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The Tor Browser
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s_atanf.cpp (2485B)

      1 /* s_atanf.c -- float version of s_atan.c.
      2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
      3 */
      4 
      5 /*
      6 * ====================================================
      7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
      8 *
      9 * Developed at SunPro, a Sun Microsystems, Inc. business.
     10 * Permission to use, copy, modify, and distribute this
     11 * software is freely granted, provided that this notice
     12 * is preserved.
     13 * ====================================================
     14 */
     15 
     16 //#include <sys/cdefs.h>
     17 //__FBSDID("$FreeBSD$");
     18 
     19 #include <math.h>
     20 
     21 #include "math_private.h"
     22 
     23 static const float atanhi[] = {
     24  4.6364760399e-01, /* atan(0.5)hi 0x3eed6338 */
     25  7.8539812565e-01, /* atan(1.0)hi 0x3f490fda */
     26  9.8279368877e-01, /* atan(1.5)hi 0x3f7b985e */
     27  1.5707962513e+00, /* atan(inf)hi 0x3fc90fda */
     28 };
     29 
     30 static const float atanlo[] = {
     31  5.0121582440e-09, /* atan(0.5)lo 0x31ac3769 */
     32  3.7748947079e-08, /* atan(1.0)lo 0x33222168 */
     33  3.4473217170e-08, /* atan(1.5)lo 0x33140fb4 */
     34  7.5497894159e-08, /* atan(inf)lo 0x33a22168 */
     35 };
     36 
     37 static const float aT[] = {
     38  3.3333328366e-01,
     39 -1.9999158382e-01,
     40  1.4253635705e-01,
     41 -1.0648017377e-01,
     42  6.1687607318e-02,
     43 };
     44 
     45 static const float
     46 one   = 1.0,
     47 huge   = 1.0e30;
     48 
     49 float
     50 atanf(float x)
     51 {
     52 float w,s1,s2,z;
     53 int32_t ix,hx,id;
     54 
     55 GET_FLOAT_WORD(hx,x);
     56 ix = hx&0x7fffffff;
     57 if(ix>=0x4c800000) {	/* if |x| >= 2**26 */
     58     if(ix>0x7f800000)
     59 	return x+x;		/* NaN */
     60     if(hx>0) return  atanhi[3]+*(volatile float *)&atanlo[3];
     61     else     return -atanhi[3]-*(volatile float *)&atanlo[3];
     62 } if (ix < 0x3ee00000) {	/* |x| < 0.4375 */
     63     if (ix < 0x39800000) {	/* |x| < 2**-12 */
     64 	if(huge+x>one) return x;	/* raise inexact */
     65     }
     66     id = -1;
     67 } else {
     68 x = fabsf(x);
     69 if (ix < 0x3f980000) {		/* |x| < 1.1875 */
     70     if (ix < 0x3f300000) {	/* 7/16 <=|x|<11/16 */
     71 	id = 0; x = ((float)2.0*x-one)/((float)2.0+x);
     72     } else {			/* 11/16<=|x|< 19/16 */
     73 	id = 1; x  = (x-one)/(x+one);
     74     }
     75 } else {
     76     if (ix < 0x401c0000) {	/* |x| < 2.4375 */
     77 	id = 2; x  = (x-(float)1.5)/(one+(float)1.5*x);
     78     } else {			/* 2.4375 <= |x| < 2**26 */
     79 	id = 3; x  = -(float)1.0/x;
     80     }
     81 }}
     82    /* end of argument reduction */
     83 z = x*x;
     84 w = z*z;
     85    /* break sum from i=0 to 10 aT[i]z**(i+1) into odd and even poly */
     86 s1 = z*(aT[0]+w*(aT[2]+w*aT[4]));
     87 s2 = w*(aT[1]+w*aT[3]);
     88 if (id<0) return x - x*(s1+s2);
     89 else {
     90     z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);
     91     return (hx<0)? -z:z;
     92 }
     93 }