58 lines
1.4 KiB
NASM
58 lines
1.4 KiB
NASM
; User-accessible part of FCB (12 bytes)
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%define fcb_drv 0 ; 1 byte
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%define fcb_fn 1 ; 8 bytes
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%define fcb_ext 9 ; 3 bytes
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; Drive & FS data (4 bytes)
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%define fcb_spt 12 ; byte sectors per track
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%define fcb_nos 13 ; byte number of sides/heads
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%define fcb_ss 14 ; byte sector size: 2^ss
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%define fcb_cs 15 ; byte cluster size: 2^(ss+cs)
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; Read/Write pointer (12 bytes):
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; Will be overwritten by new filename for CL=17
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%define fcb_fsize 16 ; dword file size
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%define fcb_fptr 20 ; dword handle position
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%define fcb_clus 24 ; word current cluster fptr points in
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%define fcb_co 26 ; word start sector for theoretical cluster 0
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; Link to directory item (3 bytes)
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%define fcb_ds 28 ; word directory sector
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%define fcb_do 30 ; byte directory offset
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fcb_open_rootdir:
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cmp byte [bx], 0
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jne .drivedone
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mov al, default_drive
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mov [bx], al
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.drivedone:
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mov dl, [bx]
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dec dl
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xor ax, ax
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xor dx, dx
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; set directory sector to 0 (=rootdir)
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mov [bx+fcb_ds], ax
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; load first sector
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call drive_read
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; transfer sector size
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mov ax, [diskbuf + 0x0B]
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call log2
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mov byte [bx+fcb_ss], al
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; transfer cluster size
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mov al, [diskbuf + 0x0D]
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call log2
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mov byte [bx+fcb_cs], al
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; transfer sectors per track
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mov al, [diskbuf + 0x18]
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mov byte [bx+fcb_spt], al
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; transfer number of heads/sides
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mov al, [diskbuf + 0x1A]
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mov byte [bx+fcb_nos], al
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ret
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