How to convert le_nstime() to string in Lua

Question

How do I convert TvbRange.le_nstime() to a string? I tried the following Lua:

local field_time = ProtoField.absolute_time("TIME","TIME",base.LOCAL);
...
function SCP_proto.dissector (buf, pkt, root){
 local value={
    [0] =0,
    [1] =0,
    [2] =0
  }
  ...
  for i=0,2,1 do
     ...
     local example_subtree = subtree:add(field_time,buf(offset,8):le_nstime());
     value[i] = tostring(buf(offset,8):le_nstime());
     ...
  end
}

...but value[i] = tostring(buf(offset,8):le\_nstime()) does not work the way I expected. The time format of value[i] is in seconds ("1336188353.000000150") instead of "Month|Day|Year|Time" format ("May 5, 2012 07:25:53.000000150"). However, in the Packet Details Pane, I see "May 5, 2012 07:25:53.000000150" as expected.

How can I get a formatted time-string from le_nstime() like the one I see in the protocol tree?

Wireshark 1.7, Win 7, Lua 5.1

Accepted Answer

You're looking for format_date (or format_time), as in:

  -- First, convert the NSTime to a string (which yields a decimal number).
  -- Then, convert that string into a Lua number, required by format_date().
  local seconds = tostring(buf(offset,8):le_nstime())
  seconds = tonumber(seconds)
  value[i] = format_date(seconds)

But I should point out some other things about your sample code above:

There is no base.LOCAL (despite the documentation in the Wireshark user manual...this is a bug). Since it doesn't exist, base.LOCAL is equivalent to nil.
You don't need to initialize a table with zeroes. You can simply declare the table with empty brackets, and Lua is smart enough to know what to do when you index into the table with: value[i]. (Or maybe there's omitted code that actually checks these indices for zero...weird.)
local value = {}
You don't need to convert the TvbRange into an NSTime when adding it to the tree because field_time is a ProtoField.absolute_time, which is inherently an NSTime. The endianness of the buffer is implied by TreeItem.add() and TreeItem.add_le() (you want add_le() in this case).
local example_subtree = subtree:add_le(field_time, buf(offset,8));