source: xtideuniversalbios/trunk/Assembly_Library/Src/Util/Registers.asm @ 222

; Project name  :   Assembly Library
; Description   :   Functions for register operations.


; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Registers_ExchangeDSSIwithESDI
;   Parameters
;       Nothing
;   Returns:
;       DS:SI and ES:DI are exchanged.
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Registers_ExchangeDSSIwithESDI:
    push    ds
    push    es
    pop     ds
    pop     es
    xchg    si, di
    ret


;--------------------------------------------------------------------
; Registers_CopySSBPtoESDI
; Registers_CopySSBPtoDSSI
; Registers_CopyDSSItoESDI
; Registers_CopyESDItoDSSI
;   Parameters
;       Nothing
;   Returns:
;       Copies farm pointer to different segment/pointer register pair
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
Registers_CopySSBPtoESDI:
    COPY_SSBP_TO_ESDI
    ret

%ifndef EXCLUDE_FROM_XTIDE_UNIVERSAL_BIOS
ALIGN JUMP_ALIGN
Registers_CopySSBPtoDSSI:
    COPY_SSBP_TO_DSSI
    ret

ALIGN JUMP_ALIGN
Registers_CopyDSSItoESDI:
    COPY_DSSI_TO_ESDI
    ret

ALIGN JUMP_ALIGN
Registers_CopyESDItoDSSI:
    COPY_ESDI_to_DSSI
    ret
%endif


;--------------------------------------------------------------------
; Registers_NormalizeESSI
; Registers_NormalizeESDI
;   Parameters
;       DS:SI or ES:DI: Ptr to normalize
;   Returns:
;       DS:SI or ES:DI: Normalized pointer
;   Corrupts registers:
;       AX, CX
; 
; Inline of NORMALIZE_FAR_POINTER so that we can share the last 2/3 of the 
; routine with Registers_NormalizeFinish.
; 
;--------------------------------------------------------------------
%ifndef EXCLUDE_FROM_XTIDE_UNIVERSAL_BIOS
ALIGN JUMP_ALIGN
Registers_NormalizeESSI:
    mov         cx, si
    and         si, byte 0fh
    jmp         Registers_NormalizeFinish

ALIGN JUMP_ALIGN
Registers_NormalizeESDI:
    mov         cx, di
    and         di, byte 0fh
;;; fall-through

ALIGN JUMP_ALIGN        
Registers_NormalizeFinish:      
    eSHR_IM     cx, 4
    mov         ax, es
    add         ax, cx
    mov         es, ax
    ret
%endif


;--------------------------------------------------------------------
; Registers_SetZFifNullPointerInDSSI (commented to save bytes)
;   Parameters
;       DS:SI:  Far pointer
;   Returns:
;       ZF:     Set if NULL pointer in DS:SI
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
;ALIGN JUMP_ALIGN
;Registers_SetZFifNullPointerInDSSI:
;   push    ax
;   mov     ax, ds
;   or      ax, si
;   pop     ax
;   ret