source: xtideuniversalbios/trunk/Assembly_Library/Src/Util/Size.asm@ 421

; Project name  :   Assembly Library
; Description   :   Functions for size calculations.

;
; XTIDE Universal BIOS and Associated Tools 
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2012 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
; 
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.      
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;       

struc BYTE_MULTIPLES
    .B          resb    1
    .kiB        resb    1
    .MiB        resb    1
    .GiB        resb    1
    .TiB        resb    1
endstruc

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Size_GetSizeToAXAndCharToDLfromBXDXAXwithMagnitudeInCX
;   Parameters:
;       BX:DX:AX:   Size in magnitude
;       CX:         Magnitude in BYTE_MULTIPLES
;   Returns:
;       AX:         Size in magnitude
;       CX:         Tenths
;       DL:         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, DH
;--------------------------------------------------------------------
ALIGN UTIL_SIZE_JUMP_ALIGN
Size_GetSizeToAXAndCharToDLfromBXDXAXwithMagnitudeInCX:
%ifndef USE_186     ; If 8086/8088
    push    di
%endif
    push    si

ALIGN UTIL_SIZE_JUMP_ALIGN
.MagnitudeConversionLoop:
    ePUSH_T di, .MagnitudeConversionLoop; DI corrupted only on 8086/8088 build
    test    bx, bx                      ; Bits 32...47 in use?
    jnz     SHORT Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX
    test    dx, dx                      ; Bits 16...31 in use?
    jnz     SHORT Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX
    cmp     ax, 10000                   ; 5 digits needed?
    jae     SHORT Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX
    add     sp, BYTE 2                  ; Clean return address from stack
    xchg    si, cx                      ; CX = Remainder (0...1023), SI = Magnitude

    ; Convert remainder to tenths
    xchg    bx, ax                      ; Store AX
    mov     ax, 10
    mul     cx                          ; DX:AX = remainder * 10
    eSHR_IM ax, 10                      ; Divide AX by 1024
    xchg    cx, ax                      ; CX = tenths
    xchg    ax, bx

    ; Convert magnitude to character
    mov     dl, [cs:si+.rgbMagnitudeToChar]

    pop     si
%ifndef USE_186
    pop     di
%endif
    ret
.rgbMagnitudeToChar:    db  " kMGTP"


;--------------------------------------------------------------------
; Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX
;   Parameters:
;       BX:DX:AX:   Size
;       CX:         Magnitude in BYTE_MULTIPLES
;   Returns:
;       BX:DX:AX:   Size in magnitude
;       SI:         Remainder (0...1023)
;       CX:         Magnitude in BYTE_MULTIPLES
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN UTIL_SIZE_JUMP_ALIGN
Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX:
    push    cx
    xor     si, si                  ; Zero remainder
    mov     cl, 10                  ; Divide by 1024
ALIGN UTIL_SIZE_JUMP_ALIGN
.ShiftLoop:
    call    Size_DivideBXDXAXbyTwo
    rcr     si, 1                   ; Update remainder
    loop    .ShiftLoop
    eSHR_IM si, 6                   ; Remainder to SI beginning
    pop     cx
    inc     cx                      ; Increment magnitude
    ret


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