Invalid Argument exception

[shahbaz-momi]

Hello, currently I have an N-Trig Multitouch panel hooked to the event file /dev/input/event4, and I am trying to use your library to access it. I have included all of the natives and such in the java.library.path but am getting this error even when superuser. The exception:

java.io.IOException: Invalid argument
at sun.nio.ch.FileDispatcherImpl.read0(Native Method)
at sun.nio.ch.FileDispatcherImpl.read(FileDispatcherImpl.java:46)
at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223)
at sun.nio.ch.IOUtil.read(IOUtil.java:197)
at sun.nio.ch.FileChannelImpl.read(FileChannelImpl.java:149)
at com.dgis.input.evdev.EventDevice.readEvent(EventDevice.java:269)
at com.dgis.input.evdev.EventDevice.access$1(EventDevice.java:265)
at com.dgis.input.evdev.EventDevice$1.run(EventDevice.java:200)
EVENT: null
Exception in thread "Thread-0" java.lang.NullPointerException
at com.asdev.t3.Bootstrap$1.event(Bootstrap.java:41)
at com.dgis.input.evdev.EventDevice.distributeEvent(EventDevice.java:256)
at com.dgis.input.evdev.EventDevice.access$2(EventDevice.java:253)
at com.dgis.input.evdev.EventDevice$1.run(EventDevice.java:201)
Do you why this happens? Thanks

[shahbaz-momi]

Also, it seems to corrupt my filesystem a little bit which I then later have to fix by using fsck

[LostParrot]

Hi, I tried to use this library on a Raspberry Pi and I got the same exception, but I figured out the source of the problem and managed to get it work. Basically, the problem is that this library is written for 64 bit CPU/OS only. Explanation:

The input_event structure looks like this (source):

struct input_event {
    struct timeval time;
    unsigned short type;
    unsigned short code;
    unsigned int value;
};

Here we have timeval, which has the following members (source):

time_t         tv_sec      seconds
suseconds_t    tv_usec     microseconds

These two types are represented differently on a 32 bit and a 64 bit system.

The solution:

1. Change the size of input_event from 24 to 16 bytes:

   change line 34 of the source file evdev-java/src/com/dgis/input/evdev/InputEvent.java from this:

   public static final int STRUCT_SIZE_BYTES = 24;

   to this:

   public static final int STRUCT_SIZE_BYTES = 16;

2. Change the parse function in the same source file as follows:

   public static InputEvent parse(ShortBuffer shortBuffer, String source) throws IOException {
       InputEvent e = new InputEvent();
       short a,b,c,d;
   
       a=shortBuffer.get();
       b=shortBuffer.get();
       //c=shortBuffer.get();
       //d=shortBuffer.get();
       e.time_sec = (b<<16) | a; //(d<<48) | (c<<32) | (b<<16) | a;
       a=shortBuffer.get();
       b=shortBuffer.get();
       //c=shortBuffer.get();
       //d=shortBuffer.get();
       e.time_usec = (b<<16) | a; //(d<<48) | (c<<32) | (b<<16) | a;
       e.type = shortBuffer.get();
       e.code = shortBuffer.get();
       c=shortBuffer.get();
       d=shortBuffer.get();
       e.value = (d<<16) | c;
       e.source = source;
   
       return e;
   }

I hope this will be useful also for other people.

[RomDep]

Hi, I have the same problem on a SECO SBC62, which has an armv7l 32-bit arch...
But your solution doesn't work for me !
Do you have any hints for me to help me find a way to make it work ?

[LostParrot]

Hi, maybe you should comment out everything in the above parse function, except the initialization of the variable e and the return e. If it gives no exception, then maybe you can debug it manually by checking the size and content of the shortBuffer argument in run-time, if that is possible in your set-up.

[RomDep]

Hi thanks for your help. Actually, it was a compilation and export to the board problem. Your solution was exactly what was required. A switch using System.getProperty("os.arch") could be a permanent fix of this issue.