This is a static archive of our old Q&A Site. Please post any new questions and answers at

How to create a Protofield sub array in Lua


Hi, Given the following example:

local f= mycoolprotocol.fields
f.Length = ProtoField.uint32("MCP.Length","Length",base.DEC)
f.MsgType = ProtoField.uint16("MCP.MsgType","MsgType",base.DEC)

I have declared 2 Protofields. But imagine I have a repeating group or an array of items:

And the message body looks like so:

struct person
  int16 age;
  string name;
person[] p = new person[2];

Ideally, I would like to create a subtree in Wireshark for that group

+ Persons
 + Person1
 + Person2

The problem is I don't know how to structure this in Lua. This declares 2 protofields: = Protofield.string("","name","Text")
f.age = ProtoField.uint16("MCP.age","age",base.DEC)

But I'd like to create a dynamic array of the group instead, so I can do:

subtree:add_le( f[0].name, buffer(x,y))

So, is there a Protofield.ProtoFieldArray? Is it possible? Any other ideas are welcome.


asked 12 Dec '13, 01:14

Lews%20Therin's gravatar image

Lews Therin
accept rate: 100%

edited 12 Dec '13, 01:15

One Answer:


It turns out I can reuse the same fields to build the tree.

So in pseudocode:

begin loop
  subtree= mainsubtree:add(a,buffer())
  subtree:add(, buffer(x,y))
  subtree:add(f.age, buffer(x+name.length,y))

So f.age doesn't get overwritten by a newer value. I guess it is just a placeholder for the ProtoField

answered 12 Dec '13, 06:02

Lews%20Therin's gravatar image

Lews Therin
accept rate: 100%