C++ embedding questions

[IngwiePhoenix]

Hey.

so, I just had to realize that the scripting language that I originalyl wanted to use for my project, has quite some issues. So I need to switch to ObjectScript now. And this brings questions:

1. How thread-safe is ObjectScript?
2. Can I compile/run multiple script snippets? Currently, the order would be something like: string, string, string, file, string, string. in my previous used language, ph7, the VM would reset upon each new loaded snippet.
3. What's the API to insert variables and the like into the scripting eingine?
4. Can I define getter/setter functions for some native variables?

My project is here: http://github.com/IngwiePhoenix/IceTea

Kind regards, Ingwie

[unitpoint]

1. ObjetcScript is not thread-safe.
2. You could create a lot of ObjectScript instances. They will work properly.
3. Please try to investigate datetime extension (ext-datetime). I'll write documentation later.
4. DateTime class has a lof of getter/setter methods (ext-datetime), for example __get@year, __set@year

[IngwiePhoenix]

1: Ok. Gonna use mutexes and guards then.
2: I was rather reffering to a single instance, but calling the function to run OS code off a string/file multiple times. i.e.:

os->runString(...);
os->runString(...);
os->runString(...);
os->runFile(...);
os->runString(...);

Would the VM be overridden and cleared, or would it all jsut behave like one single script? I am asking, because I may define a (scripted) function within the first call, and need that within the second.

3, 4: sure, will do! :) Thanks for that hint.

[unitpoint]

You could referring to a single instance, it's ok. The VM will not be cleared, you may define function inside of one file and use it in the second.

[IngwiePhoenix]

Awesome! ^^

I began re-writing my implementation to now use ObjectScript instead of the other scripting language, and came across OS::Vextor, OS::Value and OS::GCValue. This reminded me, that I forgot to ask, how I can create an array, object or table to return to ObjectScript. And so far, i noticed that the only documentation about the C++ API is here: https://github.com/unitpoint/objectscript/wiki/Programming-in-ObjectScript#function-in-c

Let's asume I wanted to create a function called "task" with one object-type parameter. If I was calling it like this in OS:

task {
    display = "Special special task",
    cmd = "./binary --args"
};

How would I then recieve the properties of that object in my C++ function?

Secondly, when I use os-binder's ObjectScript::def(), how can I make it pass ObjectScript's object/array/table values? In the example, you only used primitives (float).

[IngwiePhoenix]

I just had some more experiments...and it turns out, that I wouldnt get errors when I am trying to call an undefined function. My code for the testing:

#include "objectscript.h"
#include "os-binder.h"

using namespace ObjectScript;

float test(float a, float b){ return a + b; }

int main()
{
    OS * os = OS::create();

    os->setSetting(OS_SETTING_CREATE_TEXT_OPCODES, false);
    os->setSetting(OS_SETTING_CREATE_COMPILED_FILE, false);
    os->setSetting(OS_SETTING_SOURCECODE_MUST_EXIST, true);
    os->setSetting(OS_SETTING_CREATE_DEBUG_INFO, true);

    os->setGlobal(def("test", test));   // use binder

    // Testing multi-call
    os->evalFakeFile("fake.os","bla()");
    os->require("file1.os");
    os->require("file2.os");

    os->release();
    return 0;
}

I was expecting, that I get some sort of error message or a like with the first call. But I dont. O.o How do I pick up errors like that, or have I overseen some setting?

[unitpoint]

You could define global getter function to detect that error, OS script:

function __get(name){
    throw "unknown class or global property \"${name}\""
}

[unitpoint]

Let's asume I wanted to create a function called "task" with one object-type parameter. If I was calling it like this in OS:

task {
    display = "Special special task",
    cmd = "./binary --args"
};

You could iterate OS object or array using nextIteratorStep method, for example:

int my_func(OS * os, int params, int, int, void * user_param)
{
    if(os->isObject(-params+0)){
        os->pushStackValue(-params+0);
        while(os->nextIteratorStep()){
            OS::String key = os->toString(-2);
            OS::String value = os->toString(-1);
            ...
            os->pop(2);
        }
        os->pop();
        return 0;
    }
    ...
}

[IngwiePhoenix]

Cool! That would help me to turn it into a map<>. Pretty neat.
I also made __get in C++, was easier than I thought and now I know how to set exceptions.

But I now am wondering about something I just came across. I am writing a wrapper about (config4cpp)[http://config4star.org] to catch special config parts. But i have two different configs. One stays the same all the time, so its initialized directly. But the second is one that keeps changing. So I was thinking about dynamically constructing the neccessary object. I have figured out how to register primary values - numbers, strings, etc. - but how do I do functions? Are they the same typedef than the one used for regular, global, functions?

Also later, I will post a link to my embedding work, to showcase what I am doing.

[IngwiePhoenix]

https://github.com/IngwiePhoenix/IceTea/blob/master/src/os-icetea.cpp Voila.

I am trying to come up with a good solution for the config part at the bottom. I always have up to three pointers. One is the global and always active one. The other two are dynamic. So I am thinking of either using getter/setter, a prototype, or construct a new object with the above get and set method. What do you think would be the easiest to achieve?

[unitpoint]

I'd recommend to use config in JSON format if possible (see json.encode, json.decode). Or in ObjectScript format, for example OS config file my_config.os:

return {
    class = "DbConnection",
    type = "odbc",
    tablePrefix = "med_",
    params = {
        DRIVER = "{SQL Server}",
        SERVER = "test",
        DATABASE = "MIS",
        USER = "username",
        PASSWORD = "passwd",
    },
}

and load the config file:

var config = require("my_config.os")

[IngwiePhoenix]

I see. o.o

Okay, one more thing. I know that one can construct a new module, or extend one, in C++. But how do I just create a global object? Like this?

os->newObject();
os->pushCFunction(myfunc, (void*)something);
os->setProperty("func");
os->setGlobal("obj");

[unitpoint]

You can do it like this:

os->newObject();
os->pushStackValue(-1);
os->pushCFunction(myfunc, (void*)something);
os->setProperty("func");
os->setGlobal("obj");

or

os->newObject();
os->pushCFunction(myfunc, (void*)something);
os->setProperty(-2, "func");
os->setGlobal("obj");

[IngwiePhoenix]

Huh? I mean, I am getting the deal with a stack-based VM, but why do I need to set negative offsets (-1, -2) for these? Is it, so that the property is being set to the new object?

0 Object
1 CFunction

So that when then property is being set, it points to 0?
Am 25.07.2014 um 18:34 schrieb Evgeniy Golovin [email protected]:

You can do it like this:

os->newObject();
os->pushStackValue(-1);
os->pushCFunction(myfunc, (void*)something);
os->setProperty("func");
os->setGlobal("obj");
or

os->newObject();
os->pushCFunction(myfunc, (void*)something);
os->setProperty(-2, "func");
os->setGlobal("obj");
—
Reply to this email directly or view it on GitHub.

[unitpoint]

Negative offset is used for relative offset, so -1 is top stack value, -2 is value before the top value and so on. Positive offset is used for absolute offset.