2021-01-21 23:28:57 +01:00
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; FCB layout
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2021-01-05 00:29:50 +01:00
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2021-03-19 19:50:50 +01:00
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struc FCB
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FCBDRV resb 1 ; BYTE drive (0=default, 1=A:, 2=B:, ...)
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FCBFN resb 11 ; 11 BYTES filename
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FCBCLUS resw 1 ; DWORD current cluster
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FCBRN resb 1 ; BYTE record in cluster
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endstruc
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FCBSIZ equ FCB_size
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2021-02-25 01:45:56 +01:00
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section .data
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defdrv db 0
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dta dd 0
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2021-01-21 23:28:57 +01:00
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section .text
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2021-01-05 00:19:14 +01:00
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2021-01-23 18:32:53 +01:00
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; auto-complete drive field in fcb
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2021-02-25 01:45:56 +01:00
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; also logs in the drive
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; IN ds:dx far ptr FCB
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fcbdrv push ds
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push dx
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mov si, dx
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; if currently zero, ...
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mov dl, [si] ; 1-based
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2021-01-23 18:32:53 +01:00
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test dl, dl
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2021-02-25 01:45:56 +01:00
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jnz .log
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; replace with current drive
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mov dl, [cs:defdrv] ; 0-based
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2021-01-23 18:32:53 +01:00
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inc dl
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2021-02-25 01:45:56 +01:00
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mov [si], dl ; 1-based
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.log dec dl
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2021-03-19 20:26:38 +01:00
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mov ax, cs
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mov ds, ax
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2021-02-25 01:45:56 +01:00
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call logdrv ; 0-based
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pop dx
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pop ds
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; if carry flag set, resume stack at bp
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; this instant-returns some higher level procs
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jnc .ret
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mov sp, bp
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; duplicate carry bit into all 8 AL bits
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; similar to SALC instruction
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.ret sbb al, al
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ret
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; set disk transfer address
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; IN DS:DX dta ptr
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setdta mov [cs:dta], dx
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mov [cs:dta+2], ds
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ret
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; get disk transfer address
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; OUT ES:BX dta ptr
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getdta les bx, [cs:dta]
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2021-01-23 18:32:53 +01:00
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ret
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