404 lines
14 KiB
C
404 lines
14 KiB
C
/*
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* This file is part of the COMROGUE Operating System for Raspberry Pi
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*
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* Copyright (c) 2013, Eric J. Bowersox / Erbosoft Enterprises
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* All rights reserved.
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*
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* This program is free for commercial and non-commercial use as long as the following conditions are
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* adhered to.
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*
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* Copyright in this file remains Eric J. Bowersox and/or Erbosoft, and as such any copyright notices
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* in the code are not to be removed.
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*
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* Redistribution and use in source and binary forms, with or without modification, are permitted
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* provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice, this list of conditions and
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* the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
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* the following disclaimer in the documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
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* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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* "Raspberry Pi" is a trademark of the Raspberry Pi Foundation.
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*/
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#define __COMROGUE_KERNEL_LIB__
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#include <comrogue/types.h>
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#include <comrogue/internals/rbtree.h>
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#include <comrogue/internals/seg.h>
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#include <comrogue/internals/trace.h>
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#ifdef THIS_FILE
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#undef THIS_FILE
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DECLARE_THIS_FILE
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#endif
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/*------------------------------------------------------------------------------------------------------
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* An implementation of left-leaning red-black 2-3 trees as detailed in "Left-leaning Red-Black Trees,"
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* Robert Sedgwick, Princeton University, 2008 (http://www.cs.princeton.edu/~rs/talks/LLRB/LLRB.pdf).
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* See also Java source at https://gist.github.com/741080.
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*
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* Note that we store the node color as a single bit in the low-order bit of the "right" node pointer.
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* This is do-able since, for all cases, pointers to instances of RBTREENODE will be 4-byte aligned.
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*------------------------------------------------------------------------------------------------------
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*/
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/*
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* A standard compare-by-value function for tree keys, which compares the numeric values of the keys as
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* unsigned integers.
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*
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* Parameters:
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* - k1 = First key value to compare.
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* - k2 = Second key value to compare.
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*
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* Returns:
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* 0 if the keys are equal; an integer less than 0 if k1 is less than k2; an integer greater than 0 if
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* k1 is greater than k2.
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*/
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SEG_LIB_CODE INT32 RbtStdCompareByValue(TREEKEY k1, TREEKEY k2)
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{
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if (k1 == k2)
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return 0;
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if (((UINT_PTR)k1) < ((UINT_PTR)k2))
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return -1;
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return 1;
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}
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/*
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* Rotates a subtree "leftward," so that the root node of the tree is the former root node's right child.
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* The new root node inherits the former root node's color, and the former root node turns red.
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*
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* Parameters:
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* - ptn = Pointer to the root node of the subtree.
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*
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* Returns:
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* Pointer to the new root node of the subtree after the rotation.
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*/
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SEG_LIB_CODE static PRBTREENODE rotate_left(PRBTREENODE ptn)
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{
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register PRBTREENODE ptnNewRoot = rbtNodeRight(ptn);
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ASSERT(ptnNewRoot);
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rbtSetNodeRight(ptn, ptnNewRoot->ptnLeft);
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ptnNewRoot->ptnLeft = ptn;
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rbtSetNodeColor(ptnNewRoot, rbtNodeColor(ptn));
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rbtSetNodeColor(ptn, RED);
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return ptnNewRoot;
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}
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/*
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* Rotates a subtree "rightward," so that the root node of the tree is the former root node's left child.
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* The new root node inherits the former root node's color, and the former root node turns red.
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*
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* Parameters:
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* - ptn = Pointer to theroot node of the subtree.
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*
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* Returns:
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* Pointer to the new root node of the subtree after the rotation.
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*/
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SEG_LIB_CODE static PRBTREENODE rotate_right(PRBTREENODE ptn)
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{
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register PRBTREENODE ptnNewRoot = ptn->ptnLeft;
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ASSERT(ptnNewRoot);
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ptn->ptnLeft = rbtNodeRight(ptnNewRoot);
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rbtSetNodeRight(ptnNewRoot, ptn);
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rbtSetNodeColor(ptnNewRoot, rbtNodeColor(ptn));
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rbtSetNodeColor(ptn, RED);
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return ptnNewRoot;
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}
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/*
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* Flips the color of the specified node and both its immediate children.
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*
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* Parameters:
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* - ptn = Pointer to the node to be color-flipped.
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*
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* Returns:
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* Nothing.
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*/
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SEG_LIB_CODE static void color_flip(PRBTREENODE ptn)
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{
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rbtToggleColor(ptn);
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rbtToggleColor(ptn->ptnLeft);
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rbtToggleColor(rbtNodeRight(ptn));
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}
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/*
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* Fixes up the given subtree after an insertion or deletion, to ensure that it maintains the invariants
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* that no two consecutive links in the tree may be red, and that all red links must lean left.
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*
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* Parameters:
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* - ptn = Pointer to the root node of the subtree to be fixed up.
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*
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* Returns:
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* Pointer to the new root node of the subtree after fixup is performed.
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*/
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SEG_LIB_CODE static PRBTREENODE fix_up(PRBTREENODE ptn)
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{
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if (rbtIsRed(rbtNodeRight(ptn)) && !rbtIsRed(ptn->ptnLeft))
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ptn = rotate_left(ptn);
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if (rbtIsRed(ptn->ptnLeft) && rbtIsRed(ptn->ptnLeft->ptnLeft))
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ptn = rotate_right(ptn);
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if (rbtIsRed(ptn->ptnLeft) && rbtIsRed(rbtNodeRight(ptn)))
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color_flip(ptn);
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return ptn;
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}
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/*
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* Inserts a new node under the current subtree. An O(log n) operation.
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure, containing the compare function.
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* - ptnCurrent = Pointer to the current subtree we're inserting into.
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* - ptnNew = Pointer to the new tree node to be inserted. This node must have been initialized with
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* the rbtInitNode macro to contain a key, NULL left and right pointers, and be red. It is
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* assumed that the node's key does NOT already exist in the tree.
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*
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* Returns:
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* The pointer to the new subtree after the insertion is performed.
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*
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* N.B.:
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* This function is recursive; however, the nature of the tree guarantees that the stack space consumed
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* by its stack frames will be O(log n).
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*/
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SEG_LIB_CODE static PRBTREENODE insert_under(PRBTREE ptree, PRBTREENODE ptnCurrent, PRBTREENODE ptnNew)
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{
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register int cmp; /* compare result */
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if (!ptnCurrent)
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return ptnNew; /* degenerate case */
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cmp = (*(ptree->pfnTreeCompare))(ptnNew->treekey, ptnCurrent->treekey);
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ASSERT(cmp != 0);
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if (cmp < 0)
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ptnCurrent->ptnLeft = insert_under(ptree, ptnCurrent->ptnLeft, ptnNew);
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else
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rbtSetNodeRight(ptnCurrent, insert_under(ptree, rbtNodeRight(ptnCurrent), ptnNew));
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return fix_up(ptnCurrent);
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}
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/*
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* Inserts a new node into the tree. An O(log n) operation.
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure.
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* - ptnNew = Pointer to the new tree node to be inserted. This node must have been initialized with
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* the rbtInitNode macro to contain a key, NULL left and right pointers, and be red. It is
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* assumed that the node's key does NOT already exist in the tree.
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*
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* Returns:
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* Nothing.
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*/
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SEG_LIB_CODE void RbtInsert(PRBTREE ptree, PRBTREENODE ptnNew)
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{
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ptree->ptnRoot = insert_under(ptree, ptree->ptnRoot, ptnNew);
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rbtSetNodeColor(ptree->ptnRoot, BLACK);
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}
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/*
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* Locates a node in the tree by key. An O(log n) operation.
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure.
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* - key = Key value to be looked up.
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*
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* Returns:
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* Pointer to the node where the key is found, or NULL if not found.
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*/
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SEG_LIB_CODE PRBTREENODE RbtFind(PRBTREE ptree, TREEKEY key)
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{
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register PRBTREENODE ptn = ptree->ptnRoot; /* current node */
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register int cmp; /* compare result */
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while (ptn)
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{
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cmp = (*(ptree->pfnTreeCompare))(key, ptn->treekey);
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if (cmp == 0)
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break; /* found */
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else if (cmp < 0)
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ptn = ptn->ptnLeft;
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else
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ptn = rbtNodeRight(ptn);
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}
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return ptn;
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}
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/*
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* Finds the "minimum" node in the subtree (the one at the bottom end of the left spine of the subtree).
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*
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* Parameters:
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* - ptn = Pointer to the subtree to be searched.
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*
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* Returns:
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* Pointer to the leftmost node in the subtree.
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*/
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SEG_LIB_CODE static PRBTREENODE find_min(PRBTREENODE ptn)
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{
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while (ptn->ptnLeft)
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ptn = ptn->ptnLeft;
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return ptn;
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}
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/*
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* Finds the "minimum" node int he tree (the one at the bottom end of the left spine of the tree).
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure.
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*
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* Returns:
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* Pointer to the leftmost node in the tree. If the tree has no nodes, NULL is returned.
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*/
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SEG_LIB_CODE PRBTREENODE RbtFindMin(PRBTREE ptree)
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{
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return ptree->ptnRoot ? find_min(ptree->ptnRoot) : NULL;
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}
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/*
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* Fixup required to delete the leftmost node; we maintain the invariant that either the current node
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* or its left child is red. After a color flip, we resolve any successive reds on the right with rotations
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* and another color flip.
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*
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* Parameters:
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* - ptn = Pointer to root of subtree to be fixed up.
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*
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* Returns:
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* Pointer to root of subtree after fixup.
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*/
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SEG_LIB_CODE static PRBTREENODE move_red_left(PRBTREENODE ptn)
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{
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color_flip(ptn);
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if (rbtNodeRight(ptn) && rbtIsRed(rbtNodeRight(ptn)->ptnLeft))
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{
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rbtSetNodeRight(ptn, rotate_right(rbtNodeRight(ptn)));
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ptn = rotate_left(ptn);
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color_flip(ptn);
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}
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return ptn;
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}
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/*
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* Fixup required to delete an internal node, rotating left-leaning red links to the right.
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*
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* Parameters:
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* - ptn = Pointer to root of subtree to be fixed up.
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*
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* Returns:
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* Pointer to root of subtree after fixup.
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*/
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SEG_LIB_CODE static PRBTREENODE move_red_right(PRBTREENODE ptn)
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{
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color_flip(ptn);
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if (ptn->ptnLeft && rbtIsRed(ptn->ptnLeft->ptnLeft))
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{
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ptn = rotate_right(ptn);
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color_flip(ptn);
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}
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return ptn;
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}
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/*
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* Deletes the leftmost node in the subtree. (Note that "deletes" means "removes from the tree." No memory
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* delete operation is actually performed.)
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*
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* Parameters:
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* - ptn = Pointer to root of subtree to have its leftmost node deleted.
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*
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* Returns:
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* Pointer to root of subtree after having the leftmost node deleted.
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*
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* N.B.:
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* This function is recursive; however, the nature of the tree guarantees that the stack space consumed
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* by its stack frames will be O(log n).
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*/
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SEG_LIB_CODE static PRBTREENODE delete_min(PRBTREENODE ptn)
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{
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if (!(ptn->ptnLeft))
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return rbtNodeRight(ptn);
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if (!rbtIsRed(ptn->ptnLeft) && !rbtIsRed(ptn->ptnLeft->ptnLeft))
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ptn = move_red_left(ptn);
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ptn->ptnLeft = delete_min(ptn->ptnLeft);
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return fix_up(ptn);
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}
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/*
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* Detetes the node in the subtree having an arbitrary key. An O(log n) operation.
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure, containing the compare function.
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* - ptnCurrent = Pointer to the root of the current subtree we're deleting from.
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* - key = Key value we're deleting from the tree. It is assumed that this key value exists in the subtree.
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*
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* Returns:
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* Pointer to the root of the subtree after the node has been deleted.
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*
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* N.B.:
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* This function is recursive; however, the nature of the tree guarantees that the stack space consumed
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* by its stack frames (and those of delete_min, where we call it) will be O(log n).
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*/
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SEG_LIB_CODE static PRBTREENODE delete_from_under(PRBTREE ptree, PRBTREENODE ptnCurrent, TREEKEY key)
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{
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register int cmp = (*(ptree->pfnTreeCompare))(key, ptnCurrent->treekey);
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if (cmp < 0)
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{
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/* hunt down the left subtree */
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if (!rbtIsRed(ptnCurrent->ptnLeft) && !rbtIsRed(ptnCurrent->ptnLeft->ptnLeft))
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ptnCurrent = move_red_left(ptnCurrent);
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ptnCurrent->ptnLeft = delete_from_under(ptree, ptnCurrent->ptnLeft, key);
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}
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else
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{
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if (rbtIsRed(ptnCurrent->ptnLeft))
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{
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ptnCurrent = rotate_right(ptnCurrent);
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cmp = (*(ptree->pfnTreeCompare))(key, ptnCurrent->treekey);
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}
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if ((cmp == 0) && !rbtNodeRight(ptnCurrent))
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return ptnCurrent->ptnLeft; /* degenerate case */
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if ( !rbtIsRed(rbtNodeRight(ptnCurrent))
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&& (!rbtNodeRight(ptnCurrent) || !rbtIsRed(rbtNodeRight(ptnCurrent)->ptnLeft)))
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{
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ptnCurrent = move_red_right(ptnCurrent);
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cmp = (*(ptree->pfnTreeCompare))(key, ptnCurrent->treekey);
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}
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if (cmp == 0)
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{
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/*
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* Here we find the minimum node in the right subtree, unlink it, and link it into place in place of
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* ptnCurrent (i.e. node pointed to by ptnCurrent should no longer be referenced). We inherit the
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* child pointers and color of ptnCurrent (minus the reference from the right-hand tree where applicable).
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*/
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register PRBTREENODE ptnMin = find_min(rbtNodeRight(ptnCurrent));
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rbtSetNodeRight(ptnMin, delete_min(rbtNodeRight(ptnCurrent)));
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ptnMin->ptnLeft = ptnCurrent->ptnLeft;
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rbtSetNodeColor(ptnMin, rbtNodeColor(ptnCurrent));
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ptnCurrent = ptnMin;
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}
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else /* hunt down the right subtree */
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rbtSetNodeRight(ptnCurrent, delete_from_under(ptree, rbtNodeRight(ptnCurrent), key));
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}
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return fix_up(ptnCurrent);
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}
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/*
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* Detetes the node in the tree having an arbitrary key. An O(log n) operation.
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*
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* Parameters:
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* - ptree = Pointer to the tree head structure.
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* - key = Key value we're deleting from the tree. It is assumed that this key value exists in the subtree.
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*
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* Returns:
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* Nothing.
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*/
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SEG_LIB_CODE void RbtDelete(PRBTREE ptree, TREEKEY key)
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{
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ptree->ptnRoot = delete_from_under(ptree, ptree->ptnRoot, key);
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if (ptree->ptnRoot)
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rbtSetNodeColor(ptree->ptnRoot, BLACK);
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}
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