; Copyright (c) 2009-2011, Michael Alyn Miller <malyn@strangeGizmo.com>.
; All rights reserved.
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions are met:
;
; 1. Redistributions of source code must retain the above copyright notice
; unmodified, this list of conditions, and the following disclaimer.
; 2. Redistributions in binary form must reproduce the above copyright notice,
; this list of conditions and the following disclaimer in the documentation
; and/or other materials provided with the distribution.
; 3. Neither the name of Michael Alyn Miller nor the names of the contributors
; to this software may be used to endorse or promote products derived from
; this software without specific prior written permission.
;
; THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
; DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY
; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
; ======================================================================
; TASK Words
; ======================================================================
; ----------------------------------------------------------------------
; PAUSE [MFORTH] ( -- )
;
; Suspend the current task and resume execution of the next task in the
; task list. PAUSE will return to the caller when all of the tasks in
; the task list have had a chance to execute (and called PAUSE in order
; to relinquish execution to their next task).
LINKTO(LINK_TASK,0,5,'E',"SUAP")
PAUSE: ; Suspend the current task.
PUSH B ; Push the return stack pointer.
PUSH D ; Push the instruction pointer.
LXI H,0 ; Clear HL
DAD SP ; ..and get SP in HL.
MVI E,USERSAVEDSP;Put SAVEDSP variable offset into E
MOV D,B ; ..and put the Task Page into D.
SHLX ; Save the SP in SAVEDSP.
; Select the next task (which could be this task).
LHLD TICKFIRSTTASK;Get the address of the first task,
MOV A,H ; ..move the page address into A,
LHLD TICKNUMTASKS; ..get the number of tasks,
SUB L ; ..and calc the page after the last task.
DCR B ; Point B at the presumed next task,
CMP B ; ..and see if we have gone too far;
JNZ _pause1 ; ..resume that task if not,
LHLD TICKFIRSTTASK;..otherwise get the first task
MOV B,H ; ..and resume that task.
; Resume the next task.
_pause1: MVI E,USERSAVEDSP;Get SAVEDSP variable offset into E
MOV D,B ; ..and put the Task Page into D.
LHLX ; Get the saved SP from SAVEDSP
SPHL ; ..and restore SP.
MVI H,STACKGUARD; Put the stack guard into H
MVI L,STACKGUARD; ..and L,
SHLX ; ..and then save the guard to SAVEDSP.
POP D ; Pop the instruction pointer.
POP B ; Pop the return stack pointer.
NEXT
; ----------------------------------------------------------------------
; TASK [MFORTH] ( xt -- )
;
; Create a new task and prepare the task to execute xt when it is first
; resumed. xt should never return, but if it does then the task will be
; put into an infinite PAUSE loop in order to prevent the system from
; freezing.
;
; ---
; : TASK ( xt -- )
; 'FIRSTTASK @ 'NUMTASKS @ 8 LSHIFT - ( xt a-newtaskpage) 1 'NUMTASKS +!
; [HEX] 7676 OVER [HEX] 80 OR ! \ Initialize stack guard.
; 10 OVER USERBASE OR ! \ Initialize BASE.
; DUP [HEX] FA OR OVER USERSAVEDSP OR ! \ Initialize SAVEDSP.
; SWAP OVER [HEX] FE OR ! \ Push xt to the stack.
; DUP [HEX] 7F OR OVER [HEX] FC OR ! \ Push RSP to the stack.
; ['] STOPPED CFASZ + OVER [HEX] FA OR ! \ Push initial IP to the stack.
; DROP ;
LINKTO(PAUSE,0,4,'K',"SAT")
TASK: JMP ENTER
.WORD LIT,TICKFIRSTTASK,FETCH,LIT,TICKNUMTASKS,FETCH
.WORD LIT,8,LSHIFT,MINUS
.WORD ONE,LIT,TICKNUMTASKS,PLUSSTORE
.WORD LIT,07676h,OVER,LIT,080h,OR,STORE
.WORD LIT,10,OVER,LIT,USERBASE,OR,STORE
.WORD DUP,LIT,0FAh,OR,OVER,LIT,USERSAVEDSP,OR,STORE
.WORD SWAP,OVER,LIT,0FEh,OR,STORE
.WORD DUP,LIT,07Fh,OR,OVER,LIT,0FCh,OR,STORE
.WORD LIT,STOPPED,LIT,CFASZ,PLUS,OVER,LIT,0FAh,OR,STORE
.WORD DROP
.WORD EXIT
; ----------------------------------------------------------------------
; TASK-PAGE [MFORTH] ( -- a-addr )
;
; a-addr is the base address of the Task Page for the current task.
LINKTO(TASK,0,9,'E',"GAP-KSAT")
TASKPAGE: MOV H,B
MVI L,0
PUSH H
NEXT
; ======================================================================
; TASK Words (implementation details)
; ======================================================================
; ----------------------------------------------------------------------
; STOPPED [MFORTH] ( xt -- )
;
; This word never returns, but instead executes xt and then calls PAUSE
; in an infinite loop if/when that xt returns. The word is named
; "STOPPED" because the only time it will be the running word is if xt
; returns.
;
; ---
; : STOPPED ( xt -- ) EXECUTE BEGIN PAUSE AGAIN ;
LINKTO(TASKPAGE,0,7,'D',"EPPOTS")
LAST_TASK:
STOPPED: JMP ENTER
.WORD EXECUTE
_stopped1: .WORD PAUSE,branch,_stopped1
