net.cqueues: Add module that allows use of cqueues while still using net.server as main loop

net/cqueues.lua

@@ -0,0 +1,65 @@
+-- Prosody IM
+-- Copyright (C) 2014 Daurnimator
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+-- This module allows you to use cqueues with a net.server mainloop
+--
+
+local server = require "net.server";
+local cqueues = require "cqueues";
+
+-- Create a single top level cqueue
+local cq;
+
+if server.cq then -- server provides cqueues object
+	cq = server.cq;
+elseif server.get_backend() == "select" and server._addtimer then -- server_select
+	cq = cqueues.new();
+	local function step()
+		assert(cq:loop(0));
+	end
+
+	-- Use wrapclient (as wrapconnection isn't exported) to get server_select to watch cq fd
+	local handler = server.wrapclient({
+		getfd = function() return cq:pollfd(); end;
+		settimeout = function() end; -- Method just needs to exist
+		close = function() end; -- Need close method for 'closeall'
+	}, nil, nil, {});
+
+	-- Only need to listen for readable; cqueues handles everything under the hood
+	-- readbuffer is called when `select` notes an fd as readable
+	handler.readbuffer = step;
+
+	-- Use server_select low lever timer facility,
+	-- this callback gets called *every* time there is a timeout in the main loop
+	server._addtimer(function(current_time)
+		-- This may end up in extra step()'s, but cqueues handles it for us.
+		step();
+		return cq:timeout();
+	end);
+elseif server.event and server.base then -- server_event
+	cq = cqueues.new();
+	-- Only need to listen for readable; cqueues handles everything under the hood
+	local EV_READ = server.event.EV_READ;
+	server.base:addevent(cq:pollfd(), EV_READ, function(e)
+			assert(cq:loop(0));
+			-- Convert a cq timeout to an acceptable timeout for luaevent
+			local t = cq:timeout();
+			if t == 0 then -- if you give luaevent 0, it won't call this callback again
+				t = 0.000001; -- 1 microsecond is the smallest that works (goes into a `struct timeval`)
+			elseif t == nil then -- you always need to give a timeout, pick something big if we don't have one
+				t = 0x7FFFFFFF; -- largest 32bit int
+			end
+			return EV_READ, t;
+		end,
+		-- Schedule the callback to fire on first tick to ensure any cq:wrap calls that happen during start-up are serviced.
+		0.000001);
+else
+	error "NYI"
+end
+
+return {
+	cq = cq;
+}