Basic Linux Joystick support

linux-luvit-joystick.lua

local Bit = require('bit')
local FS = require('fs')
local Emitter = require('emitter')

-- http://www.mjmwired.net/kernel/Documentation/input/joystick-api.txt
function parse(buffer)
  local event = {
    time = Bit.lshift(buffer:byte(4), 24) +
           Bit.lshift(buffer:byte(3), 16) +
           Bit.lshift(buffer:byte(2), 8) +
           buffer:byte(1),
    number = buffer:byte(8),
    value = Bit.lshift(buffer:byte(6), 8) +
            buffer:byte(5)
  }
  local type = buffer:byte(7)
  if Bit.band(type, 0x80) > 0 then event.init = true end
  if Bit.band(type, 0x01) > 0 then event.type = "button" end
  if Bit.band(type, 0x02) > 0 then event.type = "axis" end
  return event
end

-- Expose as a nice Lua API
local Joystick = Emitter:extend()

function Joystick.prototype:initialize(id)
  self:wrap("on_open")
  self:wrap("on_read")
  self.id = id
  FS.open("/dev/input/js" .. id, "r", "0644", self.on_open)
end


-- Register a bound version of a method and route errors
function Joystick.prototype:wrap(name)
  local fn = self[name]
  self[name] = function (err, ...)
    if (err) then return self:emit("error", err) end
    return fn(self, ...)
  end
end

function Joystick.prototype:on_open(fd)
  self.fd = fd
  self:start_read()
end

function Joystick.prototype:start_read()
  FS.read(self.fd, null, 8, self.on_read);
end

function Joystick.prototype:on_read(chunk)
  local event = parse(chunk)
  event.id = self.id
  self:emit(event.type, event)
  if self.fd then self:start_read() end
end

function Joystick.prototype:close(callback)
  FS.close(self.fd, callback)
  self.fd = nil
end

--------------------------------------------------------------------------------

-- Sample usage
local js = Joystick:new(1)
js:on('button', p);
js:on('axis', p);


-- Close after 5 seconds
--require('timer'):set_timeout(5000, function ()
--  js:close()
--end);