buff2[0].PA = buff2[0].PAB = buff2[0].PB = 0;
buff2[1].PA = buff2[1].PAB = buff2[1].PB = 1;
buff2[2].PA = buff2[2].PAB = buff2[2].PB = 1;
ofs.write(reinterpret_cast<char*>(&buff2),BUFFER_SIZE);
ofs.flush();
buff2[0].PA = buff2[0].PAB = buff2[0].PB = 4;
buff2[1].PA = buff2[1].PAB = buff2[1].PB = 5;
buff2[2].PA = buff2[2].PAB = buff2[2].PB = 6;
ofs.seekp(0,ios::end);
ofs.write(reinterpret_cast<char*>(&buff2),BUFFER_SIZE);