1#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
2pub fn remquo(mut x: f64, mut y: f64) -> (f64, i32) {
3 let ux: u64 = x.to_bits();
4 let mut uy: u64 = y.to_bits();
5 let mut ex = ((ux >> 52) & 0x7ff) as i32;
6 let mut ey = ((uy >> 52) & 0x7ff) as i32;
7 let sx = (ux >> 63) != 0;
8 let sy = (uy >> 63) != 0;
9 let mut q: u32;
10 let mut i: u64;
11 let mut uxi: u64 = ux;
12
13 if (uy << 1) == 0 || y.is_nan() || ex == 0x7ff {
14 return ((x * y) / (x * y), 0);
15 }
16 if (ux << 1) == 0 {
17 return (x, 0);
18 }
19
20 /* normalize x and y */
21 if ex == 0 {
22 i = uxi << 12;
23 while (i >> 63) == 0 {
24 ex -= 1;
25 i <<= 1;
26 }
27 uxi <<= -ex + 1;
28 } else {
29 uxi &= (!0) >> 12;
30 uxi |= 1 << 52;
31 }
32 if ey == 0 {
33 i = uy << 12;
34 while (i >> 63) == 0 {
35 ey -= 1;
36 i <<= 1;
37 }
38 uy <<= -ey + 1;
39 } else {
40 uy &= (!0) >> 12;
41 uy |= 1 << 52;
42 }
43
44 q = 0;
45
46 if ex + 1 != ey {
47 if ex < ey {
48 return (x, 0);
49 }
50 /* x mod y */
51 while ex > ey {
52 i = uxi.wrapping_sub(uy);
53 if (i >> 63) == 0 {
54 uxi = i;
55 q += 1;
56 }
57 uxi <<= 1;
58 q <<= 1;
59 ex -= 1;
60 }
61 i = uxi.wrapping_sub(uy);
62 if (i >> 63) == 0 {
63 uxi = i;
64 q += 1;
65 }
66 if uxi == 0 {
67 ex = -60;
68 } else {
69 while (uxi >> 52) == 0 {
70 uxi <<= 1;
71 ex -= 1;
72 }
73 }
74 }
75
76 /* scale result and decide between |x| and |x|-|y| */
77 if ex > 0 {
78 uxi -= 1 << 52;
79 uxi |= (ex as u64) << 52;
80 } else {
81 uxi >>= -ex + 1;
82 }
83 x = f64::from_bits(uxi);
84 if sy {
85 y = -y;
86 }
87 if ex == ey || (ex + 1 == ey && (2.0 * x > y || (2.0 * x == y && (q % 2) != 0))) {
88 x -= y;
89 // TODO: this matches musl behavior, but it is incorrect
90 q = q.wrapping_add(1);
91 }
92 q &= 0x7fffffff;
93 let quo = if sx ^ sy { -(q as i32) } else { q as i32 };
94 if sx { (-x, quo) } else { (x, quo) }
95}
96
97#[cfg(test)]
98mod tests {
99 use super::remquo;
100
101 #[test]
102 fn test_q_overflow() {
103 // 0xc000000000000001, 0x04c0000000000004
104 let _ = remquo(-2.0000000000000004, 8.406091369059082e-286);
105 }
106}
107