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tree234.h

00001 /*
00002  * tree234.h: header defining functions in tree234.c.
00003  * 
00004  * This file is copyright 1999-2001 Simon Tatham.
00005  * 
00006  * Permission is hereby granted, free of charge, to any person
00007  * obtaining a copy of this software and associated documentation
00008  * files (the "Software"), to deal in the Software without
00009  * restriction, including without limitation the rights to use,
00010  * copy, modify, merge, publish, distribute, sublicense, and/or
00011  * sell copies of the Software, and to permit persons to whom the
00012  * Software is furnished to do so, subject to the following
00013  * conditions:
00014  * 
00015  * The above copyright notice and this permission notice shall be
00016  * included in all copies or substantial portions of the Software.
00017  * 
00018  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
00019  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
00020  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00021  * NONINFRINGEMENT.  IN NO EVENT SHALL SIMON TATHAM BE LIABLE FOR
00022  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
00023  * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
00024  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
00025  * SOFTWARE.
00026  */
00027 
00028 #ifndef TREE234_H
00029 #define TREE234_H
00030 
00031 /*
00032  * This typedef is opaque outside tree234.c itself.
00033  */
00034 typedef struct tree234_Tag tree234;
00035 
00036 typedef int (*cmpfn234) (void *, void *);
00037 
00038 /*
00039  * Create a 2-3-4 tree. If `cmp' is NULL, the tree is unsorted, and
00040  * lookups by key will fail: you can only look things up by numeric
00041  * index, and you have to use addpos234() and delpos234().
00042  */
00043 tree234 *newtree234(cmpfn234 cmp);
00044 
00045 /*
00046  * Free a 2-3-4 tree (not including freeing the elements).
00047  */
00048 void freetree234(tree234 * t);
00049 
00050 /*
00051  * Add an element e to a sorted 2-3-4 tree t. Returns e on success,
00052  * or if an existing element compares equal, returns that.
00053  */
00054 void *add234(tree234 * t, void *e);
00055 
00056 /*
00057  * Add an element e to an unsorted 2-3-4 tree t. Returns e on
00058  * success, NULL on failure. (Failure should only occur if the
00059  * index is out of range or the tree is sorted.)
00060  * 
00061  * Index range can be from 0 to the tree's current element count,
00062  * inclusive.
00063  */
00064 void *addpos234(tree234 * t, void *e, int index);
00065 
00066 /*
00067  * Look up the element at a given numeric index in a 2-3-4 tree.
00068  * Returns NULL if the index is out of range.
00069  * 
00070  * One obvious use for this function is in iterating over the whole
00071  * of a tree (sorted or unsorted):
00072  * 
00073  *   for (i = 0; (p = index234(tree, i)) != NULL; i++) consume(p);
00074  * 
00075  * or
00076  * 
00077  *   int maxcount = count234(tree);
00078  *   for (i = 0; i < maxcount; i++) {
00079  *       p = index234(tree, i);
00080  *       assert(p != NULL);
00081  *       consume(p);
00082  *   }
00083  */
00084 void *index234(tree234 * t, int index);
00085 
00086 /*
00087  * Find an element e in a sorted 2-3-4 tree t. Returns NULL if not
00088  * found. e is always passed as the first argument to cmp, so cmp
00089  * can be an asymmetric function if desired. cmp can also be passed
00090  * as NULL, in which case the compare function from the tree proper
00091  * will be used.
00092  * 
00093  * Three of these functions are special cases of findrelpos234. The
00094  * non-`pos' variants lack the `index' parameter: if the parameter
00095  * is present and non-NULL, it must point to an integer variable
00096  * which will be filled with the numeric index of the returned
00097  * element.
00098  * 
00099  * The non-`rel' variants lack the `relation' parameter. This
00100  * parameter allows you to specify what relation the element you
00101  * provide has to the element you're looking for. This parameter
00102  * can be:
00103  * 
00104  *   REL234_EQ     - find only an element that compares equal to e
00105  *   REL234_LT     - find the greatest element that compares < e
00106  *   REL234_LE     - find the greatest element that compares <= e
00107  *   REL234_GT     - find the smallest element that compares > e
00108  *   REL234_GE     - find the smallest element that compares >= e
00109  * 
00110  * Non-`rel' variants assume REL234_EQ.
00111  * 
00112  * If `rel' is REL234_GT or REL234_LT, the `e' parameter may be
00113  * NULL. In this case, REL234_GT will return the smallest element
00114  * in the tree, and REL234_LT will return the greatest. This gives
00115  * an alternative means of iterating over a sorted tree, instead of
00116  * using index234:
00117  * 
00118  *   // to loop forwards
00119  *   for (p = NULL; (p = findrel234(tree, p, NULL, REL234_GT)) != NULL ;)
00120  *       consume(p);
00121  * 
00122  *   // to loop backwards
00123  *   for (p = NULL; (p = findrel234(tree, p, NULL, REL234_LT)) != NULL ;)
00124  *       consume(p);
00125  */
00126 enum {
00127     REL234_EQ, REL234_LT, REL234_LE, REL234_GT, REL234_GE
00128 };
00129 void *find234(tree234 * t, void *e, cmpfn234 cmp);
00130 void *findrel234(tree234 * t, void *e, cmpfn234 cmp, int relation);
00131 void *findpos234(tree234 * t, void *e, cmpfn234 cmp, int *index);
00132 void *findrelpos234(tree234 * t, void *e, cmpfn234 cmp, int relation,
00133                     int *index);
00134 
00135 /*
00136  * Delete an element e in a 2-3-4 tree. Does not free the element,
00137  * merely removes all links to it from the tree nodes.
00138  * 
00139  * delpos234 deletes the element at a particular tree index: it
00140  * works on both sorted and unsorted trees.
00141  * 
00142  * del234 deletes the element passed to it, so it only works on
00143  * sorted trees. (It's equivalent to using findpos234 to determine
00144  * the index of an element, and then passing that index to
00145  * delpos234.)
00146  * 
00147  * Both functions return a pointer to the element they delete, for
00148  * the user to free or pass on elsewhere or whatever. If the index
00149  * is out of range (delpos234) or the element is already not in the
00150  * tree (del234) then they return NULL.
00151  */
00152 void *del234(tree234 * t, void *e);
00153 void *delpos234(tree234 * t, int index);
00154 
00155 /*
00156  * Return the total element count of a tree234.
00157  */
00158 int count234(tree234 * t);
00159 
00160 #endif                          /* TREE234_H */

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