// Perform a lookup in the b-tree
private static TreeNode LookupTreeNode(TreeIntermediate parent, UInt64 key, Action <TreeIntermediate> readDeferred)
{
if (parent.ReadDeferred)
{
if (readDeferred != null)
{
readDeferred(parent);
}
else
{
throw new Exception("Deferred index found, but no reader supplied");
}
}
TreeIntermediate next = null;
foreach (var n in parent.Children)
{
if (key > n.Key)
{
next = n as TreeIntermediate;
}
else if (key < n.Key)
{
if (next != null)
{
return(LookupTreeNode(next, key, readDeferred));
}
else
{
return(null); // Key does not exist
}
}
else // key matches
{
if (n is TreeIntermediate)
{
return(LookupTreeNode((TreeIntermediate)n, key, readDeferred));
}
else
{
return(n);
}
}
}
if (next != null)
{
return(LookupTreeNode(next, key, readDeferred));
}
else
{
return(null); // Key does not exist
}
}
// When a data block has a subnode, it can be a simple node, or a two-level tree
// This reads a sub node and builds suitable data structures, so that we can later access data held in it
private void ReadSubNodeBtreeUnicode(FileStream fs, UInt64 subDataBid, TreeIntermediate parent)
{
var rb = LookupDataBlock(subDataBid);
if (rb == null)
{
throw new XstException("SubNode data block does not exist");
}
int read;
byte[] buffer = ReadAndDecompress(fs, rb, out read);
var sl = Map.MapType <SLBLOCKUnicode>(buffer);
if (sl.cLevel > 0)
{
var rgbid = Map.MapArray <SIENTRYUnicode>(buffer, Marshal.SizeOf(typeof(SLBLOCKUnicode)), sl.cEnt);
foreach (var sie in rgbid)
{
var inter = new TreeIntermediate {
Key = (sie.nid & 0xffffffff)
};
parent.Children.Add(inter);
// Read child nodes in tree
ReadSubNodeBtreeUnicode(fs, sie.bid, inter);
}
}
else
{
var rgbid = Map.MapArray <SLENTRYUnicode>(buffer, Marshal.SizeOf(typeof(SLBLOCKUnicode)), sl.cEnt);
foreach (var sle in rgbid)
{
// Only use low order dword of nid
var nb = new Node {
Key = (sle.nid & 0xffffffff), DataBid = sle.bidData, SubDataBid = sle.bidSub
};
parent.Children.Add(nb);
}
}
}
// A callback to be used when searching a tree to read part of the index whose loading has been deferred
private void ReadDeferredIndex(TreeIntermediate inter)
{
using (var fs = GetReadStream())
{
if (IsUnicode4K)
{
ReadBTPageUnicode4K(fs, (ulong)inter.fileOffset, inter);
}
else if (IsUnicode)
{
ReadBTPageUnicode(fs, (ulong)inter.fileOffset, inter);
}
else
{
ReadBTPageANSI(fs, (ulong)inter.fileOffset, inter);
}
// Don't read it again
inter.fileOffset = null;
}
}
private void ReadBTPageANSI(FileStream fs, ulong fileOffset, TreeIntermediate parent)
{
fs.Seek((long)fileOffset, SeekOrigin.Begin);
var p = Map.ReadType <BTPAGEANSI>(fs);
// read entries
for (int i = 0; i < p.cEnt; i++)
{
if (p.cLevel > 0)
{
BTENTRYANSI e;
unsafe
{
e = Map.MapType <BTENTRYANSI>(p.rgentries, LayoutsA.BTPAGEEntryBytes, i * p.cbEnt, p.cbEnt);
}
var inter = new TreeIntermediate {
Key = e.btkey
};
parent.Children.Add(inter);
if (deferReadingNodes)
{
inter.fileOffset = e.BREF.ib;
}
else
{
// Read child nodes in tree
ReadBTPageANSI(fs, e.BREF.ib, inter);
inter.fileOffset = null;
}
}
else
{
if (p.pageTrailer.ptype == Eptype.ptypeNBT)
{
unsafe
{
var e = Map.MapType <NBTENTRYANSI>(p.rgentries, LayoutsA.BTPAGEEntryBytes, i * p.cbEnt, p.cbEnt);
var nb = new Node {
Key = e.nid.dwValue, Type = e.nid.nidType, DataBid = e.bidData, SubDataBid = e.bidSub, Parent = e.nidParent
};
parent.Children.Add(nb);
}
}
else if (p.pageTrailer.ptype == Eptype.ptypeBBT)
{
unsafe
{
var e = Map.MapType <BBTENTRYANSI>(p.rgentries, LayoutsA.BTPAGEEntryBytes, i * p.cbEnt, p.cbEnt);
parent.Children.Add(new DataRef {
Key = e.BREF.bid, Offset = e.BREF.ib, Length = e.cb
});
}
}
else
{
throw new XstException("Unexpected page entry type");
}
}
}
}
