/// <summary>
/// 从指定的流初始化树
/// </summary>
/// <param name="fromFile">指定的流</param>
/// <param name="seekStart">流起始查询点</param>
/// <returns>树</returns>
public static BPlusTree SetupFromExistingStream(Stream fromFile, long seekStart)
{
if (fromFile == null)
{
throw new ArgumentNullException("fromFile");
}
BPlusTree tree = new BPlusTree(fromFile, seekStart, 100, 7, (byte)1);
tree.ReadHeader();
tree.BlockFile = BlockFile.SetupFromExistingStream(
fromFile, seekStart + HeaderSize, StorageConstants.BlockFileHeaderPrefix);
if (tree.BlockFile.BlockSize != tree.BlockSize)
{
throw new BPlusTreeException("Inner and outer block sizes should match.");
}
if (tree.RootNodeBlockNumber != StorageConstants.NullBlockNumber)
{
tree.RootNode = BPlusTreeNode.MakeRoot(tree, true);
tree.RootNode.LoadFromBlock(tree.RootNodeBlockNumber);
}
return(tree);
}
/// <summary>
/// 保存键值对
/// </summary>
/// <param name="key">键</param>
/// <param name="value">值</param>
public void Set(string key, long value)
{
// 验证给定的键是否合法
if (!ValidateKey(key, this))
{
throw new BPlusTreeBadKeyValueException(
string.Format("Null or too large key cannot be inserted into tree: {0}.", key));
}
// 指定根节点
bool isRootInitialized = false;
if (this.RootNode == null)
{
this.RootNode = BPlusTreeNode.MakeRoot(this, true);
isRootInitialized = true;
}
// 每个新键值均由根节点开始插入
string splitFirstKey;
BPlusTreeNode splitNode;
this.RootNode.Insert(key, (long)value, out splitFirstKey, out splitNode);
// 发现根节点需要分割
if (splitNode != null)
{
// 分割根节点，并二分构造一个新的根节点
BPlusTreeNode oldRoot = this.RootNode;
this.RootNode = BPlusTreeNode.BinaryRoot(oldRoot, splitFirstKey, splitNode, this);
isRootInitialized = true;
}
// 是否需要将根节点写入新的块
if (isRootInitialized)
{
this.RootNodeBlockNumber = this.RootNode.DumpToNewBlock();
}
// 检测在内存中的大小 // TODO
this.ShrinkFootprint();
}