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554 serge 1 
;*****************************************************************************
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;*
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;*                            Open Watcom Project
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;*
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;*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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;*
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;*  ========================================================================
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;*
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;*    This file contains Original Code and/or Modifications of Original
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;*    Code as defined in and that are subject to the Sybase Open Watcom
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;*    Public License version 1.0 (the 'License'). You may not use this file
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;*    except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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;*    ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
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;*    provided with the Original Code and Modifications, and is also
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;*    available at www.sybase.com/developer/opensource.
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;*
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;*    The Original Code and all software distributed under the License are
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;*    distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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;*    EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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;*    ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
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;*    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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;*    NON-INFRINGEMENT. Please see the License for the specific language
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;*    governing rights and limitations under the License.
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;*
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;*  ========================================================================
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;*
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;* Description:  WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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;*               DESCRIBE IT HERE!
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;*
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;*****************************************************************************
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include mdef.inc
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include struct.inc
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                modstart        fdmd386
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                xdefp   "C",_dieeetomsbin
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                defpe   _dieeetomsbin
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ifdef __STACK__
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                mov     eax,dword ptr +4H[esp]  ; load src double ptr
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                mov     edx,dword ptr +8H[esp]  ; load dst double ptt
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else
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                push    ecx             ; save register
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endif
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; At this point:
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; eax     - ptr to IEEE source double
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; edx     - ptr to MBF dest double
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; ecx     - spare register
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; Check for IEEE Underflow first
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                mov     ecx,+4h[eax]    ; load IEEE double (hi)
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                rol     ecx,1           ; rotate sign bit away for comparisons
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                cmp     ecx,6fe00000H   ; exponent < 1023 - 128 ?
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                jae     IEEENoUnderflow ; yes, jump
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; IEEE Underflow, store MBF 0.0
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                xor     eax,eax         ; make 0
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                mov     [edx],eax       ; store MBF 0.0 (lo)
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                mov     +4h[edx],eax    ; store MBF 0.0 (hi)
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ifndef __STACK__
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                pop     ecx             ; clean up
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endif
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                ret                     ; return 0 (no overflow)
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; Check for IEEE Overflow
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IEEENoUnderflow:
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                cmp     ecx,8fc00000H   ; exponent >= 1023 + 127 ?
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                jae     IEEEOverflow    ; yes, jump
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; General IEEE case, load rest of double
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                mov     eax,[eax]       ; load IEEE double (lo)
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                ror     ecx,1           ; rotate sign bit back into place
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; At this point:
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; ecx:eax - IEEE source double
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; edx     - ptr to MBF dest double
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                push    ecx             ; save sign bit
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; shift exponent & mantissa into place
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                shld    ecx,eax,3       ; shift exponent and mantissa
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                shl     eax,3           ; :
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                mov     [edx],eax       ; save mantissa
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                rol     ecx,9           ; convert IEEE exponent to MBF
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                shr     ecx,1           ; :
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                adc     cl,cl           ; :
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                add     cl,82h          ; correct MBF exponent
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                pop     eax             ; restore sign bit
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                add     eax,eax         ; shift sign bit into carry
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                adc     ecx,ecx         ; add in sign bit
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                ror     ecx,9           ; MBF double (hi)
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                mov     +4h[edx],ecx    ; store MBF double (hi)
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                xor     eax,eax         ; 0
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ifndef __STACK__
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                pop     ecx             ; clean up
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endif
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                ret                     ; return 0 (no overflow)
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; IEEE Overflow, store maximum MBF, preserving sign
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IEEEOverflow:   or      ecx,0FFFFFFFFEh ; set MBF exponent and mantissa to maximum
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                mov     eax,ecx         ; :
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                ror     ecx,9           ; rotate sign bit into place for MBF
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                sar     eax,1           ; now -1
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                mov     +4h[edx],ecx    ; store IEEE double (hi)
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                mov     [edx],eax       ; store IEEE double (lo)
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                neg     eax             ; 1
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ifndef __STACK__
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                pop     ecx             ; clean up
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endif
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                ret                     ; return 1 (overflow)
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                endproc _dieeetomsbin
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                endmod
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                end