Add wrapper class support.

[hurry07]

hi~, suppose a method return a Buffer object, you have to code like this:

c++

void drawToBuffer(int size, nbind::cbFunction& callback) {
    nbind::Buffer buf = callback.call<nbind::Buffer>(size);
    // ... 
    buf.commit();
}

#include "nbind/nbind.h"

NBIND_GLOBAL() {
    function(drawToBuffer);
}

javascript

let result = drawToBuffer(function(size) {
    return Buffer.alloc(size);
})

I suggest two ways of interact with c++ code that will return an object of js buildin types/classes.

1. Give a constructor to nbind::Buffer, so you can create an "instance" of that type like std::vector.

nbind::Buffer drawToBuffer(bool useBackground, float rotate) {
    nbind::Buffer buf(128);
    // ... 
    buf.commit();
    return buf;
}

#include "nbind/nbind.h"
NBIND_GLOBAL() {
    function(drawToBuffer);
}

javascript:

let imageBuffer = binding.lib.drawToBuffer(false, 0);

2. Add support for js inner types binding. instead of using NBIND_CLASS, give a new micro NBIND_WRAP.

class ImageBuffer {
public:
     static nbind::Buffer toJS(ImageBuffer *);
     static nbind::Buffer toJS(ImageBuffer); // overwrite
     static ImageBuffer *fromJS(nbind::Buffer); // user should release the newly create ImageBuffer*
     static ImageBuffer fromJS(nbind::Buffer);// overwrite
     static ImageBuffer& fromJS(nbind::Buffer, ImageBuffer& objectToInit);// overwrite
public:
     unsigned char* data;
     int length;
}
void addWaterPrint(ImageBuffer);

NBIND_GLOBAL() {
    function(addWaterPrint);
}
NBIND_WRAP<nbind::Buffer>(ImageBuffer);

javascript:

let buffer = fs.readFileSync(/*...*/);
binding.lib.addWaterPrint(buffer);

another example:

class NetWorkConfig {
public:
     static std::string toJS(NetWorkConfig *); // you can join all properties to an string like hostname#port#path
     static NetWorkConfig *fromJS(std::string); // split the input string by '#' and you get [hostname,      
     static NetWorkConfig fromJS(std::string); // overwrite for different argument types.
public:
    std::string hostname;
    std::string port;
    std::string path;
}

bool setupConnection(NetWorkConfig config);

NBIND_WRAP<std::string>(NetWorkConfig);
NBIND_GLOBAL() {
    function(setupConnection);
}

javascript:

let serverAddress = 'http://some.domain.name.com#8080#/your/resource/path';
let hasConnected = binding.lib.setupConnection(serverAddress);
if(hasConnected) {
    // ...
}

[hurry07]

This is extremely useful when working with matirx operation library, there will be a great improvement when you can convert '1,0,0,0,1,0,0,0,1' to an native Matirx33 object