we got Lua running

rewrite/minBIOS.lua

@@ -0,0 +1,102 @@
+-- Minimum viable BIOS, effectively a blend between LuaBIOS and AdvancedLoader
+
+local component, computer = component, computer
+local gpu = component.list("gpu")()
+local screen = component.list("screen")()
+local eeprom = component.list("eeprom")()
+
+computer.getBootAddress = function()
+	return component.invoke(eeprom, "getData")
+end
+computer.setBootAddress = function(addr)
+	return component.invoke(eeprom, "setData", addr)
+end
+
+if gpu and screen then
+	component.invoke(gpu, "bind", screen)
+	local w, h = component.invoke(gpu, "maxResolution")
+	component.invoke(gpu, "maxResolution")
+	component.invoke(gpu, "setForeground", 0xFFFFFF)
+	component.invoke(gpu, "setBackground", 0x000000)
+	component.invoke(gpu, "fill", 1, 1, w, h, " ")
+end
+
+local function romRead(addr, path)
+	local fs = component.proxy(addr)
+	local fd = fs.open(path)
+	if not fd then return end
+	local data = ""
+	while true do
+		local chunk, err = fs.read(fd, math.huge)
+		if err then
+			fs.close(fd)
+			return nil
+		end
+		if not chunk then break end
+		data = data .. chunk
+	end
+	fs.close(fd)
+	return data
+end
+
+local function getBootCode(addr)
+	local drive = component.proxy(addr)
+	local sectorSize = drive.getSectorSize()
+	local firstSector = drive.readSector(1)
+
+	-- Generic MBR bootcode
+	if firstSector:sub(-2, -1) == "\x55\xAA" then
+		local codeEnd = sectorSize - 67 -- no laughing!!!!
+		local term = string.find(firstSector, "\0", 5, true)
+		return load(string.sub(firstSector, 5, term and (term - 1) or codeEnd))
+	end
+	-- TODO: whatever else NC might be testing
+end
+
+local paths = {
+	"init.lua",
+	"OS.lua",
+	"boot/pipes/kernel",
+}
+
+local prevboot = computer.getBootAddress()
+if prevboot then
+	if component.type(prevboot) == "filesystem" then
+		for _, path in ipairs(paths) do
+			local code = romRead(prevboot, path)
+			if code then
+				assert(load(code))(prevboot)
+				error("halted")
+			end
+		end
+	end
+	if component.type(prevboot) == "drive" then
+		local f = getBootCode(prevboot)
+		if f then
+			f(prevboot)
+			error("halted")
+		end
+	end
+end
+
+for addr in component.list("filesystem", true) do
+	for _, path in ipairs(paths) do
+		local code = romRead(addr, path)
+		if code then
+			computer.setBootAddress(addr)
+			assert(load(code))(addr)
+			error("halted")
+		end
+	end
+end
+
+for addr in component.list("drive", true) do
+	local f = getBootCode(addr)
+	if f then
+		computer.setBootAddress(addr)
+		f(addr)
+		error("halted")
+	end
+end
+
+error("no bootable medium found")