bios_bootloader.lua

local cinv = component.invoke
function binv(address, method, ...)
  local result = table.pack(pcall(cinv, address, method, ...))
  if not result[1] then
    return nil, result[2]
  else
    return table.unpack(result, 2, result.n)
  end
end
local eeprom = component.list("eeprom")()
computer.getBootAddress = function()
  return binv(eeprom, "getData")
end
computer.setBootAddress = function(address)
  return binv(eeprom, "setData", address)
end
do
  local screen = component.list("screen")()
  local gpu = component.list("gpu")()
  if gpu and screen then
    binv(gpu, "bind", screen)
    binv(gpu, "setResolution", 53, 22)
    binv(gpu, "setForeground", 0x00FF00)
  end
end
local function tryLoadFrom(address)
  local handle, reason = binv(address, "open", "/init.lua")
  if not handle then
    return nil, reason
  end
  local buffer = ""
  repeat
    local data, reason = binv(address, "read", handle, math.huge)
    if not data and reason then
      return nil, reason
    end
    buffer = buffer .. (data or "")
  until not data
  binv(address, "close", handle)
  return load(buffer, "=init")
end
function startsWith(string,start)
   return string.sub(string,1,string.len(start))==start
end
local init, reason
do
  local keyboard = component.list("keyboard")()
  local screen = component.list("screen")()
  local gpu = component.list("gpu")()
  if not keyboard then
    if gpu and screen then
      computer.beep(500, 0.4)
      binv(gpu, "fill", 1, 1, 53, 22, " ")
      binv(gpu, "set", 1, 1, "NO KEYBOARD CONNECTED")
    end
    while true do
      computer.pullSignal()
    end
  else
    local userinput = true
    local keycount = 0
    local useraddr = ""
    if gpu and screen then
      binv(gpu, "fill", 1, 1, 53, 22, " ")
      binv(gpu, "set", 1, 1, "MY BOOTLOADER")
      binv(gpu, "set", 1, 2, "ENTER FS ADDRESS OR LABEL")
      while userinput do
        binv(gpu, "set", 1, 4, ">")
        local name, _, key = computer.pullSignal()
        if name == "key_up" then
          if (key >= 0x30 and key <= 0x39) or (key >= 0x61 and key <= 0x66) or (key >= 0x41 and key <= 0x46) then
            binv(gpu, "set", 3 + keycount, 4, unicode.upper(unicode.char(key)))
            useraddr = useraddr .. unicode.lower(unicode.char(key))
            keycount = keycount + 1
          end
        end
        if keycount == 3 then
          binv(gpu, "set", 1, 6, "TRYING TO BOOT FROM FS " .. unicode.upper(useraddr))
          local addr, _
          for addr, _ in component.list("filesystem") do
            if binv(addr, "getLabel") ~= nil and startsWith(unicode.lower(binv(addr, "getLabel")), useraddr) then
              init, reason = tryLoadFrom(addr)
              if init then
                break
              end
            else
              if startsWith(addr, useraddr) then
                init, reason = tryLoadFrom(addr)
                if init then
                  break
                end
              end
            end
          end
          if init then
            userinput = false
            computer.setBootAddress(addr)
            binv(gpu, "set", 1, 7, "SUCCESS, STARTING INIT.LUA...")
          else
            binv(gpu, "set", 1, 7, "FAILURE, UNABLE TO BOOT")
            keycount = 0
            useraddr = ""
            local sTime = computer.uptime()
            while computer.uptime() < sTime + 3 do
              computer.pullSignal(0.5)
            end
            binv(gpu, "fill", 1, 4, 53, 4, " ")
            binv(gpu, "fill", 1, 6, 53, 6, " ")
            binv(gpu, "fill", 1, 7, 53, 7, " ")
          end
        end
      end
    end
  end
end
computer.beep(1000, 0.2)
init()