External buffer for nbind

ExternalBuffer.hpp

#include <cstddef>

/// A non-owning memory view in a C++ std::vector<double> like object.
class ExternalBuffer {
public:
    ExternalBuffer(double* data, size_t length):
        data_(data), length_(length) {}

    void* data() {
        return reinterpret_cast<void*>(data_);
    }

    size_t byte_length() {
        return length_ * sizeof(double);
    }

    size_t length() {
        return length_;
    }

private:
    double* data_;
    /// The actual
    size_t length_;
};

#if defined(BUILDING_NODE_EXTENSION)

#include "nbind/api.h"
#include <nan.h>
#include <node_version.h>

namespace nbind {

template <> struct BindingType<ExternalBuffer> {
	typedef ExternalBuffer Type;

	static bool checkType(WireType /*unused*/) {
		return false;
	}

	static Type fromWireType(WireType /*unused*/) {
        NBIND_ERR("can not create a BorrowedBuffer from a JS object");
        return Type(nullptr, 0);
	}

	static WireType toWireType(Type &&arg) {
        auto buffer = v8::ArrayBuffer::New(
            v8::Isolate::GetCurrent(), arg.data(), arg.byte_length()
        );
        return v8::Float64Array::New(buffer, 0, arg.length());
	}
};

#elif defined(__EMSCRIPTEN__)

// TODO

#endif

} // namespace