Java Native Access (JNA) return types of void *

[burnumd]

Hi all,

I'm trying to access a C library in Java and, while going through the various type mappings, I found that one of the functions returns type void *. There didn't appear to be any info on the Java/Native Type Conversions page. Can I safely map to Java's void?

[H_P]

Hello burnmd,

I am also stuck at the same place.

Though its been really long since you posted the question, I was wondering if you remember the mapping.

Thanks,

H

[JosAH]

Hello burnmd,

I am also stuck at the same place.

Though its been really long since you posted the question, I was wondering if you remember the mapping.

Thanks,

H

If anything else fails cast your void* to a jlong. A jlong is a Java long and it is large enough to contain a pointer (on most architectures).

kind regards,

Jos

[H_P]

Hello JosAH,

Thank you for your quick response.
The variable void* xyz, in my the C code, can point to a data array of any size (char, short, int, long, etc.), including structures of data containing different sized members.

Can I achieve that by using jlong xyz, in jna, where it will be able to point to data array of char, short or a larger data structure?

Thanks,

Regards,

H.

[H_P]

JosAH,
How is casting *void xyz into Pointer xyz different from casting it into jlong xyz. When would you choose to use Pointer xyz v/s jlong xyz.

[JavaJuJitZu]

Hi H_P i think what JOSAH meant was that a pointer essentially contains a numerical memory reference, so a jlong should be able to preserve the information in the void*.

A quick search I have found an example of the void* being cast to a Pointer and it would seem this is the preferred method.

Documentation - jnaerator - Behaviour of JNAerator for different inputs - Project Hosting on Google Code
This is a jna generator if you have the c header files. The documentation explains the tools casting strategy. From what i have read it will translate void* to Pointer as it is the only option.

I haven't actually played with JNA so take my information as opinion only and perhaps research a little more.