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142 lines
4.5 KiB
C
142 lines
4.5 KiB
C
/*
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* $Id: math_atan2f.c,v 1.4 2006-01-08 12:04:23 obarthel Exp $
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*
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* :ts=4
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*
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* Portable ISO 'C' (1994) runtime library for the Amiga computer
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* Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Neither the name of Olaf Barthel nor the names of contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* PowerPC math library based in part on work by Sun Microsystems
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, 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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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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#ifndef _MATH_HEADERS_H
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#include "math_headers.h"
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#endif /* _MATH_HEADERS_H */
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/****************************************************************************/
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#if defined(FLOATING_POINT_SUPPORT)
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/****************************************************************************/
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static const float
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tiny = 1.0e-30,
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zero = 0.0,
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pi_o_4 = 7.8539818525e-01, /* 0x3f490fdb */
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pi_o_2 = 1.5707963705e+00, /* 0x3fc90fdb */
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pi = 3.1415925026e+00, /* 0x40490fda */
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pi_lo = 1.5099578832e-07; /* 0x34222168 */
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float
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atan2f(float y, float x)
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{
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float z;
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LONG k,m,hx,hy,ix,iy;
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GET_FLOAT_WORD(hx,x);
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ix = hx&0x7fffffff;
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GET_FLOAT_WORD(hy,y);
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iy = hy&0x7fffffff;
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if((ix>0x7f800000)||
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(iy>0x7f800000)) /* x or y is NaN */
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return x+y;
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if(hx==0x3f800000) return atanf(y); /* x=1.0 */
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m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
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/* when y = 0 */
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if(iy==0) {
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switch(m) {
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case 0:
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case 1: return y; /* atan(+-0,+anything)=+-0 */
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case 2: return pi+tiny;/* atan(+0,-anything) = pi */
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case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
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}
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}
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/* when x = 0 */
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if(ix==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
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/* when x is INF */
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if(ix==0x7f800000) {
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if(iy==0x7f800000) {
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switch(m) {
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case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
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case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
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case 2: return (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
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case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
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}
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} else {
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switch(m) {
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case 0: return zero ; /* atan(+...,+INF) */
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case 1: /* atan(-...,+INF) */
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{
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/* Make sure we return -0, not +0. If we
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say "return -zero;", GCC might optimize
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that with FLDZ, which we don't want. */
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return copysignf(zero, -1);
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}
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case 2: return pi+tiny ; /* atan(+...,-INF) */
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case 3: return -pi-tiny ; /* atan(-...,-INF) */
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}
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}
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}
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/* when y is INF */
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if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
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/* compute y/x */
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k = (iy-ix)>>23;
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if(k > 60) z=pi_o_2+(float)0.5*pi_lo; /* |y/x| > 2**60 */
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else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
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else z=atanf(fabsf(y/x)); /* safe to do y/x */
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switch (m) {
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case 0: return z ; /* atan(+,+) */
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case 1: {
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ULONG zh;
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GET_FLOAT_WORD(zh,z);
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SET_FLOAT_WORD(z,zh ^ 0x80000000U);
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}
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return z ; /* atan(-,+) */
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case 2: return pi-(z-pi_lo);/* atan(+,-) */
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default: /* case 3 */
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return (z-pi_lo)-pi;/* atan(-,-) */
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}
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}
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/****************************************************************************/
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#endif /* FLOATING_POINT_SUPPORT */
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