void DFS_VISIT(Vertex <T> v)
{
CycleChecker.Add(v, true);
Console.WriteLine("Node visited : " + v.Data.ToString());
foreach (var n in v.Neighbors)
{
//
if (GraphType == TypeOfGraph.Directed && CycleChecker.ContainsKey(n) && CycleChecker[n])
{
IsThereACycle = true;
}
if (Visited.ContainsKey(n))
{
//This node is visited (n) and its not v's parent means there exist a cycle in undirected graph
if (GraphType == TypeOfGraph.Undirected && Visited[v] != n)
{
IsThereACycle = true;
}
continue;
}
Visited.Add(n, v);
DFS_VISIT(n);
}
CycleChecker[v] = false;
}
public override Entity Resolve(Entity owner, string key, bool fallback = false)
{
using (cycleChecker = cycleChecker?.SpawnChild() ?? new CycleChecker <Resolution>(ExceptionTexts.ContentProviderCycle,
() => cycleChecker = null))
{
fallback = false;
IEntityContentProvider provider = GetContentProvider();
if (provider == null)
{
fallback = true;
provider = GetContentProvider();
}
if (provider == null)
{
throw new ContentProviderException(key, owner);
}
cycleChecker.AddItem(new Resolution(owner, key, provider));
return(provider.Resolve(owner, key, fallback));
}
IEntityContentProvider GetContentProvider()
{
return(contentResolvers.Where(r => !cycleChecker.HasItem(new Resolution(owner, key, r)))
.FirstOrDefault(r => r.CanResolve(owner, key, fallback))
?? contentResolvers.FirstOrDefault(r => r.CanResolve(owner, key, fallback)));
}
}
public void Test_Has_SelfLoop()
{
Graph graph = new Graph(1);
graph.AddEdge(0, 0);
Assert.True(CycleChecker.HasCycle(graph));
}
public void Test_NoCycle()
{
Graph graph = new Graph(3);
graph.AddEdge(0, 1);
graph.AddEdge(1, 2);
Assert.False(CycleChecker.HasCycle(graph));
}
public void Test_Has_ParallelEdge()
{
Graph graph = new Graph(2);
graph.AddEdge(0, 1);
graph.AddEdge(0, 1);
Assert.True(CycleChecker.HasCycle(graph));
}
public void Test_NoCycle()
{
Digraph graph = new Digraph(3);
graph.AddEdge(0, 1);
graph.AddEdge(0, 2);
CycleChecker checker = CycleChecker.Create(graph);
Assert.False(checker.HasCycle);
}
public void Test_HasCycle()
{
Digraph graph = new Digraph(3);
graph.AddEdge(0, 1);
graph.AddEdge(1, 2);
graph.AddEdge(2, 0);
CycleChecker checker = CycleChecker.Create(graph);
Assert.True(checker.HasCycle);
}
public void Test_GetCycle()
{
Digraph graph = new Digraph(3);
graph.AddEdge(0, 1);
graph.AddEdge(1, 2);
graph.AddEdge(2, 0);
CycleChecker checker = CycleChecker.Create(graph);
AssertUtilities.Sequence(new Int32[4] {
2, 0, 1, 2
}, checker.GetCycle());
}
public override bool CanResolve(Entity owner, string key, bool fallback = false)
{
if (cycleChecker?.HasItem(new Resolution(owner, key)) == true)
{
//break cycles before they form
return(false);
}
using (canCycleChecker = canCycleChecker?.SpawnChild() ?? new CycleChecker <Resolution>(ExceptionTexts.ContentProviderCycle,
() => canCycleChecker = null))
{
Resolution resolution = new Resolution(owner, key);
canCycleChecker.AddItem(resolution);
bool result = contentResolvers.Any(r => r.CanResolve(owner, key, false));
if (!result)
{
canCycleChecker.RemoveAfter(resolution);
result = contentResolvers.Any(r => r.CanResolve(owner, key, true));
}
return(result);
}
}
