libbanshee/engine/ufind.c

   1 /*
   2  * Copyright (c) 2000-2001
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  */
  30
  31 #include <stdio.h>
  32 #include "ufind.h"
  33 #include "assert.h"
  34
  35
  36 enum uf_type {uf_ecr,uf_link};
  37 typedef enum uf_type uf_type;
  38
  39 struct uf_element
  40 {
  41   uf_type type;
  42   int rank;
  43   void *info;
  44   struct uf_element *link;
  45 };
  46
  47 struct uf_element *new_uf_element(region r, void *info)
  48 {
  49   struct uf_element *result;
  50
  51   result = ralloc(r, struct uf_element);
  52
  53   result->type = uf_ecr;
  54   result->rank = 0;
  55   result->info = info;
  56   result->link = NULL;
  57
  58   return result;
  59 }
  60
  61 static struct uf_element *find(struct uf_element *e)
  62 {
  63
  64   if (e->type == uf_ecr)
  65     return e;
  66
  67   else if (e->link->type == uf_link)
  68     {
  69       struct uf_element *temp = e->link;
  70
  71       e->link = e->link->link;
  72
  73       return find(temp);
  74     }
  75
  76   else
  77     return e->link;
  78 }
  79
  80 bool uf_union(struct uf_element *a, struct uf_element *b)
  81 {
  82   struct uf_element *e1 = find(a);
  83   struct uf_element *e2 = find(b);
  84
  85   if ( e1 == e2 )
  86     return FALSE;
  87
  88  else if (e1->rank < e2->rank)
  89     {
  90       e1->type = uf_link;
  91       e1->link = e2;
  92
  93       return TRUE;
  94     }
  95
  96   else if (e1->rank > e2->rank)
  97     {
  98       e2->type = uf_link;
  99       e2->link = e1;
 100
 101       return TRUE;
 102     }
 103
 104   else
 105     {
 106       e2->rank++;
 107
 108       e1->type = uf_link;
 109       e1->link = e2;
 110
 111       return TRUE;
 112     }
 113
 114 }
 115
 116 bool uf_unify(combine_fn_ptr combine,
 117               struct uf_element *a, struct uf_element *b)
 118 {
 119   struct uf_element *e1 = find(a);
 120   struct uf_element *e2 = find(b);
 121
 122   if ( e1 == e2 )
 123     return FALSE;
 124
 125   else if (e1->rank < e2->rank)
 126     {
 127       e2->info = combine(e2->info,e1->info);
 128       e1->type = uf_link;
 129       e1->link = e2;
 130
 131       return TRUE;
 132     }
 133
 134   else if (e1->rank > e2->rank)
 135     {
 136       e1->info = combine(e1->info,e2->info);
 137       e2->type = uf_link;
 138       e2->link = e1;
 139
 140       return TRUE;
 141     }
 142
 143   else
 144     {
 145       e2->info = combine(e2->info, e1->info);
 146
 147       e2->rank++;
 148       e1->type = uf_link;
 149       e1->link = e2;
 150
 151       return TRUE;
 152     }
 153 }
 154
 155
 156
 157 void *uf_get_info(struct uf_element *e)
 158 {
 159   return find(e)->info;
 160 }
 161
 162
 163 bool uf_eq(struct uf_element *e1,struct uf_element *e2)
 164 {
 165   return (find(e1) == find(e2));
 166 }
 167
 168 void uf_update(struct uf_element *e,uf_info i)
 169 {
 170   find(e)->info = i;
 171 }
 172
 173
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 177