/// <summary>
/// Returns the closest successor preceding id.
/// </summary>
/// <param name="id">The id for which the closest finger should be found</param>
/// <returns>The successor node of the closest finger to id in the current node's finger table</returns>
private ChordNode FindClosestPrecedingFinger(UInt64 id)
{
// iterate downward through the finger table looking for the right finger in the right range. if the finger is
// in the range but not valid, keep moving. if the entire finger table is checked without success, check the successor
// cache - if that fails, return the local node as the closest preceding finger.
for (int i = this.FingerTable.Length - 1; i >= 0; i--)
{
// if the finger is more closely between the local node and id and that finger corresponds to a valid node, return the finger
if (this.FingerTable.Successors[i] != null && this.FingerTable.Successors[i] != ChordServer.LocalNode)
{
if (ChordServer.FingerInRange(this.FingerTable.Successors[i].ID, this.ID, id))
{
ChordInstance instance = ChordServer.GetInstance(this.FingerTable.Successors[i]);
if (ChordServer.IsInstanceValid(instance))
{
return(this.FingerTable.Successors[i]);
}
}
}
}
// at this point, not even the successor is any good so go through the successor cache and run the same test
for (int i = 0; i < this.SuccessorCache.Length; i++)
{
if (this.SuccessorCache[i] != null && this.SuccessorCache[i] != ChordServer.LocalNode)
{
if (ChordServer.FingerInRange(this.SuccessorCache[i].ID, this.ID, id))
{
ChordInstance instance = ChordServer.GetInstance(this.SuccessorCache[i]);
if (ChordServer.IsInstanceValid(instance))
{
return(this.SuccessorCache[i]);
}
}
}
}
// otherwise, if there is nothing closer, the local node is the closest preceding finger
return(ChordServer.LocalNode);
}
