;*****************************************************************************
;*
;* Open Watcom Project
;*
;* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
;*
;* ========================================================================
;*
;* This file contains Original Code and/or Modifications of Original
;* Code as defined in and that are subject to the Sybase Open Watcom
;* Public License version 1.0 (the 'License'). You may not use this file
;* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
;* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
;* provided with the Original Code and Modifications, and is also
;* available at www.sybase.com/developer/opensource.
;*
;* The Original Code and all software distributed under the License are
;* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
;* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
;* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
;* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
;* NON-INFRINGEMENT. Please see the License for the specific language
;* governing rights and limitations under the License.
;*
;* ========================================================================
;*
;* Description: WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
;* DESCRIBE IT HERE!
;*
;*****************************************************************************
include mdef.inc
include struct.inc
modstart msfs386
xdefp "C",_fmsbintoieee
defpe _fmsbintoieee
ifdef __STACK__
mov eax,dword ptr +4H[esp]
mov edx,dword ptr +8H[esp]
endif
; At this point:
; eax - ptr to MBF source float
; edx - ptr to IEEE dest float
mov eax,[eax] ; load MBF float
; MBF exponent = 0 ?
test eax,0ff000000h
jne MBFNonZero ; yes, jump
xor eax,eax ; IEEE 0.0
mov [edx],eax ; store IEEE float
ret ; return 0 (no overflow)
; At this point:
; eax - MBF source float
; edx - ptr to IEEE dest float
MBFNonZero: rol eax,9 ; rotate exponent for better analysis
shr eax,1 ; shift out
rcr al,1 ; move sign bit
adc eax,eax ; shift back
sub al,2 ; convert exponent
jc MBFExp1 ; jump if MBF exponent 1
je MBFExp2 ; jump if MBF exponent 2
ror eax,9 ; rotate so IEEE float
IEEEStore:
mov [edx],eax ; store IEEE float
xor eax,eax ; return 0 (no overflow)
ret ; :
MBFExp1: and al,1 ; zero exponent except implied 1
ror eax,9 ; rotate so IEEE float
sar eax,2 ; convert to IEEE denormal
adc eax,0 ; add in round bit
and eax,80FFFFFFh ; zero surplus sign bits
jmp short IEEEStore ; continue
MBFExp2: or al,1 ; set implied 1
ror eax,9 ; rotate so IEEE float
sar eax,1 ; convert to IEEE denormal
adc eax,0 ; add in round bit
and eax,80FFFFFFh ; zero surplus sign bit
jmp short IEEEStore ; continue
endproc _fmsbintoieee
endmod
end