softfloat 1.0.0

Pure software floating-point implementation, with `const` and `no_std` support
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57

use super::F32;

/// Floor (F32)
///
/// Finds the nearest integer less than or equal to `x`.
pub const fn floor(x: F32) -> F32 {
    let mut ui = x.to_bits();
    let e = (((ui >> 23) as i32) & 0xff) - 0x7f;

    if e >= 23 {
        return x;
    }
    if e >= 0 {
        let m: u32 = 0x007fffff >> e;
        if (ui & m) == 0 {
            return x;
        }
        // force_eval!(x + F32::from_bits(0x7b800000));
        if ui >> 31 != 0 {
            ui += m;
        }
        ui &= !m;
    } else {
        // force_eval!(x + F32::from_bits(0x7b800000));
        if ui >> 31 == 0 {
            ui = 0;
        } else if ui << 1 != 0 {
            return f32!(-1.0);
        }
    }
    F32::from_bits(ui)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn sanity_check() {
        assert_eq!(floor(f32!(0.5)), f32!(0.0));
        assert_eq!(floor(f32!(1.1)), f32!(1.0));
        assert_eq!(floor(f32!(2.9)), f32!(2.0));
    }

    /// The spec: https://en.cppreference.com/w/cpp/numeric/math/floor
    #[test]
    fn spec_tests() {
        // Not Asserted: that the current rounding mode has no effect.
        assert!(floor(f32!(f32::NAN)).to_native_f32().is_nan());
        for f in [0.0, -0.0, f32::INFINITY, f32::NEG_INFINITY]
            .iter()
            .copied()
        {
            assert_eq!(F32::from_native_f32(f).floor(), F32::from_native_f32(f));
        }
    }
}