source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Handlers/Int13h/Common/HCapacity.asm@ 21

; File name     :   HCapacity.asm
; Project name  :   IDE BIOS
; Created date  :   16.3.2010
; Last update   :   12.4.2010
; Author        :   Tomi Tilli
; Description   :   Functions for hard disk capacity calculations.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Calculates sector count from L-CHS values returned by INT 13h, AH=08h.
;
; HCapacity_GetSectorCountFromForeignAH08h:
; HCapacity_GetSectorCountFromOurAH08h:
;   Parameters:
;       DL:     Drive number
;       DS:     RAMVARS segment
;   Returns:
;       DX:AX:  Total sector count
;       BX:     Zero
;   Corrupts registers:
;       CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
HCapacity_GetSectorCountFromForeignAH08h:
    mov     ah, 08h         ; Get Drive Parameters
    int     INTV_DISK_FUNC
    jmp     SHORT HCapacity_ConvertAH08hReturnValuesToSectorCount

ALIGN JUMP_ALIGN
HCapacity_GetSectorCountFromOurAH08h:
    push    di
    call    AH8h_GetDriveParameters
    pop     di
    ; Fall to HCapacity_ConvertAH08hReturnValuesToSectorCount

ALIGN JUMP_ALIGN
HCapacity_ConvertAH08hReturnValuesToSectorCount:
    call    HAddress_ExtractLCHSFromBiosParams
    xor     ax, ax          ; Zero AX
    inc     cx              ; Max cylinder number to cylinder count
    xchg    al, bh          ; AX=Max head number, BX=Sectors per track
    inc     ax              ; AX=Head count
    mul     bx              ; AX=Head count * Sectors per track
    mul     cx              ; DX:AX = Total sector count
    xor     bx, bx          ; Zero BX for 48-bit sector count
    ret


;--------------------------------------------------------------------
; Converts sector count to hard disk size.
;
; HCapacity_ConvertSectorCountToSize:
;   Parameters:
;       BX:DX:AX:   Total sector count
;   Returns:
;       AX:         Size in magnitude
;       SI:         Tenths
;       CX:         Magnitude character:
;                       'k' = *1024   B = kiB
;                       'M' = *1024 kiB = MiB
;                       'G' = *1024 MiB = GiB
;                       'T' = *1024 GiB = TiB
;                       'P' = *1024 TiB = PiB
;   Corrupts registers:
;       BX, DX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
HCapacity_ConvertSectorCountToSize:
    call    HCapacity_ConvertSectorCountToKiB
    mov     cx, 1                   ; Magnitude is 1 for kiB
ALIGN JUMP_ALIGN
.MagnitudeLoop:
    test    bx, bx                  ; Bits 32...47 in use?
    jnz     SHORT .ShiftByMagnitude ;  If so, jump to shift
    test    dx, dx                  ; Bits 16...31 in use?
    jnz     SHORT .ShiftByMagnitude ;  If so, jump to shift
    cmp     ax, 10000               ; 5 digits needed?
    jb      SHORT .ShiftComplete    ;  If less, all done
ALIGN JUMP_ALIGN
.ShiftByMagnitude:
    call    HCapacity_ShiftForNextMagnitude
    jmp     SHORT .MagnitudeLoop
ALIGN JUMP_ALIGN
.ShiftComplete:
    mov     bx, cx                  ; Copy shift count to BX
    mov     cl, [cs:bx+.rgbMagnitudeToChar]
    jmp     SHORT HCapacity_ConvertSizeRemainderToTenths
ALIGN WORD_ALIGN
.rgbMagnitudeToChar:    db  " kMGTP"

;--------------------------------------------------------------------
; Converts 48-bit sector count to size in kiB.
;
; HCapacity_ConvertSectorCountToKiB:
;   Parameters:
;       BX:DX:AX:   Total sector count
;   Returns:
;       BX:DX:AX:   Total size in kiB
;       CF:         Remainder from division
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
HCapacity_ConvertSectorCountToKiB:
HCapacity_DivideSizeByTwo:
    shr     bx, 1                   ; Divide sector count by 2...
    rcr     dx, 1                   ; ...to get disk size in...
    rcr     ax, 1                   ; ...kiB
    ret

;--------------------------------------------------------------------
; Divides size by 1024 and increments magnitude.
;
; HCapacity_ShiftForNextMagnitude:
;   Parameters:
;       BX:DX:AX:   Size in magnitude
;       CX:         Magnitude (0=B, 1=kiB, 2=MiB...)
;   Returns:
;       BX:DX:AX:   Size in magnitude
;       SI:         Remainder (0...1023)
;       CX:         Magnitude (1=kiB, 2=MiB...)
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
HCapacity_ShiftForNextMagnitude:
    push    cx
    xor     si, si                  ; Zero remainder
    mov     cl, 10                  ; Divide by 1024
ALIGN JUMP_ALIGN
.ShiftLoop:
    call    HCapacity_DivideSizeByTwo
    rcr     si, 1                   ; Update remainder
    loop    .ShiftLoop
    eSHR_IM si, 6                   ; Remainder to SI beginning
    pop     cx
    inc     cx                      ; Increment shift count
    ret

;--------------------------------------------------------------------
; Converts remainder from HCapacity_ShiftForNextMagnitude to tenths.
;
; HCapacity_ConvertSizeRemainderToTenths:
;   Parameters:
;       BX:DX:AX:   Size in magnitude
;       SI:         Remainder from last magnitude division (0...1023)
;   Returns:
;       BX:DX:AX:   Size in magnitude
;       SI:         Tenths
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
HCapacity_ConvertSizeRemainderToTenths:
    push    dx
    push    ax

    mov     ax, 10
    mul     si                  ; DX:AX = remainder * 10
    eSHR_IM ax, 10              ; Divide AX by 1024
    xchg    si, ax              ; SI = tenths

    pop     ax
    pop     dx
    ret