source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Menus/DriveXlate.asm@ 497

; Project name  :   XTIDE Universal BIOS
; Description   :   Functions for swapping drive letters.

;
; 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
;       

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; DriveXlate_ConvertDriveLetterInDLtoDriveNumber
;   Parameters:
;       DS:     RAMVARS segment
;       DL:     Drive letter ('A'...)
;   Returns:
;       DL:     Drive number (0xh for Floppy Drives, 8xh for Hard Drives)
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
DriveXlate_ConvertDriveLetterInDLtoDriveNumber:
    call    DriveXlate_GetLetterForFirstHardDriveToAX
    cmp     dl, al
    jb      SHORT .ConvertLetterInDLtoFloppyDriveNumber

    ; Convert letter in DL to Hard Drive number
    sub     dl, al
    or      dl, 80h
    ret

.ConvertLetterInDLtoFloppyDriveNumber:
    sub     dl, DEFAULT_FLOPPY_DRIVE_LETTER
    ret

%ifdef MODULE_HOTKEY
%if HotkeyBar_FallThroughTo_DriveXlate_ConvertDriveLetterInDLtoDriveNumber <> DriveXlate_ConvertDriveLetterInDLtoDriveNumber
    %error "DriveXlate_ConvertDriveLetterInDLtoDriveNumber must be at the top of DriveXlate.asm, and that file must immediately follow HotKeys.asm"
%endif      
%endif
        
;--------------------------------------------------------------------
; DriveXlate_ConvertDriveNumberFromDLtoDriveLetter
;   Parameters:
;       DL:     Drive number (0xh for Floppy Drives, 8xh for Hard Drives)
;       DS:     RAMVARS Segment
;   Returns:
;       DL:     Drive letter ('A'...)
;       CF:     Set if Hard Drive
;               Clear if Floppy Drive
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
DriveXlate_ConvertDriveNumberFromDLtoDriveLetter:
    test    dl, dl
    jns     SHORT .GetDefaultFloppyDrive

    ; Store default hard drive to boot from
    call    DriveXlate_GetLetterForFirstHardDriveToAX
    sub     dl, 80h
    add     dl, al
    stc
    ret

.GetDefaultFloppyDrive:
    add     dl, DEFAULT_FLOPPY_DRIVE_LETTER     ; Clears CF
    ret


;--------------------------------------------------------------------
; Returns letter for first hard disk. Usually it will be 'C' but it
; can be higher if more than two floppy drives are found.
;
; DriveXlate_GetLetterForFirstHardDriveToAX
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       AX:     Upper case letter for first hard disk
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
DriveXlate_GetLetterForFirstHardDriveToAX:
    call    FloppyDrive_GetCountToAX
    add     al, DEFAULT_FLOPPY_DRIVE_LETTER
    MAX_U   al, DEFAULT_HARD_DRIVE_LETTER
    ret
                

;--------------------------------------------------------------------
; DriveXlate_ToOrBack
;   Parameters:
;       DL:     Drive number to be possibly translated
;       DS:     RAMVARS segment
;   Returns:
;       DL:     Translated drive number
;   Corrupts registers:
;       DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
DriveXlate_ToOrBack:
    xchg    di, ax                  ; Backup AX

    mov     ah, 80h                 ; Assume hard disk
    mov     al, [RAMVARS.xlateVars+XLATEVARS.bHDSwap]
    test    dl, ah                  ; Hard disk?
    jnz     SHORT .SwapDrive        ; If so, jump to swap
    mov     al, [RAMVARS.xlateVars+XLATEVARS.bFDSwap]
    cbw

ALIGN JUMP_ALIGN
.SwapDrive:
    cmp     ah, dl                  ; Swap DL from 00h/80h to xxh?
    je      SHORT .SwapToXXhInAL
    cmp     al, dl                  ; Swap DL from xxh to 00h/80h?
    jne     SHORT .RestoreAXandReturn
    mov     al, ah
ALIGN JUMP_ALIGN
.SwapToXXhInAL:
    mov     dl, al
ALIGN JUMP_ALIGN
.RestoreAXandReturn:
    xchg    ax, di                  ; Restore AX
    ret


;--------------------------------------------------------------------
; Resets drive swapping variables to defaults (no swapping).
;
; DriveXlate_Reset
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DI, DL
;--------------------------------------------------------------------
DriveXlate_Reset:
    xor     dl, dl              ; no translation for a floppy
    ;; fall through to DriveXlate_SetDriveToSwap

;--------------------------------------------------------------------
; Stores drive to be swapped.
;
; DriveXlate_SetDriveToSwap
;   Parameters:
;       DL:     Drive to swap to 00h or 80h
;       DS:     RAMVARS segment
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DI
;--------------------------------------------------------------------
DriveXlate_SetDriveToSwap:
    mov     ax, 8000h           ; Default mapping (no translation)
    test    dl, dl              ; Floppy drive?
    js      SHORT .SetHardDriveToSwap
    mov     al, dl              ; Store floppy translation
    SKIP2B  di
.SetHardDriveToSwap:    
    mov     ah, dl              ; Store HD translation
    mov     WORD [RAMVARS.xlateVars+XLATEVARS.wFDandHDswap], ax
    ret