check for a keystroke, not WAIT for a keystroke

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Diguidi

Joined: 11 Sep 2009
Posts: 9
Location: France

Diguidi 26 Sep 2009, 15:06

hi everybody ! i've a problem with a little program :

debut:
xor ah,ah
int 0x16

mov dl,al
mov ah,0x2
int 0x21

jmp debut

this program waits for a keystroke and then, displays it to the standard output.

what i want to do now, is to check for a keystroke but not wait for.

i've tried this :

debut:
mov ah,0x1
int 0x16

mov dl,al
mov ah,0x2
int 0x21

jmp debut

the problem is that, instead of show me just one character a time, i have : (if the keystroke is 'a' for example) aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...
it doesn't stop and i don't know what's going on

if anybody knows something interesting on this, i wait his answer eagerly Smile

Regards,

26 Sep 2009, 15:06

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4623
Location: Argentina

LocoDelAssembly 26 Sep 2009, 15:12

Diguidi, the problem is that Int16/AH=01 does not remove the keystroke from the buffer. The code you need is something like this:

Code:

get_keystroke:
  mov ah, 1
  int $16
  jz do_something_while_there_is_no_keystroke
; We already have our keystroke but we are going to call Int16/AH=0 to remove it (and get it again)
  xor ah, ah
  int $16

26 Sep 2009, 15:12

Diguidi

Joined: 11 Sep 2009
Posts: 9
Location: France

Diguidi 26 Sep 2009, 15:22

ok we call another function which removes the keystroke from the buffer.

there is no function which clears the buffer only ?

thanks LocoDelAssembly

26 Sep 2009, 15:22

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4623
Location: Argentina

LocoDelAssembly 26 Sep 2009, 15:42

Not sure but I wouldn't advice it as you may miss some keystrokes that way. If you need a clear procedure then you could use this:

Code:

clear_keystroke_buffer.remove:
  mov ah, 0
  int $16

clear_keystroke_buffer: ; Call here
  mov ah, 1
  int $16
  jnz .remove

  ret

26 Sep 2009, 15:42

Diguidi

Joined: 11 Sep 2009
Posts: 9
Location: France

Diguidi 26 Sep 2009, 16:15

ok thanks a lot !

26 Sep 2009, 16:15

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