How to use the ffi-napi.Function function in ffi-napi

console.error("usage: node pcap.js /path/to/file.pcap");
    console.error();
    process.exit();
}

/* NDPI Types */

	var voidPtr = exports.voidPtr = ref.refType(ref.types.void);
	var u_char = exports.u_char = Struct({
	  __u_char: ref.types.uchar,
	});
	var u_charPtr = exports.u_charPtr = ref.refType(u_char);
	
	var pcap_t = exports.pcap_t = voidPtr;
	var pcap_tPtr = exports.pcap_tPtr = ref.refType(pcap_t);
	var pcap_handler = exports.pcap_handler = ffi.Function(ref.types.void, [
	  ref.refType(ref.types.uchar),
	  voidPtr,
	  ref.refType(ref.types.uchar),
	]);
	var pcap_handlerPtr = exports.pcap_handlerPtr = ref.refType(pcap_handler);
	
	var uint8_t = exports.uint8_t = voidPtr;
	var uint8_tPtr = exports.uint8_tPtr = ref.refType(uint8_t);


/* callback */ 
	const onProto = function(id, packet) {
		if (id > 0) { console.log("Proto: "+packet+" ("+id+")") }
	}

	var callback = exports.callback = ffi.Function(ref.types.void, [

ref.refType(ref.types.uchar),
	  voidPtr,
	  ref.refType(ref.types.uchar),
	]);
	var pcap_handlerPtr = exports.pcap_handlerPtr = ref.refType(pcap_handler);
	
	var uint8_t = exports.uint8_t = voidPtr;
	var uint8_tPtr = exports.uint8_tPtr = ref.refType(uint8_t);


/* callback */ 
	const onProto = function(id, packet) {
		if (id > 0) { console.log("Proto: "+packet+" ("+id+")") }
	}

	var callback = exports.callback = ffi.Function(ref.types.void, [
	  ref.types.int32,
	  ref.refType(uint8_t),
	]);

	var ndpi = ffi.Library('../ndpiexlib.so', {
	  init: [ref.types.void, [
	  ]],
	  setDatalinkType: [ref.types.void, [
	      pcap_tPtr,
	  ]],
	  processPacket: [ref.types.void, [
	    voidPtr,
	    uint8_t,
	  ]],
	  finish: [ref.types.void, [
	  ]],

/* APP VARS */

	var voidPtr = exports.voidPtr = ref.refType(ref.types.void);
	var u_char = exports.u_char = Struct({
	  __u_char: ref.types.uchar,
	});
	var u_charPtr = exports.u_charPtr = ref.refType(u_char);
	
	var uint8_t = exports.uint8_t = voidPtr;
	var uint8_tPtr = exports.uint8_tPtr = ref.refType(uint8_t);
	
	// var callbackPtr = ffi.Callback(ref.types.void, [ ref.types.int32, ref.refType(ref.types.uchar) ], onProto);
	// var callbackF = ffi.ForeignFunction(callbackPtr, ref.types.void, [ ref.types.int32, ref.refType(ref.types.uchar) ]);

	var callback = exports.callback = ffi.Function(ref.types.void, [
	  ref.types.int32,
	  ref.refType(ref.types.uchar),
	]);
		
	var pcap_t = exports.pcap_t = voidPtr;
	var pcap_tPtr = exports.pcap_tPtr = ref.refType(pcap_t);
	var pcap_handler = exports.pcap_handler = ffi.Function(ref.types.void, [
	  ref.refType(ref.types.uchar),
	  voidPtr,
	  ref.refType(ref.types.uchar),
	]);
	var pcap_handlerPtr = exports.pcap_handlerPtr = ref.refType(pcap_handler);
	
	// PCAP Header
	var pcap_pkthdr = exports.pcap_pkthdr = Struct({
	  'ts_sec': 'long',

var u_charPtr = exports.u_charPtr = ref.refType(u_char);
	
	var uint8_t = exports.uint8_t = voidPtr;
	var uint8_tPtr = exports.uint8_tPtr = ref.refType(uint8_t);
	
	// var callbackPtr = ffi.Callback(ref.types.void, [ ref.types.int32, ref.refType(ref.types.uchar) ], onProto);
	// var callbackF = ffi.ForeignFunction(callbackPtr, ref.types.void, [ ref.types.int32, ref.refType(ref.types.uchar) ]);

	var callback = exports.callback = ffi.Function(ref.types.void, [
	  ref.types.int32,
	  ref.refType(ref.types.uchar),
	]);
		
	var pcap_t = exports.pcap_t = voidPtr;
	var pcap_tPtr = exports.pcap_tPtr = ref.refType(pcap_t);
	var pcap_handler = exports.pcap_handler = ffi.Function(ref.types.void, [
	  ref.refType(ref.types.uchar),
	  voidPtr,
	  ref.refType(ref.types.uchar),
	]);
	var pcap_handlerPtr = exports.pcap_handlerPtr = ref.refType(pcap_handler);
	
	// PCAP Header
	var pcap_pkthdr = exports.pcap_pkthdr = Struct({
	  'ts_sec': 'long', 
	  'ts_usec': 'long',
	  'incl_len': 'int',
	  'orig_len': 'int'
	});
	
	var pktHdr = exports.pktHdr = new pcap_pkthdr;
	pktHdr = ref.refType(ref.types.void);