forked from KolibriOS/kolibrios
100 lines
3.5 KiB
NASM
100 lines
3.5 KiB
NASM
;*****************************************************************************
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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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.8087
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modstart _7fu8386
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xdefp __FSU87
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xdefp __FDU87
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defpe __FSU87
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sub esp,12
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mov [esp],eax
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fld dword ptr [esp]
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jmp short convert
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defpe __FDU87
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sub esp,12
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mov [esp],eax
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mov 4[esp],edx
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fld qword ptr [esp]
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; fall through
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convert:
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push ecx
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fstp tbyte ptr 4[esp] ; get number out in memory
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mov ax,12[esp] ; pick up sign/exponent
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and ax,7fffh ; isolate exponent
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sub ax,16383 ; remove bias
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jl ret_zero ; if less than .5, return zero
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cmp ax,64 ; are we too big?
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jae ret_inf ; if so, return infinity
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mov cl,63 ; calculate shift count
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sub cl,al ; ...
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mov eax,4[esp] ; pick up mantissa
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mov edx,8[esp] ; ...
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je negate ; skip out if no shifting
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L2:
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shr edx,1 ; shift down one bit
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rcr eax,1 ; ...
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dec cl ; are we done?
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jne L2 ; do it again if not
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negate:
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test byte ptr 13[esp],80h ; is number negative?
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jns done ; if not, we're done
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neg edx ; negate number
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neg eax ; ...
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sbb edx,0 ; ...
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done:
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pop ecx ; ...
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add esp,12 ; outta here
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ret ; ...
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ret_zero:
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xor edx,edx
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xor eax,eax
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jmp done
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ret_inf:
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mov edx,0ffffffffh
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mov eax,edx
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jmp done
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endproc __FDU87
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endproc __FSU87
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endmod
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end
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