/* origin: FreeBSD /usr/src/lib/msun/src/e_remainder.c */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunSoft, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/* remainder(x,p)
* Return :
* returns x REM p = x - [x/p]*p as if in infinite
* precise arithmetic, where [x/p] is the (infinite bit)
* integer nearest x/p (in half way case choose the even one).
* Method :
* Based on fmod() return x-[x/p]chopped*p exactlp.
*/
#include "libm.h"
static const double zero = 0.0;
double remainder(double x, double p)
{
int32_t hx,hp;
uint32_t sx,lx,lp;
double p_half;
EXTRACT_WORDS(hx, lx, x);
EXTRACT_WORDS(hp, lp, p);
sx = hx & 0x80000000;
hp &= 0x7fffffff;
hx &= 0x7fffffff;
/* purge off exception values */
if ((hp|lp) == 0) /* p = 0 */
return (x*p)/(x*p);
if (hx >= 0x7ff00000 || /* x not finite */
(hp >= 0x7ff00000 && (hp-0x7ff00000 | lp) != 0)) /* p is NaN */
// FIXME: why long double?
return ((long double)x*p)/((long double)x*p);
if (hp <= 0x7fdfffff)
x = fmod(x, p+p); /* now x < 2p */
if (((hx-hp)|(lx-lp)) == 0)
return zero*x;
x = fabs(x);
p = fabs(p);
if (hp < 0x00200000) {
if (x + x > p) {
x -= p;
if (x + x >= p)
x -= p;
}
} else {
p_half = 0.5*p;
if (x > p_half) {
x -= p;
if (x >= p_half)
x -= p;
}
}
GET_HIGH_WORD(hx, x);
if ((hx&0x7fffffff) == 0)
hx = 0;
SET_HIGH_WORD(x, hx^sx);
return x;
}
