Allow bytes to be sized by a packet key.

* src/api/bytes.lua: allow strings in the legth parameter
to indicate that a key must be dereferenced to calculate the
length of the array. Add a refkey parameter for that case.
* src/spackets_w3gs.lua: Adjust W3GS_INCOMING_ACTION packet
description to use the previous feature.

src/api/bytes.lua

@@ -3,24 +3,49 @@
 --
 --  Creates a field for an array of bytes.
 --
---  Quick call:
+--  Quick call: ( label, length, refkey )
+--  Table call: { label=..., length=..., refkey=... }
 --    @par label   Name of the field. It will be used as a label for the
 --                 field's node at the dissection tree.
---    @par length  Length of the array. 
+--    @par length  Length of the array.
+--                 If it is numeric, it indicates an array of that fixed
+--                 legth.
+--                 If it is a string, it specifies one of the following
+--                 values:
+--                   * "key": use the key parameter to set the length of
+                              the array.
+--    @par refkey  Key that holds the length of the array. It must have
+--                 been initialized by a former field.
+--                 Required if the length parameter is "key".
 --
 --]]
 do
+	local valid_lengths = {
+		key = true
+	}
 	local template = {
 		protofield_type = "bytes",
 		size = function(self, state)
-			return self.length
+			if type(self.length) == "number" then
+				return self.length
+			end
+			if type(self.length) ~= "string"
+					or not valid_lengths[self.length] then
+				error("length has an invalid value: "
+					 .. tostring(self.length))
+			end
+			local length = state.packet[self.refkey]
+			if length == nil then
+				error("key '" .. self.refkey .. "' has not been defined")
+			end
+			return length
 		end,
 		length = 1,
 	}
 
 	function bytes(...)
 		local args = make_args_table_with_positional_map(
-				{"label", "length"},
+				{"label", "length", "refkey"},
 #if LUA_VERSION >= 510
 				...
 #else

src/packet-bnetp.lua

@@ -1,4 +1,4 @@
---[[ packet-bnetp.lua build on Thu Aug  6 20:00:04 2015
+--[[ packet-bnetp.lua build on Sat Aug  8 01:56:29 2015
 
 packet-bnetp is a Wireshark plugin written in Lua for dissecting the Battle.net® protocol. 
 Homepage: https://github.com/diegonc/packet-bnetp/
@@ -1377,24 +1377,49 @@ end
 --
 --  Creates a field for an array of bytes.
 --
---  Quick call:
+--  Quick call: ( label, length, refkey )
+--  Table call: { label=..., length=..., refkey=... }
 --    @par label   Name of the field. It will be used as a label for the
 --                 field's node at the dissection tree.
---    @par length  Length of the array. 
+--    @par length  Length of the array.
+--                 If it is numeric, it indicates an array of that fixed
+--                 legth.
+--                 If it is a string, it specifies one of the following
+--                 values:
+--                   * "key": use the key parameter to set the length of
+                              the array.
+--    @par refkey  Key that holds the length of the array. It must have
+--                 been initialized by a former field.
+--                 Required if the length parameter is "key".
 --
 --]]
 do
+	local valid_lengths = {
+		key = true
+	}
 	local template = {
 		protofield_type = "bytes",
 		size = function(self, state)
-			return self.length
+			if type(self.length) == "number" then
+				return self.length
+			end
+			if type(self.length) ~= "string"
+					or not valid_lengths[self.length] then
+				error("length has an invalid value: "
+					 .. tostring(self.length))
+			end
+			local length = state.packet[self.refkey]
+			if length == nil then
+				error("key '" .. self.refkey .. "' has not been defined")
+			end
+			return length
 		end,
 		length = 1,
 	}
 
 	function bytes(...)
 		local args = make_args_table_with_positional_map(
-				{"label", "length"},
+				{"label", "length", "refkey"},
 				...
 		)
 
@@ -3195,8 +3220,8 @@ end
 	uint16("Send interval"),
 	uint16("CRC-16 encryption"),
 	uint8("Player number"),
-	uint16("Length of action data"),
-	bytes("Action data"),
+	uint16 {"Length of action data", key="action_length"},
+	bytes("Action data", "key", "action_length"),
 },
 [0xF70F] = { -- 0x0F
 	uint8("Player count"),

src/spackets_w3gs.lua

@@ -349,8 +349,8 @@
 	uint16("Send interval"),
 	uint16("CRC-16 encryption"),
 	uint8("Player number"),
-	uint16("Length of action data"),
-	bytes("Action data"),
+	uint16 {"Length of action data", key="action_length"},
+	bytes("Action data", "key", "action_length"),
 },
 --[[doc
     Message ID:    0x0F