222 lines
4.5 KiB
NASM
222 lines
4.5 KiB
NASM
boots segment
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.386
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org 7C00h
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;org 100h
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assume cs:boots,ds:boots
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start:
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jmp boot
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bootdb db 'COS2000A' ;Fabricant + n°série Formatage
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sizec dw 512 ;octet/secteur
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db 1 ;secteur/cluster
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reserv dw 1 ;secteur reserv‚
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nbfat db 2 ;nb de copie de la FAT
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nbfit dw 224 ;taille rep racine
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allclu dw 2880 ;nb secteur du volume si < 32 még
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db 0F0h ;Descripteur de média
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fatsize dw 9 ;secteur/FAT
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nbtrack dw 18 ;secteur/piste
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head dw 2 ;nb de tˆteb de lecture/écriture
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hidden dd 0 ;nombre de secteur cach‚s
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dd 0 ;si nbsecteur = 0 nbsect ; the number of sectors
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bootdrv db 0 ;Lecteur de d‚marrage
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bootsig db 0 ;NA
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db 29h ;boot signature 29h
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bootsig2 dd 01020304h ;no de serie
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pope db 'COS2000 ' ;nom de volume
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db 'FAT12 ' ;FAT
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specialboot:
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errorloading db ' Erreur !!',0dh,0ah,0
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okloading db 'Recherche noyau',0Dh,0ah,' - system.sys',0
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syst db ' Ok',0dh,0ah,'Chargement',0
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dot db '.',0
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Sys db 'SYSTEME SYS'
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errorboot:
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mov si,offset errorloading
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call showstr
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mov ah,0
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int 16h
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int 19h
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boot:
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mov Bootdrv,dl
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cli
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mov ax,09000h
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mov ss,ax
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mov sp,0FFFFh
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sti
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boot2:
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push cs
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push cs
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pop es
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pop ds
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xor ax,ax
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int 13h
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jc errorboot
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mov si,offset okloading
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call showstr
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mov cx,Reserv
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add cx,word ptr [offset Hidden]
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adc cx,word ptr [offset Hidden+2]
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push cx
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mov bx,fatsize
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mov di,offset bufferfat
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readfat:
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call readsector
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inc cx
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add di,sizec
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dec bx
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jnz readfat
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pop cx
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xor ax,ax
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mov al,NbFat
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mov bx,FatSize
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mul bx
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add cx,ax
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mov ax,32
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mul nbfit
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div sizec
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add ax,cx
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sub ax,2
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mov word ptr [offset bootsig],ax
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xor dx,dx
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CheckRoot:
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mov di,offset buffer
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call readsector
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jc errorboot
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xor bx,bx
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findnext:
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cmp byte ptr [di],0
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je errorboot
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cmp byte ptr [di],0E5h
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je no
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cmp byte ptr [di],041h
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je no
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mov si,offset dot
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call showstr
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push di cx
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mov si,offset sys
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mov cx,11
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rep cmpsb
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pop cx di
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je oksystem
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no:
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add di,32
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add bx,32
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inc dx
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cmp dx,nbfit
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ja errorboot
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cmp bx,sizec
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jb findnext
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inc cx
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jmp Checkroot
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oksystem:
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mov si,offset syst
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call showstr
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mov cx,[di+26]
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mov ax,0900h
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mov es,ax
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push es
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mov di,100h
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push di
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mov si,offset dot
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xor ax,ax
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fatagain:
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cmp cx,0FF0h
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jae finishload
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push cx
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add cx,word ptr [offset bootsig]
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call readsector
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pop cx
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jc errorboot
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inc ax
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call showstr
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add di,sizec
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call getfat
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jnc fatagain
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finishload:
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db 0CBh
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;=============READSECTOR (Fonction 01H)===============
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;Lit le secteur CX et le met en es:di
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;-> AH=1
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;<- Flag Carry si erreur
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;=====================================================
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ReadSector:
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push ax bx cx dx si
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mov ax,cx
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xor dx,dx
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div nbtrack
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inc dl
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mov bl,dl
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xor dx,dx
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div head
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mov dh, 0
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xchg dl,dh
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mov cx,ax
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xchg cl,ch
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shl cl,6
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or cl, bl
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mov bx,di
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mov SI, 4
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mov AL, 1
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TryAgain:
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mov AH, 2
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int 13h
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jnc Done
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dec SI
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jnz TryAgain
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Done:
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pop si dx cx bx ax
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ret
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getfat:
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push ax bx dx di
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mov di,offset bufferfat
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mov ax,cx
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mov bx,ax
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and bx,0000000000000001b
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shr ax,1
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mov cx,3
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mul cx
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add di,ax
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cmp bx,0h
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jnz evenfat
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oddfat:
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mov dx,[di]
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and dx,0FFFh
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mov cx,dx
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jmp endfat
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evenfat:
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mov dx,[di+1]
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and dx,0FFF0h
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shr dx,4
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mov cx,dx
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endfat:
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pop di dx bx ax
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ret
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showstr:
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push ax bx si
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again:
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lodsb
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or al,al
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jz fin
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mov ah,0Eh
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mov bx,07h
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int 10h
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jmp again
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fin:
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pop si bx ax
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ret
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Buffer equ $
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BufferFat equ $+2048
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boots ends
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end start
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