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/* |
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** Copyright (C) 2003 by Kevin L. Mitchell <klmitch@mit.edu> |
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** |
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** This library is free software; you can redistribute it and/or |
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** modify it under the terms of the GNU Library General Public |
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** License as published by the Free Software Foundation; either |
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** version 2 of the License, or (at your option) any later version. |
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** |
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** This library is distributed in the hope that it will be useful, |
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** but WITHOUT ANY WARRANTY; without even the implied warranty of |
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** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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** Library General Public License for more details. |
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** |
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** You should have received a copy of the GNU Library General Public |
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** License along with this library; if not, write to the Free |
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** Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
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** MA 02111-1307, USA |
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** |
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** @(#)$Id: _rb_rotate.c,v 1.1 2003/06/28 18:48:21 klmitch Exp $ |
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*/ |
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#include "dbprim.h" |
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#include "dbprim_int.h" |
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|
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RCSTAG("@(#)$Id: _rb_rotate.c,v 1.1 2003/06/28 18:48:21 klmitch Exp $"); |
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|
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/* Swap a child with its parent, effecting a rotation */ |
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void |
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_rb_rotate(rb_tree_t *tree, rb_node_t *child) |
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{ |
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rb_node_t *parent; |
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|
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if (!(parent = child->rn_parent)) /* make sure it has a parent... */ |
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return; |
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|
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/* Figure out what points to the parent and repoint it to the child */ |
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if (!parent->rn_parent) /* is the parent the root? */ |
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tree->rt_root = child; |
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else if (rn_isleft(parent)) /* OK, is it a left node? */ |
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parent->rn_parent->rn_left = child; |
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else /* ok, must be a right node */ |
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parent->rn_parent->rn_right = child; |
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|
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/* Now update the parent pointers of parent and child... */ |
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child->rn_parent = parent->rn_parent; |
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parent->rn_parent = child; |
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|
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/* Finally, move the child nodes around a little... */ |
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if (parent->rn_right == child) { /* right child? */ |
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if (child->rn_left) /* update grandchild's parent pointer */ |
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child->rn_left->rn_parent = parent; |
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parent->rn_right = child->rn_left; /* then move the child to the parent */ |
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child->rn_left = parent; /* Finally, link the parent to the child */ |
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} else { /* OK, left child! */ |
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if (child->rn_right) /* update grandchild's parent pointer */ |
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child->rn_right->rn_parent = parent; |
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parent->rn_left = child->rn_right; /* then move the child to the parent */ |
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child->rn_right = parent; /* Finally, link the parent to the child */ |
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} |
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} |
