145 lines
5.7 KiB
NASM
145 lines
5.7 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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;
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include mdef.inc
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include struct.inc
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modstart fdi4386
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xdefp __FDI4
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xdefp __RDI4
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xdefp __FDU4
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xdefp __RDU4
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;[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
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;[]
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;[] __FDU4 convert double float EDX:EAX into 32-bit integer EAX
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;[] Input: EDX:EAX - double precision floating point number
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;[] Output: EAX - 32-bit integer
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;[]
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;[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]
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; convert floating double to 4-byte integer with rounding
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defpe __RDU4
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mov AL,80h+20h ; indicate we are rounding
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jmp short DtoI ; do it
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defpe __RDI4
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mov AL,80h+1Fh ; indicate we are rounding
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jmp short DtoI ; do it
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defpe __FDI4
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mov AL,1Fh ; indicate we are truncating
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jmp short DtoI ; do it
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; convert floating double to 4-byte integer with truncation
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defpe __FDU4
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mov AL,20h ; indicate we are truncating
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DtoI: _shl EDX,1 ; get sign
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rcr AH,1 ; AH <-- sign
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shr AH,1 ; shift sign bit over 1
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or AH,AL ; get rounding bit
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shr EDX,1 ; restore exponent to its place
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; high bit of AH is rounding bit
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; next bit is the sign bit
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;<~> Shift real right four places so that exponent occupies an entire
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;<~> word and the mantissa occupies the remaining words. We do not need
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;<~> AX because we only need 32 sig digits
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push ECX ; save ECX
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mov ECX,EDX ; get high part
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sar ECX,20 ; get exponent to the bottom
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and CX,07FFh ; isolate exponent
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sub CX,03FEh ; remove bias from exponent
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jl short DIzero ; if |real| < .5 goto DIzero
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cmp CX,20h ; if exponent > 32
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jg short DIo_f ; goto DIo_flow
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and AL,3Fh ; isolate # of significant bits
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cmp CL,AL ; quit if number too big
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jg short DIo_f ; goto DIo_flow
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mov CH,AH ; save rounding/truncation bit
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and EDX,000FFFFFh ; isolate top 20 bits of fraction
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and EAX,0FFF00000h ; isolate next 12 bits of fraction
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or EDX,EAX ; glue them together
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rol EDX,12 ; and rotate into position
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stc ; set carry and
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rcr EDX,1 ; restore implied 1/2 bit
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rcr CH,1 ; save rounding bit
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cmp CL,32 ; if want 32 bits
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_if e ; then
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mov EAX,EDX ; - get them
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_shl CH,1 ; - get rounding bit
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_else ; else
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sub EAX,EAX ; - zero result register
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shld EAX,EDX,CL ; - shift answer into EAX
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shl EDX,CL ; - shift rounding bit into position
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_shl CH,1 ; - get rid of rounding bit from CH
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_shl EDX,1 ; - get proper rounding bit
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_endif ; endif
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mov CL,0FFh ; get mask
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rcr CL,1 ; get rounding bit
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and CH,CL ; mask it with rounding control bit
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_shl CH,1 ; get rounding bit
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adc EAX,0 ; add it to the integer to round it up
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_shl CH,1 ; get sign
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_if c ; if negative
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neg EAX ; - negate integer
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_endif ; endif
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pop ECX ; restore ECX
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ret ; return
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DIo_f:
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mov EAX,80000000h ; set answer to largest negative number
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pop ECX ; restore ECX
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ret ; return
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; jmp I4OverFlow ; report overflow
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DIzero: sub EAX,EAX ; set result to zero
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pop ECX ; restore ECX
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ret
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endproc __FDU4
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endproc __FDI4
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endproc __RDI4
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endproc __RDU4
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endmod
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end
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