public static AllocPageTypes BelongedPageType(this AllocBlock block)
{
AllocPageTypes pageType;
Type type = block.GetType();
if (type == typeof(DataBlock))
{
pageType = AllocPageTypes.Data;
}
else if (type == typeof(SkipListNodeBlock))
{
pageType = AllocPageTypes.SkipListNode;
}
else if (type == typeof(IndexBlock))
{
pageType = AllocPageTypes.Index;
}
else if (type == typeof(TableBlock))
{
pageType = AllocPageTypes.Table;
}
else
{
throw new Exception("Wrong Block Type!");
}
return(pageType);
}
/// <summary>
/// 添加一个准备从数据库文件中删除的块。
/// </summary>
/// <param name="block"></param>
public void Delete(AllocBlock block)
{
if (block.ThisPos == 0)// 尝试删除一个连在文件里的位置都没有的块。这个块似乎在文件里根本不存在。
{
throw new Exception("Deleting [{0}] but it's position still not set!");
}
if (!this.oldDeletingBlockPositions.Contains(block.ThisPos))
{
this.oldDeletingBlockPositions.Add(block.ThisPos);
this.deletingBlockList.Add(block);
}
else
{
throw new Exception(string.Format("{0} already instantiated!", block));
}
}
/// <summary>
/// 添加一个准备写入数据库的块。
/// </summary>
/// <param name="block"></param>
public void Add(AllocBlock block)
{
if (block.ThisPos == 0)// 这是一个新建的块。
{
if (!this.addlingBlockList.Contains(block))
{
this.addlingBlockList.Add(block);
}
}
else// 这是已有的块。
{
if (this.oldAddingBlockPositions.Contains(block.ThisPos))
{
// 此时说明你重复反序列化了同一个块，这将导致数据混乱。
throw new Exception(string.Format("Block [{0}] already in transaction.", block));
}
this.addlingBlockList.Add(block);
this.oldAddingBlockPositions.Add(block.ThisPos);
}
}
private void DoCommit()
{
DBHeaderBlock dbHeaderBlock = this.fileDBContext.headerBlock;
FileStream fs = this.fileDBContext.fileStream;
// 给所有的块安排数据库文件中的位置。
List <Block> arrangedBlocks = new List <Block>();
while (arrangedBlocks.Count < this.addlingBlockList.Count)
{
for (int i = this.addlingBlockList.Count - 1; i >= 0; i--)// 后加入列表的先处理。
{
AllocBlock block = this.addlingBlockList[i];
if (arrangedBlocks.Contains(block))
{
continue;
}
bool done = block.ArrangePos();
if (done)
{
if (block.ThisPos == 0)
{
byte[] bytes = block.ToBytes();
if (bytes.Length > Consts.maxAvailableSpaceInPage)
{
throw new Exception("Block size is toooo large!");
}
AllocPageTypes pageType = block.BelongedPageType();
IList <AllocatedSpace> spaces = this.fileDBContext.Alloc(bytes.LongLength, pageType);
block.ThisPos = spaces[0].position;
}
arrangedBlocks.Add(block);
}
}
}
// 根据要删除的块，更新文件头。
foreach (var block in this.deletingBlockList)
{
long pagePos = block.ThisPos.PagePos();
PageHeaderBlock page;
if (!this.affectedPages.TryGetValue(pagePos, out page))
{
page = fs.ReadBlock <PageHeaderBlock>(pagePos);
this.affectedPages.Add(pagePos, page);
}
byte[] bytes = block.ToBytes();
Int16 length = (Int16)bytes.Length;
if (length > Consts.maxAvailableSpaceInPage)
{
throw new Exception(string.Format("Block [{0}]'s serialized bytes is more than {1}", block, Consts.maxAvailableSpaceInPage));
}
page.OccupiedBytes -= length;
if (page.OccupiedBytes < Consts.minOccupiedBytes)
{
throw new Exception(string.Format("DB Error: {0}'s Occupied bytes is less than {1}", page, Consts.minOccupiedBytes));
}
if (page.OccupiedBytes == Consts.minOccupiedBytes)// 此页已成为新的空白页。
{
// page 加入空白页链表。
//DBHeaderBlock dbHeader = this.fileDBContext.headerBlock;
page.NextPagePos = dbHeaderBlock.FirstEmptyPagePos;
dbHeaderBlock.FirstEmptyPagePos = page.ThisPos;
}
}
// 准备恢复文件。
string journalFilename = this.fileDBContext.JournalFileName;
FileStream journalFile = new FileStream(journalFilename,
FileMode.Create, FileAccess.ReadWrite, FileShare.None, Consts.pageSize);
foreach (Block block in this.addlingBlockList)
{
Consts.formatter.Serialize(journalFile, block);
}
foreach (PageHeaderBlock block in this.affectedPages.Values)
{
if (block.IsDirty)
{
Consts.formatter.Serialize(journalFile, block);
}
}
if (dbHeaderBlock.IsDirty)
{
Consts.formatter.Serialize(journalFile, dbHeaderBlock);
}
journalFile.Flush();
// 写入所有的更改。
foreach (Block block in this.addlingBlockList)
{
fs.WriteBlock(block);
}
foreach (PageHeaderBlock block in this.affectedPages.Values)
{
if (block.IsDirty)
{
fs.WriteBlock(block);
block.IsDirty = false;
}
}
if (dbHeaderBlock.IsDirty)
{
fs.WriteBlock(dbHeaderBlock);
dbHeaderBlock.IsDirty = false;
}
fs.Flush();
// 删除恢复文件。
journalFile.Close();
journalFile.Dispose();
File.Delete(journalFilename);
// 恢复Transaction最初的状态。
this.addlingBlockList.Clear();
this.oldAddingBlockPositions.Clear();
this.deletingBlockList.Clear();
this.oldDeletingBlockPositions.Clear();
this.affectedPages.Clear();
//if (actUnlockDB == null) { actUnlockDB = new Action(UnlockDB); }
UnlockDB();
this.level = 0;
}
