JNA Pointer retrieving value

Question

I'm using JNA to access a dll and everything work fine ... while i'm in debug !!!

The problem is when i run my java code in non debug mode.

The purpose of the dll is to be called by passing somme parameters in a string and filling a char pointer with the result.

So to retrieve the result in java i'm using a PointerByReference object. When i'm in debug there's no problem , i have got the right result but there's only one charactere in my result in a standard running process.

This is my java call :

PointerByReference EXMES = new PointerByReference();
PointerByReference SCHAINE = new PointerByReference();
DoubleByReference dateDujour = new DoubleByReference(DATEJOUR);

log.debug(String.format("Appel avec les arguments : ECHAINE=[%s]; DATEJOUR=[%s]", echaine, sdf.format(dateEngagement)));

Map<String, Object> options = new HashMap<String, Object>();
options.put(Library.OPTION_TYPE_MAPPER, W32APITypeMapper.ASCII);

log.error(String.format("Default Charset : [%s]", Charset.defaultCharset().displayName()));
Native.setProtected(true);
MyNativeLibrary library = (MyNativeLibrary) Native.loadLibrary("myLib", MyNativeLibrary.class, options);
library = (MyNativeLibrary) Native.synchronizedLibrary(library);

String chaineAscii = new String("DATE_NAISSANCE\n19780102\nMEDIA\n4\n".getBytes(Charset.forName("US-ASCII")));

log.error(String.format("ECHAINE [%s]", chaineAscii));

library.SATINTS(chaineAscii, SCHAINE, dateDujour, EXMES);

String chaineSortie = new String(SCHAINE.getPointer().getString(0, false).getBytes(Charset.forName("US-ASCII")));
String chaineExmes = new String(EXMES.getPointer().getString(0, false).getBytes(Charset.forName("US-ASCII")));

log.debug(String.format("Retour taille Prexis : SCHAINE=[%d]; EXMES=[%d]", chaineSortie.length(), chaineExmes.length()));
log.debug(String.format("Retour Prexis : SCHAINE=[%s]; EXMES=[%s]", chaineSortie, chaineExmes));

This is the extract of my C function:

#define PRX_ALPHA char
#define EALPHA PRX_ALPHA *
#define SALPHA PRX_ALPHA *

EALPHA CHAINE;
SALPHA SCHAINE;
EDATE DATEJOUR;
SALPHA EXMES;

int winapi myFunction(
CHAINE,
SCHAINE,
DATEJOUR,
EXMES
) {


// Do something with the CHAINE and DATEJOUR then fill SCHAINE and EXMES with an answer
to my call

Thnaks in advance for every help, i'm stuck

technomage · Accepted Answer · 2011-07-01 11:41:21Z

7

PointerByReference is equivalent to void** in C. This does not match your native function prototype.

String is equivalent to const char*. Any changes made by your native code to the memory pointed to by that argument will be ignored. If you want to provide your native code a buffer to populate, use either byte[] or Memory.

Memory.getString(0) or Native.toString(byte[]) may then be used to construct a Java String from the result, instead of your rather verbose String constructor.

answered Jul 1, 2011 at 11:41

technomage

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