Lua is a promising language on embedded systems of intelligent devices. The language is elegant, clean, and it costs reasonable resources but can be programmed very fast and easily.
Lask provides a foundation library wrapping the posix API and an async I/O communication framework for the lua programing language.
The main goal is to relieve embedded C programmers(like myself) of endless cross-compiling, and help them to finish their job as quickly as their web development fellows.
###An ECHO-SERVER for example.
####Multi Process Style
require 'std'
local listen_fd = socket.tcpserver('0.0.0.0', 9988)
local function serve_the_client(fd)
while true do
local input = os.read(fd)
if not input then
break
end
os.write(fd, input)
end
os.close(fd)
end
while true do
local fd = socket.accept(listen_fd)
if fd >= 0 then
if os.fork() == 0 then
serve_the_client(fd)
os.exit(0)
else
os.close(fd)
end
end
end####IO-Multiplexing Style
require 'std'
local listen_fd = socket.tcpserver('0.0.0.0', 9988)
local fd_set = {listen_fd}
while true do
for _, fd in pairs(poll.select(fd_set) or NULL) do
if fd == listen_fd then
local peer_fd = socket.accept(listen_fd)
if peer_fd >= 0 then
table.insert(fd_set, peer_fd)
end
else
local input = os.read(fd)
if input then
os.write(fd, input)
else
os.close(fd)
table.remove(fd_set, table.find(fd_set, fd))
end
end
end
end####Using the Async I/O Framework (tasklet) At a glance, the tasklet way uses more code than the other two, but the truth is it's far more powerful and flexible.
local tasklet = require 'tasklet'
require 'tasklet.channel.streamserver'
require 'tasklet.channel.stream'
local ch_server = tasklet.create_tcpserver_channel('0.0.0.0', 9988)
if not ch_server then
io.stderr:write('failed to start echo-server, socket error')
os.exit(1)
end
local function serve_the_client(fd)
local ch = tasklet.stream_channel.new(fd)
local buf = buffer.new()
tasklet.start_task(function ()
while true do
local input = ch:read(nil, 5) -- read the input in 5 seconds or we'll just quit
if not input then
break
end
buf:rewind():putstr(input, '\n')
ch:write(buf)
end
ch:close()
end)
end
tasklet.start_task(function ()
while true do
local fd = ch_server:accept()
if fd >= 0 then
serve_the_client(fd)
end
end
end)
tasklet.loop()####Echo over SSL using tasklet
require 'std'
local ssl = require 'ssl'
local tasklet = require 'tasklet.channel.sslstream'
require 'tasklet.channel.streamserver'
local ch_server = tasklet.create_tcpserver_channel('0.0.0.0', 9988)
local ctx = ssl.context.new('sslv23')
if ctx:load_verify_locations('root.pem') ~= 0 or
ctx:use_certfile('server.pem') ~= 0 or
ctx:use_keyfile('server_key.pem', 'passwd') ~= 0 or
not ch_server then
io.stderror('initialization failed')
os.exit(1)
end
tasklet.sslstream_channel.ctx = ctx
local function serve_the_client(fd)
local ch = tasklet.sslstream_channel.new(fd)
tasklet.start_task(function ()
if ch:handshake(5) == 0 then -- finish the handshaking in 5 seconds
local buf = buffer.new()
while true do
local input = ch:read(nil, 5) -- read the input in 5 seconds
if not input then
break
end
buf:rewind():putstr(input, '\n')
ch:write(buf)
end
end
ch:close()
end)
end
tasklet.start_task(function ()
while true do
local fd = ch_server:accept()
if fd >= 0 then
serve_the_client(fd)
end
end
end)
tasklet.loop()