/* ========================================================================== ** * ubi_BinTree.c * * Copyright (C) 1991-1998 by Christopher R. Hertel * * Email: crh@ubiqx.mn.org * -------------------------------------------------------------------------- ** * * This module implements a simple binary tree. * * -------------------------------------------------------------------------- ** * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library 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 * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this library; if not, write to the Free * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * -------------------------------------------------------------------------- ** * * Log: ubi_BinTree.c,v * Revision 4.1 1998/03/31 06:11:57 crh * Thomas Aglassinger sent E'mail pointing out errors in the * dereferencing of function pointers, and a missing typecast. * Thanks, Thomas! * * Revision 4.0 1998/03/10 03:19:22 crh * Added the AVL field 'balance' to the ubi_btNode structure. This means * that all BinTree modules now use the same basic node structure, which * greatly simplifies the AVL module. * Decided that this was a big enough change to justify a new major revision * number. 3.0 was an error, so we're at 4.0. * * Revision 2.6 1998/01/24 06:27:46 crh * Added ubi_trCount() macro. * * Revision 2.5 1997/12/23 03:56:29 crh * In this version, all constants & macros defined in the header file have * the ubi_tr prefix. Also cleaned up anything that gcc complained about * when run with '-pedantic -fsyntax-only -Wall'. * * Revision 2.4 1997/07/26 04:11:10 crh * + Just to be annoying I changed ubi_TRUE and ubi_FALSE to ubi_trTRUE * and ubi_trFALSE. * + There is now a type ubi_trBool to go with ubi_trTRUE and ubi_trFALSE. * + There used to be something called "ubi_TypeDefs.h". I got rid of it. * + Added function ubi_btLeafNode(). * * Revision 2.3 1997/06/03 05:16:17 crh * Changed TRUE and FALSE to ubi_TRUE and ubi_FALSE to avoid conflicts. * Also changed the interface to function InitTree(). See the comments * for this function for more information. * * Revision 2.2 1995/10/03 22:00:07 CRH * Ubisized! * * Revision 2.1 95/03/09 23:37:10 CRH * Added the ModuleID static string and function. These modules are now * self-identifying. * * Revision 2.0 95/02/27 22:00:17 CRH * Revision 2.0 of this program includes the following changes: * * 1) A fix to a major typo in the RepaceNode() function. * 2) The addition of the static function Border(). * 3) The addition of the public functions FirstOf() and LastOf(), which * use Border(). These functions are used with trees that allow * duplicate keys. * 4) A complete rewrite of the Locate() function. Locate() now accepts * a "comparison" operator. * 5) Overall enhancements to both code and comments. * * I decided to give this a new major rev number because the interface has * changed. In particular, there are two new functions, and changes to the * Locate() function. * * Revision 1.0 93/10/15 22:44:59 CRH * With this revision, I have added a set of #define's that provide a single, * standard API to all existing tree modules. Until now, each of the three * existing modules had a different function and typedef prefix, as follows: * * Module Prefix * ubi_BinTree ubi_bt * ubi_AVLtree ubi_avl * ubi_SplayTree ubi_spt * * To further complicate matters, only those portions of the base module * (ubi_BinTree) that were superceeded in the new module had the new names. * For example, if you were using ubi_SplayTree, the locate function was * called "ubi_sptLocate", but the next and previous functions remained * "ubi_btNext" and "ubi_btPrev". * * This was not too terrible if you were familiar with the modules and knew * exactly which tree model you wanted to use. If you wanted to be able to * change modules (for speed comparisons, etc), things could get messy very * quickly. * * So, I have added a set of defined names that get redefined in any of the * descendant modules. To use this standardized interface in your code, * simply replace all occurances of "ubi_bt", "ubi_avl", and "ubi_spt" with * "ubi_tr". The "ubi_tr" names will resolve to the correct function or * datatype names for the module that you are using. Just remember to * include the header for that module in your program file. Because these * names are handled by the preprocessor, there is no added run-time * overhead. * * Note that the original names do still exist, and can be used if you wish * to write code directly to a specific module. This should probably only be * done if you are planning to implement a new descendant type, such as * red/black trees. CRH * * V0.0 - June, 1991 - Written by Christopher R. Hertel (CRH). * * ========================================================================== ** */ #include "../includes.h" #include "ubi_BinTree.h" /* Header for this module */ /* ========================================================================== ** * Static data. */ static char ModuleID[] = "ubi_BinTree\n\ \tRevision: 4.1\n\ \tDate: 1998/03/31 06:11:57\n\ \tAuthor: crh\n"; /* ========================================================================== ** * Internal (private) functions. */ static ubi_btNodePtr qFind( ubi_btCompFunc cmp, ubi_btItemPtr FindMe, register ubi_btNodePtr p ) /* ------------------------------------------------------------------------ ** * This function performs a non-recursive search of a tree for a node * matching a specific key. It is called "qFind()" because it is * faster that TreeFind (below). * * Input: * cmp - a pointer to the tree's comparison function. * FindMe - a pointer to the key value for which to search. * p - a pointer to the starting point of the search.

* is considered to be the root of a subtree, and only * the subtree will be searched. * * Output: * A pointer to a node with a key that matches the key indicated by * FindMe, or NULL if no such node was found. * * Note: In a tree that allows duplicates, the pointer returned *might * not* point to the (sequentially) first occurance of the * desired key. * ------------------------------------------------------------------------ ** */ { int tmp; while( p && (( tmp = ubi_trAbNormal((*cmp)(FindMe, p)) ) != ubi_trEQUAL) ) p = p->Link[tmp]; return( p ); } /* qFind */ static ubi_btNodePtr TreeFind( ubi_btItemPtr findme, ubi_btNodePtr p, ubi_btNodePtr *parentp, char *gender, ubi_btCompFunc CmpFunc ) /* ------------------------------------------------------------------------ ** * TreeFind() searches a tree for a given value (findme). It will return a * pointer to the target node, if found, or NULL if the target node was not * found. * * TreeFind() also returns, via parameters, a pointer to the parent of the * target node, and a LEFT or RIGHT value indicating which child of the * parent is the target node. *If the target is not found*, then these * values indicate the place at which the target *should be found*. This * is useful when inserting a new node into a tree or searching for nodes * "near" the target node. * * The parameters are: * * findme - is a pointer to the key information to be searched for. * p - points to the root of the tree to be searched. * parentp - will return a pointer to a pointer to the !parent! of the * target node, which can be especially usefull if the target * was not found. * gender - returns LEFT or RIGHT to indicate which child of *parentp * was last searched. * CmpFunc - points to the comparison function. * * This function is called by ubi_btLocate() and ubi_btInsert(). * ------------------------------------------------------------------------ ** */ { register ubi_btNodePtr tmp_p = p; ubi_btNodePtr tmp_pp = NULL; signed char tmp_gender = ubi_trEQUAL; int tmp_cmp; while( tmp_p && (ubi_trEQUAL != (tmp_cmp = ubi_trAbNormal((*CmpFunc)(findme, tmp_p)))) ) { tmp_pp = tmp_p; /* Keep track of previous node. */ tmp_gender = (signed char)tmp_cmp; /* Keep track of sex of child. */ tmp_p = tmp_p->Link[tmp_cmp]; /* Go to child. */ } *parentp = tmp_pp; /* Return results. */ *gender = tmp_gender; return( tmp_p ); } /* TreeFind */ static void ReplaceNode( ubi_btNodePtr *parent, ubi_btNodePtr oldnode, ubi_btNodePtr newnode ) /* ------------------------------------------------------------------------ ** * Remove node oldnode from the tree, replacing it with node newnode. * * Input: * parent - A pointer to he parent pointer of the node to be * replaced. may point to the Link[] field of * a parent node, or it may indicate the root pointer at * the top of the tree. * oldnode - A pointer to the node that is to be replaced. * newnode - A pointer to the node that is to be installed in the * place of <*oldnode>. * * Notes: Don't forget to free oldnode. * Also, this function used to have a really nasty typo * bug. "oldnode" and "newnode" were swapped in the line * that now reads: * ((unsigned char *)newnode)[i] = ((unsigned char *)oldnode)[i]; * Bleah! * ------------------------------------------------------------------------ ** */ { register int i; register int btNodeSize = sizeof( ubi_btNode ); for( i = 0; i < btNodeSize; i++ ) /* Copy node internals to new node. */ ((unsigned char *)newnode)[i] = ((unsigned char *)oldnode)[i]; (*parent) = newnode; /* Old node's parent points to new child. */ /* Now tell the children about their new step-parent. */ if( oldnode->Link[ubi_trLEFT] ) (oldnode->Link[ubi_trLEFT])->Link[ubi_trPARENT] = newnode; if( oldnode->Link[ubi_trRIGHT] ) (oldnode->Link[ubi_trRIGHT])->Link[ubi_trPARENT] = newnode; } /* ReplaceNode */ static void SwapNodes( ubi_btRootPtr RootPtr, ubi_btNodePtr Node1, ubi_btNodePtr Node2 ) /* ------------------------------------------------------------------------ ** * This function swaps two nodes in the tree. Node1 will take the place of * Node2, and Node2 will fill in the space left vacant by Node 1. * * Input: * RootPtr - pointer to the tree header structure for this tree. * Node1 - \ * > These are the two nodes which are to be swapped. * Node2 - / * * Notes: * This function does a three step swap, using a dummy node as a place * holder. This function is used by ubi_btRemove(). * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr *Parent; ubi_btNode dummy; ubi_btNodePtr dummy_p = &dummy; /* Replace Node 1 with the dummy, thus removing Node1 from the tree. */ if( Node1->Link[ubi_trPARENT] ) Parent = &((Node1->Link[ubi_trPARENT])->Link[(int)(Node1->gender)]); else Parent = &(RootPtr->root); ReplaceNode( Parent, Node1, dummy_p ); /* Swap Node 1 with Node 2, placing Node 1 back into the tree. */ if( Node2->Link[ubi_trPARENT] ) Parent = &((Node2->Link[ubi_trPARENT])->Link[(int)(Node2->gender)]); else Parent = &(RootPtr->root); ReplaceNode( Parent, Node2, Node1 ); /* Swap Node 2 and the dummy, thus placing Node 2 back into the tree. */ if( dummy_p->Link[ubi_trPARENT] ) Parent = &((dummy_p->Link[ubi_trPARENT])->Link[(int)(dummy_p->gender)]); else Parent = &(RootPtr->root); ReplaceNode( Parent, dummy_p, Node2 ); } /* SwapNodes */ /* -------------------------------------------------------------------------- ** * These routines allow you to walk through the tree, forwards or backwards. */ static ubi_btNodePtr SubSlide( register ubi_btNodePtr P, register int whichway ) /* ------------------------------------------------------------------------ ** * Slide down the side of a subtree. * * Given a starting node, this function returns a pointer to the LEFT-, or * RIGHT-most descendent, *or* (if whichway is PARENT) to the tree root. * * Input: P - a pointer to a starting place. * whichway - the direction (LEFT, RIGHT, or PARENT) in which to * travel. * Output: A pointer to a node that is either the root, or has no * whichway-th child but is within the subtree of P. Note that * the return value may be the same as P. The return value *will * be* NULL if P is NULL. * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr Q = NULL; while( P ) { Q = P; P = P->Link[ whichway ]; } return( Q ); } /* SubSlide */ static ubi_btNodePtr Neighbor( register ubi_btNodePtr P, register int whichway ) /* ------------------------------------------------------------------------ ** * Given starting point p, return the (key order) next or preceeding node * in the tree. * * Input: P - Pointer to our starting place node. * whichway - the direction in which to travel to find the * neighbor, i.e., the RIGHT neighbor or the LEFT * neighbor. * * Output: A pointer to the neighboring node, or NULL if P was NULL. * * Notes: If whichway is PARENT, the results are unpredictable. * ------------------------------------------------------------------------ ** */ { if( P ) { if( P->Link[ whichway ] ) return( SubSlide( P->Link[ whichway ], (char)ubi_trRevWay(whichway) ) ); else while( P->Link[ ubi_trPARENT ] ) { if( (P->Link[ ubi_trPARENT ])->Link[ whichway ] == P ) P = P->Link[ ubi_trPARENT ]; else return( P->Link[ ubi_trPARENT ] ); } } return( NULL ); } /* Neighbor */ static ubi_btNodePtr Border( ubi_btRootPtr RootPtr, ubi_btItemPtr FindMe, ubi_btNodePtr p, int whichway ) /* ------------------------------------------------------------------------ ** * Given starting point p, which has a key value equal to *FindMe, locate * the first (index order) node with the same key value. * * This function is useful in trees that have can have duplicate keys. * For example, consider the following tree: * Tree Traversal * 2 If

points to the root and is RIGHT, 3 * / \ then the return value will be a pointer to the / \ * 2 2 RIGHT child of the root node. The tree on 2 5 * / / \ the right shows the order of traversal. / / \ * 1 2 3 1 4 6 * * Input: RootPtr - Pointer to the tree root structure. * FindMe - Key value for comparisons. * p - Pointer to the starting-point node. * whichway - the direction in which to travel to find the * neighbor, i.e., the RIGHT neighbor or the LEFT * neighbor. * * Output: A pointer to the first (index, or "traversal", order) node with * a Key value that matches *FindMe. * * Notes: If whichway is PARENT, or if the tree does not allow duplicate * keys, this function will return

. * ------------------------------------------------------------------------ ** */ { register ubi_btNodePtr q; /* Exit if there's nothing that can be done. */ if( !ubi_trDups_OK( RootPtr ) || (ubi_trPARENT == whichway) ) return( p ); /* First, if needed, move up the tree. We need to get to the root of the * subtree that contains all of the matching nodes. */ q = p->Link[ubi_trPARENT]; while( q && (ubi_trEQUAL == ubi_trAbNormal( (*(RootPtr->cmp))(FindMe, q) )) ) { p = q; q = p->Link[ubi_trPARENT]; } /* Next, move back down in the "whichway" direction. */ q = p->Link[whichway]; while( q ) { q = qFind( RootPtr->cmp, FindMe, q ); if( q ) { p = q; q = p->Link[whichway]; } } return( p ); } /* Border */ /* ========================================================================== ** * Exported utilities. */ long ubi_btSgn( register long x ) /* ------------------------------------------------------------------------ ** * Return the sign of x; {negative,zero,positive} ==> {-1, 0, 1}. * * Input: x - a signed long integer value. * * Output: the "sign" of x, represented as follows: * -1 == negative * 0 == zero (no sign) * 1 == positive * * Note: This utility is provided in order to facilitate the conversion * of C comparison function return values into BinTree direction * values: {LEFT, PARENT, EQUAL}. It is INCORPORATED into the * ubi_trAbNormal() conversion macro! * * ------------------------------------------------------------------------ ** */ { return( (x)?((x>0)?(1):(-1)):(0) ); } /* ubi_btSgn */ ubi_btNodePtr ubi_btInitNode( ubi_btNodePtr NodePtr ) /* ------------------------------------------------------------------------ ** * Initialize a tree node. * * Input: a pointer to a ubi_btNode structure to be initialized. * Output: a pointer to the initialized ubi_btNode structure (ie. the * same as the input pointer). * ------------------------------------------------------------------------ ** */ { NodePtr->Link[ ubi_trLEFT ] = NULL; NodePtr->Link[ ubi_trPARENT ] = NULL; NodePtr->Link[ ubi_trRIGHT ] = NULL; NodePtr->gender = ubi_trEQUAL; NodePtr->balance = ubi_trEQUAL; return( NodePtr ); } /* ubi_btInitNode */ ubi_btRootPtr ubi_btInitTree( ubi_btRootPtr RootPtr, ubi_btCompFunc CompFunc, unsigned char Flags ) /* ------------------------------------------------------------------------ ** * Initialize the fields of a Tree Root header structure. * * Input: RootPtr - a pointer to an ubi_btRoot structure to be * initialized. * CompFunc - a pointer to a comparison function that will be used * whenever nodes in the tree must be compared against * outside values. * Flags - One bytes worth of flags. Flags include * ubi_trOVERWRITE and ubi_trDUPKEY. See the header * file for more info. * * Output: a pointer to the initialized ubi_btRoot structure (ie. the * same value as RootPtr). * * Note: The interface to this function has changed from that of * previous versions. The parameter replaces two * boolean parameters that had the same basic effect. * * ------------------------------------------------------------------------ ** */ { if( RootPtr ) { RootPtr->root = NULL; RootPtr->count = 0L; RootPtr->cmp = CompFunc; RootPtr->flags = (Flags & ubi_trDUPKEY) ? ubi_trDUPKEY : Flags; } /* There are only two supported flags, and they are * mutually exclusive. ubi_trDUPKEY takes precedence * over ubi_trOVERWRITE. */ return( RootPtr ); } /* ubi_btInitTree */ ubi_trBool ubi_btInsert( ubi_btRootPtr RootPtr, ubi_btNodePtr NewNode, ubi_btItemPtr ItemPtr, ubi_btNodePtr *OldNode ) /* ------------------------------------------------------------------------ ** * This function uses a non-recursive algorithm to add a new element to the * tree. * * Input: RootPtr - a pointer to the ubi_btRoot structure that indicates * the root of the tree to which NewNode is to be added. * NewNode - a pointer to an ubi_btNode structure that is NOT * part of any tree. * ItemPtr - A pointer to the sort key that is stored within * *NewNode. ItemPtr MUST point to information stored * in *NewNode or an EXACT DUPLICATE. The key data * indicated by ItemPtr is used to place the new node * into the tree. * OldNode - a pointer to an ubi_btNodePtr. When searching * the tree, a duplicate node may be found. If * duplicates are allowed, then the new node will * be simply placed into the tree. If duplicates * are not allowed, however, then one of two things * may happen. * 1) if overwritting *is not* allowed, this * function will return FALSE (indicating that * the new node could not be inserted), and * *OldNode will point to the duplicate that is * still in the tree. * 2) if overwritting *is* allowed, then this * function will swap **OldNode for *NewNode. * In this case, *OldNode will point to the node * that was removed (thus allowing you to free * the node). * ** If you are using overwrite mode, ALWAYS ** * ** check the return value of this parameter! ** * Note: You may pass NULL in this parameter, the * function knows how to cope. If you do this, * however, there will be no way to return a * pointer to an old (ie. replaced) node (which is * a problem if you are using overwrite mode). * * Output: a boolean value indicating success or failure. The function * will return FALSE if the node could not be added to the tree. * Such failure will only occur if duplicates are not allowed, * nodes cannot be overwritten, AND a duplicate key was found * within the tree. * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr OtherP, parent = NULL; char tmp; if( !(OldNode) ) /* If they didn't give us a pointer, supply our own. */ OldNode = &OtherP; (void)ubi_btInitNode( NewNode ); /* Init the new node's BinTree fields. */ /* Find a place for the new node. */ *OldNode = TreeFind(ItemPtr, (RootPtr->root), &parent, &tmp, (RootPtr->cmp)); /* Now add the node to the tree... */ if (!(*OldNode)) /* The easy one: we have a space for a new node! */ { if (!(parent)) RootPtr->root = NewNode; else { parent->Link[(int)tmp] = NewNode; NewNode->Link[ubi_trPARENT] = parent; NewNode->gender = tmp; } (RootPtr->count)++; return( ubi_trTRUE ); } /* If we reach this point, we know that a duplicate node exists. This * section adds the node to the tree if duplicate keys are allowed. */ if( ubi_trDups_OK(RootPtr) ) /* Key exists, add duplicate */ { ubi_btNodePtr q; tmp = ubi_trRIGHT; q = (*OldNode); *OldNode = NULL; while( q ) { parent = q; if( tmp == ubi_trEQUAL ) tmp = ubi_trRIGHT; q = q->Link[(int)tmp]; if ( q ) tmp = ubi_trAbNormal( (*(RootPtr->cmp))(ItemPtr, q) ); } parent->Link[(int)tmp] = NewNode; NewNode->Link[ubi_trPARENT] = parent; NewNode->gender = tmp; (RootPtr->count)++; return( ubi_trTRUE ); } /* If we get to *this* point, we know that we are not allowed to have * duplicate nodes, but our node keys match, so... may we replace the * old one? */ if( ubi_trOvwt_OK(RootPtr) ) /* Key exists, we replace */ { if (!(parent)) ReplaceNode( &(RootPtr->root), *OldNode, NewNode ); else ReplaceNode( &(parent->Link[(int)((*OldNode)->gender)]), *OldNode, NewNode ); return( ubi_trTRUE ); } return( ubi_trFALSE ); /* Failure: could not replace an existing node. */ } /* ubi_btInsert */ ubi_btNodePtr ubi_btRemove( ubi_btRootPtr RootPtr, ubi_btNodePtr DeadNode ) /* ------------------------------------------------------------------------ ** * This function removes the indicated node from the tree. * * Input: RootPtr - A pointer to the header of the tree that contains * the node to be removed. * DeadNode - A pointer to the node that will be removed. * * Output: This function returns a pointer to the node that was removed * from the tree (ie. the same as DeadNode). * * Note: The node MUST be in the tree indicated by RootPtr. If not, * strange and evil things will happen to your trees. * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr p, *parentp; int tmp; /* if the node has both left and right subtrees, then we have to swap * it with another node. The other node we choose will be the Prev()ious * node, which is garunteed to have no RIGHT child. */ if( (DeadNode->Link[ubi_trLEFT]) && (DeadNode->Link[ubi_trRIGHT]) ) SwapNodes( RootPtr, DeadNode, ubi_btPrev( DeadNode ) ); /* The parent of the node to be deleted may be another node, or it may be * the root of the tree. Since we're not sure, it's best just to have * a pointer to the parent pointer, whatever it is. */ if (DeadNode->Link[ubi_trPARENT]) parentp = &((DeadNode->Link[ubi_trPARENT])->Link[(int)(DeadNode->gender)]); else parentp = &( RootPtr->root ); /* Now link the parent to the only grand-child and patch up the gender. */ tmp = ((DeadNode->Link[ubi_trLEFT])?ubi_trLEFT:ubi_trRIGHT); p = (DeadNode->Link[tmp]); if( p ) { p->Link[ubi_trPARENT] = DeadNode->Link[ubi_trPARENT]; p->gender = DeadNode->gender; } (*parentp) = p; /* Finished, reduce the node count and return. */ (RootPtr->count)--; return( DeadNode ); } /* ubi_btRemove */ ubi_btNodePtr ubi_btLocate( ubi_btRootPtr RootPtr, ubi_btItemPtr FindMe, ubi_trCompOps CompOp ) /* ------------------------------------------------------------------------ ** * The purpose of ubi_btLocate() is to find a node or set of nodes given * a target value and a "comparison operator". The Locate() function is * more flexible and (in the case of trees that may contain dupicate keys) * more precise than the ubi_btFind() function. The latter is faster, * but it only searches for exact matches and, if the tree contains * duplicates, Find() may return a pointer to any one of the duplicate- * keyed records. * * Input: * RootPtr - A pointer to the header of the tree to be searched. * FindMe - An ubi_btItemPtr that indicates the key for which to * search. * CompOp - One of the following: * CompOp Return a pointer to the node with * ------ --------------------------------- * ubi_trLT - the last key value that is less * than FindMe. * ubi_trLE - the first key matching FindMe, or * the last key that is less than * FindMe. * ubi_trEQ - the first key matching FindMe. * ubi_trGE - the first key matching FindMe, or the * first key greater than FindMe. * ubi_trGT - the first key greater than FindMe. * Output: * A pointer to the node matching the criteria listed above under * CompOp, or NULL if no node matched the criteria. * * Notes: * In the case of trees with duplicate keys, Locate() will behave as * follows: * * Find: 3 Find: 3 * Keys: 1 2 2 2 3 3 3 3 3 4 4 Keys: 1 1 2 2 2 4 4 5 5 5 6 * ^ ^ ^ ^ ^ * LT EQ GT LE GE * * That is, when returning a pointer to a node with a key that is LESS * THAN the target key (FindMe), Locate() will return a pointer to the * LAST matching node. * When returning a pointer to a node with a key that is GREATER * THAN the target key (FindMe), Locate() will return a pointer to the * FIRST matching node. * * See Also: ubi_btFind(), ubi_btFirstOf(), ubi_btLastOf(). * ------------------------------------------------------------------------ ** */ { register ubi_btNodePtr p; ubi_btNodePtr parent; char whichkid; /* Start by searching for a matching node. */ p = TreeFind( FindMe, RootPtr->root, &parent, &whichkid, RootPtr->cmp ); if( p ) /* If we have found a match, we can resolve as follows: */ { switch( CompOp ) { case ubi_trLT: /* It's just a jump to the left... */ p = Border( RootPtr, FindMe, p, ubi_trLEFT ); return( Neighbor( p, ubi_trLEFT ) ); case ubi_trGT: /* ...and then a jump to the right. */ p = Border( RootPtr, FindMe, p, ubi_trRIGHT ); return( Neighbor( p, ubi_trRIGHT ) ); default: p = Border( RootPtr, FindMe, p, ubi_trLEFT ); return( p ); } } /* Else, no match. */ if( ubi_trEQ == CompOp ) /* If we were looking for an exact match... */ return( NULL ); /* ...forget it. */ /* We can still return a valid result for GT, GE, LE, and LT. * points to a node with a value that is either just before or * just after the target value. * Remaining possibilities are LT and GT (including LE & GE). */ if( (ubi_trLT == CompOp) || (ubi_trLE == CompOp) ) return( (ubi_trLEFT == whichkid) ? Neighbor( parent, whichkid ) : parent ); else return( (ubi_trRIGHT == whichkid) ? Neighbor( parent, whichkid ) : parent ); } /* ubi_btLocate */ ubi_btNodePtr ubi_btFind( ubi_btRootPtr RootPtr, ubi_btItemPtr FindMe ) /* ------------------------------------------------------------------------ ** * This function performs a non-recursive search of a tree for any node * matching a specific key. * * Input: * RootPtr - a pointer to the header of the tree to be searched. * FindMe - a pointer to the key value for which to search. * * Output: * A pointer to a node with a key that matches the key indicated by * FindMe, or NULL if no such node was found. * * Note: In a tree that allows duplicates, the pointer returned *might * not* point to the (sequentially) first occurance of the * desired key. In such a tree, it may be more useful to use * ubi_btLocate(). * ------------------------------------------------------------------------ ** */ { return( qFind( RootPtr->cmp, FindMe, RootPtr->root ) ); } /* ubi_btFind */ ubi_btNodePtr ubi_btNext( ubi_btNodePtr P ) /* ------------------------------------------------------------------------ ** * Given the node indicated by P, find the (sorted order) Next node in the * tree. * Input: P - a pointer to a node that exists in a binary tree. * Output: A pointer to the "next" node in the tree, or NULL if P pointed * to the "last" node in the tree or was NULL. * ------------------------------------------------------------------------ ** */ { return( Neighbor( P, ubi_trRIGHT ) ); } /* ubi_btNext */ ubi_btNodePtr ubi_btPrev( ubi_btNodePtr P ) /* ------------------------------------------------------------------------ ** * Given the node indicated by P, find the (sorted order) Previous node in * the tree. * Input: P - a pointer to a node that exists in a binary tree. * Output: A pointer to the "previous" node in the tree, or NULL if P * pointed to the "first" node in the tree or was NULL. * ------------------------------------------------------------------------ ** */ { return( Neighbor( P, ubi_trLEFT ) ); } /* ubi_btPrev */ ubi_btNodePtr ubi_btFirst( ubi_btNodePtr P ) /* ------------------------------------------------------------------------ ** * Given the node indicated by P, find the (sorted order) First node in the * subtree of which *P is the root. * Input: P - a pointer to a node that exists in a binary tree. * Output: A pointer to the "first" node in a subtree that has *P as its * root. This function will return NULL only if P is NULL. * Note: In general, you will be passing in the value of the root field * of an ubi_btRoot structure. * ------------------------------------------------------------------------ ** */ { return( SubSlide( P, ubi_trLEFT ) ); } /* ubi_btFirst */ ubi_btNodePtr ubi_btLast( ubi_btNodePtr P ) /* ------------------------------------------------------------------------ ** * Given the node indicated by P, find the (sorted order) Last node in the * subtree of which *P is the root. * Input: P - a pointer to a node that exists in a binary tree. * Output: A pointer to the "last" node in a subtree that has *P as its * root. This function will return NULL only if P is NULL. * Note: In general, you will be passing in the value of the root field * of an ubi_btRoot structure. * ------------------------------------------------------------------------ ** */ { return( SubSlide( P, ubi_trRIGHT ) ); } /* ubi_btLast */ ubi_btNodePtr ubi_btFirstOf( ubi_btRootPtr RootPtr, ubi_btItemPtr MatchMe, ubi_btNodePtr p ) /* ------------------------------------------------------------------------ ** * Given a tree that a allows duplicate keys, and a pointer to a node in * the tree, this function will return a pointer to the first (traversal * order) node with the same key value. * * Input: RootPtr - A pointer to the root of the tree. * MatchMe - A pointer to the key value. This should probably * point to the key within node *p. * p - A pointer to a node in the tree. * Output: A pointer to the first node in the set of nodes with keys * matching . * Notes: Node *p MUST be in the set of nodes with keys matching * . If not, this function will return NULL. * ------------------------------------------------------------------------ ** */ { /* If our starting point is invalid, return NULL. */ if( !p || ubi_trAbNormal( (*(RootPtr->cmp))( MatchMe, p ) != ubi_trEQUAL ) ) return( NULL ); return( Border( RootPtr, MatchMe, p, ubi_trLEFT ) ); } /* ubi_btFirstOf */ ubi_btNodePtr ubi_btLastOf( ubi_btRootPtr RootPtr, ubi_btItemPtr MatchMe, ubi_btNodePtr p ) /* ------------------------------------------------------------------------ ** * Given a tree that a allows duplicate keys, and a pointer to a node in * the tree, this function will return a pointer to the last (traversal * order) node with the same key value. * * Input: RootPtr - A pointer to the root of the tree. * MatchMe - A pointer to the key value. This should probably * point to the key within node *p. * p - A pointer to a node in the tree. * Output: A pointer to the last node in the set of nodes with keys * matching . * Notes: Node *p MUST be in the set of nodes with keys matching * . If not, this function will return NULL. * ------------------------------------------------------------------------ ** */ { /* If our starting point is invalid, return NULL. */ if( !p || ubi_trAbNormal( (*(RootPtr->cmp))( MatchMe, p ) != ubi_trEQUAL ) ) return( NULL ); return( Border( RootPtr, MatchMe, p, ubi_trRIGHT ) ); } /* ubi_btLastOf */ ubi_trBool ubi_btTraverse( ubi_btRootPtr RootPtr, ubi_btActionRtn EachNode, void *UserData ) /* ------------------------------------------------------------------------ ** * Traverse a tree in sorted order (non-recursively). At each node, call * (*EachNode)(), passing a pointer to the current node, and UserData as the * second parameter. * Input: RootPtr - a pointer to an ubi_btRoot structure that indicates * the tree to be traversed. * EachNode - a pointer to a function to be called at each node * as the node is visited. * UserData - a generic pointer that may point to anything that * you choose. * Output: A boolean value. FALSE if the tree is empty, otherwise TRUE. * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr p; if( !(p = ubi_btFirst( RootPtr->root )) ) return( ubi_trFALSE ); while( p ) { (*EachNode)( p, UserData ); p = ubi_btNext( p ); } return( ubi_trTRUE ); } /* ubi_btTraverse */ ubi_trBool ubi_btKillTree( ubi_btRootPtr RootPtr, ubi_btKillNodeRtn FreeNode ) /* ------------------------------------------------------------------------ ** * Delete an entire tree (non-recursively) and reinitialize the ubi_btRoot * structure. Note that this function will return FALSE if either parameter * is NULL. * * Input: RootPtr - a pointer to an ubi_btRoot structure that indicates * the root of the tree to delete. * FreeNode - a function that will be called for each node in the * tree to deallocate the memory used by the node. * * Output: A boolean value. FALSE if either input parameter was NULL, else * TRUE. * * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr p, q; if( !(RootPtr) || !(FreeNode) ) return( ubi_trFALSE ); p = ubi_btFirst( RootPtr->root ); while( p ) { q = p; while( q->Link[ubi_trRIGHT] ) q = SubSlide( q->Link[ubi_trRIGHT], ubi_trLEFT ); p = q->Link[ubi_trPARENT]; if( p ) p->Link[ ((p->Link[ubi_trLEFT] == q)?ubi_trLEFT:ubi_trRIGHT) ] = NULL; (*FreeNode)((void *)q); } (void)ubi_btInitTree( RootPtr, RootPtr->cmp, RootPtr->flags ); return( ubi_trTRUE ); } /* ubi_btKillTree */ ubi_btNodePtr ubi_btLeafNode( ubi_btNodePtr leader ) /* ------------------------------------------------------------------------ ** * Returns a pointer to a leaf node. * * Input: leader - Pointer to a node at which to start the descent. * * Output: A pointer to a leaf node selected in a somewhat arbitrary * manner. * * Notes: I wrote this function because I was using splay trees as a * database cache. The cache had a maximum size on it, and I * needed a way of choosing a node to sacrifice if the cache * became full. In a splay tree, less recently accessed nodes * tend toward the bottom of the tree, meaning that leaf nodes * are good candidates for removal. (I really can't think of * any other reason to use this function.) * + In a simple binary tree or an AVL tree, the most recently * added nodes tend to be nearer the bottom, making this a *bad* * way to choose which node to remove from the cache. * + Randomizing the traversal order is probably a good idea. You * can improve the randomization of leaf node selection by passing * in pointers to nodes other than the root node each time. A * pointer to any node in the tree will do. Of course, if you * pass a pointer to a leaf node you'll get the same thing back. * * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr follower = NULL; int whichway = ubi_trLEFT; while( NULL != leader ) { follower = leader; leader = follower->Link[ whichway ]; if( NULL == leader ) { whichway = ubi_trRevWay( whichway ); leader = follower->Link[ whichway ]; } } return( follower ); } /* ubi_btLeafNode */ int ubi_btModuleID( int size, char *list[] ) /* ------------------------------------------------------------------------ ** * Returns a set of strings that identify the module. * * Input: size - The number of elements in the array . * list - An array of pointers of type (char *). This array * should, initially, be empty. This function will fill * in the array with pointers to strings. * Output: The number of elements of that were used. If this value * is less than , the values of the remaining elements are * not guaranteed. * * Notes: Please keep in mind that the pointers returned indicate strings * stored in static memory. Don't free() them, don't write over * them, etc. Just read them. * ------------------------------------------------------------------------ ** */ { if( size > 0 ) { list[0] = ModuleID; if( size > 1 ) list[1] = NULL; return( 1 ); } return( 0 ); } /* ubi_btModuleID */ /* ========================================================================== */