From 4a664bb2e5da2fa68d82db26554fa0fc9b73441b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20N=C3=BCcke?= <florian@nuecke.de>
Date: Thu, 24 Oct 2013 18:34:15 +0200
Subject: [PATCH] some cleanup; automatically restarting the shell if it stops
 (avoids the occasional ctrl+c shutting down the computer); added os.sleep and
 extended event.wait to take a filter, which basically makes it similar to
 cc's pullEvent with an optional timeout; determining io buffer size based on
 current free ram and added a minimum size; some better "sandboxing" for
 programs (which really isn't that, just making automatic listener cleanup as
 consistent as possible); using error messages in (uncaught) exceptions where
 possible, making for some nicer error messages, for example for out of memory
 errors when pushing results from the host side; made difftime a lua function;
 properly initializing text renderer on multi-screens; added program for paged
 file viewing

---
 assets/opencomputers/lua/kernel.lua           | 205 ++++++++++--------
 assets/opencomputers/lua/rom/bin/cat.lua      |   2 +-
 assets/opencomputers/lua/rom/bin/less.lua     |  46 ++++
 assets/opencomputers/lua/rom/bin/sh.lua       |  33 +--
 assets/opencomputers/lua/rom/bin/shutdown.lua |   2 +-
 assets/opencomputers/lua/rom/lib/event.lua    |  38 ++--
 assets/opencomputers/lua/rom/lib/io.lua       |   2 +-
 assets/opencomputers/lua/rom/lib/os.lua       |   4 +-
 assets/opencomputers/lua/rom/lib/shell.lua    | 184 +++++++++-------
 assets/opencomputers/lua/rom/lib/term.lua     |   2 +-
 com/naef/jnlua/LuaError.java                  |   7 +-
 li/cil/oc/common/tileentity/Screen.scala      |   3 +-
 li/cil/oc/server/component/Computer.scala     |  49 +++--
 li/cil/oc/util/LuaStateFactory.scala          |  10 -
 14 files changed, 336 insertions(+), 251 deletions(-)
 create mode 100644 assets/opencomputers/lua/rom/bin/less.lua

diff --git a/assets/opencomputers/lua/kernel.lua b/assets/opencomputers/lua/kernel.lua
index c975e2af7..a67aa3a02 100644
--- a/assets/opencomputers/lua/kernel.lua
+++ b/assets/opencomputers/lua/kernel.lua
@@ -2,14 +2,50 @@
      computer crashes. It should never ever return "normally", only when an
      error occurred. Shutdown / reboot are signalled via special yields. ]]
 
+local deadline = 0
+
+local function checkDeadline()
+  if os.realTime() > deadline then
+    error("too long without yielding", 0)
+  end
+end
+
+local function checkArg(n, have, ...)
+  have = type(have)
+  local function check(want, ...)
+    if not want then
+      return false
+    else
+      return have == want or check(...)
+    end
+  end
+  if not check(...) then
+    local msg = string.format("bad argument #%d (%s expected, got %s)", n, table.concat({...}, " or "), have)
+    error(msg, 2)
+  end
+end
+
 --[[ Set up the global environment we make available to userland programs. ]]
-local sandbox = {
+local sandbox
+sandbox = {
   -- Top level values. The selection of kept methods rougly follows the list
   -- as available on the Lua wiki here: http://lua-users.org/wiki/SandBoxes
   assert = assert,
   error = error,
-  pcall = pcall,
-  xpcall = xpcall,
+  load = function(ld, source, mode, env)
+    assert((mode or "t") == "t", "unsupported mode")
+    return load(ld, source, "t", env or sandbox)
+  end,
+  pcall = function(...)
+    local result = table.pack(pcall(...))
+    checkDeadline()
+    return table.unpack(result, 1, result.n)
+  end,
+  xpcall = function(...)
+    local result = table.pack(xpcall(...))
+    checkDeadline()
+    return table.unpack(result, 1, result.n)
+  end,
 
   ipairs = ipairs,
   next = next,
@@ -30,6 +66,8 @@ local sandbox = {
 
   _VERSION = "Lua 5.2",
 
+  checkArg = checkArg,
+
   bit32 = {
     arshift = bit32.arshift,
     band = bit32.band,
@@ -45,10 +83,48 @@ local sandbox = {
     rshift = bit32.rshift
   },
 
+  --[[ Install wrappers for coroutine management that reserves the first value
+       returned by yields for internal stuff. Used for sleeping and message
+       calls (sendToAddress) that happen synchronized (Server thread).
+  --]]
   coroutine = {
     create = coroutine.create,
     running = coroutine.running,
-    status = coroutine.status
+    resume = function(co, ...)
+      local args = table.pack(...)
+      while true do
+        if not debug.gethook(co) then -- don't reset counter
+          debug.sethook(co, checkDeadline, "", 10000)
+        end
+        local result = table.pack(coroutine.resume(co, table.unpack(args, 1, args.n)))
+        checkDeadline()
+        if result[1] then
+          local isSystemYield = coroutine.status(co) ~= "dead" and result[2] ~= nil
+          if isSystemYield then
+            args = table.pack(coroutine.yield(result[2]))
+          else
+            return true, table.unpack(result, 3, result.n)
+          end
+        else -- error: result = (bool, string)
+          return table.unpack(result, 1, result.n)
+        end
+      end
+    end,
+    status = coroutine.status,
+    yield = function(...)
+      return coroutine.yield(nil, ...)
+    end,
+    wrap = function(f) -- for sandbox's coroutine.resume
+      local co = sandbox.coroutine.create(f)
+      return function(...)
+        local result = table.pack(sandbox.coroutine.resume(co, ...))
+        if result[1] then
+          return table.unpack(result, 2, result.n)
+        else
+          error(result[2], 0)
+        end
+      end
+    end
   },
 
   math = {
@@ -75,7 +151,10 @@ local sandbox = {
     pow = math.pow,
     rad = math.rad,
     random = math.random,
-    randomseed = math.randomseed,
+    randomseed = function(seed)
+      checkArg(1, seed, "number")
+      math.randomseed(seed)
+    end,
     sin = math.sin,
     sinh = math.sinh,
     sqrt = math.sqrt,
@@ -86,7 +165,9 @@ local sandbox = {
   os = {
     clock = os.clock,
     date = os.date,
-    difftime = os.difftime,
+    difftime = function(t2, t1)
+      return t2 - t1
+    end,
     time = os.time,
     uptime = os.uptime,
     freeMemory = os.freeMemory,
@@ -114,7 +195,11 @@ local sandbox = {
     uchar = string.uchar,
     ulen = string.ulen,
     ureverse = string.ureverse,
-    usub = string.usub
+    usub = string.usub,
+    trim = function(s) -- from http://lua-users.org/wiki/StringTrim
+      local from = s:match("^%s*()")
+      return from > #s and "" or s:match(".*%S", from)
+    end
   },
 
   table = {
@@ -133,90 +218,6 @@ local sandbox = {
 }
 sandbox._G = sandbox
 
-function sandbox.load(ld, source, mode, env)
-  assert((mode or "t") == "t", "unsupported mode")
-  return load(ld, source, "t", env or sandbox)
-end
-
-function sandbox.checkArg(n, have, ...)
-  have = type(have)
-  local function check(want, ...)
-    if not want then
-      return false
-    else
-      return have == want or check(...)
-    end
-  end
-  if not check(...) then
-    local msg = string.format("bad argument #%d (%s expected, got %s)", n, table.concat({...}, " or "), have)
-    --error(debug.traceback(msg, 2), 0)
-    error(msg, 2)
-  end
-end
-
--------------------------------------------------------------------------------
-
---[[ Install wrappers for coroutine management that reserves the first value
-     returned by yields for internal stuff. Used for sleeping and message
-     calls (sendToAddress) that happen synchronized (Server thread).
---]]
-local deadline = 0
-
-local function checkDeadline()
-  if os.realTime() > deadline then
-    error("too long without yielding", 0)
-  end
-end
-
-function sandbox.coroutine.resume(co, ...)
-  local args = table.pack(...)
-  while true do
-    if not debug.gethook(co) then -- don't reset counter
-      debug.sethook(co, checkDeadline, "", 10000)
-    end
-    local result = table.pack(coroutine.resume(co, table.unpack(args, 1, args.n)))
-    checkDeadline()
-    if result[1] then
-      local isSystemYield = coroutine.status(co) ~= "dead" and result[2] ~= nil
-      if isSystemYield then
-        args = table.pack(coroutine.yield(result[2]))
-      else
-        return true, table.unpack(result, 3, result.n)
-      end
-    else -- error: result = (bool, string)
-      return table.unpack(result, 1, result.n)
-    end
-  end
-end
-
-function sandbox.coroutine.yield(...)
-  return coroutine.yield(nil, ...)
-end
-
-function sandbox.coroutine.wrap(f) -- for sandbox's coroutine.resume
-  local co = sandbox.coroutine.create(f)
-  return function(...)
-    local result = table.pack(sandbox.coroutine.resume(co, ...))
-    if result[1] then
-      return table.unpack(result, 2, result.n)
-    else
-      error(result[2], 0)
-    end
-  end
-end
-
-function sandbox.pcall(...)
-  local result = table.pack(pcall(...))
-  checkDeadline()
-  return table.unpack(result, 1, result.n)
-end
-
-function sandbox.xpcall(...)
-  local result = table.pack(xpcall(...))
-  checkDeadline()
-  return table.unpack(result, 1, result.n)
-end
-
 -------------------------------------------------------------------------------
 
 function sandbox.os.shutdown(reboot)
@@ -238,11 +239,17 @@ end
 sandbox.driver = {}
 
 function sandbox.driver.componentType(address)
+  checkArg(1, address, "string")
   return nodeName(address)
 end
 
 do
-  local env = setmetatable({ send = sendToAddress },
+  local function send(address, name, ...)
+    checkArg(1, address, "string")
+    checkArg(2, name, "string")
+    return sendToAddress(address, name, ...)
+  end
+  local env = setmetatable({send = send},
                            { __index = sandbox, __newindex = sandbox })
   for name, code in pairs(drivers()) do
     local driver, reason = load(code, "=" .. name, "t", env)
@@ -270,7 +277,10 @@ local function main(args)
 
     -- Custom dofile implementation since we don't have the baselib yet.
     local function dofile(file)
-      local stream = fs.open(file)
+      local stream, reason = fs.open(file)
+      if not stream then
+        error(reason)
+      end
       if stream then
         local buffer = ""
         repeat
@@ -281,10 +291,12 @@ local function main(args)
         until not data
         stream:close()
         stream = nil
-        local program = sandbox.load(buffer, "=" .. file)
+        local program, reason = sandbox.load(buffer, "=" .. file)
         buffer = nil
         if program then
           return program()
+        else
+          error("error loading lib '" .. file .. "': " .. reason)
         end
       end
     end
@@ -306,8 +318,9 @@ local function main(args)
 
     return coroutine.create(function(...)
       sandbox.event.fire(...) -- handle the first signal
-      sandbox.os.execute("/bin/sh")
-      coroutine.yield(false) -- this should never return, so we shut down
+      while true do
+        sandbox.os.execute("/bin/sh")
+      end
     end)
   end
   local co = bootstrap()
diff --git a/assets/opencomputers/lua/rom/bin/cat.lua b/assets/opencomputers/lua/rom/bin/cat.lua
index 1b97f7313..c57987002 100644
--- a/assets/opencomputers/lua/rom/bin/cat.lua
+++ b/assets/opencomputers/lua/rom/bin/cat.lua
@@ -5,7 +5,7 @@ if #args == 0 then
 end
 
 for i = 1, #args do
-  local file, reason = io.open(shell.resolve(args[i]), "r")
+  local file, reason = io.open(shell.resolve(args[i]))
   if not file then
     print(reason)
     return
diff --git a/assets/opencomputers/lua/rom/bin/less.lua b/assets/opencomputers/lua/rom/bin/less.lua
new file mode 100644
index 000000000..f2c986953
--- /dev/null
+++ b/assets/opencomputers/lua/rom/bin/less.lua
@@ -0,0 +1,46 @@
+local args = shell.parse(...)
+if #args == 0 then
+  print("Usage: less <filename1>")
+  return
+end
+
+local file, reason = io.open(shell.resolve(args[1]))
+if not file then
+  print(reason)
+  return
+end
+
+local line = nil
+while true do
+  local w, h = gpu.resolution()
+  term.clear()
+  term.cursorBlink(false)
+  local i = 1
+  while i < h do
+    if not line then
+      line = file:read("*l")
+      if not line then -- eof
+        return 
+      end
+    end
+    if line:ulen() > w then
+      print(line:usub(1, w))
+      line = line:usub(w + 1)
+    else
+      print(line)
+      line = nil
+    end
+    i = i + 1
+  end
+  term.cursor(1, h)
+  term.write(":")
+  term.cursorBlink(true)
+  local event, address, char, code = event.wait("key_down")
+  if component.isPrimary(address) then
+    if code == keyboard.keys.q then
+      term.cursorBlink(false)
+      term.clearLine()
+      return
+    end
+  end
+end
diff --git a/assets/opencomputers/lua/rom/bin/sh.lua b/assets/opencomputers/lua/rom/bin/sh.lua
index 34230f589..2034283d3 100644
--- a/assets/opencomputers/lua/rom/bin/sh.lua
+++ b/assets/opencomputers/lua/rom/bin/sh.lua
@@ -1,33 +1,24 @@
-local args = table.pack(...)
-if args.n > 0 then
-  os.execute(table.concat(args, " ", 1, args.n))
-  return
-end
-
-local function trim(s) -- from http://lua-users.org/wiki/StringTrim
-  local from = s:match"^%s*()"
-  return from > #s and "" or s:match(".*%S", from)
-end
-local dir = shell.cwd() -- backup in case we're being run by another shell
-local running = true
-
-while running do
+local history = {}
+while true do
   if not term.isAvailable() then -- don't clear when opened by another shell
     while not term.isAvailable() do
-      event.wait()
+      os.sleep()
     end
     term.clear()
     print("OpenOS v1.0 (" .. math.floor(os.totalMemory() / 1024) .. "k RAM)")
   end
-  while running and term.isAvailable() do
-    io.write("> ")
-    local command = io.read()
+  while term.isAvailable() do
+    term.write("# ")
+    local command = term.read(history)
     if not command then
       return -- eof
     end
-    command = trim(command)
+    while #history > 10 do
+      table.remove(history, 1)
+    end
+    command = string.trim(command)
     if command == "exit" then
-      running = false
+      return
     elseif command ~= "" then
       local result, reason = os.execute(command)
       if not result then
@@ -36,5 +27,3 @@ while running do
     end
   end
 end
-
-shell.cwd(dir) -- restore
diff --git a/assets/opencomputers/lua/rom/bin/shutdown.lua b/assets/opencomputers/lua/rom/bin/shutdown.lua
index 97b019755..5730b6c51 100644
--- a/assets/opencomputers/lua/rom/bin/shutdown.lua
+++ b/assets/opencomputers/lua/rom/bin/shutdown.lua
@@ -1,2 +1,2 @@
-print("Shutting down...")
+term.clear()
 os.shutdown()
\ No newline at end of file
diff --git a/assets/opencomputers/lua/rom/lib/event.lua b/assets/opencomputers/lua/rom/lib/event.lua
index a6f837975..a05cf1ea1 100644
--- a/assets/opencomputers/lua/rom/lib/event.lua
+++ b/assets/opencomputers/lua/rom/lib/event.lua
@@ -21,10 +21,15 @@ end
 
 event = {}
 
---[[ Error handler for ALL event callbacks. If this returns a value,
-     the error will be rethrown, possibly leading to a computer crash. ]]
+--[[ Error handler for ALL event callbacks. If this doesn't return `true`,
+     the error will be printed and the computer will shut down. ]]
 function event.error(message)
-  return debug.traceback(message)
+  local log = io.open("tmp/event.log", "a")
+  if log then
+    log:write(message .. "\n")
+    log:close()
+  end
+  return true
 end
 
 function event.fire(name, ...)
@@ -41,9 +46,11 @@ function event.fire(name, ...)
     -- Copy the listener lists because they may be changed by callbacks.
     local listeners = copy(listenersFor(name, false), listenersFor(name, true))
     for _, callback in ipairs(listeners) do
-      local result, message = xpcall(callback, event.error, name, ...)
-      if not result and message then -- only if handler returned something.
-        error(message, 0)
+      local result, message = pcall(callback, name, ...)
+      if not result then
+        if not event.error or not event.error(message) then
+          os.shutdown()
+        end
       elseif result and message == false then
         break
       end
@@ -57,9 +64,9 @@ function event.fire(name, ...)
     end
   end
   for _, callback in ipairs(elapsed) do
-    local result, message = xpcall(callback, event.error)
-    if not result and message then -- only if handler returned something.
-      error(message, 0)
+    local result, message = pcall(callback)
+    if not result and not (event.error and event.error(message)) then
+      os.shutdown()
     end
   end
 end
@@ -114,9 +121,10 @@ function event.timer(timeout, callback)
   return id
 end
 
-function event.wait(seconds)
-  seconds = seconds or 0/0
-  checkArg(1, seconds, "number")
+function event.wait(filter, seconds)
+  checkArg(1, filter, "string", "nil")
+  seconds = seconds or (filter and math.huge or 0/0)
+  checkArg(2, seconds, "number")
   local function isNaN(n) return n ~= n end
   local target = os.uptime() + (isNaN(seconds) and 0 or seconds)
   repeat
@@ -126,6 +134,10 @@ function event.wait(seconds)
         closest = info.after
       end
     end
-    event.fire(os.signal(nil, closest - os.uptime()))
+    local signal = table.pack(os.signal(nil, closest - os.uptime()))
+    event.fire(table.unpack(signal, 1, signal.n))
+    if filter and type(signal[1]) == "string" and signal[1]:match(filter) then
+      return table.unpack(signal, 1, signal.n)
+    end
   until os.uptime() >= target
 end
diff --git a/assets/opencomputers/lua/rom/lib/io.lua b/assets/opencomputers/lua/rom/lib/io.lua
index b633f72d5..4521e3b71 100644
--- a/assets/opencomputers/lua/rom/lib/io.lua
+++ b/assets/opencomputers/lua/rom/lib/io.lua
@@ -255,7 +255,7 @@ function file.new(mode, stream, nogc)
     mode = mode,
     stream = stream,
     buffer = "",
-    bufferSize = math.min(8 * 1024, os.totalMemory() / 8),
+    bufferSize = math.max(128, math.min(8 * 1024, os.freeMemory() / 8)),
     bufferMode = "full"
   }
 
diff --git a/assets/opencomputers/lua/rom/lib/os.lua b/assets/opencomputers/lua/rom/lib/os.lua
index c672ff3de..ef4808d63 100644
--- a/assets/opencomputers/lua/rom/lib/os.lua
+++ b/assets/opencomputers/lua/rom/lib/os.lua
@@ -25,7 +25,9 @@ os.remove = driver.filesystem.remove
 
 os.rename = driver.filesystem.rename
 
-os.sleep = event.wait
+function os.sleep(timeout)
+  event.wait(nil, timeout)
+end
 
 function os.tmpname()
   if driver.filesystem.exists("tmp") then
diff --git a/assets/opencomputers/lua/rom/lib/shell.lua b/assets/opencomputers/lua/rom/lib/shell.lua
index 82625454e..3cbfb149e 100644
--- a/assets/opencomputers/lua/rom/lib/shell.lua
+++ b/assets/opencomputers/lua/rom/lib/shell.lua
@@ -1,7 +1,7 @@
 local cwd = "/"
 local path = {"/bin/", "/usr/bin/", "/home/bin/"}
 local aliases = {dir="ls", move="mv", rename="mv", copy="cp", del="rm",
-                 md="mkdir", cls="clear"}
+                 md="mkdir", cls="clear", more="less"}
 
 local function findFile(name, path, ext)
   checkArg(1, name, "string")
@@ -45,6 +45,93 @@ local function findFile(name, path, ext)
   return false
 end
 
+-------------------------------------------------------------------------------
+-- We pseudo-sandbox programs we start via the shell. Pseudo because it's
+-- really just a matter of convenience: listeners and timers get automatically
+-- cleaned up when the program exits/crashes. This can be easily circumvented
+-- by getting the parent environment via `getmetatable(_ENV).__index`. But if
+-- you do that you will probably know what you're doing.
+function newEnvironment()
+  local listeners, timers, e = {[false]={}, [true]={}}, {}, {}
+  local env = setmetatable(e, {__index=_ENV})
+
+  e._G = e
+  e.event = {}
+  function e.event.ignore(name, callback, weak)
+    weak = weak or false
+    if listeners[weak][name] and listeners[weak][name][callback] then
+      listeners[weak][name][callback] = nil
+      return event.ignore(name, callback, weak)
+    end
+    return false
+  end
+  function e.event.listen(name, callback, weak)
+    weak = weak or false
+    if event.listen(name, callback, weak) then
+      listeners[weak][name] = listeners[weak][name] or {}
+      listeners[weak][name][callback] = true
+      return true
+    end
+    return false
+  end
+  function e.event.cancel(timerId)
+    if timers[timerId] then
+      timers[timerId] = nil
+      return event.cancel(timerId)
+    end
+    return false
+  end
+  function e.event.timer(timeout, callback)
+    local id
+    local function onTimer()
+      timers[id] = nil
+      callback()
+    end
+    id = event.timer(timeout, onTimer)
+    timers[id] = true
+    return id
+  end
+  function e.event.interval(frequency, callback)
+    local interval = {}
+    local function onTimer()
+      interval.id = env.event.timer(frequency, onTimer)
+      callback()
+    end
+    interval.id = env.event.timer(frequency, onTimer)
+    return interval
+  end
+  setmetatable(e.event, {__index=event, __newindex=event})
+
+  function e.load(ld, source, mode, environment)
+    return load(ld, source, mode, environment or env)
+  end
+  function e.loadfile(filename, mode, environment)
+    return loadfile(filename, mode, environment or env)
+  end
+  function e.dofile(filename)
+    local program, reason = env.loadfile(filename)
+    if not program then
+      return env.error(reason, 0)
+    end
+    return program()
+  end
+
+  function cleanup()
+    for weak, list in pairs(listeners) do
+      for name, callbacks in pairs(list) do
+        for callback in pairs(callbacks) do
+          event.ignore(name, callback, weak)
+        end
+      end
+    end
+    for id in pairs(timers) do
+      event.cancel(id)
+    end
+  end
+
+  return env, cleanup
+end
+
 -------------------------------------------------------------------------------
 
 shell = {}
@@ -82,91 +169,13 @@ function shell.execute(program, ...)
   if not where then
     return nil, "program not found"
   end
-
-  -- Track listeners and timers registered by spawned programs so we can kill
-  -- them all when the coroutine dies. Note that this is only intended as a
-  -- convenience, and is easily circumvented (e.g. by using dofile or such).
-  local listeners, weakListeners, timers = {}, {}, {}
-  local pevent = {}
-  function pevent.ignore(name, callback, weak)
-    local list
-    if weak then
-      if weakListeners[name] and weakListeners[name][callback] then
-        list = weakListeners
-      end
-    elseif listeners[name] and listeners[name][callback] then
-      list = listeners
-    end
-    if list then
-      event.ignore(name, callback)
-      list[name][callback] = nil
-      return true
-    end
-    return false
-  end
-  function pevent.listen(name, callback, weak)
-    if event.listen(name, callback, weak) then
-      if weak then
-        weakListeners[name] = weakListeners[name] or {}
-        weakListeners[name][callback] = true
-      else
-        listeners[name] = listeners[name] or {}
-        listeners[name][callback] = nil
-      end
-      return true
-    end
-    return false
-  end
-  function pevent.cancel(timerId)
-    if timers[timerId] then
-      timers[timerId] = nil
-      return event.cancel(timerId)
-    end
-    return false
-  end
-  function pevent.timer(timeout, callback)
-    local id
-    local function onTimer()
-      timers[id] = nil
-      callback()
-    end
-    id = event.timer(timeout, onTimer)
-    timers[id] = true
-    return id
-  end
-  function pevent.interval(timeout, callback)
-    local interval = {}
-    local function onTimer()
-      interval.id = pevent.timer(timeout, onTimer)
-      callback()
-    end
-    interval.id = pevent.timer(timeout, onTimer)
-    return interval
-  end
-  pevent = setmetatable(pevent, {__index = event, __metatable = {}})
-  local env = setmetatable({event = pevent}, {__index = _ENV, __metatable = {}})
-
+  local env, cleanup = newEnvironment()
   program, reason = loadfile(where, "t", env)
   if not program then
     return nil, reason
   end
-
   local result = table.pack(pcall(program, ...))
-
-  for name, list in pairs(listeners) do
-    for listener in pairs(list) do
-      event.ignore(name, listener, false)
-    end
-  end
-  for name, list in pairs(weakListeners) do
-    for listener in pairs(list) do
-      event.ignore(name, listener, true)
-    end
-  end
-  for id in pairs(timers) do
-    event.cancel(id)
-  end
-
+  cleanup()
   return table.unpack(result, 1, result.n)
 end
 
@@ -187,6 +196,19 @@ function shell.parse(...)
   return args, options
 end
 
+function shell.path(...)
+  local result = table.concat(path, ":")
+  local args = table.pack(...)
+  if args.n > 0 then
+    checkArg(1, args[1], "string")
+    path = {}
+    for segment in string:gmatch(args[1], "[^:]") do
+      table.insert(path, string.trim(segment))
+    end
+  end
+  return result
+end
+
 function shell.resolve(path)
   if path:usub(1, 1) == "/" then
     return fs.canonical(path)
diff --git a/assets/opencomputers/lua/rom/lib/term.lua b/assets/opencomputers/lua/rom/lib/term.lua
index 996b4169b..9ea675911 100644
--- a/assets/opencomputers/lua/rom/lib/term.lua
+++ b/assets/opencomputers/lua/rom/lib/term.lua
@@ -312,7 +312,7 @@ function term.read(history)
   event.listen("clipboard", onClipboard)
   term.cursorBlink(true)
   while term.isAvailable() and not result and not forceReturn do
-    event.wait()
+    os.sleep()
   end
   if history[#history] == "" then
     table.remove(history)
diff --git a/com/naef/jnlua/LuaError.java b/com/naef/jnlua/LuaError.java
index ebd03f7c7..9f62ba085 100644
--- a/com/naef/jnlua/LuaError.java
+++ b/com/naef/jnlua/LuaError.java
@@ -54,7 +54,12 @@ class LuaError {
 			sb.append(message);
 		}
 		if (cause != null) {
-			sb.append(cause);
+			if (cause.getMessage() != null) {
+				sb.append(cause.getMessage());
+			}
+			else {
+				sb.append(cause);
+			}
 		}
 		return sb.toString();
 	}
diff --git a/li/cil/oc/common/tileentity/Screen.scala b/li/cil/oc/common/tileentity/Screen.scala
index 6216c57e1..c045be2b6 100644
--- a/li/cil/oc/common/tileentity/Screen.scala
+++ b/li/cil/oc/common/tileentity/Screen.scala
@@ -33,7 +33,7 @@ abstract class Screen extends Rotatable with component.Screen.Environment with R
    * into an OpenGL display list, and only re-compiling that list when the
    * text/display has actually changed.
    */
-  var hasChanged = false
+  var hasChanged = true
 
   /**
    * Check for multi-block screen option in next update. We do this in the
@@ -133,6 +133,7 @@ abstract class Screen extends Rotatable with component.Screen.Environment with R
         current.screens.foreach {
           screen =>
             screen.shouldCheckForMultiBlock = false
+            screen.hasChanged = true
             pending.remove(screen)
             queue += screen
         }
diff --git a/li/cil/oc/server/component/Computer.scala b/li/cil/oc/server/component/Computer.scala
index 35a6bacda..045f28ec0 100644
--- a/li/cil/oc/server/component/Computer.scala
+++ b/li/cil/oc/server/component/Computer.scala
@@ -92,8 +92,10 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
 
   // ----------------------------------------------------------------------- //
 
-  def recomputeMemory() = if (lua != null)
+  def recomputeMemory() = if (lua != null) {
+    lua.gc(LuaState.GcAction.COLLECT, 0)
     lua.setTotalMemory(kernelMemory + owner.installedMemory)
+  }
 
   // ----------------------------------------------------------------------- //
 
@@ -165,9 +167,21 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
       rom.foreach(rom => rom.network.foreach(_.remove(rom)))
       tmp.foreach(tmp => tmp.network.foreach(_.remove(tmp)))
       owner.network.foreach(_.sendToVisible(owner, "computer.stopped"))
-      // Clear any screens we use while we're at it.
-      owner.network.foreach(_.sendToNeighbors(owner, "gpu.fill",
-        1.0, 1.0, Double.PositiveInfinity, Double.PositiveInfinity, " ".getBytes("UTF-8")))
+
+      // If there was an error message (i.e. the computer crashed) display it on
+      // any screens we used (stored in GPUs).
+      if (message.isDefined) {
+        println(message.get) // TODO remove this at some point (add a tool that can read these error messages?)
+
+        // Clear any screens we use before displaying the error message on them.
+        owner.network.foreach(_.sendToNeighbors(owner, "gpu.fill",
+          1.0, 1.0, Double.PositiveInfinity, Double.PositiveInfinity, " ".getBytes("UTF-8")))
+        owner.network.foreach(network => {
+          for ((line, row) <- message.get.replace("\t", "  ").lines.zipWithIndex) {
+            network.sendToNeighbors(owner, "gpu.set", 1.0, 1.0 + row, line.getBytes("UTF-8"))
+          }
+        })
+      }
     }
 
     // Signal stops to the network. This is used to close file handles, for example.
@@ -176,18 +190,6 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
     }
     wasRunning = isRunning
 
-    // If there was an error message (i.e. the computer crashed) display it on
-    // any screens we used (stored in GPUs).
-    if (message.isDefined) {
-      println(message.get)
-      owner.network.foreach(network => {
-        for ((line, row) <- message.get.replace("\t", "  ").lines.zipWithIndex) {
-          network.sendToNeighbors(owner, "gpu.set", 1.0, 1.0 + row, line.getBytes("UTF-8"))
-        }
-      })
-      message = None
-    }
-
     // Check if we should switch states.
     stateMonitor.synchronized(state match {
       // Computer is rebooting.
@@ -306,8 +308,7 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
         if (nbt.hasKey("message"))
           message = Some(nbt.getString("message"))
 
-        // Clean up some after we're done and limit memory again.
-        lua.gc(LuaState.GcAction.COLLECT, 0)
+        // Limit memory again.
         recomputeMemory()
 
         // Ensure the executor is started in the next update if necessary.
@@ -350,7 +351,6 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
     }
 
     // Unlimit memory while persisting.
-    val memory = lua.getTotalMemory
     lua.setTotalMemory(Integer.MAX_VALUE)
     try {
       // Try persisting Lua, because that's what all of the rest depends on.
@@ -400,9 +400,8 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
       }
     }
     finally {
-      // Clean up some after we're done and limit memory again.
-      lua.gc(LuaState.GcAction.COLLECT, 0)
-      lua.setTotalMemory(memory)
+      // Limit memory again.
+      recomputeMemory()
     }
   }
 
@@ -437,6 +436,9 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
   // ----------------------------------------------------------------------- //
 
   private def init(): Boolean = {
+    // Reset error state.
+    message = None
+
     // Creates a new state with all base libraries and the persistence library
     // loaded into it. This means the state has much more power than it
     // rightfully should have, so we sandbox it a bit in the following.
@@ -748,6 +750,9 @@ class Computer(val owner: Computer.Environment) extends Persistable with Runnabl
     assert(lua.isThread(1))
 
     try {
+      // Help out the GC a little. The emergency GC has a few limitations that
+      // will make it free less memory than doing a full step manually.
+      lua.gc(LuaState.GcAction.COLLECT, 0)
       // Resume the Lua state and remember the number of results we get.
       cpuStart = System.nanoTime()
       val results = if (callReturn) {
diff --git a/li/cil/oc/util/LuaStateFactory.scala b/li/cil/oc/util/LuaStateFactory.scala
index 380923df5..261d89412 100644
--- a/li/cil/oc/util/LuaStateFactory.scala
+++ b/li/cil/oc/util/LuaStateFactory.scala
@@ -163,16 +163,6 @@ object LuaStateFactory {
       })
       state.setField(-2, "date")
 
-      // Custom os.difftime(). For most Lua implementations this would be the
-      // same anyway, but just to be on the safe side.
-      state.pushScalaFunction(lua => {
-        val t2 = lua.checkNumber(1)
-        val t1 = lua.checkNumber(2)
-        lua.pushNumber(t2 - t1)
-        1
-      })
-      state.setField(-2, "difftime")
-
       // Pop the os table.
       state.pop(1)