git.distorted.org.uk Git - u/mdw/putty/blob - tree234.h

   1 /*
   2  * tree234.h: header defining functions in tree234.c.
   3  *
   4  * This file is copyright 1999-2001 Simon Tatham.
   5  *
   6  * Permission is hereby granted, free of charge, to any person
   7  * obtaining a copy of this software and associated documentation
   8  * files (the "Software"), to deal in the Software without
   9  * restriction, including without limitation the rights to use,
  10  * copy, modify, merge, publish, distribute, sublicense, and/or
  11  * sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following
  13  * conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be
  16  * included in all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  20  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  21  * NONINFRINGEMENT.  IN NO EVENT SHALL SIMON TATHAM BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
  23  * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  25  * SOFTWARE.
  26  */
  27
  28 #ifndef TREE234_H
  29 #define TREE234_H
  30
  31 /*
  32  * This typedef is opaque outside tree234.c itself.
  33  */
  34 typedef struct tree234_Tag tree234;
  35
  36 typedef int (*cmpfn234) (void *, void *);
  37
  38 /*
  39  * Create a 2-3-4 tree. If `cmp' is NULL, the tree is unsorted, and
  40  * lookups by key will fail: you can only look things up by numeric
  41  * index, and you have to use addpos234() and delpos234().
  42  */
  43 tree234 *newtree234(cmpfn234 cmp);
  44
  45 /*
  46  * Free a 2-3-4 tree (not including freeing the elements).
  47  */
  48 void freetree234(tree234 * t);
  49
  50 /*
  51  * Add an element e to a sorted 2-3-4 tree t. Returns e on success,
  52  * or if an existing element compares equal, returns that.
  53  */
  54 void *add234(tree234 * t, void *e);
  55
  56 /*
  57  * Add an element e to an unsorted 2-3-4 tree t. Returns e on
  58  * success, NULL on failure. (Failure should only occur if the
  59  * index is out of range or the tree is sorted.)
  60  *
  61  * Index range can be from 0 to the tree's current element count,
  62  * inclusive.
  63  */
  64 void *addpos234(tree234 * t, void *e, int index);
  65
  66 /*
  67  * Look up the element at a given numeric index in a 2-3-4 tree.
  68  * Returns NULL if the index is out of range.
  69  *
  70  * One obvious use for this function is in iterating over the whole
  71  * of a tree (sorted or unsorted):
  72  *
  73  *   for (i = 0; (p = index234(tree, i)) != NULL; i++) consume(p);
  74  *
  75  * or
  76  *
  77  *   int maxcount = count234(tree);
  78  *   for (i = 0; i < maxcount; i++) {
  79  *       p = index234(tree, i);
  80  *       assert(p != NULL);
  81  *       consume(p);
  82  *   }
  83  */
  84 void *index234(tree234 * t, int index);
  85
  86 /*
  87  * Find an element e in a sorted 2-3-4 tree t. Returns NULL if not
  88  * found. e is always passed as the first argument to cmp, so cmp
  89  * can be an asymmetric function if desired. cmp can also be passed
  90  * as NULL, in which case the compare function from the tree proper
  91  * will be used.
  92  *
  93  * Three of these functions are special cases of findrelpos234. The
  94  * non-`pos' variants lack the `index' parameter: if the parameter
  95  * is present and non-NULL, it must point to an integer variable
  96  * which will be filled with the numeric index of the returned
  97  * element.
  98  *
  99  * The non-`rel' variants lack the `relation' parameter. This
 100  * parameter allows you to specify what relation the element you
 101  * provide has to the element you're looking for. This parameter
 102  * can be:
 103  *
 104  *   REL234_EQ     - find only an element that compares equal to e
 105  *   REL234_LT     - find the greatest element that compares < e
 106  *   REL234_LE     - find the greatest element that compares <= e
 107  *   REL234_GT     - find the smallest element that compares > e
 108  *   REL234_GE     - find the smallest element that compares >= e
 109  *
 110  * Non-`rel' variants assume REL234_EQ.
 111  *
 112  * If `rel' is REL234_GT or REL234_LT, the `e' parameter may be
 113  * NULL. In this case, REL234_GT will return the smallest element
 114  * in the tree, and REL234_LT will return the greatest. This gives
 115  * an alternative means of iterating over a sorted tree, instead of
 116  * using index234:
 117  *
 118  *   // to loop forwards
 119  *   for (p = NULL; (p = findrel234(tree, p, NULL, REL234_GT)) != NULL ;)
 120  *       consume(p);
 121  *
 122  *   // to loop backwards
 123  *   for (p = NULL; (p = findrel234(tree, p, NULL, REL234_LT)) != NULL ;)
 124  *       consume(p);
 125  */
 126 enum {
 127     REL234_EQ, REL234_LT, REL234_LE, REL234_GT, REL234_GE
 128 };
 129 void *find234(tree234 * t, void *e, cmpfn234 cmp);
 130 void *findrel234(tree234 * t, void *e, cmpfn234 cmp, int relation);
 131 void *findpos234(tree234 * t, void *e, cmpfn234 cmp, int *index);
 132 void *findrelpos234(tree234 * t, void *e, cmpfn234 cmp, int relation,
 133                     int *index);
 134
 135 /*
 136  * Delete an element e in a 2-3-4 tree. Does not free the element,
 137  * merely removes all links to it from the tree nodes.
 138  *
 139  * delpos234 deletes the element at a particular tree index: it
 140  * works on both sorted and unsorted trees.
 141  *
 142  * del234 deletes the element passed to it, so it only works on
 143  * sorted trees. (It's equivalent to using findpos234 to determine
 144  * the index of an element, and then passing that index to
 145  * delpos234.)
 146  *
 147  * Both functions return a pointer to the element they delete, for
 148  * the user to free or pass on elsewhere or whatever. If the index
 149  * is out of range (delpos234) or the element is already not in the
 150  * tree (del234) then they return NULL.
 151  */
 152 void *del234(tree234 * t, void *e);
 153 void *delpos234(tree234 * t, int index);
 154
 155 /*
 156  * Return the total element count of a tree234.
 157  */
 158 int count234(tree234 * t);
 159
 160 #endif                          /* TREE234_H */