public static BTreePage ReadFromStream(Stream stream, BlockRef blockRef)
{
long offset = (long)blockRef.ib;
stream.Seek(offset, SeekOrigin.Begin);
byte[] buffer = new byte[Length];
stream.Read(buffer, 0, Length);
PageTypeName ptype = (PageTypeName)buffer[PageTrailer.OffsetFromPageStart + 0];
BTreePage page;
byte cLevel = buffer[491];
if (cLevel > 0)
{
// If cLevel is greater than 0, then each entry in the array is of type BTENTRY.
page = new BTreeIndexPage(buffer);
}
else
{
// If cLevel is 0, then each entry is either of type BBTENTRY or NBTENTRY, depending on the ptype of the page.
if (ptype == PageTypeName.ptypeBBT)
{
page = new BlockBTreeLeafPage(buffer);
}
else if (ptype == PageTypeName.ptypeNBT)
{
page = new NodeBTreeLeafPage(buffer);
}
else
{
throw new ArgumentException("BTreePage has incorrect ptype");
}
}
page.Offset = (ulong)blockRef.ib;
if (blockRef.bid.Value != page.BlockID.Value)
{
throw new InvalidBlockIDException();
}
uint crc = PSTCRCCalculation.ComputeCRC(buffer, PageTrailer.OffsetFromPageStart);
if (page.pageTrailer.dwCRC != crc)
{
throw new InvalidChecksumException();
}
uint signature = BlockTrailer.ComputeSignature(blockRef.ib, blockRef.bid.Value);
if (page.pageTrailer.wSig != signature)
{
throw new InvalidChecksumException();
}
return(page);
}
public void CreateNewRoot()
{
BTreeIndexPage newRoot = BTreeIndexPage.GetEmptyIndexPage(m_bTreeRootPage.pageTrailer.ptype, m_bTreeRootPage.cLevel + 1);
BTreeIndexEntry rootIndexEntry = new BTreeIndexEntry();
// We make sure the old root page has been updated (to prevent the BlockID from changing during update)
UpdatePage(m_bTreeRootPage);
rootIndexEntry.btkey = m_bTreeRootPage.PageKey;
rootIndexEntry.BREF.bid = m_bTreeRootPage.BlockID;
rootIndexEntry.BREF.ib = 0; // this will tell BufferedBTreePageStore that the block hasn't been written yet
newRoot.IndexEntryList.Add(rootIndexEntry);
AddPage(newRoot);
m_bTreeRootPage.ParentPage = newRoot;
m_bTreeRootPage = newRoot;
}
/// <param name="blockID">BlockID of the child page with the new key</param>
protected void UpdateIndexEntry(BTreeIndexPage indexPage, BlockID blockIDOfChild, ulong newKeyOfChild)
{
for (int index = 0; index < indexPage.IndexEntryList.Count; index++)
{
BTreeIndexEntry entry = indexPage.IndexEntryList[index];
if (entry.BREF.bid.Value == blockIDOfChild.Value)
{
entry.btkey = newKeyOfChild;
UpdatePageAndReferences(indexPage); // parents will now refer to the new blockID
if (index == 0 && indexPage.ParentPage != null)
{
// page key has been modified, we must update the parent as well
UpdateIndexEntry(indexPage.ParentPage, indexPage.BlockID, indexPage.PageKey);
}
}
}
}
private void CascadeUpReferenceUpdate(BTreeIndexPage indexPage, ulong oldBlockID, ulong newBlockID)
{
int index = indexPage.GetIndexOfBlockID(oldBlockID);
if (index >= 0)
{
BTreeIndexEntry entry = indexPage.IndexEntryList[index];
entry.BREF.bid = new BlockID(newBlockID);
entry.BREF.ib = 0; // this will tell BufferedBTreePageStore that the block hasn't been written yet
ulong currentBlockID = indexPage.BlockID.Value;
UpdatePage(indexPage);
if (currentBlockID != indexPage.BlockID.Value &&
indexPage.ParentPage != null)
{
CascadeUpReferenceUpdate(indexPage.ParentPage, currentBlockID, indexPage.BlockID.Value);
}
}
}
public BTreeIndexPage Split()
{
int newNodeStartIndex = IndexEntryList.Count / 2;
BTreeIndexPage newPage = new BTreeIndexPage();
// blockID will be given when the page will be added
newPage.cEntMax = cEntMax;
newPage.cbEnt = cbEnt;
newPage.cLevel = cLevel;
newPage.pageTrailer.ptype = pageTrailer.ptype;
for (int index = newNodeStartIndex; index < IndexEntryList.Count; index++)
{
newPage.IndexEntryList.Add(IndexEntryList[index]);
}
IndexEntryList.RemoveRange(newNodeStartIndex, IndexEntryList.Count - newNodeStartIndex);
return(newPage);
}
protected void InsertIndexEntry(BTreeIndexPage indexPage, BTreeIndexEntry entryToInsert)
{
if (indexPage.IndexEntryList.Count < BTreeIndexPage.MaximumNumberOfEntries)
{
int insertIndex = indexPage.InsertSorted(entryToInsert);
UpdatePageAndReferences(indexPage);
if (insertIndex == 0 && indexPage.ParentPage != null)
{
// page key has been modified, we must update the parent
UpdateIndexEntry(indexPage.ParentPage, indexPage.BlockID, indexPage.PageKey);
}
}
else
{
// The tree node is full, we have to split it
BTreeIndexPage newPage = indexPage.Split();
if (newPage.PageKey < entryToInsert.btkey)
{
newPage.InsertSorted(entryToInsert);
}
else
{
int insertIndex = indexPage.InsertSorted(entryToInsert);
if (insertIndex == 0 && indexPage.ParentPage != null)
{
// page key has been modified, we must update the parent
UpdateIndexEntry(indexPage.ParentPage, indexPage.BlockID, indexPage.PageKey);
}
}
UpdatePageAndReferences(indexPage);
AddPage(newPage);
if (indexPage.ParentPage == null)
{
// this is a root page and it's full, we have to create a new root
CreateNewRoot();
}
// We made sure we have a parent to add our new page to
InsertIndexEntry(indexPage.ParentPage, newPage.PageKey, newPage.BlockID);
}
}
