public static MPTNode Decode(byte[] data)
{
if (data is null || data.Length == 0)
{
return(null);
}
MPTNode node;
using (BinaryReader reader = new BinaryReader(new MemoryStream(data, false), Encoding.UTF8))
{
var nodeType = (NodeType)reader.ReadByte();
switch (nodeType)
{
case NodeType.BranchNode:
{
node = new BranchNode();
break;
}
case NodeType.ExtensionNode:
{
node = new ExtensionNode();
break;
}
case NodeType.LeafNode:
{
node = new LeafNode();
break;
}
default:
throw new System.InvalidOperationException();
}
node.DecodeSpecific(reader);
}
return(node);
}
private bool Put(ref MPTNode node, byte[] path, MPTNode val)
{
switch (node)
{
case LeafNode leafNode:
{
if (val is LeafNode v)
{
if (path.Length == 0)
{
node = v;
db.Put(node);
return(true);
}
var branch = new BranchNode();
branch.Children[BranchNode.ChildCount - 1] = leafNode;
Put(ref branch.Children[path[0]], path.Skip(1), v);
db.Put(branch);
node = branch;
return(true);
}
return(false);
}
case ExtensionNode extensionNode:
{
if (path.AsSpan().StartsWith(extensionNode.Key))
{
var result = Put(ref extensionNode.Next, path.Skip(extensionNode.Key.Length), val);
if (result)
{
extensionNode.SetDirty();
db.Put(extensionNode);
}
return(result);
}
var prefix = extensionNode.Key.CommonPrefix(path);
var pathRemain = path.Skip(prefix.Length);
var keyRemain = extensionNode.Key.Skip(prefix.Length);
var son = new BranchNode();
MPTNode grandSon1 = HashNode.EmptyNode();
MPTNode grandSon2 = HashNode.EmptyNode();
Put(ref grandSon1, keyRemain.Skip(1), extensionNode.Next);
son.Children[keyRemain[0]] = grandSon1;
if (pathRemain.Length == 0)
{
Put(ref grandSon2, pathRemain, val);
son.Children[BranchNode.ChildCount - 1] = grandSon2;
}
else
{
Put(ref grandSon2, pathRemain.Skip(1), val);
son.Children[pathRemain[0]] = grandSon2;
}
db.Put(son);
if (prefix.Length > 0)
{
var exNode = new ExtensionNode()
{
Key = prefix,
Next = son,
};
db.Put(exNode);
node = exNode;
}
else
{
node = son;
}
return(true);
}
case BranchNode branchNode:
{
bool result;
if (path.Length == 0)
{
result = Put(ref branchNode.Children[BranchNode.ChildCount - 1], path, val);
}
else
{
result = Put(ref branchNode.Children[path[0]], path.Skip(1), val);
}
if (result)
{
branchNode.SetDirty();
db.Put(branchNode);
}
return(result);
}
case HashNode hashNode:
{
MPTNode newNode;
if (hashNode.IsEmptyNode)
{
if (path.Length == 0)
{
newNode = val;
}
else
{
newNode = new ExtensionNode()
{
Key = path,
Next = val,
};
db.Put(newNode);
}
node = newNode;
if (val is LeafNode)
{
db.Put(val);
}
return(true);
}
newNode = Resolve(hashNode);
if (newNode is null)
{
return(false);
}
node = newNode;
return(Put(ref node, path, val));
}
default:
throw new System.InvalidOperationException("Invalid node type.");
}
}
private bool TryDelete(ref MPTNode node, byte[] path)
{
switch (node)
{
case LeafNode _:
{
if (path.Length == 0)
{
node = HashNode.EmptyNode();
return(true);
}
return(false);
}
case ExtensionNode extensionNode:
{
if (path.AsSpan().StartsWith(extensionNode.Key))
{
var result = TryDelete(ref extensionNode.Next, path.Skip(extensionNode.Key.Length));
if (!result)
{
return(false);
}
if (extensionNode.Next is HashNode hashNode && hashNode.IsEmptyNode)
{
node = extensionNode.Next;
return(true);
}
if (extensionNode.Next is ExtensionNode en)
{
extensionNode.Key = extensionNode.Key.Concat(en.Key);
extensionNode.Next = en.Next;
}
extensionNode.SetDirty();
db.Put(extensionNode);
return(true);
}
return(false);
}
case BranchNode branchNode:
{
bool result;
if (path.Length == 0)
{
result = TryDelete(ref branchNode.Children[BranchNode.ChildCount - 1], path);
}
else
{
result = TryDelete(ref branchNode.Children[path[0]], path.Skip(1));
}
if (!result)
{
return(false);
}
List <byte> childrenIndexes = new List <byte>();
for (int i = 0; i < BranchNode.ChildCount; i++)
{
if (branchNode.Children[i] is HashNode hn && hn.IsEmptyNode)
{
continue;
}
childrenIndexes.Add((byte)i);
}
if (childrenIndexes.Count > 1)
{
branchNode.SetDirty();
db.Put(branchNode);
return(true);
}
var lastChildIndex = childrenIndexes[0];
var lastChild = branchNode.Children[lastChildIndex];
if (lastChildIndex == BranchNode.ChildCount - 1)
{
node = lastChild;
return(true);
}
if (lastChild is HashNode hashNode)
{
lastChild = Resolve(hashNode);
if (lastChild is null)
{
throw new System.ArgumentNullException("Invalid hash node");
}
}
if (lastChild is ExtensionNode exNode)
{
exNode.Key = Helper.Concat(childrenIndexes.ToArray(), exNode.Key);
exNode.SetDirty();
db.Put(exNode);
node = exNode;
return(true);
}
var newNode = new ExtensionNode()
{
Key = childrenIndexes.ToArray(),
Next = lastChild,
};
node = newNode;
db.Put(newNode);
return(true);
}
case HashNode hashNode:
{
if (hashNode.IsEmptyNode)
{
return(true);
}
var new_node = Resolve(hashNode);
if (new_node is null)
{
return(false);
}
node = new_node;
return(TryDelete(ref node, path));
}
default:
return(false);
}
}