Hi Claudio,
Thanks for you informing about new JNA version. I try to use JNA provided
API. It works well. The updated code is as following:
public SchedParameter[] getSchedulerParameters() throws LibvirtException {
IntByReference nParams = new IntByReference();
SchedParameter[] returnValue = new SchedParameter[0];
- String scheduler = libvirt.virDomainGetSchedulerType(VDP, nParams);
+ Pointer pScheduler = libvirt.virDomainGetSchedulerType(VDP,
+ nParams);
processError();
- if (scheduler != null) {
+ if (pScheduler != null) {
+ String scheduler = pScheduler.getString(0);
+ Native.free(Pointer.nativeValue(pScheduler));
virSchedParameter[] nativeParams = new
virSchedParameter[nParams.getValue()];
returnValue = new SchedParameter[nParams.getValue()];
libvirt.virDomainGetSchedulerParameters(VDP, nativeParams,
nParams);
If there is no issue. I recommend to use this solution to enhance all JNA code.
BTW:
Not all the returned String should be freed by JNA. For example, In Domain
Class, the result returned by the method getName/ getUUIDString
can't be freed. Because the reference were not allocated temporarily. We must
analyze case by case.
B.R.
Benjamin Wang
-----Original Message-----
From: Claudio Bley [mailto:cb...@av-test.de]
Sent: 2012年10月11日 23:36
To: Benjamin Wang (gendwang)
Cc: veill...@redhat.com; libvir-list@redhat.com; Yang Zhou (yangzho)
Subject: Re: [libvirt] Memory free in libvirt JNA
At Thu, 11 Oct 2012 08:37:23 +0000,
Benjamin Wang (gendwang) wrote:
>
> Hi Claudio,
> Sorry for my late response.
> I have gone through Claudio's solution. It's good. But I think this is not
> a common solution. There are two points:
> 1. This solution must use Pointerbyreference to encapsulate the
> Pointer. This is not clean.
Yes, as I said, this adds another level of indirection --- which is pretty
useless in Java.
> 2. Libvirt provides virFree method. But a common library could not
> provide memory management functions.
Sorry, I don't get your point here.
> My proposal is as following:
> 1. Add a new Class Libc.java
> public interface Libc extends Library{
> Libc INSTANCE = (Libc) Native.loadLibrary("c", Libc.class);
>
> public void free(Pointer p);
> }
Not every platform has a shared library called "c". On Windows this would be
msvcrt.dll for the Microsoft runtime. So, you would need to branch on the
platform to load whatever library seems appropriate.
Also, I just discovered that since version 3.3.0 JNA provides a public free
method itself.
Since I get crashes when using callback functions with JNA 3.2.7 in certain
circumstances it is better just to require a newer version of JNA, IMHO.
I'll post a few patches with improvements and memory fixes tomorrow.
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