msbasic/flow2.s

216 lines
5.1 KiB
ArmAsm
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2008-10-18 07:43:05 +00:00
.segment "CODE"
; ----------------------------------------------------------------------------
; "RUN" COMMAND
; ----------------------------------------------------------------------------
RUN:
bne L27CF
jmp SETPTRS
L27CF:
jsr CLEARC
jmp L27E9
; ----------------------------------------------------------------------------
; "GOSUB" STATEMENT
;
; LEAVES 7 BYTES ON STACK:
; 2 -- RETURN ADDRESS (NEWSTT)
; 2 -- TXTPTR
; 2 -- LINE #
; 1 -- GOSUB TOKEN
; ----------------------------------------------------------------------------
GOSUB:
lda #$03
jsr CHKMEM
lda TXTPTR+1
pha
lda TXTPTR
pha
lda CURLIN+1
pha
lda CURLIN
pha
lda #TOKEN_GOSUB
pha
L27E9:
jsr CHRGOT
jsr GOTO
jmp NEWSTT
; ----------------------------------------------------------------------------
; "GOTO" STATEMENT
; ALSO USED BY "RUN" AND "GOSUB"
; ----------------------------------------------------------------------------
GOTO:
jsr LINGET
jsr REMN
lda CURLIN+1
cmp LINNUM+1
bcs L2809
tya
sec
adc TXTPTR
ldx TXTPTR+1
bcc L280D
inx
bcs L280D
L2809:
lda TXTTAB
ldx TXTTAB+1
L280D:
.ifdef KBD
jsr LF457
bne UNDERR
.else
jsr FL1
bcc UNDERR
.endif
lda LOWTRX
sbc #$01
sta TXTPTR
lda LOWTRX+1
sbc #$00
sta TXTPTR+1
L281E:
rts
; ----------------------------------------------------------------------------
; "POP" AND "RETURN" STATEMENTS
; ----------------------------------------------------------------------------
POP:
bne L281E
lda #$FF
.ifdef CONFIG_2
sta FORPNT+1 ; bugfix, wrong in AppleSoft II
.else
sta FORPNT
.endif
jsr GTFORPNT
txs
cmp #TOKEN_GOSUB
beq RETURN
ldx #ERR_NOGOSUB
.byte $2C
UNDERR:
ldx #ERR_UNDEFSTAT
jmp ERROR
; ----------------------------------------------------------------------------
SYNERR2:
jmp SYNERR
; ----------------------------------------------------------------------------
RETURN:
pla
pla
sta CURLIN
pla
sta CURLIN+1
pla
sta TXTPTR
pla
sta TXTPTR+1
; ----------------------------------------------------------------------------
; "DATA" STATEMENT
; EXECUTED BY SKIPPING TO NEXT COLON OR EOL
; ----------------------------------------------------------------------------
DATA:
jsr DATAN
; ----------------------------------------------------------------------------
; ADD (Y) TO TXTPTR
; ----------------------------------------------------------------------------
ADDON:
tya
clc
adc TXTPTR
sta TXTPTR
bcc L2852
inc TXTPTR+1
L2852:
rts
; ----------------------------------------------------------------------------
; SCAN AHEAD TO NEXT ":" OR EOL
; ----------------------------------------------------------------------------
DATAN:
ldx #$3A
.byte $2C
REMN:
ldx #$00
stx CHARAC
ldy #$00
sty ENDCHR
L285E:
lda ENDCHR
ldx CHARAC
sta CHARAC
stx ENDCHR
L2866:
lda (TXTPTR),y
beq L2852
cmp ENDCHR
beq L2852
iny
cmp #$22
.ifndef CONFIG_11
beq L285E
bne L2866
.else
bne L2866
beq L285E
.endif
; ----------------------------------------------------------------------------
; "IF" STATEMENT
; ----------------------------------------------------------------------------
IF:
jsr FRMEVL
jsr CHRGOT
cmp #TOKEN_GOTO
beq L2884
lda #TOKEN_THEN
jsr SYNCHR
L2884:
lda FAC
bne L288D
; ----------------------------------------------------------------------------
; "REM" STATEMENT, OR FALSE "IF" STATEMENT
; ----------------------------------------------------------------------------
REM:
jsr REMN
beq ADDON
L288D:
jsr CHRGOT
bcs L2895
jmp GOTO
L2895:
jmp EXECUTE_STATEMENT
; ----------------------------------------------------------------------------
; "ON" STATEMENT
;
; ON <EXP> GOTO <LIST>
; ON <EXP> GOSUB <LIST>
; ----------------------------------------------------------------------------
ON:
jsr GETBYT
pha
cmp #TOKEN_GOSUB
beq L28A4
L28A0:
cmp #TOKEN_GOTO
bne SYNERR2
L28A4:
dec FAC_LAST
bne L28AC
pla
jmp EXECUTE_STATEMENT1
L28AC:
jsr CHRGET
jsr LINGET
cmp #$2C
beq L28A4
pla
L28B7:
rts