I am learning from "Programing in Lua" by Roberto Ierusalimschy, and I found that in the book, the example of Sandboxing uses the function setfenv() to change the environment of a given function, but in lua 5.2 this function is no longer available.
I tried to load some values from a file (a configuration file) into a field in a table, but, in lua 5.2 I can't use setfenv ( so I can load the values in the given environment). After reading some articles about lua 5.2 I found that each function may have (or not) an upvalue called _ENV which serves as the environment, so, I tried the following code:
function sandbox(sb_func, sb_env)
if not sb_func then return nil, "sandbox function not valid" end
sb_orig_env = _ENV
_ENV = sb_env -- yes, replaces the global _ENV
pcall_res, message = pcall( sb_func )
local modified_env = _ENV -- gets the environment that was used in the pcall( sb_func )
_ENV = sb_orig_env
return true, modified_env
end
function readFile(filename)
code = loadfile(filename)
res, table = sandbox(code, {})
if res then
--[[ Use table (modified_env) ]]--
else
print("Code not valid")
end
Replacing _ENV in the 'sandbox' function works well (can't access the regular fields), but, when the 'code' is executed it seems that it ignores that I replaced _ENV, it still can access regular fields (print, loadfile, dofile, etc).
Reading a little more, I found that lua 5.2 provides a function for this purpose, this function is loadin(env, chunk), which runs the given chunk in the given environment, but, when I try to add this function to my code, the function doesn't exist ( Is not present in the global _G field).
Some help will be appreciated.
When you assign to _ENV from within sandbox, you're not overwriting the global environment--you're replacing the _ENV upvalue of the currently running code. Adding calls to print(_ENV) may help you better understand the identities of the tables involved.
For example:
function print_env()
print(_ENV)
end
function sandbox()
print(_ENV) -- prints: "table: 0x100100610"
-- need to keep access to a few globals:
_ENV = { print = print, print_env = print_env, debug = debug, load = load }
print(_ENV) -- prints: "table: 0x100105140"
print_env() -- prints: "table: 0x100105140"
local code1 = load('print(_ENV)')
code1() -- prints: "table: 0x100100610"
debug.setupvalue(code1, 1, _ENV) -- set our modified env
code1() -- prints: "table: 0x100105140"
local code2 = load('print(_ENV)', nil, nil, _ENV) -- pass 'env' arg
code2() -- prints: "table: 0x100105140"
end
The loadin function was present in some pre-release versions of Lua 5.2 but was removed before the final release. Instead, the Lua 5.2 load and loadfile functions take an env argument. You can also modify the _ENV of another function using debug.setupvalue.
Related
I have a SWIG generated R wrapper which contains the following setClass operations:
setClass('_p_f_p_struct_parameters_p_struct_chromosome_p_struct_dataSet__double',
prototype = list(parameterTypes = c('_p_parameters', '_p_chromosome', '_p_dataSet'),
returnType = '_p_f_p_struct_parameters_p_struct_chromosome_p_struct_dataSet__double'),
contains = 'CRoutinePointer')
setClass('_p_f_p_struct_parameters_p_p_struct_chromosome_p_p_struct_chromosome_int_int__void',
prototype = list(parameterTypes = c('_p_parameters', '_p_p_chromosome', '_p_p_chromosome', '_int', '_int'),
returnType = '_p_f_p_struct_parameters_p_p_struct_chromosome_p_p_struct_chromosome_int_int__void'),
contains = 'CRoutinePointer')
These operation do not appear to be behaving as expected. When I call a function with the output being the creation of a _p_parameters object (defined above), I get the following error:
Error in getClass(Class, where = topenv(parent.frame())) :
“_p_parameters” is not a defined class
The setClass therefore seems to be not doing it's thing.
I tried to manually set the _p_parameters class via:
p_parameters<-setClass(Class="_p_parameters", representation = representation(ref = "externalptr"))
But this does not seem to work as when I try and modify other parameters (or even print parameters via an inbuilt function) the terminal crashes and hangs.
For reference, the final lines in initialiseParameters (the function which initially own _p_parameters) are calling the native C function via .Call then assigning the external pointer to a new object of class _p_paramters as follows:
;ans = .Call('R_swig_initialiseParameters', numInputs, numNodes, numOutputs, arity, as.logical(.copy), PACKAGE='cgp');
ans <- new("_p_parameters", ref=ans) ;
I've read various R doc on new(), setClass, S3/S4 classes but nothing seems to clarify what I'm meant to be doing here.
Any suggestions on where to start or tutorials that would give a good heads up would be most welcome.
Please keep in mind the C code is not mine (but is freely available under GNU), I am not a C programmer and am only weakly-moderately proficient in R. So please be gentle :)
Cheers.
PS: If I call the function in R terminal via .Call it works as expected (so it doesn't seem to e a C function error)
I thought I should post the solution I have to this. The least I could do for a 'tumbleweed' medal haha.
The only solution I could find to this is to comment out the following line:
ans <- new("_p_parameters", ref=ans) ;
in all function that try to create an R object.
The resulting memory pointer is then assigned to an R object at function call.
It's dirty, but I couldn't work out how to create an object from a memory pointer (at least from within the functions themselves).
It seems to work so I guess it will do.
I am working on a scripting layer for my game engine. Currently I am using a Script as a Class, adding a method to the "Table" named new. This function basically created an instantiated copy of the Class. I call this function from the C API when an instance of the script is needed.
function PlayerController:new(o)
print('A new instance of the PlayerController has been created');
o = o or {}
setmetatable(o, self)
self.__index = self
return o
end
My question is: How can I take the above Lua code, and move that into C so it is not required to be added to every script file I write for this system?
You might want to create a class declaration function to do this for you. Here is a complete "helper.lua" file:
local lib = {type = 'helper'}
local CALL_TO_NEW = {__call = function(lib, ...) return lib.new(...) end}
function lib.class(class_name, tbl)
local lib = tbl or {}
lib.type = class_name
lib.__index = lib
-- Default "new" method
function lib.new()
return setmetatable({}, lib)
end
-- Enable foo.Bar() instead of foo.Bar.new()
return setmetatable(lib, CALL_TO_NEW)
end
return lib
Usage example:
local helper = require 'helper'
local lib = helper.class 'foo.Bar'
-- optional new function if there needs to be some argument handling
function lib.new(args)
local self = {}
-- ...
return setmetatable(self, lib)
end
return lib
lub.class
This is a real world minimal class declaration and setup system. It is used in many luarocks such as xml, yaml, dub, etc:
documentation
source code
I run Lua scripts inside c application in a separate task, I added a feature to check on the status of the running script if it's still running or completed.
I want to add some info in case of running script, I want to add the percentage executed from the running script, does Lua support this info by any mean.
I tried to use the info reported in Lua_debug, but it doesn't look to be correct (Like currentlin, definedline), I need the percentage over the whole script not just for a specific function.
You could set a debug hook and listen to the hook events:
Ideone
local script = [[
print 'hello'
print 'world'
for i=0,3 do
local answer = 42
end
]]
local script_function = loadstring(script)
local function count_lines ()
local count = 0
for k,v in script:gmatch '\n' do count = count+1 end
return count
end
local function trace(total_lines)
local max_last_line = 0
return function(info,line_number)
if line_number > max_last_line then
print(tostring(line_number/total_lines*100)..'%')
max_last_line = line_number
end
end
end
local lines = count_lines()
local thread = coroutine.create( script_function )
debug.sethook(thread, trace(lines), "l")
coroutine.resume(thread)
output:
20%
hello
40%
world
60%
80%
100%
However, it is to mention that it's still quite hard to get meaningful numbers from such a progress report - if you organize your code and the only statement at the end is the call to some kind of main, the progress will be 100%, whereas the number wouldn't represent anything useful. You could also track the lines and measure coverage, but naturally, 100% coverage is not something that you normally have during an execution run. You could also try to build a system for progress reporting and call a function like
ReportProgress( tasks / all_tasks )
which would be bound to C and would generate the necessary progress update
I have a chunk of PHP code that I'd like to include on a number of different pages but be able to update in one location (hence my use of an include file). However, the chunk of code needs to appear inside a while loop -- specifically inside a while loop that is echoing out MySQL rows.
However, there are roughly 200 rows in the MySQL query I'm echoing, so having an include in the loop really slows things down. I've tried making what's in the include file a function, like shown below, then including once at the top of the page and referencing the function inside the loop, but it it doesn't seem to work (I just don't get any data in the variables I'm setting, etc.)
How does one put a chunk of code inside a loop without using include?
Thanks very much.
function CYCalc()
{
// If the company's current fiscal quarter
// is equal to the current calendar quarter,
// use the company's fiscal years as calendar years
if ($UniverseResult[CurQ] == "Q1" && $UniverseResult[CurYear] == "2012") {
$C2011Sales = number_format($UniverseResult[SalesYear2]/1000000,1);
$C2012Sales = number_format($UniverseResult[SalesYear3]/1000000,1);
$C2011EPS = $UniverseResult[EPSYear2];
$C2012EPS = $UniverseResult[EPSYear3];
}
}
Remember PHP's scoping rules. Variables defined in the global scope are not visible inside functions unless you explicitly declare them as global within the function:
<?php
$x = 7;
function y() {
echo $x; // undefined
}
function z() {
global $x;
echo $x; // 7
}
function a($x) {
echo $x; // 7
}
For your CYCalc() to work, you'd need to declare $UniverseResult global as per z() above, or pass it in as a parameter as per a() above.
I have the following lua script :
module("modoo",package.seeall)
foo=1
bar={12,34}
Which works fine using the cli, such as :
> dofile "mod_modoo.lua"
> =modoo.foo
1
> =modoo
table: 0x86ce058
As far as I understood, it works like a table, but whenever I try loading it as a table, a nil value is pushed onto the stack. Every other table works normally.
I thought using lua_getglobal wouldn't work with modules, but I couldn't find the proper way to load it either ; how should I do it ?
Load Lua modules with require like lua.c does. See http://www.lua.org/source/5.1/lua.c.html#dolibrary
Instead of using module and dofile, it is better practice in Lua 5.1 to simply return a table representing your module when the script is run. All functions and variables should be declared as local within the module script so that the returned table provides the only access point and no globals from other modules are trampled. The module should be imported using require as follows.
mod_modoo.lua:
return { foo = 1, bar = { 12, 34 } }
modoo_test.lua:
> local modoo = require "mod_modoo"
However, it is often nice to bring the module table (i.e. modoo) in as a global without explicitly assigning it. To do so, assign the module table a global reference in addition to returning it from the script. In that case, the module can be used as follows:
mod_modoo.lua:
modoo = { foo = 1, bar = { 12, 34 } }
return modoo
modoo_test.lua:
> require "mod_modoo"
> print(modoo.foo)
1
See the Lua Module Function Critiqued article for more information on the matter.