Java /dev/input/eventX

I answered this question on the project's issues page.

by attilapara
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; 

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;
    }