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2644 clevermous 1 
; Callbacks which implement tmpdisk-specific disk functions for tmpdisk.asm.
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; The first argument of every callback is .userdata = userdata arg of AddDisk.
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; For tmpdisk, .userdata is the disk id, one of 0,...,max_num_disks-1.
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DISK_STATUS_OK              = 0 ; success
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DISK_STATUS_GENERAL_ERROR   = -1; if no other code is suitable
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DISK_STATUS_INVALID_CALL    = 1 ; invalid input parameters
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DISK_STATUS_NO_MEDIA        = 2 ; no media present
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DISK_STATUS_END_OF_MEDIA    = 3 ; end of media while reading/writing data
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; The last function that is called for the given disk. The kernel calls it when
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; the kernel has finished all operations with the disk and it is safe to free
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; all driver-specific data identified by 'userdata'.
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proc tmpdisk_close
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  virtual at esp+4
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    .userdata dd ?
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  end virtual
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; Free the memory for disk and zero global variables.
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        mov     edx, [.userdata]
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        mov     [disk_sizes+edx*4], 0
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        xor     eax, eax
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        xchg    eax, [disk_pointers+edx*4]
5044 clevermous 24 
        invoke  KernelFree, eax
2644 clevermous 25 
        retn    4
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endp
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struc DISKMEDIAINFO
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{
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  .flags      dd ?
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DISK_MEDIA_READONLY = 1
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  .sectorsize dd ?
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  .capacity   dq ?
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}
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virtual at 0
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DISKMEDIAINFO DISKMEDIAINFO
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end virtual
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; Returns information about disk media.
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proc tmpdisk_querymedia
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  virtual at esp+4
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    .userdata dd ?
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    .info dd ?
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  end virtual
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; Media is always present, sector size is always 512 bytes,
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; the size of disk in sectors is stored in a global variable.
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        mov     edx, [.userdata]
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        mov     ecx, [.info]
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        mov     [ecx+DISKMEDIAINFO.flags], 0
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        mov     [ecx+DISKMEDIAINFO.sectorsize], 512
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        mov     eax, [disk_sizes+edx*4]
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        mov     dword [ecx+DISKMEDIAINFO.capacity], eax
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        mov     dword [ecx+DISKMEDIAINFO.capacity+4], 0
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; Return zero as an indicator of success.
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        xor     eax, eax
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        retn    8
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endp
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; Reads one or more sectors from the device.
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tmpdisk_read:
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        xor     edx, edx ; 0 = reading
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        jmp     tmpdisk_readwrite
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; Writes one or more sectors to the device.
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tmpdisk_write:
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        mov     dl, 1 ; 1 = writing
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; Fall through to tmpdisk_readwrite.
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; Common procedure for reading and writing.
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; dl = 0 for reading, dl = 1 for writing.
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; Arguments of tmpdisk_read and tmpdisk_write are the same,
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; they continue to be stack arguments of this procedure.
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proc tmpdisk_readwrite \
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  userdata:dword, \
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  buffer:dword, \
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  start_sector:qword, \
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  numsectors_ptr:dword
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; 1. Save used registers to be stdcall.
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        push    esi edi
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        mov     esi, [userdata]
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        mov     edi, [numsectors_ptr]
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; 1. Determine number of sectors to be transferred.
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; This is either the requested number of sectors or number of sectors
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; up to the disk boundary, depending of what is less.
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        xor     ecx, ecx
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; 1a. Test whether [start_sector] is less than [disk_sizes] for selected disk.
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; If so, calculate number of sectors between [start_sector] and [disk_sizes].
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; Otherwise, the actual number of sectors is zero.
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        cmp     dword [start_sector+4], ecx
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        jnz     .got_number
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        mov     eax, [disk_sizes+esi*4]
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        sub     eax, dword [start_sector]
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        jbe     .got_number
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; 1b. Get the requested number of sectors.
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        mov     ecx, [edi]
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; 1c. If it is greater than number of sectors calculated in 1a, use the value
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; from 1a.
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        cmp     ecx, eax
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        jb      .got_number
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        mov     ecx, eax
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.got_number:
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; 2. Compare the actual number of sectors with requested. If they are
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; equal, set eax (it will be the returned value) to zero. Otherwise,
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; use DISK_STATUS_END_OF_MEDIA.
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        xor     eax, eax
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        cmp     ecx, [edi]
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        jz      @f
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        mov     al, DISK_STATUS_END_OF_MEDIA
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@@:
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; 3. Store the actual number of sectors.
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        mov     [edi], ecx
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; 4. Calculate source and destination addresses.
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        mov     edi, dword [start_sector]
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        shl     edi, 9
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        add     edi, [disk_pointers+esi*4]
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        mov     esi, [buffer]
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; 5. Calculate number of dwords to be transferred.
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        shl     ecx, 9-2
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; 6. Now esi = [buffer], edi = pointer inside disk.
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; This is normal for write operations;
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; exchange esi and edi for read operations.
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        test    dl, dl
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        jnz     @f
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        xchg    esi, edi
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@@:
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; 7. Copy data.
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        rep movsd
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; 8. Restore used registers to be stdcall and return.
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; The value in eax was calculated in step 2.
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        pop     edi esi
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        ret
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endp
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; The kernel calls this function when initializing cache subsystem for
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; the media. This call allows the driver to adjust the cache size.
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proc tmpdisk_adjust_cache_size
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  virtual at esp+4
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    .userdata dd ?
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    .suggested_size dd ?
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  end virtual
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; Since tmpdisk does not need cache, just return 0.
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        xor     eax, eax
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        retn    8
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endp