Pass an int to a node.js addon

[NodeNinja]

My original c++  function had the following signature

unsigned char* random(int length);

To use this as an add-on I modified it to 

Handle<Value> random(const Arguments& args) {

if(args[0]->IsInt32()){

Local<Int32> length = args[0]->ToInt32();

// Now here I want to create an array like this "unsigned char* buffer = new unsigned char[length];"  using the length variable

// but it gives me an error saying length is undefined

//1.  how do I convert Local<Int32> to int ???

// 2. How to return the array from this function??

}

}

[James Jiang]

Can Cast do that?

[NodeNinja]

On Friday, October 26, 2012 2:44:27 PM UTC+5:30, James Jiang wrote:

Can Cast do that?

I found on the web that something like this can do the trick

if(args[0]->IsInt32() ){

   int32_t  intVal = args[0]->ToInt32()->Value();

}

[Ben Noordhuis]

int length = args[0]->Int32Value();
if (length <= 0) {
return ThrowException(Exception::Error(String::New("BAM")));

[NodeNinja]

int length = args[0]->Int32Value();
if (length <= 0) {
  return ThrowException(Exception::Error(String::New("BAM")));
}
unsigned char* buffer = new unsigned char[length];

Thanks for that info Ben,

Further to that is there a way to pass and return array of pointers I have something like (unsigned int **)

[Dean Mao]

If you want some crazy v8 type conversion library, there is v8-juice:

http://code.google.com/p/v8-juice/wiki/ConvertingTypes

I've not used it before, but it came highly recommended from others.  It's not too useful for converting one type, but if you have composite types, it might make things easier.

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[Ben Noordhuis]

Yep. Here is how you accept one:

if (!args[0]->IsArray()) {

return ThrowException(Exception::Error(String::New("BAM")));
}

Local<Array> array = Local<Array>::Cast(args[0]);
uint32_t len = array->Length();
Local<Value> first = array->Get(0);

And this is how you create one:

Local<Array> array = Array::New(32); // 32=initial length, optional
array->Set(0, String::New("first"));

[NodeNinja]

If you want some crazy v8 type conversion library, there is v8-juice:

http://code.google.com/p/v8-juice/wiki/ConvertingTypes

 

Thats wonderful info Dan!! Many thanks!

--------------------------

Ben, Thanks for the code snippet is an array of pointers also created in the same style?

 

[Ben Noordhuis]

On Sun, Oct 28, 2012 at 4:52 AM, NodeNinja <aeon...@gmail.com> wrote:
> Ben, Thanks for the code snippet is an array of pointers also created in the
> same style?

Depends on what you mean by 'pointer'. JS the language doesn't have a
concept of pointers. V8 lets you store pointers with
v8::Object::SetPointerInInternalField() but those are visible only to
C++, not JS.