Lay out skeletons for FCB handling
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31c6ef5876
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5
Makefile
5
Makefile
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@ -6,10 +6,11 @@ QEMU = qemu-system-i386
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QEMU_ARGS = $(addprefix --option-rom ,$(ROMS))
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VERSION = $(shell git log -1 --format=%cd --date=format:%Y%m%d)
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LABEL = RDOS $(VERSION)
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PRODUCT = rdos
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LABEL = $(PRODUCT) $(VERSION)
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NASM = nasm
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NASM_ARGS = -s -Ilib -DVERSION=$(VERSION)
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NASM_ARGS = -s -Ilib -DPRODUCT=$(PRODUCT) -DVERSION=$(VERSION)
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KVM = $(shell test -w /dev/kvm && echo 1)
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@ -14,6 +14,9 @@ bootsect: equ 0x7C00 ; our origin before reloc
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%include "inc/bpb.asm"
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%define V 0x %+ VERSION
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dd V, V
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times ( 0x0B - ($-$$) ) db 0
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params: times bpb_size db 0
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@ -22,12 +22,18 @@ print_banner: mov si, banner
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cmp al, 0x0D
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jnz .loop
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call dskrst
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mov dl, 0
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call dsksel
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hlt: hlt
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jmp hlt
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banner: db "rdos kernel", 0x0A, 0x0D
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%defstr VERSIONSTR VERSION
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banner: db "RDOS ", VERSIONSTR, 0x0A, 0x0D
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end: align 512
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%include "kernel/drive.asm"
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section .bss
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167
kernel/drive.asm
167
kernel/drive.asm
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@ -1,159 +1,40 @@
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section .bss
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drives: equ 16
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; ptr into currently selected drive
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drive_ptr: resw 1
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drive_table: resb (drives * drive_size)
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; DX and CX for int 13 CHS access
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chs_dx: resw 1
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chs_cx: resw 1
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; drive selected for I/O
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dsknum: resb 1
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; current sector number
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dskseek: resd 1
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; disk buffer for I/O operations
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diskbuf: resb 1024
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dskbuf: resb 512
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section .text
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drives_init: ; CX = number of floppy drives in the system
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int 0x11
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mov cl, 6
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shr ax, cl
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inc ax
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and ax, 3
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mov cx, ax
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mov bx, drive_table
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xor dx, dx
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.loop: push cx
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push dx
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mov [bx+drive.biosnum], dl
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mov byte [bx+drive.flag], 1 ; 1 = drive letter used
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; query bios for floppy format
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mov ah, 8
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push bx
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int 0x13
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pop bx
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; set up defaults if invalid data or fail
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jc .defs
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test cx, cx
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jnz .load
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.defs: ; use defaults: 360k, 40 cyl, 9 sects
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les di, [0x1e * 4]
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mov cx, 0x270
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mov dh, 1
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.load: ; copy dpt
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push es
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push ds
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pop es
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pop ds
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push cx
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mov si, di
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lea di, [bx+drive.dpt]
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mov cx, 11
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rep movsb
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pop cx
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; restore ds
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push cs
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pop ds
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; get and save number of cylinders
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mov ax, cx
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xchg al, ah
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rol ah, 1
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rol ah, 1
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and ax, 0x03FF
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inc ax
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mov [bx+drive.cylinders], ax
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; save spt
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mov ax, cx
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and al, 0x3F
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mov [bx+drive.dpt+dpt.lastsector], al
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; multiply with heads and save sectors per cylinder
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inc dh
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mul dh ; ax = al * dh
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mov [bx+drive.spc], ax
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; advance loop
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pop dx
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pop cx
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inc dl
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add bx, drive_size
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loop .loop
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ret
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ret: ret
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; select drive
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; IN dl drive number
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drive_select: xor dh, dh
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mov ax, drive_size
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mul dx
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add ax, drive_table
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mov word [drive_ptr], ax
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ret
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; reset currently selected drive
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drive_reset: mov bx, [drive_ptr]
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mov dl, [bx+drive.biosnum]
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; our ptr = CX:BX
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lea bx, [bx+drive.dpt]
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mov cx, ds
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; toggle in our ptr
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mov si, [0x1E*4]
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xchg bx, [si]
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xchg cx, [si+2]
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; do the call
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xor ax, ax
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int 0x13
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pushf
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; restore original ptr
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xchg bx, [si]
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xchg cx, [si+2]
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; pass int 13 flags
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popf
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ret
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; query status of selected drive
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; OUT ah
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drive_status: mov bx, [drive_ptr]
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mov dl, [bx+drive.biosnum]
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mov ah, 1
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int 0x13
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ret
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; set sector for read/write operation
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; IN dx:ax 32-bit sector number
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drive_seek: mov bx, [drive_ptr]
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div word [bx+drive.spc]
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xchg ax, dx
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; dx = cylinder, ax = head * spt + sector
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div byte [bx+drive.dpt+dpt.lastsector]
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; dx = cylinder, al = head, ah = sector
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xchg dl, dh
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dsksel: cmp dl, 1
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jnc ret
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mov al, dl
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and al, 0x02
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ror dl, 1
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ror dl, 1
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or dl, ah
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inc dx
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; al: head number
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; dh bit 0-7: cylinder bits 0-7
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; dl bit 0-5: sector bits 0-5
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; dl bit 6-7: cylinder bits 8-9
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xchg al, ah
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mov al, [bx+drive.biosnum]
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; store
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mov word [chs_dx], ax
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mov word [chs_cx], dx
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cmp dl, byte [dsknum]
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je ret
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call dskrst
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int 3
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ret
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drive_read: mov ax, 0x0201
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mov cx, [chs_cx]
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mov dx, [chs_dx]
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mov bx, diskbuf
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int 0x13
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dskrst: call flush
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mov ax, 0xFFFF
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mov [dsknum], al
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mov [dskseek], ax
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mov [dskseek+2], ax
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ret
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drive_write: mov ax, 0x0301
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mov cx, [chs_cx]
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mov dx, [chs_dx]
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mov bx, diskbuf
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int 0x13
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ret
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; flush buffer if dirty
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flush: ret
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@ -0,0 +1,55 @@
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; in FCB required
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; word offset in rootdir
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; used for search
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; word current cluster
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; byte record num in cluster
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; FCB open
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fcbopn: ; call fcbfst
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; copy match
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; store cluster number in fcb
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; record = 0
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ret
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; FCB close
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fcbcls: ; flush disk buffer
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ret
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; FCB find first
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fcbfst: ; init search state in FCB
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; jmp to fcbnxt
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ret
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; FCB find next
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fcbnxt: ; load rootdir sector from state
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; search until next match
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; next sec & loop if mismatch
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; err exit if no further matches
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ret
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; FCB delete file
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fcbdel: ; call fcbfst
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; get search state, load root dir from there
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; mark file as deleted
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ret
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; FCB read
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; read sector from cluster into diskbuf
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fcbrd: ; read record from sector
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; advance record num, carry over to cluster
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ret
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; FCB write
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fcbwr: ; read sector from cluster into diskbuf
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; write record into sector
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; mark buffer dirty
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; advance record num, carry over to cluster
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ret
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; FCB create
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fcbcre:
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ret
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; FCB rename
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fcbren:
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ret
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