SDL  2.0
e_atan2.c File Reference
#include "math_libm.h"
#include "math_private.h"
+ Include dependency graph for e_atan2.c:

Go to the source code of this file.

Functions

double attribute_hidden __ieee754_atan2 (double y, double x)
 

Variables

static const double tiny = 1.0e-300
 
static const double zero = 0.0
 
static const double pi_o_4 = 7.8539816339744827900E-01
 
static const double pi_o_2 = 1.5707963267948965580E+00
 
static const double pi = 3.1415926535897931160E+00
 
static const double pi_lo = 1.2246467991473531772E-16
 

Function Documentation

◆ __ieee754_atan2()

double attribute_hidden __ieee754_atan2 ( double  y,
double  x 
)

Definition at line 50 of file e_atan2.c.

51 {
52  double z;
53  int32_t k,m,hx,hy,ix,iy;
54  u_int32_t lx,ly;
55 
56  EXTRACT_WORDS(hx,lx,x);
57  ix = hx&0x7fffffff;
58  EXTRACT_WORDS(hy,ly,y);
59  iy = hy&0x7fffffff;
60  if(((ix|((lx|-(int32_t)lx)>>31))>0x7ff00000)||
61  ((iy|((ly|-(int32_t)ly)>>31))>0x7ff00000)) /* x or y is NaN */
62  return x+y;
63  if(((hx-0x3ff00000)|lx)==0) return atan(y); /* x=1.0 */
64  m = ((hy>>31)&1)|((hx>>30)&2); /* 2*sign(x)+sign(y) */
65 
66  /* when y = 0 */
67  if((iy|ly)==0) {
68  switch(m) {
69  case 0:
70  case 1: return y; /* atan(+-0,+anything)=+-0 */
71  case 2: return pi+tiny;/* atan(+0,-anything) = pi */
72  case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
73  }
74  }
75  /* when x = 0 */
76  if((ix|lx)==0) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
77 
78  /* when x is INF */
79  if(ix==0x7ff00000) {
80  if(iy==0x7ff00000) {
81  switch(m) {
82  case 0: return pi_o_4+tiny;/* atan(+INF,+INF) */
83  case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
84  case 2: return 3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
85  case 3: return -3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
86  }
87  } else {
88  switch(m) {
89  case 0: return zero ; /* atan(+...,+INF) */
90  case 1: return -zero ; /* atan(-...,+INF) */
91  case 2: return pi+tiny ; /* atan(+...,-INF) */
92  case 3: return -pi-tiny ; /* atan(-...,-INF) */
93  }
94  }
95  }
96  /* when y is INF */
97  if(iy==0x7ff00000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
98 
99  /* compute y/x */
100  k = (iy-ix)>>20;
101  if(k > 60) z=pi_o_2+0.5*pi_lo; /* |y/x| > 2**60 */
102  else if(hx<0&&k<-60) z=0.0; /* |y|/x < -2**60 */
103  else z=atan(fabs(y/x)); /* safe to do y/x */
104  switch (m) {
105  case 0: return z ; /* atan(+,+) */
106  case 1: {
107  u_int32_t zh;
108  GET_HIGH_WORD(zh,z);
109  SET_HIGH_WORD(z,zh ^ 0x80000000);
110  }
111  return z ; /* atan(-,+) */
112  case 2: return pi-(z-pi_lo);/* atan(+,-) */
113  default: /* case 3 */
114  return (z-pi_lo)-pi;/* atan(-,-) */
115  }
116 }

References atan(), EXTRACT_WORDS, fabs(), GET_HIGH_WORD, k, pi, pi_lo, pi_o_2, pi_o_4, SET_HIGH_WORD, tiny, and zero.

Variable Documentation

◆ pi

const double pi = 3.1415926535897931160E+00
static

Definition at line 47 of file e_atan2.c.

Referenced by __ieee754_atan2().

◆ pi_lo

const double pi_lo = 1.2246467991473531772E-16
static

Definition at line 48 of file e_atan2.c.

Referenced by __ieee754_atan2().

◆ pi_o_2

const double pi_o_2 = 1.5707963267948965580E+00
static

Definition at line 46 of file e_atan2.c.

Referenced by __ieee754_atan2().

◆ pi_o_4

const double pi_o_4 = 7.8539816339744827900E-01
static

Definition at line 45 of file e_atan2.c.

Referenced by __ieee754_atan2().

◆ tiny

const double tiny = 1.0e-300
static

Definition at line 43 of file e_atan2.c.

Referenced by __ieee754_atan2().

◆ zero

const double zero = 0.0
static

Definition at line 44 of file e_atan2.c.

Referenced by __ieee754_atan2(), and SDL_PrivateJoystickAxis().

pi_o_2
static const double pi_o_2
Definition: e_atan2.c:46
fabs
double fabs(double x)
Definition: s_fabs.c:22
pi_o_4
static const double pi_o_4
Definition: e_atan2.c:45
pi
static const double pi
Definition: e_atan2.c:47
z
GLdouble GLdouble z
Definition: SDL_opengl_glext.h:407
EXTRACT_WORDS
#define EXTRACT_WORDS(ix0, ix1, d)
Definition: math_private.h:99
SET_HIGH_WORD
#define SET_HIGH_WORD(d, v)
Definition: math_private.h:137
x
GLint GLint GLint GLint GLint x
Definition: SDL_opengl.h:1574
int32_t
signed int int32_t
Definition: SDL_config_windows.h:62
u_int32_t
unsigned int u_int32_t
Definition: math_private.h:31
tiny
static const double tiny
Definition: e_atan2.c:43
y
GLint GLint GLint GLint GLint GLint y
Definition: SDL_opengl.h:1574
m
const GLfloat * m
Definition: SDL_opengl_glext.h:6095
atan
double atan(double x)
Definition: s_atan.c:71
k
return Display return Display Bool Bool int int int return Display XEvent Bool(*) XPointer return Display return Display Drawable _Xconst char unsigned int unsigned int return Display Pixmap Pixmap XColor XColor unsigned int unsigned int return Display _Xconst char char int char return Display Visual unsigned int int int char unsigned int unsigned int int int return Display Window Cursor return Display Window return Display Drawable GC int int unsigned int unsigned int return Display Drawable GC int int _Xconst char int return Display Drawable GC int int unsigned int unsigned int return Display return Display Cursor return Display GC return XModifierKeymap return char Display Window int return Display return Display int int int return Display long XVisualInfo int return Display Window Atom long long Bool Atom Atom int unsigned long unsigned long k)
Definition: SDL_x11sym.h:80
zero
static const double zero
Definition: e_atan2.c:44
GET_HIGH_WORD
#define GET_HIGH_WORD(i, d)
Definition: math_private.h:109
pi_lo
static const double pi_lo
Definition: e_atan2.c:48