/// <summary>
/// searches for the longest prefix match
/// </summary>
public (string key, TValue value, bool found) LongestPrefix(string prefix)
{
LeafNode <TValue> last = null;
var node = _root;
var search = prefix;
//for {
while (true)
{
// Look for a leaf node
if (node.IsLeaf)
{
last = node.Leaf;
}
// Check for key exhaution
if (search.Length == 0)
{
break;
}
// Look for an edge
if (!node.TryGetEdge(search[0], out node))
{
break;
}
// Consume the search prefix
if (search.StartsWith(node.Prefix))
{
search = search.Substring(node.Prefix.Length);
}
else
{
break;
}
}
return(last != null ? (last.Key, last.Value, true) : (string.Empty, default(TValue), false));
}
/// <summary>
/// adds new entry or updates an existing entry
/// </summary>
/// <returns>is entry updated, and old value if it was</returns>
public (TValue oldValue, bool updated) Insert(string key, TValue value)
{
_values[key] = value;
var node = _root;
var search = key;
while (true)
{
// Handle key exhaution
if (search.Length == 0)
{
if (node.IsLeaf)
{
var old = node.Leaf.Value;
node.Leaf.Value = value;
return(old, true);
}
node.Leaf = new LeafNode <TValue>
{
Key = key,
Value = value,
};
return(default(TValue), false);
}
var parent = node;
// Look for the edge
// No edge, create one
if (!node.TryGetEdge(search[0], out node))
{
parent.AddEdge(search[0], new Node <TValue>
{
Leaf = new LeafNode <TValue>
{
Key = key,
Value = value,
},
Prefix = search,
});
return(default(TValue), false);
}
// Determine longest prefix of the search key on match
var commonPrefix = StringHelpers.FindLongestPrefix(search, node.Prefix);
if (commonPrefix == node.Prefix.Length)
{
search = search.Substring(commonPrefix);
continue;
}
// Split the node
var child = new Node <TValue>
{
Prefix = search.Substring(0, commonPrefix),
};
parent.SetEdge(search[0], child);
// Restore the existing node
child.AddEdge(node.Prefix[commonPrefix], node);
node.Prefix = node.Prefix.Substring(commonPrefix);
// Create a new leaf node
var leaf = new LeafNode <TValue>
{
Key = key,
Value = value,
};
// If the new key is a subset, add to to this node
search = search.Substring(commonPrefix);
if (search.Length == 0)
{
child.Leaf = leaf;
return(default(TValue), false);
}
// Create a new edge for the node
child.AddEdge(search[0], new Node <TValue>
{
Leaf = leaf,
Prefix = search,
});
return(default(TValue), false);
}
}
public void Clear()
{
Leaf = null;
Prefix = string.Empty;
Edges.Clear();
}
