source: xtideuniversalbios/trunk/Assembly_Library/Src/Util/Registers.asm@ 465

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

;
; 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

;--------------------------------------------------------------------
; 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 OR EXCLUDE_FROM_XTIDECFG
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