ef_remainder.c

来自「Newlib 嵌入式 C库 标准实现代码」· C语言 代码 · 共 69 行

/* ef_remainder.c -- float version of e_remainder.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, [e-mail].
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

#include "fdlibm.h"

#ifdef __STDC__
static const float zero = 0.0;
#else
static float zero = 0.0;
#endif


#ifdef __STDC__
	float __ieee754_remainderf(float x, float p)
#else
	float __ieee754_remainderf(x,p)
	float x,p;
#endif
{
	__int32_t hx,hp;
	__uint32_t sx;
	float p_half;

	GET_FLOAT_WORD(hx,x);
	GET_FLOAT_WORD(hp,p);
	sx = hx&0x80000000;
	hp &= 0x7fffffff;
	hx &= 0x7fffffff;

    /* purge off exception values */
	if(FLT_UWORD_IS_ZERO(hp)||
	   !FLT_UWORD_IS_FINITE(hx)||
	   FLT_UWORD_IS_NAN(hp))
	    return (x*p)/(x*p);


	if (hp<=FLT_UWORD_HALF_MAX) x = __ieee754_fmodf(x,p+p); /* now x < 2p */
	if ((hx-hp)==0) return zero*x;
	x  = fabsf(x);
	p  = fabsf(p);
	if (hp<0x01000000) {
	    if(x+x>p) {
		x-=p;
		if(x+x>=p) x -= p;
	    }
	} else {
	    p_half = (float)0.5*p;
	    if(x>p_half) {
		x-=p;
		if(x>=p_half) x -= p;
	    }
	}
	GET_FLOAT_WORD(hx,x);
	SET_FLOAT_WORD(x,hx^sx);
	return x;
}