238 lines
10 KiB
NASM
238 lines
10 KiB
NASM
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;*****************************************************************************
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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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; double modf( double value, double *iptr );
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;
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; Description:
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; The modf function breaks the argument value into integral and
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; fractional parts, each of which has the same sign as the argument.
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; It stores the integral part as a double in the object pointed to
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; by iptr.
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;
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; Returns:
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; The modf function returns the signed fractional part of value.
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;
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; 18-oct-86 ... Fraction in Modf not computed right
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; significant digits
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;
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include mdef.inc
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include struct.inc
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modstart amodf386
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xdefp __ModF
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xdefp __ZBuf2F
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;[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
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;[]
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;[] __ModF
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;[]
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;[] void __ModF( double near *AX, double near *DX );
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;[] Input: EAX - pointer to double precision float
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;[] EDX - place to store integral part
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;[] Output: [EAX] - fractional part of value.
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;[] [EDX] - integral part of value
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;[]
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;[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
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defpe __ModF
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push EBP ; save BP
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push ESI ; save SI
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push EDI ; save DI
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push ECX ; save CX
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push EBX ; save BX
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mov ESI,EDX ; get address for ipart
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mov EBP,EAX ; get address of float
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mov EAX,0[EBP] ; get float
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mov EDX,4[EBP] ; . . .
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xchg ESI,EBP ; flip pointers
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mov 0[EBP],EAX ; store integral part of value
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mov 4[EBP],EDX ; . . .
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_guess ; guess: fraction is zero
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mov ECX,EDX ; - get exponent
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and ECX,7FF00000h ; - get exponent part of R into DI
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je short done ; - set integer part to 0 if exponent = 0
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cmp ECX,(3FFh+52) shl 20; - check for exponent > 52
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_quif b ; - quit if fraction not zero
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xchg EBP,ESI ; - get address of fractional part
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done: sub EAX,EAX ; - set fraction(or integer) to 0
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mov 4[EBP],EAX ; - . . .
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mov 0[EBP],EAX ; - . . .
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pop EBX ; - restore BX
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pop ECX ; - restore CX
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pop EDI ; - restore DI
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pop ESI ; - restore SI
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pop EBP ; - restore BP
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ret ; - return
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_endguess ; endguess
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mov EDI,ECX ; save exponent
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shr ECX,20 ; move exponent to bottom
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sub CX,03FFh ; remove bias
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jb done ; quit if number < 1.0
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push EDX ; save sign
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sub EAX,EAX ; initialize mask to 0
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mov EDX,0FFF00000h ; ...
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cmp CL,20 ; if exponent > 20
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_if a ; then
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sar EDX,21 ; - set ESI to all ones
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rcr EAX,1 ; - set high bit of EBX
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sub CL,21 ; - get shift count for second part
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sar EAX,CL ; - create rest of mask
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_else ; else
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sar EDX,CL ; - create mask in high part only
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_endif ; endif
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and 4[EBP],EDX ; mask off the remaining fraction bits
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and 0[EBP],EAX ; . . .
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not EDX ; complement the mask to get fractional part
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not EAX ; . . .
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mov EBP,ESI ; get address of fractional part
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and EDX,4[EBP] ; get fraction bits
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and EAX,0[EBP] ; . . .
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call Norm ; normalize the fraction
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pop ESI ; restore sign
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or EDX,EDX ; if fraction is not 0
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_if ne ; then
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and ESI,80000000h ; - isolate sign
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or EDX,ESI ; - set sign in fractional part
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_endif ; endif
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mov 4[EBP],EDX ; store fractional part
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mov 0[EBP],EAX ; . . .
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pop EBX ; restore BX
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pop ECX ; restore CX
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pop EDI ; restore DI
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pop ESI ; restore SI
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pop EBP ; restore BP
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ret ; return
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endproc __ModF
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;<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
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;<> <>
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;<> __ZBuf2F - convert buffer of significant digits into floating <>
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;<> void __ZBuf2F( char near *buf, double near *value ) <>
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;<> <>
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;<> input: EAX - address of buffer of significant digits <>
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;<> EDX - place to store value <>
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;<> output: [EDX] - floating point number <>
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;<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
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defpe __ZBuf2F
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push EBP ; save BP
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push ESI ; save SI
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push EDI ; save DI
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push ECX ; save CX
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push EBX ; save BX
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push EDX ; save pointer to result
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mov ESI,EAX ; get address of buffer
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sub EDX,EDX ; set 54-bit integer to 0
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sub ECX,ECX ; . . .
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sub EAX,EAX ; zero out EAX
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_loop ; loop (convert digits into 54-bit int)
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mov AL,[ESI] ; - get next digit
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cmp AL,0 ; - quit if at end of buffer
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_quif e ; - . . .
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;[] multiply current value in EDX:ECX by 10
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mov EDI,EDX ; - save current value
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mov EBX,ECX ; - ...
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_shl ECX,1 ; - multiply number by 4
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_rcl EDX,1 ; - by shifting left 2 places
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_shl ECX,1 ; - . . .
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_rcl EDX,1 ; - . . .
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add ECX,EBX ; - add original value
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adc EDX,EDI ; - (this will make it times 5)
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_shl ECX,1 ; - shift left to make it times 10
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_rcl EDX,1 ; - . . .
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and AL,0Fh ; - isolate binary digit
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add ECX,EAX ; - add in current digit
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adc EDX,0 ; - . . .
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inc ESI ; - point to next digit in buffer
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_endloop ; endloop
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mov EAX,ECX ; get low order word into EAX
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;[] Turn the integer in EDX:EAX into a real number
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mov EDI,(3FFh+52) shl 20; set exponent
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call Norm ; convert the 52 bit integer to a float
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pop EBP ; restore pointer to result
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mov 4[EBP],EDX ; store result
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mov 0[EBP],EAX ; . . .
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pop EBX ; restore BX
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pop ECX ; restore CX
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pop EDI ; restore DI
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pop ESI ; restore SI
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pop EBP ; restore BP
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ret ; return to caller
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endproc __ZBuf2F
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;[] Norm normalizes an unsigned real in EDX:EAX
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;[] expects the exponent to be in EDI. The real returned is in 'packed'
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;[] format
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;[] ESI is destroyed
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Norm proc near ; normalize floating point number
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sub ESI,ESI ; clear out SI
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or ESI,EAX ; see if the integer is zero
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or ESI,EDX ; . . .
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je short Z_52ret ; if integer is zero, return to caller
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test EDX,0FFF00000h ; see if we have to shift forward or backward
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_if e ; if (we haven't shifted msb into bit 53)
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_loop ; - loop
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sub EDI,00100000h ; - - exp <-- exp - 1
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_shl EAX,1 ; - - shift integer left by 1 bit
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_rcl EDX,1 ; - - . . .
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test EDX,0FFF00000h;
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_until ne ; - until( msb is shifted into bit 53 )
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_else ; else (we must shift to the right)
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test EDX,0FFE00000h ; -
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je short done1 ; - if msb is bit 53, we are done
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_loop ; - loop
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add EDI,00100000h ; - - exp <-- exp + 1
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shr EDX,1 ; - - shift integer right by 1 bit
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rcr EAX,1 ; - - . . .
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rcr ESI,1 ; - - save lsb
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test EDX,0FFE00000h; -
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_until e ; - until( msb is bit 53 )
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_rcl ESI,1 ; - get lsb
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adc EAX,0 ; - and use it to round off the number
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adc EDX,0 ; - . . .
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_endif ; endif
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done1: and EDX,000FFFFFh ; clear out implied bit
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or EDX,EDI ; put in exponent
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Z_52ret:ret ; return
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endproc Norm
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endmod
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end
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