ZigZag Encode

To encode a value using ZigZag Encoding you can use the ZigZagEncodeAttribute

This will cause negative values to be encoded as positive so that the sign bit is not lost when packing.

This works best with VarIntBlocks but also works with BitCount.

This attribute can not be used on the same field as BitCountFromRange, this is because BitCountFromRange already ensures negative values are packed correctly.

note

The sign of a value will take up 1 bit, so if the value is in the range -+100 it will need a bit count of 8

Use cases

• A value that can be negative or positive

Supported Types

• Byte
• Short
• Int
• Long
• Enum

Example 1

A modifier that can be added to a character value to increase or decrease it

public class MyNetworkBehaviour : NetworkBehaviour 
{
    [SyncVar, BitCount(8), ZigZagEncode]
    public int modifier;
}

Range = 200 so bit count is 8, causing the real range to be -128 to 127

modifier = 57 will serialize to 0111_0010

modifier = -57 will serialize to 0111_0001

modifier = -110 will serialize to 1101_1011, even tho -110 is out of range there is enough range because bit count rounds up.

modifier = 130 (out of range) will serialize to 0000_0100

Generated Code

Source:

[SyncVar, BitCount(8), ZigZagEncode]
public int myValue;

Generated:

public override bool SerializeSyncVars(NetworkWriter writer, bool initialState)
{
    ulong syncVarDirtyBits = base.SyncVarDirtyBits;
    bool result = base.SerializeSyncVars(writer, initialize);

    if (initialState) 
    {
        writer.Write((ulong)ZigZag.Encode(this.myValue), 8);
        return true;
    }

    writer.Write(syncVarDirtyBits, 1);
    if ((syncVarDirtyBits & 1UL) != 0UL)
    {
        writer.Write((ulong)ZigZag.Encode(this.myValue), 8);
        result = true;
    }

    return result;
}

public override void DeserializeSyncVars(NetworkReader reader, bool initialState)
{
    base.DeserializeSyncVars(reader, initialState);

    if (initialState)
    {
        this.myValue = ZigZag.Decode(reader.Read(8));
        return;
    }

    ulong dirtyMask = reader.Read(1);
    if ((dirtyMask & 1UL) != 0UL)
    {
        this.myValue = ZigZag.Decode(reader.Read(8));
    }
}

last updated for Mirage v101.8.0