/* ========================================================================== ** * ubi_SplayTree.c * * Copyright (C) 1993-1998 by Christopher R. Hertel * * Email: crh@ubiqx.mn.org * -------------------------------------------------------------------------- ** * * This module implements "splay" trees. Splay trees are binary trees * that are rearranged (splayed) whenever a node is accessed. The * splaying process *tends* to make the tree bushier (improves balance), * and the nodes that are accessed most frequently *tend* to be closer to * the top. * * References: "Self-Adjusting Binary Search Trees", by Daniel Sleator and * Robert Tarjan. Journal of the Association for Computing * Machinery Vol 32, No. 3, July 1985 pp. 652-686 * * See also: http://www.cs.cmu.edu/~sleator/ * * -------------------------------------------------------------------------- ** * * 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_SplayTree.c,v * Revision 4.4 1998/06/04 21:29:27 crh * Upper-cased defined constants (eg UBI_BINTREE_H) in some header files. * This is more "standard", and is what people expect. Weird, eh? * * Revision 4.3 1998/06/03 17:45:05 crh * Further fiddling with sys_include.h. It's now in ubi_BinTree.h which is * included by all of the binary tree files. * * Also fixed some warnings produced by lint on Irix 6.2, which doesn't seem * to like syntax like this: * * if( (a = b) ) * * The fix was to change lines like the above to: * * if( 0 != (a=b) ) * * Which means the same thing. * * Reminder: Some of the ubi_tr* macros in ubi_BinTree.h are redefined in * ubi_AVLtree.h and ubi_SplayTree.h. This allows easy swapping * of tree types by simply changing a header. Unfortunately, the * macro redefinitions in ubi_AVLtree.h and ubi_SplayTree.h will * conflict if used together. You must either choose a single tree * type, or use the underlying function calls directly. Compare * the two header files for more information. * * Revision 4.2 1998/06/02 01:29:14 crh * Changed ubi_null.h to sys_include.h to make it more generic. * * Revision 4.1 1998/05/20 04:37:54 crh * The C file now includes ubi_null.h. See ubi_null.h for more info. * * Revision 4.0 1998/03/10 03:41:33 crh * Minor comment changes. The revision number is now 4.0 to match the * BinTree and AVLtree modules. * * Revision 2.7 1998/01/24 06:37:08 crh * Added a URL for more information. * * Revision 2.6 1997/12/23 04:01:12 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 2.5 1997/07/26 04:15:42 crh * + Cleaned up a few minor syntax annoyances that gcc discovered for me. * + Changed ubi_TRUE and ubi_FALSE to ubi_trTRUE and ubi_trFALSE. * * Revision 2.4 1997/06/03 04:42:21 crh * Changed TRUE and FALSE to ubi_TRUE and ubi_FALSE to avoid causing * problems. * * Revision 2.3 1995/10/03 22:19:07 CRH * Ubisized! * Also, added the function ubi_sptSplay(). * * Revision 2.1 95/03/09 23:54:42 CRH * Added the ModuleID static string and function. These modules are now * self-identifying. * * Revision 2.0 95/02/27 22:34:46 CRH * This module was updated to match the interface changes made to the * ubi_BinTree module. In particular, the interface to the Locate() function * has changed. See ubi_BinTree for more information on changes and new * functions. * * The revision number was also upped to match ubi_BinTree. * * Revision 1.1 93/10/18 20:35:16 CRH * I removed the hard-coded logical device names from the include file * specifications. CRH * * Revision 1.0 93/10/15 23:00:15 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 * * Revision 0.1 93/04/25 22:03:32 CRH * Simply changed the <exec/types.h> #include reference the .c file to * use <stdlib.h> instead. The latter is portable, the former is not. * * Revision 0.0 93/04/21 23:05:52 CRH * Initial version, written by Christopher R. Hertel. * This module implements Splay Trees using the ubi_BinTree module as a basis. * * ========================================================================== ** */ #include "ubi_SplayTree.h" /* Header for THIS module. */ /* ========================================================================== ** * Static data. */ static char ModuleID[] = "ubi_SplayTree\n\ \tRevision: 4.4 \n\ \tDate: 1998/06/04 21:29:27 \n\ \tAuthor: crh \n"; /* ========================================================================== ** * Private functions... */ static void Rotate( ubi_btNodePtr p ) /* ------------------------------------------------------------------------ ** * This function performs a single rotation, moving node *p up one level * in the tree. * * Input: p - a pointer to an ubi_btNode in a tree. * * Output: None. * * Notes: This implements a single rotation in either direction (left * or right). This is the basic building block of all splay * tree rotations. * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr parentp; ubi_btNodePtr tmp; char way; char revway; parentp = p->Link[ubi_trPARENT]; /* Find parent. */ if( parentp ) /* If no parent, then we're already the root. */ { way = p->gender; revway = ubi_trRevWay(way); tmp = p->Link[(int)revway]; parentp->Link[(int)way] = tmp; if( tmp ) { tmp->Link[ubi_trPARENT] = parentp; tmp->gender = way; } tmp = parentp->Link[ubi_trPARENT]; p->Link[ubi_trPARENT] = tmp; p->gender = parentp->gender; if( tmp ) tmp->Link[(int)(p->gender)] = p; parentp->Link[ubi_trPARENT] = p; parentp->gender = revway; p->Link[(int)revway] = parentp; } } /* Rotate */ static ubi_btNodePtr Splay( ubi_btNodePtr SplayWithMe ) /* ------------------------------------------------------------------------ ** * Move the node indicated by SplayWithMe to the root of the tree by * splaying the tree. * * Input: SplayWithMe - A pointer to an ubi_btNode within a tree. * * Output: A pointer to the root of the splay tree (i.e., the same as * SplayWithMe). * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr parent; while( NULL != (parent = SplayWithMe->Link[ubi_trPARENT]) ) { if( parent->gender == SplayWithMe->gender ) /* Zig-Zig */ Rotate( parent ); else { if( ubi_trEQUAL != parent->gender ) /* Zig-Zag */ Rotate( SplayWithMe ); } Rotate( SplayWithMe ); /* Zig */ } /* while */ return( SplayWithMe ); } /* Splay */ /* ========================================================================== ** * Exported utilities. */ ubi_trBool ubi_sptInsert( 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 * splay 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; if( !(OldNode) ) OldNode = &OtherP; if( ubi_btInsert( RootPtr, NewNode, ItemPtr, OldNode ) ) { RootPtr->root = Splay( NewNode ); return( ubi_trTRUE ); } /* Splay the unreplacable, duplicate keyed, unique, old node. */ RootPtr->root = Splay( (*OldNode) ); return( ubi_trFALSE ); } /* ubi_sptInsert */ ubi_btNodePtr ubi_sptRemove( 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; (void)Splay( DeadNode ); /* Move dead node to root. */ if( NULL != (p = DeadNode->Link[ubi_trLEFT]) ) { /* If left subtree exists... */ ubi_btNodePtr q = DeadNode->Link[ubi_trRIGHT]; p->Link[ubi_trPARENT] = NULL; /* Left subtree node becomes root.*/ p->gender = ubi_trPARENT; p = ubi_btLast( p ); /* Find rightmost left node... */ p->Link[ubi_trRIGHT] = q; /* ...attach right tree. */ if( q ) q->Link[ubi_trPARENT] = p; RootPtr->root = Splay( p ); /* Resplay at p. */ } else { if( NULL != (p = DeadNode->Link[ubi_trRIGHT]) ) { /* No left, but right subtree exists... */ p->Link[ubi_trPARENT] = NULL; /* Right subtree root becomes... */ p->gender = ubi_trPARENT; /* ...overall tree root. */ RootPtr->root = p; } else RootPtr->root = NULL; /* No subtrees => empty tree. */ } (RootPtr->count)--; /* Decrement node count. */ return( DeadNode ); /* Return pointer to pruned node. */ } /* ubi_sptRemove */ ubi_btNodePtr ubi_sptLocate( 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(). * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr p; p = ubi_btLocate( RootPtr, FindMe, CompOp ); if( p ) RootPtr->root = Splay( p ); return( p ); } /* ubi_sptLocate */ ubi_btNodePtr ubi_sptFind( 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_sptLocate(). * ------------------------------------------------------------------------ ** */ { ubi_btNodePtr p; p = ubi_btFind( RootPtr, FindMe ); if( p ) RootPtr->root = Splay( p ); return( p ); } /* ubi_sptFind */ void ubi_sptSplay( ubi_btRootPtr RootPtr, ubi_btNodePtr SplayMe ) /* ------------------------------------------------------------------------ ** * This function allows you to splay the tree at a given node, thus moving * the node to the top of the tree. * * Input: * RootPtr - a pointer to the header of the tree to be splayed. * SplayMe - a pointer to a node within the tree. This will become * the new root node. * Output: None. * * Notes: This is an uncharacteristic function for this group of modules * in that it provides access to the internal balancing routines, * which would normally be hidden. * Splaying the tree will not damage it (assuming that I've done * *my* job), but there is overhead involved. I don't recommend * that you use this function unless you understand the underlying * Splay Tree principles involved. * ------------------------------------------------------------------------ ** */ { RootPtr->root = Splay( SplayMe ); } /* ubi_sptSplay */ int ubi_sptModuleID( int size, char *list[] ) /* ------------------------------------------------------------------------ ** * Returns a set of strings that identify the module. * * Input: size - The number of elements in the array <list>. * 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 <list> that were used. If this value * is less than <size>, 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 ) return( 1 + ubi_btModuleID( --size, &(list[1]) ) ); return( 1 ); } return( 0 ); } /* ubi_sptModuleID */ /* ================================ The End ================================= */