e_acosf.cpp

这是整套横扫千军3D版游戏的源码

/* See the import.pl script for potential modifications */
/* e_acosf.c -- Simple version of e_acos.c.
 * Conversion to Simple 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.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: e_acosf.c,v 1.5f 1995/05/12 04:57:16 jtc Exp $";
#endif

#include "SMath.h"
#include "math_private.h"

namespace streflop_libm {
#ifdef __STDC__
static const Simple 
#else
static Simple 
#endif
one =  1.0000000000e+00f, /* 0x3F800000 */
pi =  3.1415925026e+00f, /* 0x40490fda */
pio2_hi =  1.5707962513e+00f, /* 0x3fc90fda */
pio2_lo =  7.5497894159e-08f, /* 0x33a22168 */
pS0 =  1.6666667163e-01f, /* 0x3e2aaaab */
pS1 = -3.2556581497e-01f, /* 0xbea6b090 */
pS2 =  2.0121252537e-01f, /* 0x3e4e0aa8 */
pS3 = -4.0055535734e-02f, /* 0xbd241146 */
pS4 =  7.9153501429e-04f, /* 0x3a4f7f04 */
pS5 =  3.4793309169e-05f, /* 0x3811ef08 */
qS1 = -2.4033949375e+00f, /* 0xc019d139 */
qS2 =  2.0209457874e+00f, /* 0x4001572d */
qS3 = -6.8828397989e-01f, /* 0xbf303361 */
qS4 =  7.7038154006e-02f; /* 0x3d9dc62e */

#ifdef __STDC__
	Simple __ieee754_acosf(Simple x)
#else
	Simple __ieee754_acosf(x)
	Simple x;
#endif
{
	Simple z,p,q,r,w,s,c,df;
	int32_t hx,ix;
	GET_FLOAT_WORD(hx,x);
	ix = hx&0x7fffffff;
	if(ix==0x3f800000) {		/* |x|==1 */
	    if(hx>0) return 0.0f;	/* acos(1) = 0  */
	    else return pi+(Simple)2.0f*pio2_lo;	/* acos(-1)= pi */
	} else if(ix>0x3f800000) {	/* |x| >= 1 */
	    return (x-x)/(x-x);		/* acos(|x|>1) is NaN */
	}
	if(ix<0x3f000000) {	/* |x| < 0.5f */
	    if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
	    z = x*x;
	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
	    r = p/q;
	    return pio2_hi - (x - (pio2_lo-x*r));
	} else  if (hx<0) {		/* x < -0.5f */
	    z = (one+x)*(Simple)0.5f;
	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
	    s = __ieee754_sqrtf(z);
	    r = p/q;
	    w = r*s-pio2_lo;
	    return pi - (Simple)2.0f*(s+w);
	} else {			/* x > 0.5f */
	    int32_t idf;
	    z = (one-x)*(Simple)0.5f;
	    s = __ieee754_sqrtf(z);
	    df = s;
	    GET_FLOAT_WORD(idf,df);
	    SET_FLOAT_WORD(df,idf&0xfffff000);
	    c  = (z-df*df)/(s+df);
	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
	    r = p/q;
	    w = r*s+c;
	    return (Simple)2.0f*(df+w);
	}
}
}