added a CLI tool to parse MQTT packets from a text file with HEX traffic

tools/parse-packets-from-file.lua

@@ -0,0 +1,92 @@
+#!/usr/bin/env lua
+local mqtt = require("mqtt")
+local protocol = require("mqtt.protocol")
+local protocol4 = require("mqtt.protocol4")
+local protocol5 = require("mqtt.protocol5")
+local extract_hex = require("mqtt.tools").extract_hex
+
+local input_file_arg = arg[1]
+local protocol_version_arg = arg[2]
+
+local protocol_module
+
+
+-- checking args
+if not input_file_arg then
+	print("Parse a HEX file with MQTT traffic")
+	print()
+	print("Usage:")
+	print(string.format("    %s <input-file> [protocol-version]", arg[0]))
+	print()
+	print("    <input-file>       - path to the text file with HEX strings of MQTT protocol")
+	print("    [protocol-version] - optional, either 4 or 5, for MQTT v3.1.1 or MQTT v5.0 respectively")
+	print("                         will be auto-detected if not provided")
+	os.exit(1)
+end
+if protocol_version_arg == "4" then
+	protocol_module = protocol4
+elseif protocol_version_arg == "5" then
+	protocol_module = protocol5
+end
+print(string.format("-- using protocol version %s", protocol_version_arg))
+
+-- reading hex file
+local file = assert(io.open(input_file_arg), "failed to read input file")
+local hex = file:read("*a")
+hex = extract_hex(hex)
+
+-- decode hex data
+local data = {}
+for i = 1, hex:len() / 2 do
+	local byte = hex:sub(i*2 - 1, i*2)
+	data[#data + 1] = string.char(tonumber(byte, 16))
+end
+data = table.concat(data)
+local data_size = data:len()
+local pos = 1
+print(string.format("-- hex-decoded %d bytes from <input-file> %s", data_size, input_file_arg))
+
+-- create read function
+local function read_func(size)
+	if pos > data_size then
+		return false, "end of the input data"
+	end
+	local res = data:sub(pos, pos + size - 1)
+	if res:len() ~= size then
+		return false, "not enough unparsed data"
+	end
+	pos = pos + size
+	return res
+end
+
+-- returns amount of the available input data
+local function available()
+	return data_size - pos + 1
+end
+
+-- parse all packets from the input file
+while available() > 0 do
+	local packet, err
+	if not protocol_module then
+		-- expecting a CONNECT packet first in the input
+		packet, err = protocol.parse_packet_connect(read_func)
+	else
+		packet, err = protocol_module.parse_packet(read_func)
+	end
+	if not packet then
+		print("next packet parsing error:", err)
+		break
+	end
+	print(packet)
+	if packet.type == protocol.packet_type.CONNECT and not protocol_module then
+		if packet.version == mqtt.v311 then
+			protocol_module = protocol4
+		elseif packet.version == mqtt.v50 then
+			protocol_module = protocol5
+		else
+			error("unexpected CONNECT packet version: "..tostring(packet.version))
+		end
+	end
+end
+
+print(string.format("-- done, %d bytes left in the input buffer", available()))