;
; Brainfuck interpreter by Thorham
;
; 68000+ AmigaOs2+
;
; Cell size is a byte
;
    incdir  "asminc:"

    include "dos/dosextens.i"
    include "lvo/lvos.i"

execBase equ 4

start

; parse command line parameter

    move.l  a0,fileName

    move.b  (a0)+,d0
    beq     exit ; no parameter

    cmp.b   #'"',d0 ; filter out double quotes
    bne     .loop

    addq.l  #1,fileName

.loop
    move.b  (a0)+,d0

    cmp.b   #'"',d0 ; filter out double quotes
    beq     .done

    cmp.b   #32,d0
    bge     .loop

.done
    clr.b   -(a0) ; end of string

; open dos library

    move.l  execBase,a6

    lea     dosName,a1
    moveq   #36,d0
    jsr     _LVOOpenLibrary(a6)
    move.l  d0,dosBase
    beq     exit

; get stdin and stdout handles

    move.l  dosBase,a6

    jsr     _LVOInput(a6)
    move.l  d0,stdIn
    beq     exit

    jsr     _LVOOutput(a6)
    move.l  d0,stdOut
    beq     exit

    move.l  stdIn,d1
    jsr     _LVOFlush(a6)

; open file

    move.l  fileName,d1
    move.l  #MODE_OLDFILE,d2
    jsr     _LVOOpen(a6)
    move.l  d0,fileHandle
    beq     exit

; examine file

    lea     fileInfoBlock,a4

    move.l  fileHandle,d1
    move.l  a4,d2
    jsr     _LVOExamineFH(a6)
    tst.w   d0
    beq     exit

; exit if the file is a folder

    tst.l   fib_DirEntryType(a4)
    bge     exit

; allocate file memory

    move.l  execBase,a6

    move.l  fib_Size(a4),d0
    beq     exit ; exit if file is empty
    clr.l   d1
    jsr     _LVOAllocVec(a6)
    move.l  d0,program
    beq     exit

; read file

    move.l  dosBase,a6

    move.l  fileHandle,d1
    move.l  program,d2
    move.l  fib_Size(a4),d3
    jsr     _LVORead(a6)
    tst     d0
    ble     exit ; exit if read didn't succeed

; close file

    move.l  fileHandle,d1
    jsr     _LVOClose(a6)
    clr.l   fileHandle

; clear tape (bss section is allocated by os but not cleared)

    lea     tape,a0
    lea     tapeEnd,a1

.loopClear
    clr.b   (a0)+
    cmp.l   a0,a1
    bne     .loopClear

; interpreter

    move.l  program,a2
    lea     tape,a3

    clr.l   d2

    move.l  a2,d6 ; start of program
    move.l  a2,d7 ; end of program
    add.l   fib_Size(a4),d7

loop
    move.b  (a2)+,d2

    cmp.b   #">",d2
    beq     .incPtr

    cmp.b   #"<",d2
    beq     .decPtr

    cmp.b   #"+",d2
    beq     .incMem

    cmp.b   #"-",d2
    beq     .decMem

    cmp.b   #".",d2
    beq     .outMem

    cmp.b   #",",d2
    beq     .inMem

    cmp.b   #"[",d2
    beq     .jmpForward

    cmp.b   #"]",d2
    beq     .jmpBack

; next command

.next
    cmp.l   d7,a2 ; test end of program
    blt     loop

; end of program reached

    bra     exit

; command implementations

.incPtr
    addq.l  #1,a3
    cmp.l   #tapeEnd,a3 ; test end of tape
    bge     exit
    bra     .next

.decPtr
    subq.l  #1,a3
    cmp.l   #tape,a3 ; test start of tape
    blt     exit
    bra     .next

.incMem
    addq.b  #1,(a3)
    bra     .next

.decMem
    subq.b  #1,(a3)
    bra     .next

.outMem
    move.l  stdOut,d1
    move.b  (a3),d2
    jsr     _LVOFPutC(a6)
    bra     .next

.inMem
    move.l  stdIn,d1
    jsr     _LVOFGetC(a6)

    cmp.b   #27,d0 ; convert escape to 0
    bne     .notEscape
    moveq   #0,d0
.notEscape
    move.b  d0,(a3)

    bra     .next

.jmpForward
    tst.b   (a3)
    bne     .next

    move.l  a2,a4
    clr.l   d3

.loopf
    cmp.l   d7,a4 ; test end of program
    bge     exit

    move.b  (a4)+,d2

    cmp.b   #"[",d2
    bne     .lf

    addq.l  #1,d3
    bra     .loopf
.lf
    cmp.b   #"]",d2
    bne     .loopf

    subq.l  #1,d3
    bge     .loopf

    move.l  a4,a2
    bra     .next

.jmpBack
    tst.b   (a3)
    beq     .next

    move.l  a2,a4
    clr.l   d3

.loopb
    move.b  -(a4),d2

    cmp.l   d6,a4 ; test start of program
    blt     exit

    cmp.b   #"]",d2
    bne     .lb

    addq.l  #1,d3
    bra     .loopb
.lb
    cmp.b   #"[",d2
    bne     .loopb

    subq.l  #1,d3
    bgt     .loopb

    move.l  a4,a2
    bra     .next

; cleanup and exit

exit
    move.l  dosBase,a6

    move.l  fileHandle,d1
    beq     .noFile
    jsr     _LVOClose(a6)
.noFile

    move.l  execBase,a6

    move.l  program,a1
    tst.l   a1
    beq     .noMem
    jsr     _LVOFreeVec(a6)
.noMem

    move.l  dosBase,a1
    tst.l   a1
    beq     .noLib
    jsr     _LVOCloseLibrary(a6)
.noLib

    rts

; data

    section data,data_p

dosBase
    dc.l    0

fileName
    dc.l    0

fileHandle
    dc.l    0

fileInfoBlock
    dcb.b   fib_SIZEOF

stdIn
    dc.l    0

stdOut
    dc.l    0

program
    dc.l    0

dosName
    dc.b    "dos.library",0

; tape memory

    section mem,bss_p

tape
    ds.b    1024*64
tapeEnd