public static T ReadBlock <T>(this FileStream fileStream, long position) where T : Block
{
T block = null;
Block b = BlockCache.TryGetSunkBlock(position);// 如果已经从数据库读出来过，就不应再读了。
if (b != null)
{
block = b as T;
if (block == null)
{
throw new Exception("Two types of Block exists in the same position!");
}
}
else
{
fileStream.Seek(position, SeekOrigin.Begin);
object obj = Consts.formatter.Deserialize(fileStream);
block = obj as T;
block.ThisPos = position;
BlockCache.AddSunkBlock(block);
}
return(block);
}
public static void WriteBlock(this FileStream fileStream, Block block)
{
if (fileStream.Length < block.ThisPos)
{
fileStream.SetLength(block.ThisPos);
}
fileStream.Seek(block.ThisPos, SeekOrigin.Begin);
Consts.formatter.Serialize(fileStream, block);
BlockCache.TryRemoveFloatingBlock(block); // 如果是new Block()，需要在此时从floating列表移除
BlockCache.AddSunkBlock(block); // 如果是new Block()，需要在此时加入sunk字典
}