Access to the DLL library made in Delphi from Java

Question

I am developing a tool for biometric recognition using the SDK provided in DLL format, developed in Delphi. For DLL access from Java, I am using JNA.

The digital template (the most important part) is an object that refers to this excerpt (in Delphi):

type
  CIS_Digital = packed record
    intSize: integer;
    pDigital: Pointer
  end;

pCIS_Digital = ^CIS_Digital;

How to develop something equivalent in Java?

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Basically, I need to call the following DLL functions:

SDK_CIS_Iniciar(int cnpj, int detectaFake);
SDK_CIS_LerDigital(pCIS_Digital digital);
SDK_CIS_CompararDigital(pCIS_Digital amostra1, pCIS_Digital amostra2);
SDK_CIS_Finalizar();

Looking at the example provided, developed in Delphi, I saw that the object pCIS_Digital, past SDK_CIS_LerDigital() and SDK_CIS_CompararDigital(), is the type (type) declared in the code snippet above.

In the same example, before calling the method SDK_CIS_LerDigital(), the object pCIS_Digital is instantiated and goes empty where it is then "filled" through the function.

The reader is the Techmag Bioflex, which is based on Futronic readers (FS-80).

Searching, I saw that the object pCIS_Digital (from the code snippet), access the memory to read the information the reader writes to it.

After a lot of research, think that I must develop some equivalent object in Java, extending from the classes Structure or Memory, jna.

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Update: Information about my code

I read and store my fingerprint twice using the method SDK_CIS_LerDigital, then compare the two using the method SDK_CIS_CompararDigital, who always returns 0 (unexecuted command).

"Printei" the objects intSize and pDigital after reading the digital, intSize returns 0 and pDigital returns null.

Interface with DLL methods:

public interface SDK_CIS extends StdCallLibrary {

static SDK_CIS INSTANCE = (SDK_CIS) Native.loadLibrary("SDK_CIS", SDK_CIS.class);

    public String SDK_CIS_Versao();

    public String SDK_CIS_Retorno(int resposta);

    public int SDK_CIS_Iniciar(long cnpj, int fake);

    public int SDK_CIS_Finalizar();

    public int SDK_CIS_LerDigital(CIS_Digital.ByReference digital);

    public int SDK_CIS_CancelarLeitura();

    public int SDK_CIS_CompararDigital(CIS_Digital.ByReference pAmostra1, CIS_Digital.ByReference pAmostra2);
}

Class extending Structure, referring to the Cis_digital object:

public class CIS_Digital extends Structure {

    public static class ByReference extends CIS_Digital implements Structure.ByReference {}

    public int intSize;
    public Pointer pDigital;

    @Override
    protected List<String> getFieldOrder() {
        return Arrays.asList("intSize", "pDigital");
    }
}

Method responsible for reading twice any digital and comparing them:

public void leEcomparaDigitais() {

        SDK_CIS leitor = SDK_CIS.INSTANCE;

        try {
            // TROQUEI MEU CNPJ POR ZEROS, PARA NÃO EXPOR MINHA LICENÇA    
            leitor.SDK_CIS_Iniciar(Long.parseLong("00000000000000"), 0);

            CIS_Digital.ByReference amostra1 = new CIS_Digital.ByReference();

            leitor.SDK_CIS_LerDigital(amostra1);

            try {
                // AGUARDA 1 SEGUNDO PARA LER PELA SEGUNDA VEZ
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            CIS_Digital.ByReference amostra2 = new CIS_Digital.ByReference();

            leitor.SDK_CIS_LerDigital(amostra2);

            int resp = leitor.SDK_CIS_CompararDigital(amostra1, amostra2);

            // EXIBE RESPOSTA
            // 0 -> COMANDO NAO EXECUTADO
            // 1 -> COMANDO EXECUTADO COM SUCESSO
            System.out.println(resp);

        } finally {
            leitor.SDK_CIS_Finalizar();
        }
    }

Answer 1

This may be an error due to calling convention of the functions in the DLL.

Assuming you have the original DLL source code in Delphi, you can change the calling convention functions including the clause stdcall at the end of the definition, for example:

function foobar( x: Integer ): Integer; stdcall;

I hope it will be useful!