public RowsetHolder(ColumnInfo[] columnTypes, Memory <byte> storage, bool init)
{
System.Diagnostics.Debug.Assert(BitConverter.IsLittleEndian, "Rowset holder fixed assumes that we are running on little endian");
this.rowSize = GetRowSize(columnTypes);
this.storage = storage;
this.rowCount = 0;
// bit for every row.
// align on upper boundary.
this.reservedPresenceBitmaskCount = (ushort)UtilStructures.IntCeil.CeilDiv(storage.Length, (rowSize * 8));
// TODO: In this implementation each value in tuple can't be bigger than 256 bytes.
// Since this is only for fixed data this should be fine.
this.reservedColumnTupleOffsetsCount = (ushort)(columnTypes.Length * sizeof(ushort));
if (init)
{
// set bitmask to 0.
for (int i = 0; i < this.reservedPresenceBitmaskCount; i++)
{
this.storage.Span[i] = 0;
}
int pos = this.reservedPresenceBitmaskCount;
this.storage.Span[pos] = 0;
for (int i = 0; i < columnTypes.Length - 1; i++)
{
this.storage.Span[pos + 1] = (byte)(this.storage.Span[pos] + columnTypes[i].GetSize());
pos++;
}
}
else
{
// Set row count.
this.rowCount = BitArray.CountSet(storage.Span.Slice(0, this.reservedPresenceBitmaskCount));
}
// Align so start is divisible by 4.
// TODO: Need to measure perf.
int dataStartUnAligned = this.reservedPresenceBitmaskCount + this.reservedColumnTupleOffsetsCount;
this.dataStartPosition = (ushort)(((dataStartUnAligned + 4 - 1) / 4) * 4);
maxRowCount = (ushort)((storage.Length - dataStartPosition) / rowSize);
}
