A script engine for C++

This project allow the interoperability between C++ and scripting languages. C++ features like virtual functions, inheritance, exceptions are exposed to script language.

Multiple scripting language are supported (for now only Google V8 is implemented, next step is Python).

Main features are:

• Use C++ class and functions from script
• No required changes of existing classes
• Derivation of classes (even abstract) in script and use in C++
• Automatic conversion of native types and STL containers (list, map, vector)
• User defined type conversions
• Throw exception from script and catch in C++ and viceversa
• Simple API designed for easy usage in mind.

See how to interface C++ class and functions to script engine.

For more details, see Reference.

email << "stefano.marocco" << "@" << "gmail.com";

How to interface C++ and scripting languages

This example show how:

Bind classes and functions to script engine
Class instantiation and usage
Derive classes and override functions in Javascript
Exception handling

Full source: http://code.google.com/p/nasiu-scripting/source/browse/trunk/examples/nasiu/scripting/v8w/example1.cpp Classes and functions binding

Our example class and functions definition:

class A {
    int n_;
    public: A(); A(int n); virtual ~A();

    void method0();
    void method1(int a);
    int get_n() const;
    void set_n(int n);
};

int func1(A* a) {
    std::cout << "func1 " << a->get_n() << std::endl; return a->get_n();
}

Adapt class for script:

NASIU_V8W_ADAPT_CLASS(
    A, ,
    (int),
    (method0) (method1),
    ("n", get_n, set_n)
    ("n1", get_n, ));

Bind class and function to script engine:

using namespace nasiu::scripting;

script_engine se;
se.bind_class();
se.bind_function("func1", func1);

Assign script scope variables:

se.set("var1", "var1-content"); 
se.set("var2", 10000); 
se.set("var3", new A(84));

Instantiation and invocation

Use the function func1 and a script variable:

se.exec("func1(new A(var2))");

Instantiate A from Javascript and use in C++.

A* a1 = se.eval("new A(20)");

cout << "a1.n=" << a1->get_n() << endl;

Return the class from Javascript, instantiate, use, delete in C++:

class_type type_A = se.eval >("A");

A* a2 = type_A.new_instance(30);
cout << "a2.n=" << a2->get_n() << endl;

delete a2;

Function overriding

Override some functions of A in Javascript, return the class and use in C++:

class_type type_ExtA = se.eval(
    "ExtA = function(n)"
    "{"
    " var base = new A(n);"
    " base.proto = ExtA.prototype;"
    " return base;" "};"
    "ExtA.prototype.proto = A.prototype;"
    "ExtA.prototype.method1 = function(n)"
    "{"
    " A.prototype.method1.call(this, n*n);"
    "};"
    "ExtA.prototype.method0 = function(n)"
    "{"
    " A.prototype.method0.call(this);"
    "};"
    "ExtA" );

A* a3 = type_ExtA.new_instance(40);
cout << "a3.n=" << a3->get_n() << endl;
cout << "a3.method0() ";
a3->method0();
cout << endl;
cout << "a3.method1() ";
a3->method1(40);
cout << endl;

delete a3;

Exception handling

Define a Javascript function that throw a exception and catch it in C++:

function<tags::v8w> js_func = se.eval<function<tags::v8w> >( 
    "(function (a, b)" "{" " throw a + b;" "})" ); 
    try { 
        js_func.call<void>(10, 30); 
    } 
    catch (script_exception& e) { cout << "js_func exception: " << e.what() << endl; }

Catch C++ exceptions from Javascript:

void func2(int n) { throw "native exception"; }
se.bind_function("func2", func2);

se.exec(
    "try "
    "{"
    " func2(20);"
    "}"
    "catch (e)"
    "{"
    " /* ... */"
    "};" );