public static void WriteToFile(DataUnit dataPage, BinaryWriter writer)
{
long initPos = writer.Seek(100L + (dataPage.UnitID * 0x1000L));
writer.Write((byte) dataPage.Type);
writer.Write(dataPage.NextUnitID);
writer.Write(dataPage.IsEmpty);
writer.Write(dataPage.DataBlockLength);
if (!dataPage.IsEmpty)
{
writer.Seek(initPos + 8L);
writer.Write(dataPage.DataBlock, 0, dataPage.DataBlockLength);
}
}
public static void ReadFromFile(DataUnit dataPage, BinaryReader reader, bool onlyHeader)
{
long initPos = reader.Seek(100L + (dataPage.UnitID * 0x1000L));
if (reader.ReadByte() != 1)
{
throw new FileDBException("PageID {0} is not a Data Page", new object[] { dataPage.UnitID });
}
dataPage.NextUnitID = reader.ReadUInt32();
dataPage.IsEmpty = reader.ReadBoolean();
dataPage.DataBlockLength = reader.ReadInt16();
if (!dataPage.IsEmpty && !onlyHeader)
{
reader.Seek(initPos + 8L);
dataPage.DataBlock = reader.ReadBytes(dataPage.DataBlockLength);
}
}
public static DataUnit GetNewDataPage(DataUnit basePage, Engine engine)
{
if (basePage.NextUnitID != uint.MaxValue)
{
UnitFactory.WriteToFile(basePage, engine.Writer);
DataUnit dataPage = UnitFactory.GetDataPage(basePage.NextUnitID, engine.Reader, false);
engine.Header.FreeDataPageID = dataPage.NextUnitID;
if (engine.Header.FreeDataPageID == uint.MaxValue)
{
engine.Header.LastFreeDataPageID = uint.MaxValue;
}
return dataPage;
}
Header header = engine.Header;
uint pageID = ++header.LastPageID;
DataUnit newPage = new DataUnit(pageID);
basePage.NextUnitID = newPage.UnitID;
UnitFactory.WriteToFile(basePage, engine.Writer);
return newPage;
}
public static DataUnit GetDataPage(uint pageID, BinaryReader reader, bool onlyHeader)
{
DataUnit dataPage = new DataUnit(pageID);
ReadFromFile(dataPage, reader, onlyHeader);
return dataPage;
}
