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Problems with JNA

3 replies [Last post]
Joined: 2009-05-13

Hi, I am new to the jna and I have the following method to define on the Java Interface that instantiates my dll and contains its methods:

<br />
DRV_EXPORT LumiStatus STDCALL LumiQueryNumberDevices(uint &nNumDevices,  char* const strIPList);<br />

First of all the jna specification states that in case of unsigned types I should use the java type correspondent to the native signed type and pass its value as a two's complement of the original value, therefore the first paramenter on the function above would be an int on java. Is this correct?

If for example I wanted to pass 3 as an argument for the first parameter, should I pass 1 (3 = 11 -> inverted = 00, 00 + 1 = 01 = 1) or 4294967293 (11 inverted considering 32 bits = 11111111111111111111111111111100 + 1 = 11111111111111111111111111111101 = 4294967293)?

Also this function returns the typedef enum below:

<br />
typedef enum tagLUMI_ERROR<br />
{<br />
	LUMI_STATUS_OK					= 0,			/* Operation completed successfully */<br />
	LUMI_STATUS_ERROR_DEVICE_OPEN			= 0x0001,		/* Could not find or open requested<br />
																biometric reader */<br />
	LUMI_STATUS_ERROR_DEVICE_CLOSE			= 0x0002,		/* Could not close biometric reader<br />
																or release allocated resources */<br />
	LUMI_STATUS_ERROR_CMD_NOT_SUPPORTED		= 0x0004,		/* This command is not supported on<br />
																current platform */<br />
	LUMI_STATUS_ERROR_COMM_LINK			= 0x0008,		/* General internal communication problem<br />
																prevented execution of command */<br />
	LUMI_STATUS_ERROR_PREPROCESSOR			= 0x0010,		/* Minimum thresholds for processing<br />
																quality were not achieved */<br />
	LUMI_STATUS_ERROR_CALIBRATION			= 0x0020,		/* Calibration cycle failed due to<br />
																inoperable hardware state */<br />
	LUMI_STATUS_ERROR_BUSY				= 0x0040,		/* Device is busy processing previous<br />
																command */<br />
	LUMI_STATUS_ERROR_INVALID_PARAMETER		= 0x0080,		/* Parameter or input is out of range */<br />
	LUMI_STATUS_ERROR_TIMEOUT			= 0x0100,		/* Event did not occur within programmed<br />
																time interval */<br />
	LUMI_STATUS_ERROR_INVALID_TEMPLATE		= 0x0200,		/* Supplied input template is invalid */<br />
	LUMI_STATUS_ERROR_MEMORY_ALLOCATION		= 0x0400,		/* Unable to allocate memory */<br />
	LUMI_STATUS_ERROR_INVALID_DEVICE_ID		= 0x0800,		/* Invalid connection handle */<br />
	LUMI_STATUS_ERROR_INVALID_CONNECTION_ID		= 0x1000,		/* Invalid instance ID */<br />
	LUMI_STATUS_ERROR_CONFIG_UNSUPPORTED    	= 0x2000,		/* Current configuration or policy does not<br />
																support the function that was just called */<br />
	LUMI_STATUS_UNSUPPORTED				= 0x4000,		/* The function is not currently supported by the SDK*/<br />
	LUMI_STATUS_INTERNAL_ERROR			= 0x8000,		/* An internal error occurred */<br />
	LUMI_STATUS_INVALID_PARAMETER			= 0x8001,		/* Invalid parameter or non allocated buffer passed to function*/<br />
	LUMI_STATUS_DEVICE_TIMEOUT			= 0x8002,		/* Biometric sensor is accessed by another process */<br />
	LUMI_STATUS_INVALID_OPTION			= 0x8004,		/* Invalid option, invalid argument, or invalid<br />
																argument size passed to function LumiSetOption*/<br />
	LUMI_STATUS_ERROR_MISSING_SPOOFTPL          	= 0x8008,       	/* Missing Spoof template from Composite image or ANSI<br />
																378 Template */<br />
	LUMI_STATUS_CANCELLED_BY_USER		       	= 0x8010,		/* If the LumiPresenceDetectCallback returns -2, then<br />
																the SDK will return this status code during capture*/<br />
	LUMI_STATUS_INVALID_FOLDER			= 0x8020,		/* Function LumiSetDCOptions returns this code if the folder<br />
																doesn't exist */<br />
	LUMI_STATUS_DC_OPTIONS_NOT_SET			= 0x8040,		/* Function LumiSaveLastCapture returns this code if the<br />
																(Data Collection) option was not set OR set to a non<br />
																existing folder */<br />
} LumiStatus;<br />

What is the equivalent of this enum in java?

Should I create a enum with the same members and values as above, or perhaps a class that extends enum and has variables with the same name and value as above?

Please help me.


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Joined: 2009-05-30

According to the JNA mailing list, Native-side C enum are integer values. Java-side, they are enum objects. You have to tell JNA how to translate to the native value,
either with a TypeMapper or by making the enum objects implement NativeMapped.

Joined: 2005-11-01

In C, an enum is a way of managing aliases for numbers, but fundamentally they are all int values.
In Java, an enum is a group of objects (you cannot set the ordinal value of the enums, but can associate a value with each enum value)

AFAIK, the simplest thing to do is to treat the enum as an int value. You can then have a Map or Map if you like.

Joined: 2009-05-13

I've done a lot of search through the web on this subject lately and now it seems that maybe I might be better off using a helper program that I made sometime ago, that encapsulated some of the functions of this dll and made them simpler to use. Therefore instead of using functions that return the LumiStatus enum I would be using functions that return more common types like int or uchar*.

The thing is that those functions are inside a C++ class (code below). Is there a way to use jna with this class, or is it better if I just put those methods outside of the class and use them as standard C functions?


#include "stdafx.h"
#include "LumiAPI.h"
#include "LumidigmException.h"

using namespace std;
using namespace System::Runtime::InteropServices;

namespace ItautecLumidigmHelper
class LumidigmHelper

// Struct que contém os dados das imagens capturadas pelo Lumidigm.
struct LumidigmImageData
uint imageWidth; // Largura da imagem
uint imageHeight; // Altura da imagem
uint imageBPP; // Bits per pixel da imagem
uint imageDPI; // DPI da imagem

// Essa função verifica quantos dispositivos estão conectados com o
// computador no qual ela está sendo executada.
// @return O número de dispositivos da forma uint.
static uint getNumConnectedDevices()
LumiStatus status;
uint numDevices;

status = LumiQueryNumberDevices(numDevices, "");

if (status != LUMI_STATUS_OK)
throw LumidigmException(status);

return numDevices;

// Construtor
// OBS: Esse construtor assume que o dispositivo a ser inicializado é o de
// número 0.

// Construtor
// @param uint DeviceNumber Número do dispositivo a ser inicializado.
LumidigmHelper(uint deviceNumber);

// Captura a imagem do dedo do usuário e gera um novo template.
// @return o novo template gerado.
uchar* generateTemplate();

// Captura a imagem do dedo do usuário e realiza um match entre o template
// gerado a partir do dedo do usuário e o template fornecido.
// @param uchar* fingerTemplate Template a ser comparado.
// @return score da comparação entre os dois templates.
uint verify(uchar* fingerTemplate, uint templateSize);

// Captura uma imagem com o Lumidigm.
// @return string de dados que representa a imagem capturada.
uchar* capturaImagem();

// Retorna dados sobre as imagens capturadas, como altura, largura, etc.
// @return Struct do tipo LumidigmImage com os dados sobre as
// imagens capturadas.
LumidigmImageData getImgData();

// Destructor
// Fecha a conexão com o Lumidgm.


LUMI_HANDLE deviceHandle;

LumidigmImageData imgData;