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skrzyp |
//===========================================================================
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//
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// e_fmod.c
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//
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// Part of the standard mathematical function library
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//
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//===========================================================================
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// ####ECOSGPLCOPYRIGHTBEGIN####
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// -------------------------------------------
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// This file is part of eCos, the Embedded Configurable Operating System.
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// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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//
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// eCos is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 2 or (at your option) any later
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// version.
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//
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// eCos is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with eCos; if not, write to the Free Software Foundation, Inc.,
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// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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// As a special exception, if other files instantiate templates or use
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// macros or inline functions from this file, or you compile this file
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// and link it with other works to produce a work based on this file,
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// this file does not by itself cause the resulting work to be covered by
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// the GNU General Public License. However the source code for this file
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// must still be made available in accordance with section (3) of the GNU
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// General Public License v2.
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//
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// This exception does not invalidate any other reasons why a work based
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// on this file might be covered by the GNU General Public License.
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// -------------------------------------------
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// ####ECOSGPLCOPYRIGHTEND####
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//===========================================================================
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//#####DESCRIPTIONBEGIN####
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//
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// Author(s): jlarmour
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// Contributors: jlarmour
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// Date: 1998-02-13
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// Purpose:
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// Description:
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// Usage:
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//
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//####DESCRIPTIONEND####
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//
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//===========================================================================
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// CONFIGURATION
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#include <pkgconf/libm.h> // Configuration header
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// Include the Math library?
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#ifdef CYGPKG_LIBM
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// Derived from code with the following copyright
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/* @(#)e_fmod.c 1.3 95/01/18 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunSoft, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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* __ieee754_fmod(x,y)
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* Return x mod y in exact arithmetic
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* Method: shift and subtract
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*/
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#include "mathincl/fdlibm.h"
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static const double one = 1.0, Zero[] = {0.0, -0.0,};
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double __ieee754_fmod(double x, double y)
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{
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int n,hx,hy,hz,ix,iy,sx,i;
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unsigned lx,ly,lz;
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hx = CYG_LIBM_HI(x); /* high word of x */
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lx = CYG_LIBM_LO(x); /* low word of x */
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hy = CYG_LIBM_HI(y); /* high word of y */
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ly = CYG_LIBM_LO(y); /* low word of y */
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sx = hx&0x80000000; /* sign of x */
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hx ^=sx; /* |x| */
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hy &= 0x7fffffff; /* |y| */
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/* purge off exception values */
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if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
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((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
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return (x*y)/(x*y);
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if(hx<=hy) {
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if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
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if(lx==ly)
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return Zero[(unsigned)sx>>31]; /* |x|=|y| return x*0*/
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}
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/* determine ix = ilogb(x) */
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if(hx<0x00100000) { /* subnormal x */
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if(hx==0) {
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for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
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} else {
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for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
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}
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} else ix = (hx>>20)-1023;
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/* determine iy = ilogb(y) */
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if(hy<0x00100000) { /* subnormal y */
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if(hy==0) {
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for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
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} else {
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for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
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}
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} else iy = (hy>>20)-1023;
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/* set up {hx,lx}, {hy,ly} and align y to x */
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if(ix >= -1022)
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hx = 0x00100000|(0x000fffff&hx);
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else { /* subnormal x, shift x to normal */
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n = -1022-ix;
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if(n<=31) {
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hx = (hx<<n)|(lx>>(32-n));
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lx <<= n;
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} else {
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hx = lx<<(n-32);
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lx = 0;
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}
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}
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if(iy >= -1022)
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hy = 0x00100000|(0x000fffff&hy);
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else { /* subnormal y, shift y to normal */
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n = -1022-iy;
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if(n<=31) {
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hy = (hy<<n)|(ly>>(32-n));
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ly <<= n;
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} else {
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hy = ly<<(n-32);
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ly = 0;
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}
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}
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/* fix point fmod */
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n = ix - iy;
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while(n--) {
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hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
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else {
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if((hz|lz)==0) /* return sign(x)*0 */
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return Zero[(unsigned)sx>>31];
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hx = hz+hz+(lz>>31); lx = lz+lz;
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}
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}
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hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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if(hz>=0) {hx=hz;lx=lz;}
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/* convert back to floating value and restore the sign */
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if((hx|lx)==0) /* return sign(x)*0 */
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return Zero[(unsigned)sx>>31];
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while(hx<0x00100000) { /* normalize x */
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hx = hx+hx+(lx>>31); lx = lx+lx;
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iy -= 1;
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}
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if(iy>= -1022) { /* normalize output */
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hx = ((hx-0x00100000)|((iy+1023)<<20));
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CYG_LIBM_HI(x) = hx|sx;
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CYG_LIBM_LO(x) = lx;
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} else { /* subnormal output */
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n = -1022 - iy;
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if(n<=20) {
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lx = (lx>>n)|((unsigned)hx<<(32-n));
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hx >>= n;
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} else if (n<=31) {
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lx = (hx<<(32-n))|(lx>>n); hx = sx;
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} else {
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lx = hx>>(n-32); hx = sx;
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}
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CYG_LIBM_HI(x) = hx|sx;
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CYG_LIBM_LO(x) = lx;
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x *= one; /* create necessary signal */
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}
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return x; /* exact output */
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}
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#endif // ifdef CYGPKG_LIBM
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// EOF e_fmod.c
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