javacjnaftdijnaerator

JNA: conversion between void** and void*

I generated a JNA from a header file and here is the two functions of interest.

FT_STATUS FT_OpenEx(void* pArg1,int Flags,void** pHandle);

FT_STATUS FT_Close(void* ftHandle);

And here is how it got converted in the JNA.

int FT_OpenEx(String pArg1, int Flags, PointerByReference pHandle);

int FT_Close(Pointer ftHandle);

I call FT_OpenEx passing a PointerByReference and then get the pointer and pass it to FT_Close. The code executes but I receive an FT_INVALID_HANDLE, which is returned by FT_Close.

Here is the java code

 Pointer handle;
 PointerByReference pbr = new PointerByReference();
 int status = Ftd2xxLibrary.INSTANCE.FT_OpenEx(serialNumber, Ftd2xxLibrary.FT_OPEN_BY_SERIAL_NUMBER, pbr);

 handle = pbr.getPointer();

 status = Ftd2xxLibrary.INSTANCE.FT_Close(handle);

My guess is that the pointer I pass on to FT_Close is not actually pointing at the right address. What is the proper way to pass from void** to void* in java using JNA?

Solution

  • Turns out the error was on

    handle = pbr.getPointer();

    It should be

    handle = pbr.getValue();