;license:BSD-3-Clause
;minimal open/read binary file in ProDOS filesystem
;copyright (c) Peter Ferrie 2016-2018
!cpu 6502
!to "proboothd",plain
*=$800

                ;zpage usage, arbitrary selection except for the "ProDOS constant" ones
                command   = $42         ;ProDOS constant
                unit      = $43         ;ProDOS constant
                adrlo     = $44         ;ProDOS constant
                adrhi     = $45         ;ProDOS constant
                bloklo    = $46         ;ProDOS constant
                blokhi    = $47         ;ProDOS constant

                A2L       = $3e
                A2H       = $3f
                sizehi    = $53

                ;constants
                scrn2p2   = $f87b
                dirbuf    = $1e00       ;for size-optimisation

                !byte 1
                tay
-               txa
                jsr scrn2p2
                ora #$c0
                sta $be30, y
                sta slot+2
                sta entry+2
slot            lda $cfff
                sta entry+1

                lda fakeMLI_e-$100, y
                sta $be00+fakeMLI_e-fakeMLI, y
                iny
                bne -
                stx $bf30
                sty $200

opendir         ;read volume directory key block
                ldx #2

                ;include volume directory header in count

firstent        lda #>dirbuf
                sta adrhi
                sta A2H
                jsr seekread
                lda #4
                sta A2L
nextent         ldy #0

                ;match name lengths before attempting to match names

                lda (A2L), y
                and #$0f
                tax
                inx
-               cmp filename, y
                beq foundname

                ;move to next directory in this block

                clc
                lda A2L
                adc #$27
                sta A2L
                bcc +

                ;there can be only one page crossed, so we can increment instead of adc

                inc A2H
+               cmp #$ff ;4+($27*$0d)
                bne nextent

                ;read next directory block when we reach the end of this block

                ldx dirbuf+2
                ldy dirbuf+3
                bcs firstent

foundname       iny
                lda (A2L), y
                dex
                bne -
                stx $ff

                ;cache KEY_POINTER

                ldy #$11
                lda (A2L), y
                tax
                iny
                lda (A2L), y
                tay
        
readfile        jsr seekread
                inc adrhi
                inc adrhi

                ;fetch data block and read it

blockind        ldy $ff
                inc $ff
                ldx dirbuf, y
                lda dirbuf+256, y
                tay
                bne readfile
                txa
                bne readfile

readdone        jmp $2000

seekread        stx bloklo
                sty blokhi
entry           jmp $d1d1

fakeMLI         bne retcall
readblk         dey
                dey
                sty adrhi
                tay
                jsr seekread
retcall         pla
                tax
                inx
                inx
                inx
                txa
                pha
                rts
fakeMLI_e

filename        !byte filename_e - filename_b
filename_b      !text "LAUNCHER.SYSTEM" ;your start-up file, file is max 40kb
filename_e

*=$9f8
!byte $D3,$C1,$CE,$A0,$C9,$CE,$C3,$AE