160 lines
7.0 KiB
NASM
160 lines
7.0 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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; This module converts a string to long_double
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; void __ZBuf2LD( char *buf, long_double *value );
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;
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include mdef.inc
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include struct.inc
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modstart bufld386
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xdefp __ZBuf2LD
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;<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
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;<> <>
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;<> __ZBuf2LD - convert buffer of significant digits into floating <>
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;<> void __ZBuf2LD( char *buf, long_double *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 __ZBuf2LD
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push EBP ; save EBP
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push ESI ; save ESI
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push EDI ; save EDI
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push ECX ; save ECX
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push EBX ; save EBX
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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 96-bit integer to 0
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sub ECX,ECX ; ...
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sub EBP,EBP ; ...
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sub EAX,EAX ; zero out EAX
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_loop ; loop (convert digits into 64-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:EBP by 10
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mov EDI,EDX ; - save current value
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mov EBX,ECX ; - ...
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mov EAX,EBP ; - ...
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_shl EBP,1 ; - multiply number by 4
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_rcl ECX,1 ; - by shifting left 2 places
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_rcl EDX,1 ; - ...
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_shl EBP,1 ; - ...
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_rcl ECX,1 ; - ...
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_rcl EDX,1 ; - ...
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add EBP,EAX ; - add original value
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adc ECX,EBX ; - (this will make it times 5)
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adc EDX,EDI ; - ...
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_shl EBP,1 ; - shift left to make it times 10
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_rcl ECX,1 ; - ...
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_rcl EDX,1 ; - ...
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sub EAX,EAX ; - zero eax
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mov AL,[ESI] ; - get next digit
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and AL,0Fh ; - isolate binary digit
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add EBP,EAX ; - add in current digit
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adc ECX,0 ; - ...
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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:EBP into a real number
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mov EDI,3FFFh+63+32 ; set exponent
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call Norm ; convert the 64 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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mov 8[EBP],SI ; ...
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pop EBX ; restore EBX
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pop ECX ; restore ECX
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pop EDI ; restore EDI
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pop ESI ; restore ESI
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pop EBP ; restore EBP
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ret ; return to caller
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endproc __ZBuf2LD
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;[] Norm normalizes an unsigned real in EDX:EAX:EBP i.e grab top 64 bits
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;[] expects the exponent to be in EDI.
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;[] SI contains the new exponent
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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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or ESI,EBP ; ...
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_if ne ; if number is non-zero
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or EDX,EDX ; - see if high word is 0
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_if e ; - if high word is 0
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mov EDX,EAX ; - - shift by 32-bits
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mov EAX,EBP ; - - ...
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sub EBP,EBP ; - - ...
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sub EDI,32 ; - - adjust exponent by 32
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_endif ; - endif
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or EDX,EDX ; - see if high word is 0
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_if e ; - if high word is 0
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mov EDX,EAX ; - - shift by 32-bits
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mov EAX,EBP ; - - ...
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sub EBP,EBP ; - - ...
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sub EDI,32 ; - - adjust exponent by 32
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_endif ; - endif
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_loop ; - loop
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or EDX,EDX ; - - quit if high bit is on
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_quif s ; - - ...
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dec EDI ; - - decrement exponent
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_shl EBP,1 ; - - shift integer left by 1 bit
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_rcl EAX,1 ; - - ...
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_rcl EDX,1 ; - - ...
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_endloop ; - endloop
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_shl EBP,1 ; - get top bit of extra word
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adc EAX,0 ; - round up
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adc EDX,0 ; - ...
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_if c ; - if carry out the top
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rcr EDX,1 ; - - shift fraction back 1
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inc EDI ; - - increment exponent
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_endif ; - endif
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mov ESI,EDI ; - get exponent
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_endif ; endif
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ret ; return
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endproc Norm
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endmod
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end
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