public BlockHeader(BinaryDeserializer Reader)
{
this.BytesUsed = Reader.ReadUInt16(); // 0: Counts number of bytes used in block, excluding the node header, and the last block link (14 bytes in total).
this.SizeSubtree = Reader.ReadUInt32(); // 2: Order statistic tree, counting number of objects rooted at the current node.
this.LastBlockIndex = Reader.ReadBlockLink(); // 6: Last block link.
this.ParentBlockIndex = Reader.ReadBlockLink(); // 10: Parent block link.
}
private async Task <ulong?> GoToObject(ulong ObjectIndex, uint BlockIndex)
{
if (ObjectIndex == 0)
{
if (await this.GoToFirst(BlockIndex))
{
return(1);
}
else
{
return(null);
}
}
object ObjectId;
int Len;
int Pos;
uint BlockLink;
bool IsEmpty;
byte[] Block = await this.LoadBlock(BlockIndex);
BinaryDeserializer Reader = new BinaryDeserializer(this.file.CollectionName, this.file.Encoding, Block, this.file.BlockLimit);
BlockHeader Header = new BlockHeader(Reader);
ulong Count = 0;
ulong?SubtreeCount;
if (ObjectIndex >= Header.SizeSubtree && Header.SizeSubtree < uint.MaxValue)
{
return(Header.SizeSubtree);
}
do
{
Pos = Reader.Position;
BlockLink = Reader.ReadBlockLink(); // Block link.
ObjectId = this.recordHandler.GetKey(Reader); // Object ID of object.
IsEmpty = (ObjectId == null);
if (IsEmpty)
{
break;
}
Len = this.recordHandler.GetPayloadSize(Reader); // Remaining length of object.
Reader.Position += Len;
if (BlockLink != 0)
{
SubtreeCount = await this.GoToObject(ObjectIndex - Count, BlockLink);
if (SubtreeCount.HasValue)
{
Count += SubtreeCount.Value;
if (Count > ObjectIndex)
{
return(Count);
}
}
else
{
return(null);
}
}
if (Count++ == ObjectIndex)
{
this.currentBlockIndex = BlockIndex;
this.currentBlock = Block;
this.currentReader = Reader;
this.currentHeader = Header;
await this.LoadObject(ObjectId, Pos + 4);
return(Count);
}
}while (Reader.BytesLeft >= 4);
if (Header.LastBlockIndex != 0)
{
SubtreeCount = await this.GoToObject(ObjectIndex - Count, Header.LastBlockIndex);
if (SubtreeCount.HasValue)
{
Count += SubtreeCount.Value;
if (Count == ObjectIndex)
{
return(Count);
}
}
else
{
return(null);
}
}
return(Count);
}
