/* A splay-tree datatype. | |

Copyright (C) 1998-2015 Free Software Foundation, Inc. | |

Contributed by Mark Mitchell (mark@markmitchell.com). | |

This file is part of the GNU Offloading and Multi Processing Library | |

(libgomp). | |

Libgomp is free software; you can redistribute it and/or modify it | |

under the terms of the GNU General Public License as published by | |

the Free Software Foundation; either version 3, or (at your option) | |

any later version. | |

Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY | |

WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | |

FOR A PARTICULAR PURPOSE. See the GNU General Public License for | |

more details. | |

Under Section 7 of GPL version 3, you are granted additional | |

permissions described in the GCC Runtime Library Exception, version | |

3.1, as published by the Free Software Foundation. | |

You should have received a copy of the GNU General Public License and | |

a copy of the GCC Runtime Library Exception along with this program; | |

see the files COPYING3 and COPYING.RUNTIME respectively. If not, see | |

<http://www.gnu.org/licenses/>. */ | |

/* The splay tree code copied from include/splay-tree.h and adjusted, | |

so that all the data lives directly in splay_tree_node_s structure | |

and no extra allocations are needed. */ | |

/* For an easily readable description of splay-trees, see: | |

Lewis, Harry R. and Denenberg, Larry. Data Structures and Their | |

Algorithms. Harper-Collins, Inc. 1991. | |

The major feature of splay trees is that all basic tree operations | |

are amortized O(log n) time for a tree with n nodes. */ | |

#include "libgomp.h" | |

#include "splay-tree.h" | |

extern int splay_compare (splay_tree_key, splay_tree_key); | |

/* Rotate the edge joining the left child N with its parent P. PP is the | |

grandparents' pointer to P. */ | |

static inline void | |

rotate_left (splay_tree_node *pp, splay_tree_node p, splay_tree_node n) | |

{ | |

splay_tree_node tmp; | |

tmp = n->right; | |

n->right = p; | |

p->left = tmp; | |

*pp = n; | |

} | |

/* Rotate the edge joining the right child N with its parent P. PP is the | |

grandparents' pointer to P. */ | |

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; | |

} | |

/* Bottom up splay of KEY. */ | |

static void | |

splay_tree_splay (splay_tree sp, splay_tree_key key) | |

{ | |

if (sp->root == NULL) | |

return; | |

do { | |

int cmp1, cmp2; | |

splay_tree_node n, c; | |

n = sp->root; | |

cmp1 = splay_compare (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 = splay_compare (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); | |

} | |

/* Insert a new NODE into SP. The NODE shouldn't exist in the tree. */ | |

attribute_hidden void | |

splay_tree_insert (splay_tree sp, splay_tree_node node) | |

{ | |

int comparison = 0; | |

splay_tree_splay (sp, &node->key); | |

if (sp->root) | |

comparison = splay_compare (&sp->root->key, &node->key); | |

if (sp->root && comparison == 0) | |

gomp_fatal ("Duplicate node"); | |

else | |

{ | |

/* Insert it at the root. */ | |

if (sp->root == NULL) | |

node->left = node->right = NULL; | |

else if (comparison < 0) | |

{ | |

node->left = sp->root; | |

node->right = node->left->right; | |

node->left->right = NULL; | |

} | |

else | |

{ | |

node->right = sp->root; | |

node->left = node->right->left; | |

node->right->left = NULL; | |

} | |

sp->root = node; | |

} | |

} | |

/* Remove node with KEY from SP. It is not an error if it did not exist. */ | |

attribute_hidden void | |

splay_tree_remove (splay_tree sp, splay_tree_key key) | |

{ | |

splay_tree_splay (sp, key); | |

if (sp->root && splay_compare (&sp->root->key, key) == 0) | |

{ | |

splay_tree_node left, right; | |

left = sp->root->left; | |

right = sp->root->right; | |

/* One of the children is now the root. Doesn't matter much | |

which, so long as we preserve the properties of the tree. */ | |

if (left) | |

{ | |

sp->root = left; | |

/* If there was a right child as well, hang it off the | |

right-most leaf of the left child. */ | |

if (right) | |

{ | |

while (left->right) | |

left = left->right; | |

left->right = right; | |

} | |

} | |

else | |

sp->root = right; | |

} | |

} | |

/* Lookup KEY in SP, returning NODE if present, and NULL | |

otherwise. */ | |

attribute_hidden splay_tree_key | |

splay_tree_lookup (splay_tree sp, splay_tree_key key) | |

{ | |

splay_tree_splay (sp, key); | |

if (sp->root && splay_compare (&sp->root->key, key) == 0) | |

return &sp->root->key; | |

else | |

return NULL; | |

} |