/// <summary>
/// Create new Page based on pre-defined PageID and PageType
/// </summary>
public BasePage(PageBuffer buffer, uint pageID, PageType pageType)
{
_buffer = buffer;
ENSURE(buffer.Slice(PAGE_HEADER_SIZE, PAGE_SIZE - PAGE_HEADER_SIZE - 1).All(0), "new page buffer must be empty before use in a new page");
// page information
this.PageID = pageID;
this.PageType = pageType;
this.PrevPageID = uint.MaxValue;
this.NextPageID = uint.MaxValue;
// transaction information
this.ColID = uint.MaxValue;
this.TransactionID = uint.MaxValue;
this.IsConfirmed = false;
// block information
this.ItemsCount = 0;
this.UsedBytes = 0;
this.FragmentedBytes = 0;
this.NextFreePosition = PAGE_HEADER_SIZE; // 32
this.HighestIndex = byte.MaxValue; // empty - not used yet
// default values
this.IsDirty = false;
// writing direct into buffer in Ctor() because there is no change later (write once)
_buffer.Write(this.PageID, P_PAGE_ID);
_buffer.Write((byte)this.PageType, P_PAGE_TYPE);
}
/// <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));
}