/// <summary>
/// Del an item from the second item. Delete is expensive as it has to search throught all records.
/// </summary>
/// <param name="SectionPosition"></param>
/// <param name="BlockPosition"></param>
public void Del(long SectionPosition, long BlockPosition)
{
ItemHeader header = loadHeader(SectionPosition);
if (header.BlockPosition <= 0)
{
return;
}
Item nextitem = loadItem(header.FirstRecordPointer);
if (nextitem.ContentBlockPosition == BlockPosition)
{
header.FirstRecordPointer = nextitem.NextRecord;
header.counter = header.counter - 1;
Stream.Position = header.BlockPosition;
Stream.Write(header.ToBytes(), 0, 14);
}
else
{
bool delok = Del(nextitem, BlockPosition);
if (delok)
{
header.counter = header.counter - 1;
Stream.Position = header.BlockPosition;
Stream.Write(header.ToBytes(), 0, 14);
}
}
}
private void Add(ItemHeader header, long BlockPosition)
{
Item item = new Item();
item.ContentBlockPosition = BlockPosition;
item.NextRecord = header.FirstRecordPointer;
long writeposition = Stream.Length;
Stream.Position = writeposition;
Stream.Write(item.ToBytes(), 0, 18);
header.FirstRecordPointer = writeposition;
header.counter = header.counter + 1;
Stream.Position = header.BlockPosition;
Stream.Write(header.ToBytes(), 0, 14);
}
private ItemHeader CreateNewSection()
{
ItemHeader header = new ItemHeader();
header.counter = 0;
header.FirstRecordPointer = 0;
Int64 writeposition;
writeposition = Stream.Length;
Stream.Position = writeposition;
Stream.Write(header.ToBytes(), 0, 14);
header.BlockPosition = writeposition;
return(header);
}
/// <summary>
/// Dequeue one item
/// </summary>
/// <param name="SectionPosition"></param>
/// <returns></returns>
public long DeQueue(long SectionPosition)
{
lock (_object)
{
ItemHeader header = loadHeader(SectionPosition);
if (header.counter < 1)
{
return(-1);
}
Item item = loadItem(header.FirstRecordPointer);
header.counter = header.counter - 1;
header.FirstRecordPointer = item.NextRecord;
Stream.Position = header.BlockPosition;
Stream.Write(header.ToBytes(), 0, 14);
return(item.ContentBlockPosition);
}
}