Clear computer memory?

Dave-ee Jones, on 26 July 2017 - 06:18 AM said:

Potentially already thought of before, but I'll give it a go..

Multi-layer OS.
Granted, the one shown below is only two layers, but basically what happens is the OS has 2 (or more) coroutines running - one which runs background processes like timers (like the clock), more important key pressses (like ones that handle "Home", "Back", "Task Manager" etc.), change variables in the background as needed (even things as simple as changing UI colours). This layer will be the BASE. The next layer up can be the OS layer. This is what you see and what you can do. It handles all on-screen UI interaction and handles all the functions that you would expect from a UI.
You click on "Control Panel" you expect the Control Panel to open, where you can change user details, UI colours, system options etc.
You click on "Create a window" and you can create a second window that has DJShell running in it.

It just works, and works better than the one coroutine trying to handle everything at once. Most real OS' use the same technique, you just don't notice it as an end-user because it's not meant to be noticed - it's just meant to work.
Plus, you can have a more constant feel with the OS, accessing windows, taskbar or a specific key from ANYWHERE in the OS, not just where the OS is listening. Because of the BASE layer, the OS will ALWAYS be listening to certain commands, as long as it is running.



"Home", "Back", "Forward" and "Task Manager" can be described as something like Android's Home, Back and Running Processes buttons. These (being on CC) are bound to specific keys, which can be accessed from anywhere in the OS.

Pretty nifty idea, though I've never seen an OS that utilises this layer system enough.

Dave-ee Jones, on 07 August 2017 - 06:49 AM said:

So what if you made a program that catches reboot/shutdown sequences (Ctrl + R/S, os.shutdown(), os.reboot(), shell.run("reboot"), shell.run("shutdown") etc.) and just clears memory while starting a clean shell/startup program?

local mt = {__index = _G, __metatable = function() return nil end}
while true do
    local env = {}
    env._G = env
    setmetatable(env, mt)
    os.run(env, multishell and "/rom/programs/advanced/multishell" or "/rom/programs/shell")
end

The Crazy Phoenix, on 07 August 2017 - 08:02 PM said:

As Bomb Bloke has already pointed out, it is not possible to do that.

However, it is still possible to clear the RAM by manipulating the subprograms' environment table.

local mt = {__index = _G, __metatable = function() return nil end}
while true do
	local env = {}
	env._G = env
	setmetatable(env, mt)
	os.run(env, multishell and "/rom/programs/advanced/multishell" or "/rom/programs/shell")
end

That will reset the environment and restart the shell every time the shell is exited.

Bomb Bloke, on 07 August 2017 - 08:35 AM said:

Even prior to that, making your computer boot from a disk drive placed on top of it will ensure that any other drives connected will be ignored.

The Crazy Phoenix, on 07 August 2017 - 08:02 PM said:

However, it is still possible to clear the RAM by manipulating the subprograms' environment table.

Bomb Bloke, on 08 August 2017 - 02:48 AM said:

The Crazy Phoenix, on 07 August 2017 - 08:02 PM said:

However, it is still possible to clear the RAM by manipulating the subprograms' environment table.

Creating a system that allows a full reset without a reboot would be much trickier. Function environments, as well as sub-tables within _G, won't reset that way.

local env = {}
local tcp = {{_G, env}}
while #tcp > 0 do
	local current = tcp[#tcp]
	tcp[#tcp] = nil
	for key, value in pairs(current[1]) do
		if type(value) == "table" then
			tcp[#tcp + 1] = {value, current[2][key]}
		elseif type(value) == "function" then
			current[2][key] = function()
				_ENV = env
				value()
			end
			-- You can use setfenv but it will modify the original function.
		else
			current[2][key] =  value
		end
	end
end

local env = {}
local tcp = {{_G, env}}
local cpd = {[_G] = env}
while #tcp > 0 do
	local current = tcp[#tcp]
	tcp[#tcp] = nil
	for key, value in pairs(current[1]) do
		if type(value) == "table" then
			if cpd[value] then
				current[2][key] = cpd[value]
			else
				current[2][key] = {}
				tcp[#tcp + 1] = {value, current[2][key]}
				cpd[value] = current[2][key]
			end
		elseif type(value) == "function" then
			current[2][key] = function()
				_ENV = env
				value()
			end
			-- You can use setfenv but it will modify the original function.
		else
			current[2][key] =  value
		end
	end
end