- }
+static inline void
+rotate_right (splay_tree_node *pp, splay_tree_node p, splay_tree_node n)
+{
+ splay_tree_node tmp;
+ tmp = n->left;
+ n->left = p;
+ p->right = tmp;
+ *pp = n;
}
-/* Splay SP around KEY. */
+/* Bottom up splay of key. */
static void
splay_tree_splay (splay_tree sp, splay_tree_key key)
if (sp->root == 0)
return;
- splay_tree_splay_helper (sp, key, &sp->root,
- /*grandparent=*/0, /*parent=*/0);
+ do {
+ int cmp1, cmp2;
+ splay_tree_node n, c;
+
+ n = sp->root;
+ cmp1 = (*sp->comp) (key, n->key);
+
+ /* Found. */
+ if (cmp1 == 0)
+ return;
+
+ /* Left or right? If no child, then we're done. */
+ if (cmp1 < 0)
+ c = n->left;
+ else
+ c = n->right;
+ if (!c)
+ return;
+
+ /* Next one left or right? If found or no child, we're done
+ after one rotation. */
+ cmp2 = (*sp->comp) (key, c->key);
+ if (cmp2 == 0
+ || (cmp2 < 0 && !c->left)
+ || (cmp2 > 0 && !c->right))
+ {
+ if (cmp1 < 0)
+ rotate_left (&sp->root, n, c);
+ else
+ rotate_right (&sp->root, n, c);
+ return;
+ }
+
+ /* Now we have the four cases of double-rotation. */
+ if (cmp1 < 0 && cmp2 < 0)
+ {
+ rotate_left (&n->left, c, c->left);
+ rotate_left (&sp->root, n, n->left);
+ }
+ else if (cmp1 > 0 && cmp2 > 0)
+ {
+ rotate_right (&n->right, c, c->right);
+ rotate_right (&sp->root, n, n->right);
+ }
+ else if (cmp1 < 0 && cmp2 > 0)
+ {
+ rotate_right (&n->left, c, c->right);
+ rotate_left (&sp->root, n, n->left);
+ }
+ else if (cmp1 > 0 && cmp2 < 0)
+ {
+ rotate_left (&n->right, c, c->left);
+ rotate_right (&sp->root, n, n->right);
+ }
+ } while (1);
}
/* Call FN, passing it the DATA, for every node below NODE, all of
OSDN Git Service
