java - JNA communication to Native Code -

i have native function , null value in jna when attach device system think have problem in lpvoid maping jna idea appreciated.

cp210x_getproductstring( dword devicenum,lpvoid devicestring,dword options) 

1. devicenum — index of device product description string, serial number, or full path desired.
2. devicestring — variable of type cp210x_device_string returning null-terminated serial number, device description or full path string.
3. options — flag determines if devicestring contains product description, serial number, or full-path string

jna code:

public class helloworld {      public interface clibrary extends library{         clibrary instance = (clibrary) native.loadlibrary(             (platform.iswindows() ? "cp210xmanufacturing.dll" : "c"),             clibrary.class);          int cp210x_getproductstring(int dn,string [] ds,int op);     }      public static void main(string[] args) {         int dn=0;         string dsc = new string[100];         if(clibrary.instance.cp210x_getproductstring(dn, dsc,                cp210x.cp210x_return_serial_number) == cp210x.cp210x_success){         {             for(int i=0;i<dsc.length;i++)                 system.out.print(dsc[i]);             }          }     } } 

don't know if work, this description of cp210x_getproductstring think have pass byte[] length 256 function (the buffer fill string).

 int cp210x_getproductstring(int dn,byte[] ds,int op);   //use  byte[] rawstring = new byte[256];  int dn = ...;  int op = ...;  cp210x_getproductstring(dn,rawstring,op);  //you might have choose different charset here  //since don't know encoding string uses used default  string product = new string(rawstring,charset.defaultcharset());