public static long GetPosOfFirstPage(this DBHeaderBlock dbHeaderBlock, AllocPageTypes type)
{
long position;
switch (type)
{
case AllocPageTypes.Table:
position = dbHeaderBlock.FirstTablePagePos;
break;
case AllocPageTypes.Index:
position = dbHeaderBlock.FirstIndexPagePos;
break;
case AllocPageTypes.SkipListNode:
position = dbHeaderBlock.FirstSkipListNodePagePos;
break;
case AllocPageTypes.Data:
position = dbHeaderBlock.FirstDataPagePos;
break;
default:
throw new NotImplementedException();
}
return(position);
}
private static void SortPage(AllocPageTypes type, PageHeaderBlock page, FileStream fs, Transaction ts, Blocks.DBHeaderBlock dbHeader)
{
long headPos = dbHeader.GetPosOfFirstPage(type);
if (headPos == 0)// 一个页也没有。
{
dbHeader.SetPosOfFirstPage(type, page.ThisPos);
}
else
{
PageHeaderBlock head = GetPageHeaderBlock(fs, ts, headPos);
if (page.AvailableBytes >= head.AvailableBytes)// 与第一个页进行比较。
{
page.NextPagePos = head.ThisPos;
dbHeader.SetPosOfFirstPage(type, page.ThisPos);
}
else// 与后续的页进行比较。
{
PageHeaderBlock current = head;
while (current.NextPagePos != 0)
{
PageHeaderBlock next = GetPageHeaderBlock(fs, ts, current.NextPagePos);
if (page.AvailableBytes >= next.AvailableBytes)
{
if (next.ThisPos != current.NextPagePos)
{
throw new Exception(string.Format("this should not happen."));
}
page.NextPagePos = current.NextPagePos; // next.ThisPos;
current.NextPagePos = page.ThisPos;
break;
}
else
{
current = next;
}
}
if (current.NextPagePos == 0)
{
current.NextPagePos = page.ThisPos;
}
if (!ts.affectedPages.ContainsKey(current.ThisPos))
{
ts.affectedPages.Add(current.ThisPos, current);
}
}
}
}
public static void SetPosOfFirstPage(this DBHeaderBlock dbHeaderBlock, AllocPageTypes type, long value)
{
switch (type)
{
case AllocPageTypes.Table:
dbHeaderBlock.FirstTablePagePos = value;
break;
case AllocPageTypes.Index:
dbHeaderBlock.FirstIndexPagePos = value;
break;
case AllocPageTypes.SkipListNode:
dbHeaderBlock.FirstSkipListNodePagePos = value;
break;
case AllocPageTypes.Data:
dbHeaderBlock.FirstDataPagePos = value;
break;
default:
throw new NotImplementedException();
}
}
public static IList <AllocatedSpace> Alloc(this FileDBContext db, long length, AllocPageTypes type)
{
// 由于一页能用的空间很有限，所以可能需要从多个页上获取空间。
IList <AllocatedSpace> result = new List <AllocatedSpace>();
FileStream fs = db.fileStream;
long allocated = 0;
while (allocated < length)
{
Int16 partLength = (length - allocated >= Consts.maxAvailableSpaceInPage) ? Consts.maxAvailableSpaceInPage : (Int16)(length - allocated);
// 找出一个可用空间充足的指定类型的页。
PageHeaderBlock page = PickPage(db, partLength, type);
if (!db.transaction.affectedPages.ContainsKey(page.ThisPos))// 加入缓存备用。
{
db.transaction.affectedPages.Add(page.ThisPos, page);
}
AllocatedSpace item = new AllocatedSpace(page.ThisPos + Consts.pageSize - page.AvailableBytes - partLength, (Int16)length);
result.Add(item);
allocated += partLength;
}
return(result);
}
private static PageHeaderBlock PickPage(this FileDBContext db, Int16 allocatingLength, AllocPageTypes type)
{
PageHeaderBlock page;
FileStream fs = db.fileStream;
Transaction ts = db.transaction;
DBHeaderBlock dbHeader = db.headerBlock;
// 找到第一个给定类型的页的位置。
long pagePos = dbHeader.GetPosOfFirstPage(type);
if (pagePos == 0)// 尚无给定类型的页。
{
page = db.AllocEmptyPageOrNewPage();
page.AvailableBytes -= allocatingLength;
page.OccupiedBytes += allocatingLength;
dbHeader.SetPosOfFirstPage(type, page.ThisPos);
}
else
{
// 最前面的table页的可用空间是最大的（这需要在后续操作中进行排序）
PageHeaderBlock firstTablePage = GetTablePage(fs, ts, pagePos);
if (firstTablePage.AvailableBytes >= allocatingLength)// 此页的空间足够用。
{
// 把此页从Page链表中移除。
dbHeader.SetPosOfFirstPage(type, firstTablePage.NextPagePos);
firstTablePage.NextPagePos = 0;
page = firstTablePage;
}
else// 此页的空间不够用，还是要申请一个新页。
{
page = db.AllocEmptyPageOrNewPage();
}
page.AvailableBytes -= allocatingLength;
page.OccupiedBytes += allocatingLength;
// 对申请的类型的页的链表进行排序。呼应上面的排序需求。
SortPage(type, page, fs, ts, dbHeader);
}
return(page);
}
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;
}
