internal void Write(Stream writer, BitAccess bits) {
bits.MinCapacity(56);
bits.WriteBytes(magic); // 0..31
bits.WriteInt32(pageSize); // 32..35
bits.WriteInt32(freePageMap); // 36..39
bits.WriteInt32(pagesUsed); // 40..43
bits.WriteInt32(directorySize); // 44..47
bits.WriteInt32(zero); // 48..51
bits.WriteInt32(directoryRoot); // 52..55
writer.Seek(0, SeekOrigin.Begin);
bits.WriteBuffer(writer, 56);
}