Hi,
Some days ago, searching for info on Gforth's multitasking, I found a
link Anton Ertl mentioned in <comp.alt.forth>
(http://compgroups.net/comp.lang.forth/looking-for-more-gforth-documentation/1259909):
<http://egesund.org/forth/forth.htm>.
With the help of that little example and Gforth's <tasker.fs>, I did
many tries and finally understood how the thing works. I wrote four
little demos. The last one shows two counters on the screen while the
input line works normally.
One interesting problem was how to manage the cursor: the word used to
get the current cursor position, 'xy', uses 'key', so the normal (say
"non-multitasking") 'key' has to be reactivated before executing 'xy'.
Another problem was at first the tasks run only when a key was pressed.
The reason was Gforth's 'u8key' is not affected by changing the action
of 'key' because it's written with 'defers key'. Is there any reason
for that? Finally I decided to write a modified version of 'u8key',
'task-u8key'.
Since multitasking is not documented in Gforth (yet), I think my tries
can be useful to others. I will publish them in my website as soon as
possible and will announce here; but here you are the last one, the most
interesting:
========================= START OF CODE ========================
\ multitasking_test_03.fs
\
\ Test program
\ to learn how to use the Gforth's multitasking.
\
\ By Marcos Cruz (programandala.net)
\
\ Change log:
\
\ 2013-06-27 Start. First working version.
\ 2013-07-09 <galope/xy.fs> temporarily merged.
\ **************************************************************
\ Requirements
\ Save the original behaviour of 'key',
\ before the tasker changes it:
' key defer@ constant ((key))
require tasker.fs
require random.fs
false [if]
require galope/xy.fs
[else]
\ ----8<--------------------------------------------------------
\ galope/xy.fs
\ Current cursor coordinates
\ This file is part of Galope
\ (Gforth Accessory Library of Particular Elements)
\ Extracted and modified from:
\ ansi.4th
\ ANSI Terminal words for kForth
\ Copyright (c) 1999--2004 Krishna Myneni
\ Creative Consulting for Research and Education
\ This software is provided under the terms of the GNU
\ General Public License.
\ Modifications:
\ Copyright (C) 2012 Marcos Cruz (programandala.net)
\ History
\ 2012-04 Extracted from a program of mine.
\ 2012-04-29 Added 'at-x' and 'at-y'.
\ 2012-05-08 'at-x' and 'at-y' moved to their own files.
\ 2013-06-26 Fixed some comments.
\ 2013-06-26 Gforth's 'esc[' used instead of 'ansi_escape'.
base @ decimal
: number<c> ( c -- n )
\ Read a decimal numeric entry delimited by character c.
\ xxx todo move this word to its own file:
\ xxx todo choose a better name?:
\ number/c
\ keys/c>decimal
\ keys>#
\ keys>number
\ keys>#number
\ xxx todo no final char: finish at the first non-digit instead
>r 0
begin key dup r@ <>
while swap 10 * swap '0' - +
repeat r> 2drop
;
: xy ( -- u1 u2 )
\ Return the current cursor position.
\ u1 = current column
\ u2 = current line
esc[ ." 6n"
key key 2drop \ erase: <esc> [
';' number<c> 'R' number<c>
1- swap 1-
;
base !
\ ----8<--------------------------------------------------------
[then]
\ **************************************************************
\ Main
16 newtask constant taksk_1_id
16 newtask constant taksk_2_id
: task-u8key ( -- u )
\ Multitasking version of Gforth's u8key (defined in <utf-8.fs>).
\ Changes: 'defers key' to 'task-key'.
task-key dup max-single-byte u< ?exit \ special case ASCII
dup $ff = ?exit \ special resize character
dup $c2 u< if utf-8-err throw then \ malformed character
$7f and $40 >r
begin dup r@ and
while
r@ xor
6 lshift r> 5 lshift >r >r task-key
dup $c0 and $80 <> if utf-8-err throw then
$3f and r> or
repeat rdrop
;
: untasked_output ( -- )
\ Set the basic output words to their non-multitasking defaults.
['] (emit) is emit
['] (type) is type
;
: tasked_output ( -- )
\ Set the basic output words to their multitasking versions.
['] task-emit is emit
['] task-type is type
;
: untasked_key ( -- )
\ Set 'key' to its non-multitasking default.
((key)) is key
;
: untasked_xkey ( -- )
\ Set 'xkey' to its non-multitasking default.
['] u8key is xkey
;
: untasked_input ( -- )
\ Set the basic input words to their non-multitasking defaults.
untasked_key untasked_xkey
;
: tasked_key ( -- )
\ Set 'key' to its multitasking version.
['] task-key is key
;
: tasked_xkey ( -- )
\ Set 'xkey' to its multitasking version.
['] task-u8key is xkey
;
: tasked_input ( -- )
\ Set the basic input words to their multitasking versions.
tasked_key tasked_xkey
;
' page alias (page) \ original 'page'
defer page
: tasked_page ( -- )
\ Safe version of 'page' when multitasking.
untasked_output (page) tasked_output
;
' tasked_page is page
: (xy) ( -- u1 u2 )
\ Safe version of 'xy' when multitasking.
untasked_key xy tasked_key
;
2048 value /ms \ interval
: time? ( -- flag )
\ Is it time to execute a task?
utime drop /ms mod 0=
;
variable counter1
: (task1) ( -- )
1 counter1 +!
untasked_output
(xy) 0 0 at-xy counter1 ? at-xy
tasked_output
;
: task1 ( -- )
taksk_1_id activate
begin time? if (task1) then pause again
;
variable counter2
: (task2) ( -- )
10 counter2 +!
untasked_output
(xy) 10 10 at-xy counter2 ? at-xy
tasked_output
;
: task2 ( -- )
taksk_2_id activate
begin time? if (task2) then pause again
;
: run ( -- )
page task1 task2
untasked_output
0 rows 3 - at-xy
." The counters run even when no key is pressed."
tasked_input
;
page
.( multitasking_test_03.fs) cr
.( Type RUN to start the demo.) cr cr
========================== END OF CODE =========================
I'd appreciate any comment, correction or improvement.
Has someone written other examples or documentation on multitasking?
Thank you.
Marcos
--
http://programandala.net
