void Initialise()
{
if ( F.Length == 0 ) // New file : create Root page.
{
Root = new IndexPage( Inf, null, Database );
AllocPageId( Root );
}
else
{
PageAlloc = (long) ( ( F.Length + IndexPage.PageSize - 1 ) / IndexPage.PageSize );
Root = GetPage( 0 ); // Maybe could delay this until first use of the index ( as index may never be used at all ).
}
Saved = true;
}
public bool Saved = false; // Indicates whether tree has been saved to disk.
void Insert(IndexFile ixf, ref IndexFileRecord r)
{
if (Free == 0 && NodeAlloc == MaxNode) // Page is full, have to split it.
{
PageParent pp;
if (this == ixf.Root)
{
pp = new PageParent(Inf, null, Database);
ixf.AllocPageId(this);
pp.FirstPage = PageId;
ixf.Root = pp;
ixf.PageMap[0] = pp;
}
else
{
pp = (PageParent)ixf.PageMap[ParentId];
}
IndexPage left = Clone();
left.PageId = PageId;
left.FirstPage = FirstPage;
ixf.PageMap[PageId] = left;
IndexPage right = Clone();
ixf.AllocPageId(right);
var div = new IndexFileRecord(); // IndexFileRecord that divides page into left/right, will be inserted into parent page.
Divide(left, right, ref div);
right.FirstPage = div.Child;
div.Child = right.PageId;
pp.Insert(ixf, ref div);
// Insert into either left or right depending on comparison with sv.
(Compare(ref r, ref div) < 0 ? left : right).Insert(ref r, false);
// Console.WriteLine( "Insert Split, NodeAlloc=" + NodeAlloc + " MaxNode=" + MaxNode + "ixf.PageAlloc=" + ixf.PageAlloc );
// Console.WriteLine( "Split div=" + div.ToString(ixf.Inf) );
// ixf.Dump();
}
else
{
Insert(ref r, false);
}
}
public void PrepareToCommit() // Writes pages to the underlying file ( which will be fully buffered ).
{
if ( Saved ) return;
// Save the pages.
foreach ( G.KeyValuePair<long,IndexPage> pair in PageMap )
{
IndexPage p = pair.Value;
if ( !p.Saved )
{
p.WriteHeader();
F.Position = (long)p.PageId * IndexPage.PageSize;
// For last page, only write the amount actually used (so file size is minimised)
F.Write( p.Data, 0, p.PageId == PageAlloc-1 ? p.Size() : IndexPage.PageSize );
p.Saved = true;
}
}
Saved = true;
}
public void AllocPageId( IndexPage p )
{
p.PageId = PageAlloc++;
PageMap[ p.PageId ] = p;
}
