sandbox-like app loader

appbox_test.lua

local loader = require 'loader'

local app1 = loader.app('apps.simple_app', { pciaddress='0000:83:00.1', name='app1' })
local app2 = loader.app('apps.simple_app', { pciaddress='0000:83:00.2', name='app2' })
local app3 = loader.app('apps.simple_app', { pciaddress='0000:83:01.1', name='app3' })

app1.selftest()
app2.selftest()
app3.selftest()

loader.set_link(app1, 'tx', app2, 'rx')
loader.set_link(app2, 'tx', app3, 'rx')
loader.set_link(app3, 'tx', app1, 'rx')

for _ = 1, 3 do
	app1.push()
	app2.push()
	app3.push()
end

loader.lua

local loader = {}

-- loads 'dot.named' app
-- 'args' (optional) becomes the initial instance space
-- returns args or (nil, error)
-- safe version, file, syntax or initialization errors are captured
function loader.load_app(appname, args)
	local path, errmsg = package.searchpath(appname, package.path)
	if not path then return path, errmsg end

	args = args or {}
	if not getmetatable(args) then
		package.seeall(args)
	end

	local chunk, errmsg = loadfile(path, nil, args)
	if not chunk then return chunk, errmsg end

	local ok, errmsg = pcall(chunk)
	if not ok then return nil, errmsg end

	return args
end

-- same as load_app() but (re)raises errors
function loader.app(appname, args)
	return assert(loader.load_app(appname, args))
end


-- creates a link and injects into the given apps
-- with the given names in the 'input' and 'output' tables
function loader.set_link(src_app, srcname, dst_app, dstname)
	local link = link.new(dst_app)

	src_app.output = src_app.output or {}
	src_app.output[srcname] = link

	dst_app.input = dst_app.input or {}
	dst_app.input[dstname] = link

	return link
end


return loader

simple_app.lua

-- arguments are available as variables
print ("initialization time", name, pciaddress)

namecopy1 = name			-- "global" vars are instance fields
local namecopy2 = name		-- local vars are private


-- define expected functions in the instance space
function push()
	print ("pushing packets:", namecopy2)		-- local (private) vars are accessible
	print (input.rx:nreadable())				-- links are set in 'input' and 'output' tables
end


function selftest()
	print ("testing app", namecopy1)
	assert(input == nil, "shouldn't have input yet")
end