[A89] Re: OSDequeue

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[A89] Re: OSDequeue


-------------------
> 
> How do you implement this and save the key press to a variable,
every
> time I do it the thing won't work!
> 
> 
> 
> 

OSdequeue for keyboard reading is very simple.

#include <system.h>
#include <kbd.h>

short int getKey(short int wait) {
    unsigned short int key = 0;
    short int done = 0;
    void *kbq = kbd_queue();

    while (!done) {
        if (!wait || !OSdequeue(&key,kbq)) {
            done = 1;
        }
    }

    return (signed short int)key;
}

It's sometimes a good idea to cast it to a signed int to avoid
warnings between signed and unsigned comparisons, which you will often
get when comparing the KEY macros, like arrow keys KEY_LEFT.

So, if you want to use that function...

void _main(void) {
    short int key;

    key = getKey(1);
}

This will wait until a key is available and return the signed
keypress, stored in the variable key local to the _main() function.

OSdequeue() will not work if you have disabled interrupts or
redirected auto-int 1. If you did this, you will have to use low-level
keyboard reading...

Hope this helps...

John David Ratliff
jdratlif@cs.indiana.edu
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