pxfm/rounding/
trunc.rs

1/*
2 * // Copyright (c) Radzivon Bartoshyk 9/2025. All rights reserved.
3 * //
4 * // Redistribution and use in source and binary forms, with or without modification,
5 * // are permitted provided that the following conditions are met:
6 * //
7 * // 1.  Redistributions of source code must retain the above copyright notice, this
8 * // list of conditions and the following disclaimer.
9 * //
10 * // 2.  Redistributions in binary form must reproduce the above copyright notice,
11 * // this list of conditions and the following disclaimer in the documentation
12 * // and/or other materials provided with the distribution.
13 * //
14 * // 3.  Neither the name of the copyright holder nor the names of its
15 * // contributors may be used to endorse or promote products derived from
16 * // this software without specific prior written permission.
17 * //
18 * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
22 * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#[inline]
31pub const fn trunc(x: f64) -> f64 {
32    let i0 = x.to_bits() as i64;
33    let sx = i0 & (0x8000000000000000u64 as i64);
34    let j0 = ((i0 >> 52) & 0x7ff) - 0x3ff;
35    if j0 < 52 {
36        return if j0 < 0 {
37            /* The magnitude of the number is < 1 so the result is +-0.  */
38            f64::from_bits(sx as u64)
39        } else {
40            f64::from_bits((sx | (i0 & (!(0x000fffffffffffffu64 >> j0) as i64))) as u64)
41        };
42    } else if j0 == 0x400 {
43        /* x is inf or NaN.  */
44        return x + x;
45    }
46
47    x
48}
49
50#[cfg(test)]
51mod tests {
52    use super::*;
53
54    #[test]
55    fn test_trunc() {
56        assert_eq!(trunc(-1.0), -1.0);
57        assert_eq!(trunc(1.0), 1.0);
58        assert_eq!(trunc(1.234211), 1.0);
59        assert_eq!(trunc(-1.234211), -1.0);
60        assert_eq!(trunc(f64::INFINITY), f64::INFINITY);
61        assert_eq!(trunc(f64::NEG_INFINITY), f64::NEG_INFINITY);
62        assert!(trunc(f64::NAN).is_nan());
63    }
64}
pxfm/rounding/trunc.rs

pxfm/rounding/
trunc.rs
