From a555d7d9a703d0e53b22259fe3b604ee59284ccd Mon Sep 17 00:00:00 2001
From: "Franklin \"Snaipe\" Mathieu" <snaipe@diacritic.io>
Date: Sun, 6 Nov 2016 22:48:01 +0100
Subject: [PATCH] dsl: Allow usage of `_` as a name for anonymous hidden
 fields.

Fixes #10.
---
 src/wssdl/core.lua        |  4 ++--
 src/wssdl/placeholder.lua | 24 +++++++++++++++++-------
 src/wssdl/wireshark.lua   | 13 ++++++++++---
 3 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/src/wssdl/core.lua b/src/wssdl/core.lua
index 3d1aba4..18f8222 100644
--- a/src/wssdl/core.lua
+++ b/src/wssdl/core.lua
@@ -156,7 +156,7 @@ setmetatable(wssdl._packet, {
     local out = pkt._create(pkt, ...)
 
     for k, v in pairs(wssdl._current_def) do
-      if k:sub(1,1) ~= '_' then
+      if type(v) == 'table' then
         v._pktdef = nil
       end
     end
@@ -278,7 +278,7 @@ setmetatable(wssdl, {
       newpacket._properties = newprops
       setmetatable(newpacket, getmetatable(wssdl._packet))
 
-      wssdl._current_def = { _pktdef = newpacket }
+      wssdl._current_def = {}
 
       -- Switch to the packet definition metatable
       local env = setmetatable({}, packetdef_metatable)
diff --git a/src/wssdl/placeholder.lua b/src/wssdl/placeholder.lua
index 22ffb97..d902dec 100644
--- a/src/wssdl/placeholder.lua
+++ b/src/wssdl/placeholder.lua
@@ -305,14 +305,24 @@ placeholder.metatable = function(defenv, packetdef_metatable, make_pktfield)
         return nil
       end
 
-      if field._name:sub(1,1) == '_' then
-        error('wssdl: Invalid identifier for field ' .. utils.quote(field._name) .. ': Fields must not start with an underscore', 3)
-      end
-      if wssdl._current_def[field._name] and wssdl._current_def[field._name] ~= field then
-        error('wssdl: Duplicate field ' .. utils.quote(field._name) .. ' in packet definition.', 3)
-      end
+      if wssdl._current_def[field._name] ~= field then
+        if wssdl._current_def[field._name] then
+          error('wssdl: Duplicate field ' .. utils.quote(field._name) .. ' in packet definition.', 3)
+        end
 
-      wssdl._current_def[field._name] = field
+        if field._name ~= '_' then
+          if field._name:sub(1,1) == '_' then
+            error('wssdl: Invalid identifier for field ' .. utils.quote(field._name) .. ': Fields must not start with an underscore', 3)
+          end
+        else
+          local i = wssdl._current_def._anonymous_counter or 1
+          field._name = '_anonymous_' .. i .. ''
+          wssdl._current_def._anonymous_counter = i + 1
+          field._hidden = true
+        end
+
+        wssdl._current_def[field._name] = field
+      end
 
       local type = rawget(specifiers.field_types, k)
       if type == nil then
diff --git a/src/wssdl/wireshark.lua b/src/wssdl/wireshark.lua
index 079f38a..9b8911c 100644
--- a/src/wssdl/wireshark.lua
+++ b/src/wssdl/wireshark.lua
@@ -99,7 +99,9 @@ ws.make_fields = function (fields, pkt, prefix)
   local prefix = prefix or ''
 
   for i, field in ipairs(pkt._definition) do
-    make_field(fields, prefix, field)
+    if not field._hidden then
+      make_field(fields, prefix, field)
+    end
   end
 end
 
@@ -225,12 +227,17 @@ ws.dissector = function (pkt, proto)
       local labels = pktval.label[field._name] or {}
       local val = pktval.val[field._name]
       local raw = pktval.buf[field._name]
+      local node
 
       if field._type == 'packet' then
         local pktval = { buf = raw, label = labels, val = val }
-        node = tree:add(protofield, raw._self, '', unpack(labels))
+        if field._hidden then
+          node = tree:add(protofield, raw._self, '', '')
+        else
+          node = tree:add(protofield, raw._self, '', unpack(labels))
+        end
         tree_add_fields(field._packet, prefix .. field._name .. '.', node, pktval)
-      else
+      elseif not field._hidden then
         node = tree:add(protofield, raw, val, unpack(labels))
       end
     end