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7 messages in net.java.dev.jna.usersRe: [jna-users] Mapping posix message...| From | Sent On | Attachments |
|---|---|---|
| Patrick Schäfer | May 8, 2009 3:53 am | |
| Timothy Wall | May 8, 2009 4:02 am | |
| Patrick Schäfer | May 8, 2009 4:50 am | |
| Daniel Kaufmann | May 8, 2009 5:35 am | |
| Timothy Wall | May 8, 2009 5:37 am | |
| Patrick Schäfer | May 8, 2009 6:35 am | |
| Timothy Wall | May 8, 2009 6:55 am |
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| Subject: | Re: [jna-users] Mapping posix message queue in C to Java | Actions... |
|---|---|---|
| From: | Timothy Wall (twal...@dev.java.net) | |
| Date: | May 8, 2009 5:37:42 am | |
| List: | net.java.dev.jna.users | |
byte[] or Pointer will both work in this case. Typically you would use com.sun.jna.Memory, not Pointer.
If the mapping were incorrect, you'd likely crash or fail in other ways. "Invalid argument" means the *value* you passed was incorrect, so that could mean a bogus flag, a bogus message ID, or a null message pointer.
On May 8, 2009, at 7:51 AM, Patrick Schäfer wrote:
According to the man page, you need to look at the value of errno (Native.getLastError()) to determine the reason for failure if the call returns -1.
thank you for your response. Native.getLastError results in error code 22 which is "Invalid argument". I guess this means the jna mapping is incorrect?
I suppose this is due to the second argument "void *msgp"? According to the documentation void* should map to Pointer like this: int msgsnd(int msqid,Pointer msgp, int msgsz, int msgflg);
But how to instantiate a pointer? all constructors seem to be package-private.
On May 8, 2009, at 6:53 AM, Patrick Schäfer wrote:
Hi,
I am sry, but I am new to JNA.
I am trying to make a mapping for posix message queues in C (sys/ msg) to Java on my unix pc. but seem to be doing something completely wrong. Maybe anyone can help me with this?
Original C declaration int msgsnd(int msqid, const void *msgp, size_t msgsz,int msgflg); int msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp,int msgflg); int msgctl(int msqid, int cmd, struct msqid_ds *buf )
My equivalent JNA mapping int msgsnd(int msqid, byte[] msgp, int msgsz, int msgflg); int msgrcv(int msqid, byte[] msgp, int msgsz, NativeLong msgtyp, int msgflg); int msgctl(int msqid, int cmd, Structure buf );
Now I am not sure which library to load. Native.loadLibrary("sys/ msg", CLibrary.class) fails with an error.
The library "c" seems to have the function msgsnd, which I tested by Function test = NativeLibrary.getInstance("c").getFunction("msgrcv");
Therefor the library file is loaded by CLibrary INSTANCE = (CLibrary) Native.loadLibrary("c", CLibrary.class);
But trying to receive oder submit messages by int rc = CLibrary.INSTANCE.msgsnd( 0x0a0001c2, "test".getBytes(), 4, IPC_CREAT | 0666);
always results in the return code -1 without any exception or any other failure. is there a way to get further debug information?
thank you very much for any help.
Patrick