I just found this in v8.h:
/** Creates a new context. */
static Persistent<Context> New(
ExtensionConfiguration* extensions = 0,
Handle<ObjectTemplate> global_template =
Handle<ObjectTemplate>(),
Handle<Value> global_object = Handle<Value>());
You may be able to use this to call Context::New(0, GlobalTemplate,
GlobalObject);
Where GlobalObject is the object passed to evalcx.
However, it may not work; I'm not certain what would happen if you
pass an object belonging to another context as a global object of a
new context.
So, plan B might be to manually copy the items from your global object
passed to evalcx to the global object for your new context.
I hope that helps,
Alex
On Mar 2, 2009, at 11:05 AM, Isaac Z. Schlueter wrote:
>
> Thanks, Stephan.
>
> It looks like what you're doing will execute the code and set "this"
> to the object in question.
>
> However, what I'd really like to do is execute code and set a given
> object as the global scope. Here's an example with some code:
>
> var code = "var foo = 'bar';";
> var obj = { foo : "baz" };
> evalcx( code, obj ); // execute code using "obj" as the global object
> print( obj.foo ); // prints "bar"
>
> Unless I'm misreading your example, what you're describing will work
> in this case:
>
> var code = "this.foo = 'bar';";
> var obj = { foo : "baz" };
>
> But, I can already do that from JS like so:
>
> (new Function(code)).call(obj);
>
> If I could eval code in an arbitrary global scope within Javascript,
> which did not have any access to the global scope, then it would be
> possible to implement a capability-based security model.
>
> Also, it would make it possible to load and execute many different
> scripts in a row without having to "clean up" the globals that each
> one might create. After being evaluated, the temporary global scope
> could be discarded, and would be garbage collected normally.
>
> For example, let's say you have a fastcgi handler written in
> Javascript, which reads and evals the SCRIPT_FILENAME file. The
> problem is that, since the evaled code shares a global scope with the
> fcgi handler, it also shares a global scope with *every other script
> loaded by that handler.* That means that every global variable is
> persistent in memory, and only gets garbage collected when you restart
> the server. Not ideal! :)
>
> --
> Isaac Z. Schlueter
>
>
> On Mar 1, 5:06 pm, Stephan Beal <[email protected]> wrote:
>> On Mar 2, 1:34 am, "Isaac Z. Schlueter" <[email protected]> wrote:
>>
>>> I'm trying to write a function that will execute a bit of Javascript
>>> within an arbitrary global scope. Something like the "evalcx"
>>> function in the Spidermonkey shell.
>>
>>> I've got a function defined and exposed to the Javascript that takes
>>> an object as an argument, and stores it as a Handle<Object>.
>>> However,
>>> in order to create a new execution context, I need a
>>> Handle<ObjectTemplate>.
>>
>> Do you need a new Context, or just an object to eval the code in? If
>> you just need an Object to execute the code in...
>>
>> They way i ended up doing this was getting the 'eval' function from
>> my
>> local object, then using Call() on that Function object:
>>
>> TryCatch tryer;
>> Local<Value> rv;
>> Local<Function> eval = Function::Cast( *(db->jsobj-
>> >Get(String::New
>> ("eval"))) );
>> // ^^^^^ db->jsobj is my context object
>> for( int i = 0; i < argc; ++i )
>> {
>> char const * cp = reinterpret_cast<char const *>
>> ( sqlite3_value_text( argv[i] ) );
>> if( ! cp || !*cp ) continue;
>> Local<Value> arg = String::New( cp,
>> sqlite3_value_bytes( argv
>> [i] ) );
>> rv = eval->Call( db->jsobj, 1, &arg );
>> // ^^^^ that will, in theory, eval the code in the context of db-
>> >jsobj
>>
>> if( rv.IsEmpty() )
>> {
>> std::string
>> err( CastFromJS<std::string>( tryer.Exception() ) );
>> sqlite3_result_text( context, err.c_str(),
>> static_cast<int>(err.size
>> ()), SQLITE_TRANSIENT );
>> return;
>> }
>> }
> >
Alex Iskander
Web and Marketing
TPSi
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