// Searches the trie for a node starting with the given key. If multiple are found, null will be returned.
public IEnumerable <KeyValueReference <string, T> > FindByKeyStart(string _key)
{
string key = _key.ToLower();
AlphaTrieNode currentNode = rootNode;
int level = -1;
while (level < key.Length - 1)
{
level++;
// Found the key exactly here, so return it and all of its underlings.
if (currentNode.Value != null && currentNode.Value.Key == key)
{
foreach (var retKV in Traverse(currentNode))
{
yield return(retKV);
}
}
int ix;
try {
ix = AlphaTrieNode.CharToTrieNodeIndex(key[level]);
} catch (InvalidOperationException) {
yield break;
}
// Ran into a dead end.
if (currentNode.Nodes == null || currentNode.Nodes[ix] == null)
{
if (currentNode.Value == null)
{
yield break;
}
if (currentNode.Value.Key.StartsWith(key))
{
yield return(currentNode.Value);
}
yield break;
}
currentNode = currentNode.Nodes[ix];
}
foreach (var retKV in Traverse(currentNode))
{
yield return(retKV);
}
}
private void Insert(AlphaTrieNode node, KeyValueReference <string, T> insKV, int level)
{
if (node.Value != null && node.Value.Key == insKV.Key)
{
throw new InvalidOperationException("Attempted to insert duplicate key into the trie.");
}
if (node.Nodes == null && node.Value == null)
{
node.Value = insKV;
return;
}
if (node.Nodes == null && node.Value != null)
{
node.Nodes = new AlphaTrieNode[NodeCount];
// Only move the current Value if it isn't exactly there.
if (node.Value.Key.Length > level)
{
KeyValueReference <string, T> moveKV = node.Value;
node.Value = null;
int im = AlphaTrieNode.CharToTrieNodeIndex(moveKV.Key[level]);
node.Nodes[im] = new AlphaTrieNode(moveKV);
node.Branches++;
}
// If ours fits perfectly, we know we had to move the old one.
if (insKV.Key.Length == level)
{
node.Value = insKV;
return;
}
int ii = AlphaTrieNode.CharToTrieNodeIndex(insKV.Key[level]);
if (node.Nodes[ii] == null)
{
node.Nodes[ii] = new AlphaTrieNode(insKV);
node.Branches++;
}
else
{
Insert(node.Nodes[ii], insKV, level + 1);
}
return;
}
if (node.Nodes != null)
{
// If we go exactly here, stick it in the Value.
if (insKV.Key.Length == level)
{
node.Value = insKV;
return;
}
// Otherwise, make new path or follow the old path.
int ii = AlphaTrieNode.CharToTrieNodeIndex(insKV.Key[level]);
if (node.Nodes[ii] == null)
{
node.Nodes[ii] = new AlphaTrieNode(insKV);
node.Branches++;
}
else
{
Insert(node.Nodes[ii], insKV, level + 1);
}
}
}