bundles/org.simantics.db.common/src/org/simantics/db/common/recursive/FindRoots.java

   1 package org.simantics.db.common.recursive;
   2
   3 import java.util.Collections;
   4 import java.util.Set;
   5
   6 import org.simantics.db.Resource;
   7 import org.simantics.db.exception.DatabaseException;
   8
   9 import gnu.trove.set.hash.THashSet;
  10
  11 /**
  12  * Finds all roots reachable by {@code children} function
  13  */
  14 public abstract class FindRoots extends CachedRecursiveSearch<Set<Resource>> {
  15     protected abstract boolean isRoot(Resource resource) throws DatabaseException;
  16
  17     protected Set<Resource> getSourceValue(Resource resource) throws org.simantics.db.exception.DatabaseException {
  18         if(isRoot(resource))
  19             return Collections.singleton(resource);
  20         else
  21             return null;
  22     }
  23
  24     private static int sharedElements(Set<Resource> a, Set<Resource> b) {
  25         int count = 0;
  26         for(Resource r : a)
  27             if(b.contains(r))
  28                 ++count;
  29         return count;
  30     }
  31
  32     @Override
  33     protected Set<Resource> combineNotNull(Set<Resource> a, Set<Resource> b) throws DatabaseException {
  34         int aSize = a.size();
  35         int bSize = b.size();
  36
  37         int shared;
  38         if(aSize <= bSize) {
  39             shared = sharedElements(a, b);
  40             if(aSize == shared)
  41                 return b;
  42         }
  43         else {
  44             shared = sharedElements(b, a);
  45             if(bSize == shared)
  46                 return a;
  47         }
  48
  49         // Both set contain elements not in the other set
  50         THashSet<Resource> combined = new THashSet<Resource>(aSize + bSize - shared);
  51         combined.addAll(a);
  52         combined.addAll(b);
  53         return combined;
  54     }
  55 }