source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/Boot/BootMenu.asm@ 315

; Project name  :   XTIDE Universal BIOS
; Description   :   Displays Boot Menu.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Displays Boot Menu and returns Drive or Function number.
;
; BootMenu_DisplayAndReturnSelectionInDX
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       DX:     Untranslated drive number to be used for booting
;   Corrupts registers:
;       All General Purpose Registers
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_DisplayAndReturnSelectionInDX:
    call    DriveXlate_Reset
    call    BootMenuPrint_TheBottomOfScreen
    call    BootMenu_Enter          ; Get selected menuitem index to CX
    call    BootMenuPrint_ClearScreen
    call    BootMenu_GetDriveToDXforMenuitemInCX
    jnc     BootMenu_DisplayAndReturnSelectionInDX
    ret

;--------------------------------------------------------------------
; BootMenu_GetDriveToDXforMenuitemInCX_And_RamVars_GetSegmentToDS
; BootMenu_GetDriveToDXforMenuitemInCX
;   Parameters:
;       CX:     Index of menuitem selected from Boot Menu
;   Returns:
;       DX:     Drive number to be used for booting
;       DS:     RAMVARS segment
;       CF:     Set: There is a selected menu item, DL is valid
;               Clear: There is no selected menu item, DL is not valid
;   Corrupts registers:
;       AX, DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetDriveToDXforMenuitemInCX_And_RamVars_GetSegmentToDS:
    call    RamVars_GetSegmentToDS
;;; fall-through

ALIGN JUMP_ALIGN
BootMenu_GetDriveToDXforMenuitemInCX:
    cmp     cl, NO_ITEM_HIGHLIGHTED
    je      SHORT .ReturnFloppyDriveInDX    ; Clear CF if branch taken

    mov     dl, cl                          ; Copy menuitem index to DX
    call    FloppyDrive_GetCountToAX
    cmp     dl, al                          ; Floppy drive?
    jb      SHORT .ReturnFloppyDriveInDX    ; Set CF if branch taken
    or      al, 80h                         ; Or 80h into AL before the sub
                                            ; to cause CF to be set after
                                            ; and result has high order bit set
    sub     dl, al                          ; Remove floppy drives from index

.ReturnFloppyDriveInDX:
    ret


;--------------------------------------------------------------------
; Enters Boot Menu or submenu.
;
; BootMenu_Enter
;   Parameters:
;       Nothing
;   Returns:
;       CX:     Index of selected item or NO_ITEM_SELECTED
;   Corrupts registers:
;       AX, BX, DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_Enter:
    mov     bx, BootMenuEvent_Handler
    CALL_MENU_LIBRARY DisplayWithHandlerInBXandUserDataInDXAX
    xchg    cx, ax
    ret


;--------------------------------------------------------------------
; Returns number of menuitems in Boot Menu.
;
; BootMenu_GetMenuitemCountToAX
;   Parameters:
;       DS:     RAMVARS segment
;   Returns:
;       AX:     Number of boot menu items
;   Corrupts registers:
;       CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetMenuitemCountToAX:
    call    RamVars_GetHardDiskCountFromBDAtoAX
    xchg    ax, cx
    call    FloppyDrive_GetCountToAX
    add     ax, cx
    ret


;--------------------------------------------------------------------
; BootMenu_GetHeightToAHwithItemCountInAL
;   Parameters:
;       AL:     Number of menuitems
;   Returns:
;       AH:     Boot menu height
;   Corrupts registers:
;       AL, CX, DI
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetHeightToAHwithItemCountInAL:
    add     al, BOOT_MENU_HEIGHT_WITHOUT_ITEMS
    xchg    cx, ax
    CALL_DISPLAY_LIBRARY GetColumnsToALandRowsToAH
    sub     ah, MENU_SCREEN_BOTTOM_LINES*2  ; Leave space for bottom info
    cmp     ah, cl
    jb      SHORT .Return
    mov     ah, cl
ALIGN JUMP_ALIGN, ret
.Return:
    ret


;--------------------------------------------------------------------
; BootMenu_GetMenuitemToAXforAsciiHotkeyInAL
;   Parameters:
;       AL:     ASCII hotkey
;   Returns:
;       AX:     Menuitem index
;   Corrupts registers:
;       CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetMenuitemToAXforAsciiHotkeyInAL:
    call    Char_ALtoUpperCaseLetter
    cbw
    xchg    ax, cx
    call    BootMenu_GetLetterForFirstHardDiskToAL
    cmp     cl, al                      ; Letter is for Hard Disk?
    jae     SHORT .StartFromHardDiskLetter
    xchg    ax, cx
    sub     al, 'A'                     ; Letter to Floppy Drive menuitem
    ret
ALIGN JUMP_ALIGN
.StartFromHardDiskLetter:
    sub     cl, al                      ; Hard Disk index
    call    FloppyDrive_GetCountToAX
    add     ax, cx                      ; Menuitem index
                                        ; Note: no need to xchg ax, cx as above, since adding with result to ax
    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.
;
; BootMenu_GetLetterForFirstHardDiskToCL
;   Parameters:
;       Nothing
;   Returns:
;       CL:     Upper case letter for first hard disk
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetLetterForFirstHardDiskToAL:
    call    FloppyDrive_GetCountToAX
    add     al, 'A'
    cmp     al, 'C'
    ja      .Return
    mov     al, 'C'
ALIGN JUMP_ALIGN, ret
.Return:
    ret


;--------------------------------------------------------------------
; BootMenu_GetMenuitemToDXforDriveInDL
;   Parameters:
;       DL:     Drive number
;   Returns:
;       DX:     Menuitem index (assuming drive is available)
;   Corrupts registers:
;       AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_GetMenuitemToDXforDriveInDL:
    xor     dh, dh                      ; Drive number now in DX
    test    dl, dl
    jns     SHORT .ReturnItemIndexInDX  ; Return if floppy drive (HD bit not set)
    call    FloppyDrive_GetCountToAX
    and     dl, ~80h                    ; Clear HD bit
    add     dx, ax
.ReturnItemIndexInDX:
    ret


;--------------------------------------------------------------------
; Checks is drive number valid for this system.
;
; BootMenu_IsDriveInSystem
;   Parameters:
;       DL:     Drive number
;       DS:     RAMVARS segment
;   Returns:
;       CF:     Set if drive number is valid
;               Clear if drive is not present in system
;   Corrupts registers:
;       AX, CX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootMenu_IsDriveInSystem:
    test    dl, dl                              ; Floppy drive?
    jns     SHORT .IsFloppyDriveInSystem
    call    RamVars_GetHardDiskCountFromBDAtoAX ; Hard Disk count to AX
    or      al, 80h                             ; Set Hard Disk bit to AX
    jmp     SHORT .CompareDriveNumberToDriveCount
.IsFloppyDriveInSystem:
    call    FloppyDrive_GetCountToAX
.CompareDriveNumberToDriveCount:
    cmp     dl, al                              ; Set CF when DL is smaller
    ret