fontdue/platform/float/
atan2.rs

1/*
2 * origin: FreeBSD /usr/src/lib/msun/src/s_atanf.c
3 *
4 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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/// The arctangent function.
16pub fn atan2f(y: f32, x: f32) -> f32 {
17    const PI: f32 = 3.1415927410e+00; /* 0x40490fdb */
18    const PI_LO: f32 = -8.7422776573e-08; /* 0xb3bbbd2e */
19
20    if x.is_nan() || y.is_nan() {
21        return x + y;
22    }
23    let mut ix = x.to_bits();
24    let mut iy = y.to_bits();
25
26    if ix == 0x3f800000 {
27        /* x=1.0 */
28        return super::atan(y);
29    }
30    let m = ((iy >> 31) & 1) | ((ix >> 30) & 2); /* 2*sign(x)+sign(y) */
31    ix &= 0x7fffffff;
32    iy &= 0x7fffffff;
33
34    /* when y = 0 */
35    if iy == 0 {
36        return match m {
37            0 | 1 => y,   /* atan(+-0,+anything)=+-0 */
38            2 => PI,      /* atan(+0,-anything) = pi */
39            3 | _ => -PI, /* atan(-0,-anything) =-pi */
40        };
41    }
42    /* when x = 0 */
43    if ix == 0 {
44        return if m & 1 != 0 {
45            -PI / 2.
46        } else {
47            PI / 2.
48        };
49    }
50    /* when x is INF */
51    if ix == 0x7f800000 {
52        return if iy == 0x7f800000 {
53            match m {
54                0 => PI / 4.,           /* atan(+INF,+INF) */
55                1 => -PI / 4.,          /* atan(-INF,+INF) */
56                2 => 3. * PI / 4.,      /* atan(+INF,-INF)*/
57                3 | _ => -3. * PI / 4., /* atan(-INF,-INF)*/
58            }
59        } else {
60            match m {
61                0 => 0.,      /* atan(+...,+INF) */
62                1 => -0.,     /* atan(-...,+INF) */
63                2 => PI,      /* atan(+...,-INF) */
64                3 | _ => -PI, /* atan(-...,-INF) */
65            }
66        };
67    }
68    /* |y/x| > 0x1p26 */
69    if (ix + (26 << 23) < iy) || (iy == 0x7f800000) {
70        return if m & 1 != 0 {
71            -PI / 2.
72        } else {
73            PI / 2.
74        };
75    }
76
77    /* z = atan(|y/x|) with correct underflow */
78    let z = if (m & 2 != 0) && (iy + (26 << 23) < ix) {
79        /*|y/x| < 0x1p-26, x < 0 */
80        0.
81    } else {
82        super::atan(super::abs(y / x))
83    };
84    match m {
85        0 => z,                /* atan(+,+) */
86        1 => -z,               /* atan(-,+) */
87        2 => PI - (z - PI_LO), /* atan(+,-) */
88        _ => (z - PI_LO) - PI, /* case 3 */ /* atan(-,-) */
89    }
90}
91
92pub fn atan2(x: f32, y: f32) -> f32 {
93    use core::f32::consts::PI;
94    const PI_2: f32 = PI / 2.0;
95    const M_PI_2: f32 = -PI / 2.0;
96    const PI_4: f32 = PI / 4.0;
97    const PI_3_4: f32 = PI_4 * 3.0;
98    let mut r;
99    let c;
100    let abs_y = super::abs(y);
101    if x == 0.0 {
102        if y > 0.0 {
103            return PI_2;
104        }
105        if y == 0.0 {
106            return 0.0;
107        }
108        return M_PI_2;
109    } else if x > 0.0 {
110        r = (x - abs_y) / (x + abs_y);
111        c = PI_4;
112    } else {
113        r = (x + abs_y) / (abs_y - x);
114        c = PI_3_4;
115    }
116    r = 0.1963 * r * r * r - 0.9817 * r + c;
117    return super::copysign(r, y);
118}
fontdue/platform/float/atan2.rs

fontdue/platform/float/
atan2.rs
