2020-10-13 22:10:23 +02:00
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section .bss
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; default drive if field in FCB = 0
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defdrv: resb 1
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section .text
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; Helper function: read the drive number from FCB,
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; apply default if necessary,
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; and make it current I/O drive
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2021-01-05 00:19:14 +01:00
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_setdrv: mov dl, [es:bx] ; A=1
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2020-10-13 22:10:23 +02:00
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test dl, dl
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jnz .nofix
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mov dl, [defdrv] ; A=0
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inc dl
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2021-01-02 03:07:40 +01:00
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mov [es:bx], dl ; A=1
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2020-10-13 22:10:23 +02:00
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; now set as current i/o drive
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.nofix: dec dl ; A=0 for dsksel
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2020-12-16 00:29:35 +01:00
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jmp logdrv
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2021-01-05 00:19:14 +01:00
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; Load root directory entry
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; IN ax number of directory entry
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lddir: push ax
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mov cl, 4
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shr ax, cl
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xor dx, dx
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call maprd
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; get si to point to entry
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pop si
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mov cl, 5
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shl si, cl
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and si, 0x1FF
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add si, dskbuf
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ret
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; find next file
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fnfile: mov ax, [es:bx+FCBDEN]
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inc word [es:bx+FCBDEN]
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; bail out if we are at end of dir
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cmp ax, [bpb+BPBRDE]
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jnc .err
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; load entry and first byte
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push bx
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call lddir
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pop bx
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; next if hidden, dir or vol label
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test byte [si+0x0B], 0xDA
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jnz fnfile
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; bail out if end of dir
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mov al, [si]
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cmp al, 0
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je .err
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; next if deleted entry
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cmp al, 0xE5
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je fnfile
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clc
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ret
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.err: stc
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ret
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; initialize a FCB for directory scanning
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open: mov word [es:bx+FCBDEN], 0
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.search: call fnfile
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mov al, 0xFF
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jc .ret
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push si
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lea di, [bx+1]
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mov cx, 11
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rep cmpsb
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pop si
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jne .search
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mov al, 0
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.ret: ret
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putfn: mov cx, 11
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.loop: lodsb
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call pputc
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loop .loop
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ret
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