mod_pubsub_mqtt/mqtt.lib.lua
author Kim Alvefur <zash@zash.se>
Sun, 25 Jun 2023 16:27:55 +0200
changeset 5575 ca3c2d11823c
parent 5118 d2a84e6aed2b
child 5837 58df53eefa28
permissions -rw-r--r--
mod_pubsub_feeds: Track latest timestamp seen in feeds instead of last poll This should ensure that an entry that has a publish timestmap after the previously oldest post, but before the time of the last poll check, is published to the node. Previously if an entry would be skipped if it was published at 13:00 with a timestamp of 12:30, where the last poll was at 12:45. For feeds that lack a timestamp, it now looks for the first post that is not published, assuming that the feed is in reverse chronological order, then iterates back up from there.

local bit = require "bit";

local stream_mt = {};
stream_mt.__index = stream_mt;

function stream_mt:read_bytes(n_bytes)
	module:log("debug", "Reading %d bytes... (buffer: %d)", n_bytes, #self.buffer);
	local data = self.buffer;
	if not data then
		module:log("debug", "No data, pausing.");
		data = coroutine.yield();
		module:log("debug", "Have %d bytes of data now (want %d)", #data, n_bytes);
	end
	if #data >= n_bytes then
		data, self.buffer = data:sub(1, n_bytes), data:sub(n_bytes+1);
	elseif #data < n_bytes then
		module:log("debug", "Not enough data (only %d bytes out of %d), pausing.", #data, n_bytes);
		self.buffer = data..coroutine.yield();
		module:log("debug", "Now we have %d bytes, reading...", #data);
		return self:read_bytes(n_bytes);
	end
	module:log("debug", "Returning %d bytes (buffer: %d)", #data, #self.buffer);
	return data;
end

function stream_mt:read_string()
	local len1, len2 = self:read_bytes(2):byte(1,2);
	local len = bit.lshift(len1, 8) + len2;
	return self:read_bytes(len), len+2;
end

local packet_type_codes = {
	"connect", "connack",
	"publish", "puback", "pubrec", "pubrel", "pubcomp",
	"subscribe", "subak", "unsubscribe", "unsuback",
	"pingreq", "pingresp",
	"disconnect"
};

function stream_mt:read_packet()
	local packet = {};
	local header = self:read_bytes(1):byte();
	packet.type = packet_type_codes[bit.rshift(bit.band(header, 0xf0), 4)];
	packet.dup = bit.band(header, 0x08) == 0x08;
	packet.qos = bit.rshift(bit.band(header, 0x06), 1);
	packet.retain = bit.band(header, 0x01) == 0x01;

	-- Get length
	local length, multiplier = 0, 1;
	repeat
		local digit = self:read_bytes(1):byte();
		length = length + bit.band(digit, 0x7f)*multiplier;
		multiplier = multiplier*128;
	until bit.band(digit, 0x80) == 0;
	packet.length = length;
	if packet.type == "connect" then
		if self:read_string() ~= "MQTT" then
			module:log("warn", "Unexpected packet signature!");
			packet.type = nil; -- Invalid packet
		else
			packet.version = self:read_bytes(1):byte();
			packet.connect_flags = self:read_bytes(1):byte();
			packet.keepalive_timer = self:read_bytes(1):byte();
			length = length - 11;
		end
	elseif packet.type == "publish" then
		packet.topic = self:read_string();
		length = length - (#packet.topic+2);
		if packet.qos == 1 or packet.qos == 2 then
			packet.id = self:read_bytes(2);
			length = length - 2;
		end
	elseif packet.type == "subscribe" then
		if packet.qos == 1 or packet.qos == 2 then
			packet.id = self:read_bytes(2);
			length = length - 2;
		end
		local topics = {};
		while length > 0 do
			local topic, len = self:read_string();
			table.insert(topics, topic);
			self:read_bytes(1); -- QoS not used
			length = length - (len+1);
		end
		packet.topics = topics;
	end
	if length > 0 then
		packet.data = self:read_bytes(length);
	end
	return packet;
end

local function new_parser(self)
	return coroutine.wrap(function (data)
		self.buffer = data;
		while true do
			data = coroutine.yield(self:read_packet());
			module:log("debug", "Parser: %d new bytes", #data);
			self.buffer = (self.buffer or "")..data;
		end
	end);
end

function stream_mt:feed(data)
	module:log("debug", "Feeding %d bytes", #data);
	local packets = {};
	local packet = self.parser(data);
	while packet do
		module:log("debug", "Received packet");
		table.insert(packets, packet);
		packet = self.parser("");
	end
	module:log("debug", "Returning %d packets", #packets);
	return packets;
end

local function new_stream()
	local stream = setmetatable({}, stream_mt);
	stream.parser = new_parser(stream);
	return stream;
end

local function serialize_packet(packet)
	local type_num = 0;
	for i, v in ipairs(packet_type_codes) do -- FIXME: I'm so tired right now.
		if v == packet.type then
			type_num = i;
			break;
		end
	end
	local header = string.char(bit.lshift(type_num, 4));

	if packet.type == "publish" then
		local topic = packet.topic or "";
		packet.data = string.char(bit.band(#topic, 0xff00), bit.band(#topic, 0x00ff))..topic..packet.data;
	elseif packet.type == "suback" then
		local t = {};
		for _, topic in ipairs(packet.topics) do
			table.insert(t, string.char(bit.band(#topic, 0xff00), bit.band(#topic, 0x00ff))..topic.."\000");
		end
		packet.data = table.concat(t);
	end

	-- Get length
	local length = #(packet.data or "");
	repeat
		local digit = length%128;
		length = math.floor(length/128);
		if length > 0 then
			digit = bit.bor(digit, 0x80);
		end
		header = header..string.char(digit); -- FIXME: ...
	until length <= 0;

	return header..(packet.data or "");
end

return {
	new_stream = new_stream;
	serialize_packet = serialize_packet;
};