added a BIOS to go with the bootable tape creator

tapebios.lua

@@ -0,0 +1,78 @@
+local component_invoke = component.invoke
+function boot_invoke(address, method, ...)
+  local result = table.pack(pcall(component_invoke, address, method, ...))
+  if not result[1] then
+    return nil, result[2]
+  else
+    return table.unpack(result, 2, result.n)
+  end
+end
+
+-- backwards compatibility, may remove later
+local eeprom = component.list("eeprom")()
+computer.getBootAddress = function()
+  return boot_invoke(eeprom, "getData")
+end
+computer.setBootAddress = function(address)
+  return boot_invoke(eeprom, "setData", address)
+end
+
+do
+  local screen = component.list("screen")()
+  local gpu = component.list("gpu")()
+  if gpu and screen then
+    boot_invoke(gpu, "bind", screen)
+  end
+end
+local function tryLoadFrom(address)
+  if component.type(address) == "filesystem" then
+    local handle, reason = boot_invoke(address, "open", "/init.lua")
+    if not handle then
+      return nil, reason
+    end
+    local buffer = ""
+    repeat
+      local data, reason = boot_invoke(address, "read", handle, math.huge)
+      if not data and reason then
+        return nil, reason
+      end
+      buffer = buffer .. (data or "")
+    until not data
+    boot_invoke(address, "close", handle)
+    return load(buffer, "=init")
+  elseif component.type(address) == "tape_drive" then
+    boot_invoke(address,"seek",-math.huge)
+    local boottype = boot_invoke(address,"read",1)
+    if boottype == "!" then
+      local rl = tonumber(boot_invoke(address,"read",8))
+      local buffer = boot_invoke(address,"read",rl)
+      return load(buffer, "=init")
+    end
+  end
+end
+local init, reason
+if computer.getBootAddress() then
+  init, reason = tryLoadFrom(computer.getBootAddress())
+end
+if not init then
+  computer.setBootAddress()
+  local bootdevs = {}
+  for address in component.list("filesystem") do
+    bootdevs[#bootdevs+1] = address
+  end
+  for address in component.list("tape_drive") do
+    bootdevs[#bootdevs+1] = address
+  end
+  for k,address in ipairs(bootdevs) do
+    init, reason = tryLoadFrom(address)
+    if init then
+      computer.setBootAddress(address)
+      break
+    end
+  end
+end
+if not init then
+  error("no bootable medium found" .. (reason and (": " .. tostring(reason)) or ""), 0)
+end
+computer.beep(1000, 0.2)
+init()