/// <summary>
/// Read header data from byte[] buffer into local variables
/// using fixed position be be faster than use BufferReader
/// </summary>
public BasePage(PageBuffer buffer)
{
_buffer = buffer;
// page information
this.PageID = _buffer.ReadUInt32(P_PAGE_ID);
this.PageType = (PageType)_buffer.ReadByte(P_PAGE_TYPE);
this.PrevPageID = _buffer.ReadUInt32(P_PREV_PAGE_ID);
this.NextPageID = _buffer.ReadUInt32(P_NEXT_PAGE_ID);
// transaction information
this.TransactionID = _buffer.ReadUInt32(P_TRANSACTION_ID);
this.IsConfirmed = _buffer.ReadBool(P_IS_CONFIRMED);
this.ColID = _buffer.ReadUInt32(P_COL_ID);
// blocks information
this.ItemsCount = _buffer.ReadByte(P_ITEMS_COUNT);
this.UsedBytes = _buffer.ReadUInt16(P_USED_BYTES);
this.FragmentedBytes = _buffer.ReadUInt16(P_FRAGMENTED_BYTES);
this.NextFreePosition = _buffer.ReadUInt16(P_NEXT_FREE_POSITION);
this.HighestIndex = _buffer.ReadByte(P_HIGHEST_INDEX);
}
/// <summary>
/// Get a page segment item based on index slot
/// </summary>
public BufferSlice Get(byte index)
{
ENSURE(index < byte.MaxValue, "slot index must be between 0-254");
// read slot address
var positionAddr = CalcPositionAddr(index);
var lengthAddr = CalcLengthAddr(index);
// read segment position/length
var position = _buffer.ReadUInt16(positionAddr);
var length = _buffer.ReadUInt16(lengthAddr);
ENSURE(this.IsValidPos(position), "invalid segment position");
ENSURE(this.IsValidLen(length), "invalid segment length");
// return buffer slice with content only data
return(_buffer.Slice(position, length));
}
/// <summary>
/// Get a page segment item based on index slot
/// </summary>
public BufferSlice Get(byte index)
{
ENSURE(this.ItemsCount > 0, "should have items in this page");
ENSURE(this.HighestIndex != byte.MaxValue, "should be have at least 1 index in this page");
ENSURE(index <= this.HighestIndex, "get only index below highest index");
// read slot address
var positionAddr = CalcPositionAddr(index);
var lengthAddr = CalcLengthAddr(index);
// read segment position/length
var position = _buffer.ReadUInt16(positionAddr);
var length = _buffer.ReadUInt16(lengthAddr);
ENSURE(this.IsValidPos(position), "invalid segment position");
ENSURE(this.IsValidLen(length), "invalid segment length");
// return buffer slice with content only data
return(_buffer.Slice(position, length));
}