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exec.asm
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exec.asm
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;
; Title: BBC Basic Interpreter - Z80 version
; Statement Execution & Assembler Module - "EXEC"
; Author: (C) Copyright R.T.Russell 1984
; Modified By: Dean Belfield
; Created: 03/05/2022
; Last Updated: 20/09/2022
;
; Modinfo:
; 27/01/1984: Version 2.1
; 02/03/1987: Version 3.0
; 11/06/1987: Version 3.1
; 03/05/2022: Modified by Dean Belfield to assemble with ZDS
; 20/09/2022: Reformatted Z80 assembler defines to make it easier to read
.ASSUME ADL = 0
INCLUDE "equs.inc"
SEGMENT CODE
XDEF XEQ
XDEF CHAIN0
XDEF RUN
XDEF SYNTAX
XDEF ESCAPE
XDEF FN
XDEF USR
XDEF STORE5
XDEF STORE4
XDEF CHECK
XDEF TERMQ
XDEF FILL
XDEF X4OR5
XDEF MUL16
XDEF CHANEL
XREF AUTO
XREF DELETE
XREF LOAD
XREF LIST_
XREF NEW
XREF OLD
XREF RENUM
XREF SAVE
XREF SOUND
XREF CLG
XREF DRAW
XREF ENVEL
XREF GCOL
XREF MODE
XREF MOVE
XREF PLOT
XREF COLOUR
XREF EXPRS
XREF HIMEM
XREF LOAD0
XREF RANDOM
XREF CLEAR
XREF ERRTRP
XREF PAGE_
XREF DATAPTR
XREF ERRLIN
XREF TRAP
XREF NXT
XREF SETLIN
XREF CLOOP
XREF OSSHUT
XREF WARM
XREF TRACEN
XREF OUTCHR
XREF PBCDL
XREF OSCLI
XREF LISTON
XREF GETVAR
XREF PUTVAR
XREF DATPTR
XREF ERROR_
XREF EXPR
XREF CREATE
XREF EXPRI
XREF BRAKET
XREF FREE
XREF OSBPUT
XREF COUNT
XREF STR
XREF HEXSTR
XREF CRLF
XREF ITEMI
XREF FINDL
XREF TEST
XREF EXPRN
XREF DLOAD5
XREF LOADN
XREF FPP
XREF SWAP
XREF GETDEF
XREF ZERO
XREF OSBGET
XREF BUFFER
XREF CONS
XREF VAL0
XREF OSLINE
XREF CLRSCN
XREF TELL
XREF SAYLN
XREF REPORT
XREF PUTPTR
XREF PUTIME
XREF PUTIMS
XREF LOMEM
XREF WIDTH
XREF OSWRCH
XREF COMMA
XREF OSCALL
XREF SFIX
XREF LOAD4
XREF PUSHS
XREF POPS
XREF LOADS
XREF PUTCSR
XREF OUT_
;
; List of token values used in this module
;
TAND: EQU 80H
TOR: EQU 84H
TERROR: EQU 85H
LINE_: EQU 86H
OFF_: EQU 87H
STEP: EQU 88H
SPC: EQU 89H
TAB: EQU 8AH
ELSE_: EQU 8BH
THEN: EQU 8CH
LINO: EQU 8DH
TO: EQU B8H
TCMD: EQU C6H
TCALL: EQU D6H
DATA_: EQU DCH
DEF_: EQU DDH
TGOSUB: EQU E4H
TGOTO: EQU E5H
TON: EQU EEH
TPROC: EQU F2H
TSTOP: EQU FAH
;
; The command table
; Commands are tokens from C6H onwards; this lookup table is used to
; run the corresponding function; Note that DATA and DEF both use the same
; code as REM
;
CMDTAB: DW AUTO ; C6H
DW DELETE ; C7H
DW LOAD ; C8H
DW LIST_ ; C9H
DW NEW ; CAH
DW OLD ; CBH
DW RENUM ; CCH
DW SAVE ; CDH
DW PUT ; CEH
DW PTR ; CFH
DW PAGEV ; D0H
DW TIMEV ; D1H
DW LOMEMV ; D2H
DW HIMEMV ; D3H
DW SOUND ; D4H
DW BPUT ; D5H
DW CALL_ ; D6H
DW CHAIN ; D7H
DW CLR ; D8H
DW CLOSE ; D9H
DW CLG ; DAH
DW CLS ; DBH
DW REM ; DCH: DATA
DW REM ; DDH: DEF
DW DIM ; DEH
DW DRAW ; DFH
DW END_ ; E0H
DW ENDPRO ; E1H
DW ENVEL ; E2H
DW FOR ; E3H
DW GOSUB ; E4H
DW GOTO ; E5H
DW GCOL ; E6H
DW IF_ ; E7H
DW INPUT ; E8H
DW LET ; E9H
DW LOCAL_ ; EAH
DW MODE ; EBH
DW MOVE ; ECH
DW NEXT ; EDH
DW ON_ ; EEH
DW VDU ; EFH
DW PLOT ; F0H
DW PRINT_ ; F1H
DW PROC ; F2H
DW READ ; F3H
DW REM ; F4H
DW REPEAT ; F5H
DW REPOR ; F6H
DW RESTOR ; F7H
DW RETURN ; F8H
DW RUN ; F9H
DW STOP ; FAH
DW COLOUR ; FBH
DW TRACE ; FCH
DW UNTIL ; FDH
DW WIDTHV ; FEH
DW CLI ; FFH: OSCLI
;
; RUN
; RUN "filename"
;
RUN: CALL TERMQ ; Standalone RUN command?
JR Z,RUN0 ; Yes, so just RUN the code
;
; CHAIN "filename"
;
CHAIN: CALL EXPRS ; Get the filename
LD A,CR ; Terminate it with a CR
LD (DE),A
CHAIN0: LD SP,(HIMEM) ; Reset SP
CALL LOAD0 ; And load the file in
;
RUN0: LD SP,(HIMEM) ; Prepare for RUN
LD IX,RANDOM ; Pointer to the RANDOM sysvar
$$: LD A, R ; Use the R register to seed the random number generator
JR Z, $B ; Loop unti we get a non-zero value in A
RLCA ; Rotate it
RLCA
LD (IX+3),A ; And store
SBC A,A ; Depending upon the C flag, this will either be 00h or FFh
LD (IX+4),A ; And store
CALL CLEAR
LD HL,0 ; Clear the error trap sysvar
LD (ERRTRP),HL
LD HL,(PAGE_) ; Load HL with the start of program memory (PAGE)
LD A,DATA_ ; The DATA token value
CALL SEARCH ; Search for the first DATA token in the tokenised listing
LD (DATPTR),HL ; Set data pointer
LD IY,(PAGE_) ; Load IY with the start of program memory
;
XEQ0: CALL NEWLIN
XEQ: LD (ERRLIN),IY ; Error pointer
CALL TRAP ; Check keyboard
XEQ1: CALL NXT
INC IY
CP ':' ; Seperator
JR Z,XEQ1
CP CR
JR Z,XEQ0 ; New program line
SUB TCMD
JR C,LET0 ; Implied "LET"
ADD A,A
LD C,A
LD B,0
LD HL,CMDTAB
ADD HL,BC
LD A,(HL) ; Table entry
INC HL
LD H,(HL)
LD L,A
CALL NXT
JP (HL) ; Execute the statement
;
;END
;
END_: CALL SETLIN ;FIND CURRENT LINE
LD A,H
OR L ;DIRECT?
JP Z,CLOOP
LD E,0
CALL OSSHUT ;CLOSE ALL FILES
JP WARM ;"Ready"
;
NEWLIN: LD A,(IY+0) ;A=LINE LENGTH
LD BC,3
ADD IY,BC
OR A
JR Z,END_ ;LENGTH=0, EXIT
LD HL,(TRACEN)
LD A,H
OR L
RET Z
LD D,(IY-1) ;DE = LINE NUMBER
LD E,(IY-2)
SBC HL,DE
RET C
EX DE,HL
LD A,'[' ;TRACE
CALL OUTCHR
CALL PBCDL
LD A,']'
CALL OUTCHR
LD A,' '
JP OUTCHR
;
;ROUTINES FOR EACH STATEMENT:
;
;OSCLI
;
CLI: CALL EXPRS
LD A,CR
LD (DE),A
LD HL,ACCS
CALL OSCLI
JR XEQ
;
;REM, *
;
EXT: PUSH IY
POP HL
CALL OSCLI
REM: PUSH IY
POP HL
LD A,CR
LD B,A
CPIR ;FIND LINE END
PUSH HL
POP IY
JP XEQ0
;
;[LET] var = expr
;
LET0: CP ELSE_-TCMD
JR Z,REM
CP ('*'-TCMD) & 0FFH
JR Z,EXT
CP ('='-TCMD) & 0FFH
JR Z,FNEND
CP ('['-TCMD) & 0FFH
JR Z,ASM
DEC IY
LET: CALL ASSIGN
JP Z,XEQ
JR C,SYNTAX ;"Syntax error"
PUSH AF ;SAVE STRING TYPE
CALL EQUALS
PUSH HL
CALL EXPRS
POP IX
POP AF
CALL STACCS
XEQR: JP XEQ
;
ASM0: CALL NEWLIN
ASM: LD (ERRLIN),IY
CALL TRAP
CALL ASSEM
JR C,SYNTAX
CP CR
JR Z,ASM0
LD HL,LISTON
LD A,(HL)
AND 0FH
OR 30H
LD (HL),A
JR XEQR
;
VAR_: CALL GETVAR
RET Z
JP NC,PUTVAR
SYNTAX: LD A,16 ;"Syntax error"
DB 21H
ESCAPE: LD A,17 ;"Escape"
ERROR0: JP ERROR_
;
;=
;
FNEND: CALL EXPR ;FUNCTION RESULT
LD B,E
EX DE,HL
EXX ;SAVE RESULT
EX DE,HL ; IN DEB'C'D'E'
FNEND5: POP BC
LD HL,LOCCHK
OR A
SBC HL,BC
JR Z,FNEND0 ;LOCAL VARIABLE
LD HL,FNCHK
OR A
SBC HL,BC
LD A,7
JR NZ,ERROR0 ;"No FN"
POP IY
LD (ERRLIN),IY ;IN CASE OF ERROR
EX DE,HL
EXX
EX DE,HL
LD DE,ACCS
LD E,B
EX AF,AF'
RET
;
FNEND0: POP IX
POP BC
LD A,B
OR A
JP M,FNEND1 ;STRING
POP HL
EXX
POP HL
EXX
CALL STORE
JR FNEND5
FNEND1: LD HL,0
ADD HL,SP
PUSH DE
LD E,C
CALL STORES
POP DE
LD SP,HL
JR FNEND5
;
;DIM var(dim1[,dim2[,...]])[,var(...]
;DIM var expr[,var expr...]
;
DIM: CALL GETVAR ;VARIABLE
JR C,BADDIM
JP Z,DIM4
CALL CREATE
PUSH HL
POP IX
LD A,(IY)
CP '('
LD A,D
JR NZ,DIM4
PUSH HL
PUSH AF ;SAVE TYPE
LD DE,1
LD B,D ;DIMENSION COUNTER
DIM1: INC IY
PUSH BC
PUSH DE
PUSH IX
CALL EXPRI ;DIMENSION SIZE
BIT 7,H
JR NZ,BADDIM
EXX
INC HL
POP IX
INC IX
LD (IX),L ;SAVE SIZE
INC IX
LD (IX),H
POP BC
CALL MUL16 ;HL=HL*BC
JR C,NOROOM ;TOO LARGE
EX DE,HL ;DE=PRODUCT
POP BC
INC B ;DIMENSION COUNTER
LD A,(IY)
CP ',' ;ANOTHER
JR Z,DIM1
CALL BRAKET ;CLOSING BRACKET
POP AF ;RESTORE TYPE
INC IX
EX (SP),IX
LD (IX),B ;NO. OF DIMENSIONS
CALL X4OR5 ;DE=DE*n
POP HL
JR C,NOROOM
DIM3: ADD HL,DE
JR C,NOROOM
PUSH HL
INC H
JR Z,NOROOM
SBC HL,SP
JR NC,NOROOM ;OUT OF SPACE
POP HL
LD (FREE),HL
DIM2: LD A,D
OR E
JR Z,DIM5
DEC HL
LD (HL),0 ;INITIALISE ARRAY
DEC DE
JR DIM2
DIM5: CALL NXT
CP ',' ;ANOTHER VARIABLE?
JP NZ,XEQ
INC IY
CALL NXT
JR DIM
;
BADDIM: LD A,10 ;"Bad DIM"
DB 21H
NOROOM: LD A,11 ;"DIM space"
ERROR1: JP ERROR_
;
DIM4: OR A
JR Z,BADDIM
JP M,BADDIM
LD B,A
LD A,(IY-1)
CP ')'
LD A,B
JR Z,BADDIM
LD HL,(FREE)
EXX
LD HL,0
LD C,H
CALL STORE ;RESERVED AREA
CALL EXPRI
EXX
INC HL
EX DE,HL
LD HL,(FREE)
JR DIM3
;
;PRINT list...
;PRINT #channel,list...
;
PRINT_: CP '#'
JR NZ,PRINT0
CALL CHNL ;CHANNEL NO. = E
PRNTN1: CALL NXT
CP ','
JP NZ,XEQ
INC IY
PUSH DE
CALL EXPR ;ITEM TO PRINT
EX AF,AF'
JP M,PRNTN2 ;STRING
POP DE
PUSH BC
EXX
LD A,L
EXX
CALL OSBPUT
EXX
LD A,H
EXX
CALL OSBPUT
LD A,L
CALL OSBPUT
LD A,H
CALL OSBPUT
POP BC
LD A,C
CALL OSBPUT
JR PRNTN1
PRNTN2: LD C,E
POP DE
LD HL,ACCS
INC C
PRNTN3: DEC C
JR Z,PRNTN4
LD A,(HL)
INC HL
PUSH BC
CALL OSBPUT
POP BC
JR PRNTN3
PRNTN4: LD A,CR
CALL OSBPUT
JR PRNTN1
;
PRINT6: LD B,2
JR PRINTC
PRINT8: LD BC,100H
JR PRINTC
PRINT9: LD HL,STAVAR
XOR A
CP (HL)
JR Z,PRINT0
LD A,(COUNT)
OR A
JR Z,PRINT0
PRINTA: SUB (HL)
JR Z,PRINT0
JR NC,PRINTA
NEG
CALL FILL
PRINT0: LD A,(STAVAR)
LD C,A ;PRINTS
LD B,0 ;PRINTF
PRINTC: CALL TERMQ
JR Z,PRINT4
RES 0,B
INC IY
CP '~'
JR Z,PRINT6
CP ';'
JR Z,PRINT8
CP ','
JR Z,PRINT9
CALL FORMAT ;SPC, TAB, '
JR Z,PRINTC
DEC IY
PUSH BC
CALL EXPR ;VARIABLE TYPE
EX AF,AF'
JP M,PRINT3 ;STRING
POP DE
PUSH DE
BIT 1,D
PUSH AF
CALL Z,STR ;DECIMAL
POP AF
CALL NZ,HEXSTR ;HEX
POP BC
PUSH BC
LD A,C
SUB E
CALL NC,FILL ;RIGHT JUSTIFY
PRINT3: POP BC
CALL PTEXT ;PRINT
JR PRINTC
PRINT4: BIT 0,B
CALL Z,CRLF
JP XEQ
;
;
ONERR: INC IY ;SKIP "ERROR"
LD HL,0
LD (ERRTRP),HL
CALL NXT
CP OFF_
INC IY
JP Z,XEQ
DEC IY
LD (ERRTRP),IY
JP REM
;
;ON expr GOTO line[,line...] [ELSE statement]
;ON expr GOTO line[,line...] [ELSE line]
;ON expr GOSUB line[,line...] [ELSE statement]
;ON expr GOSUB line[,line...] [ELSE line]
;ON expr PROCone [,PROCtwo..] [ELSE PROCotherwise]
;ON ERROR statement [:statement...]
;ON ERROR OFF
;
ON_: CP TERROR
JR Z,ONERR ;"ON ERROR"
CALL EXPRI
LD A,(IY)
INC IY
LD E,',' ;SEPARATOR
CP TGOTO
JR Z,ON1
CP TGOSUB
JR Z,ON1
LD E,TPROC
CP E
LD A,39
JR NZ,ERROR2 ;"ON syntax"
ON1: LD D,A
EXX
PUSH HL
EXX
POP BC ;ON INDEX
LD A,B
OR H
OR L
JR NZ,ON4 ;OUT OF RANGE
OR C
JR Z,ON4
DEC C
JR Z,ON3 ;INDEX=1
ON2: CALL TERMQ
JR Z,ON4 ;OUT OF RANGE
INC IY ;SKIP DELIMITER
CP E
JR NZ,ON2
DEC C
JR NZ,ON2
ON3: LD A,E
CP TPROC
JR Z,ONPROC
PUSH DE
CALL ITEMI ;LINE NUMBER
POP DE
LD A,D
CP TGOTO
JR Z,GOTO2
CALL SPAN ;SKIP REST OF LIST
JR GOSUB1
;
ON4: LD A,(IY)
INC IY
CP ELSE_
JP Z,IF1 ;ELSE CLAUSE
CP CR
JR NZ,ON4
LD A,40
ERROR2: JP ERROR_ ;"ON range"
;
ONPROC: LD A,TON
JP PROC
;
;GOTO line
;
GOTO: CALL ITEMI ;LINE NUMBER
GOTO1: CALL TERMQ
JP NZ,SYNTAX
GOTO2: EXX
CALL FINDL
PUSH HL
POP IY
JP Z,XEQ0
LD A,41
JR ERROR2 ;"No such line"
;
;GOSUB line
;
GOSUB: CALL ITEMI ;LINE NUMBER
GOSUB1: PUSH IY ;TEXT POINTER
CALL CHECK ;CHECK ROOM
CALL GOTO1 ;SAVE MARKER
GOSCHK: EQU $
;
;RETURN
;
RETURN: POP DE ;MARKER
LD HL,GOSCHK
OR A
SBC HL,DE
POP IY
JP Z,XEQ
LD A,38
JR ERROR2 ;"No GOSUB"
;
;REPEAT
;
REPEAT: PUSH IY
CALL CHECK
CALL XEQ
REPCHK: EQU $
;
;UNTIL expr
;
UNTIL: POP BC
PUSH BC
LD HL,REPCHK
OR A
SBC HL,BC
LD A,43
JR NZ,ERROR2 ;"No REPEAT"
CALL EXPRI
CALL TEST
POP BC
POP DE
JR NZ,XEQ2 ;TRUE
PUSH DE
PUSH BC
PUSH DE
POP IY
XEQ2: JP XEQ
;
;FOR var = expr TO expr [STEP expr]
;
FORVAR: LD A,34
JR ERROR2 ;"FOR variable"
;
FOR: CALL ASSIGN
JR NZ,FORVAR ;"FOR variable"
PUSH AF ;SAVE TYPE
LD A,(IY)
CP TO
LD A,36
JR NZ,ERROR2 ;"No TO"
INC IY
PUSH IX
CALL EXPRN ;LIMIT
POP IX
POP AF
LD B,A ;TYPE
PUSH BC ;SAVE ON STACK
PUSH HL
LD HL,0
LD C,H
EXX
PUSH HL
LD HL,1 ;PRESET STEP
EXX
LD A,(IY)
CP STEP
JR NZ,FOR1
INC IY
PUSH IX
CALL EXPRN ;STEP
POP IX
FOR1: PUSH BC
PUSH HL
EXX
PUSH HL
EXX
PUSH IY ;SAVE TEXT POINTER
PUSH IX ;LOOP VARIABLE
CALL CHECK
CALL XEQ
FORCHK: EQU $
;
;NEXT [var[,var...]]
;
NEXT: POP BC ;MARKER
LD HL,FORCHK
OR A
SBC HL,BC
LD A,32
JR NZ,ERROR3 ;"No FOR"
CALL TERMQ
POP HL
PUSH HL
PUSH BC
PUSH HL
CALL NZ,GETVAR ;VARIABLE
POP DE
EX DE,HL
OR A
NEXT0: SBC HL,DE
JR NZ,NEXT1
PUSH DE
LD IX,6+2
ADD IX,SP
CALL DLOAD5 ;STEP
LD A,(IX+11) ;TYPE
POP IX
CALL LOADN ;LOOP VARIABLE
BIT 7,D ;SIGN?
PUSH AF
LD A,'+' & 0FH
CALL FPP ;ADD STEP
JR C,ERROR3
POP AF ;RESTORE TYPE
PUSH AF
CALL STORE ;UPDATE VARIABLE
LD IX,12+2
ADD IX,SP
CALL DLOAD5 ;LIMIT
POP AF
CALL Z,SWAP
LD A,0+('<'-4) & 0FH
CALL FPP ;TEST AGAINST LIMIT
JR C,ERROR3
INC H
JR NZ,LOOP_ ;KEEP LOOPING
LD HL,18
ADD HL,SP
LD SP,HL
CALL NXT
CP ','
JP NZ,XEQ
INC IY
JR NEXT
;
LOOP_: POP BC
POP DE
POP IY
PUSH IY
PUSH DE
PUSH BC
JP XEQ
;
NEXT1: LD HL,18
ADD HL,SP
LD SP,HL ;"POP" THE STACK
POP BC
LD HL,FORCHK
SBC HL,BC
POP HL ;VARIABLE POINTER
PUSH HL
PUSH BC
JR Z,NEXT0
LD A,33
ERROR3: JP ERROR_ ;"Can't match FOR"
;
;FNname
;N.B. ENTERED WITH A <> TON
;
FN: PUSH AF ;MAKE SPACE ON STACK
CALL PROC1
FNCHK: EQU $
;
;PROCname
;N.B. ENTERED WITH A = ON PROC FLAG
;
PROC: PUSH AF ;MAKE SPACE ON STACK
CALL PROC1
PROCHK: EQU $
PROC1: CALL CHECK
DEC IY
PUSH IY
CALL GETDEF
POP BC
JR Z,PROC4
LD A,30
JR C,ERROR3 ;"Bad call"
PUSH BC
LD HL,(PAGE_)
PROC2: LD A,DEF_
CALL SEARCH ;LOOK FOR "DEF"
JR C,PROC3
PUSH HL
POP IY
INC IY ;SKIP DEF
CALL NXT
CALL GETDEF
PUSH IY
POP DE
JR C,PROC6
CALL NZ,CREATE
PUSH IY
POP DE
LD (HL),E
INC HL
LD (HL),D ;SAVE ADDRESS
PROC6: EX DE,HL
LD A,CR
LD B,A
CPIR ;SKIP TO END OF LINE
JR PROC2
PROC3: POP IY ;RESTORE TEXT POINTER
CALL GETDEF
LD A,29
JR NZ,ERROR3 ;"No such FN/PROC"
PROC4: LD E,(HL)
INC HL
LD D,(HL) ;GET ADDRESS
LD HL,2
ADD HL,SP
CALL NXT ;ALLOW SPACE BEFORE (
PUSH DE ;EXCHANGE DE,IY
EX (SP),IY
POP DE
CP '(' ;ARGUMENTS?
JR NZ,PROC5
CALL NXT ;ALLOW SPACE BEFORE (
CP '('
JP NZ,SYNTAX ;"Syntax error"
PUSH IY
POP BC ;SAVE IY IN BC
EXX
CALL SAVLOC ;SAVE DUMMY VARIABLES
CALL BRAKET ;CLOSING BRACKET
EXX
PUSH BC
POP IY ;RESTORE IY
PUSH HL
CALL ARGUE ;TRANSFER ARGUMENTS
POP HL
PROC5: LD (HL),E ;SAVE "RETURN ADDRESS"
INC HL
LD A,(HL)
LD (HL),D
CP TON ;WAS IT "ON PROC" ?
JP NZ,XEQ
PUSH DE
EX (SP),IY
CALL SPAN ;SKIP REST OF ON LIST
EX (SP),IY
POP DE
LD (HL),D
DEC HL
LD (HL),E
JP XEQ
;
;LOCAL var[,var...]
;
LOCAL_: POP BC
PUSH BC
LD HL,FNCHK
OR A
SBC HL,BC
JR Z,LOCAL1
LD HL,PROCHK
OR A
SBC HL,BC
JR Z,LOCAL1
LD HL,LOCCHK
OR A
SBC HL,BC
LD A,12
JP NZ,ERROR_ ;"Not LOCAL"
LOCAL1: PUSH IY
POP BC
EXX
DEC IY
CALL SAVLOC
EXX
PUSH BC
POP IY
LOCAL2: CALL GETVAR
JP NZ,SYNTAX
OR A ;TYPE
EX AF,AF'
CALL ZERO
EX AF,AF'
PUSH AF
CALL P,STORE ;ZERO
POP AF
LD E,C
CALL M,STORES
CALL NXT
CP ','
JP NZ,XEQ
INC IY