Have you ever had to use bit shifting in real projects?

Question

Have you ever had to use bit shifting in real programming projects? Most (if not all) high level languages have shift operators in them, but when would you actually need to

Answer 1

Bit shifting is used a lot in deciphering the protocols of online games. The protocols are designed to use a little bandwidth as possible, so instead of transmitting the number of players on a server, names and so forth in int32s, all the information is packed into as few bytes as possible. It's not really necessary these days with most people using broadband, but when they were originally designed people used 56k modems for gaming, so every bit counted.

The most prominent examples of this are in Valve's multiplayer games particularly Counter-Strike, Counter-Strike Source. The Quake3 protocol is also the same, however Unreal isn't quite as slimline.

Here's an example (.NET 1.1)

string data = Encoding.Default.GetString(receive);

if ( data != "" )
{
    // If first byte is 254 then we have multiple packets
    if ( (byte) data[0] == 254 )
    {
        // High order contains count, low order index
        packetCount = ((byte) data[8]) & 15; // indexed from 0
        packetIndex = ((byte) data[8]) >> 4;
        packetCount -= 1;

        packets[packetIndex] = data.Remove(0,9);
    }
    else
    {
        packets[0] = data;

    }
}

Of course whether you view this as a real project or just a hobby (in C#) is up to you.