DEM (file format)

Note that it is not possible to edit what happens in a Source demo, it basically stores the packets right off the wire, and we don't know the packet format.

For the purpose of this, I will be referring to each collection of events as a frame. This may or may not add up to the number of frames given by the header.

Заголовок Демо

Тип	Поле	Значение
String	Заголовок	7+NULL characters, should be "HL2DEMO"
Int	Демо Протокол	Версия протокола демо, например '3'
Int	Протокол Сети	Версия Сетевого протокола
String	Имя Сервера	Длиной в 260 символов
String	Имя клиента	Длиной в 260 символов
String	Имя Карты	Длиной в 260 символов
String	Директория Игры	Длиной в 260 символов
Float	Время игры	Продолжительность записи Демо, в секундах
Int	Ticks	The number of ticks in the demo
Int	Frames	The number of frames in the demo
Int	Sign on length	?

Frame

Each frame begins with 0 or more of these commands: These are described in hl2sdk\utils\demoinfo\demoformat.h

Type	Value
dem_signon	1
dem_packet	2
dem_synctick	3
dem_consolecmd	4
dem_usercmd	5
dem_datatables	6
dem_stop	7
dem_lastcommand	dem_stop

Depending on the command that was received, a different action needs to be taken.

dem_stop, dem_lastcommand

This is a signal that the demo is over, and there is no more data to be parsed.

dem_consolecmd, dem_datatables, dem_usercmd

Read a standard data packet, deal with it as necessary.

dem_synctick, dem_signon, dem_packet

Ignore.

Standard Data "Packet"

Any time there is more than one byte to be read in, a standard format is used.

This begins with an integer that has the number of bytes in this packet.

Example code to handle this:

int ReadData(char **buffer)
{
	int len;
	fread (&len,sizeof(int),1,fDemo);
	if (len > 0)
	{
		*buffer = new char[len];
		fread(*buffer,len,1,fDemo);
	}
	return len;
}