/// <summary>
/// Retrieve the string value for a given ulong
/// key.
/// </summary>
/// <param name="key">The key whose value should be returned.</param>
/// <returns>The string value for the given key, or an empty string if not found.</returns>
public string FindKey(ulong key)
{
// determine the owning node for the key
ChordNode owningNode = ChordServer.CallFindSuccessor(key);
if (owningNode != ChordServer.LocalNode)
{
// if this is not the owning node, call
// FindKey on the remote owning node
return(ChordServer.CallFindKey(owningNode, key));
}
else
{
// if this is the owning node, check
// to see if the key exists in the data store
if (this.m_DataStore.ContainsKey(key))
{
// if the key exists, return the value
return(this.m_DataStore[key]);
}
else
{
// if the key does not exist, return empty string
return(string.Empty);
}
}
}
/// <summary>
/// Find the node that is the rightful owner of a given id.
/// </summary>
/// <param name="id">The id whose successor should be found.</param>
/// <param name="hopCount">The number of network hops taken in finding the successor.</param>
/// <returns>The ChordNode that is the Successor of a given ID value.</returns>
public ChordNode FindSuccessor(UInt64 id, int hopCountIn, out int hopCountOut)
{
// is the local node's successor the rightful owner?
if (ChordServer.IsIDInRange(id, this.ID, this.Successor.ID))
{
hopCountOut = hopCountIn;
return(this.Successor);
}
else
{
// otherwise, find the nearest preceding finger, and ask that node.
ChordNode predNode = FindClosestPrecedingFinger(id);
return(ChordServer.CallFindSuccessor(predNode, id, 0, ++hopCountIn, out hopCountOut));
}
}
/// <summary>
/// Add a key to the store. Gets a hash of the key, determines
/// the correct owning node, and stores the string value
/// on that node.
/// </summary>
/// <param name="value">The value to add.</param>
public void AddKey(string value)
{
// the key is the hash of the value to
// add to the store, and determines the
// owning NChord node
ulong key = ChordServer.GetHash(value);
// using the local node, determine the correct owning
// node for the data to be stored given the key value
ChordNode owningNode = ChordServer.CallFindSuccessor(key);
if (owningNode != ChordServer.LocalNode)
{
// if this is not the owning node, then call AddKey
// on the actual owning node
ChordServer.CallAddKey(owningNode, value);
}
else
{
// if this is the owning node, then add the
// key to the local data store
this.m_DataStore.Add(key, value);
}
}
