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\ Hypervisor Software File: buffer.fth
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\ id: @(#)buffer.fth 1.2 97/01/20
\ purpose: 
\ copyright: Copyright 1997 Sun Microsystems, Inc.  All Rights Reserved

\ Keyboard buffer definitions
\  keybuf which is defined below is scanned
\  by the refresh routine, and the keyboard-driver.  Then later
\  the keys are picked up by the monitor busywait keyboard routine, or
\  by Unix or other application programs directly.
\
\  Note that each keystroke, if typed slowly (by computer standards)
\  takes 3 bytes: a key-down, a key-up, and a keyboard-idle.  so allocate
\  three times as much room as you want to be able to type ahead.
\  typeahead won't echo immediately in the monitor, but will echo in
\  its proper place in the i/o transcript.

headerless

d# 90   constant keybufsize
keybufsize buffer: keybuf
0 	value  getptr
0 	value  putptr
0 	value  endptr

: initkeybuf ( -- )
   keybuf  is  getptr
   keybuf  is  putptr
   keybuf keybufsize + is endptr
;

\ put key into keybord buffer, ignoring overun
: bput	( key -- )	\ put key into buffer
   putptr endptr >= if
      keybuf is putptr
   then
   putptr c! putptr 1+ is putptr
;

\ clear the keyboard buffer for put task
: bputclr  ( -- )
   getptr is putptr
;

\ return the next key
: bget	( -- key )	\ Fetch a key from buffer
   getptr endptr >= if
      keybuf is getptr
   then
   getptr c@ getptr 1+ is getptr
;

\ return TRUE if keybuf is empty.
: keybuf-empty? 	( -- flag ) \ True if keybuf is empty.
   getptr putptr =
;