private Node GetRange(PrefixKey key, int range, out TValue lastMatch, out int depth)
{
Node cursor = _root;
depth = 0;
PrefixKey xor = key ^ cursor.Key;
var match = true;
lastMatch = null;
while (depth < range && match)
{
if (depth < cursor.Range)
{
if (match = !xor.IsSetAt(depth))
{
depth++;
}
}
else
{
// remember the last match
lastMatch = cursor.Data ?? lastMatch;
// advance to the next nod
var nextIndex = key.ChildIndex(depth);
var next = cursor[nextIndex];
if (next != null)
{
cursor = next;
// Contract.Assert(cursor.Range > depth);
xor = key ^ cursor.Key;
depth++;
}
else
{
match = false;
}
}
}
// Contract.Assert(this.Depth0IffRoot(cursor, depth));
// Contract.Assert(this.OnlyEndDigitIsDifferentIfNotRoot(cursor, key, range, depth));
if (depth == cursor.Range)
{
lastMatch = cursor.Data ?? lastMatch;
}
return(cursor);
}
public TValue Insert(PrefixKey key, int range, TValue value, int depth)
{
// This node is an exact "prefix" match, this might mean one of the special case applies
if (Range == depth)
{
// prefix is already covered by node, this is an null op
if (Data == value)
{
return(value);
}
if (range == Range)
{
// same range, but data is different, this means replacement
Data = value;
return(value);
}
}
// Contract.Assert(range == depth || Range == depth || key.IsSetAt(depth) != Key.IsSetAt(depth));
// split this node if needed
if (Range > depth)
{
var clone = new Node(Key, Range, Data, _children);
Data = null;
Range = depth;
_children = new Node[2];
this[Key.ChildIndex(depth)] = clone;
}
if (Range == range)
{
// where the node split is exactly the new node is supposed to be
Key = key;
Data = value;
}
else
{
var newChildIndex = key.ChildIndex(depth);
// Contract.Assert(this[newChildIndex] == null);
var newNode = new Node(key, range, value);
this[newChildIndex] = newNode;
}
return(null);
}
