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/*
* // Copyright (c) Radzivon Bartoshyk 6/2025. All rights reserved.
* //
* // Redistribution and use in source and binary forms, with or without modification,
* // are permitted provided that the following conditions are met:
* //
* // 1. Redistributions of source code must retain the above copyright notice, this
* // list of conditions and the following disclaimer.
* //
* // 2. Redistributions in binary form must reproduce the above copyright notice,
* // this list of conditions and the following disclaimer in the documentation
* // and/or other materials provided with the distribution.
* //
* // 3. Neither the name of the copyright holder nor the names of its
* // contributors may be used to endorse or promote products derived from
* // this software without specific prior written permission.
* //
* // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
use crate::bits::{get_exponent_f32, get_exponent_f64};
#[inline]
pub const fn truncf(x: f32) -> f32 {
// If x is infinity or NaN, return it.
// If it is zero also we should return it as is, but the logic
// later in this function takes care of it. But not doing a zero
// check, we improve the run time of non-zero values.
if x.is_infinite() || x.is_nan() {
return x;
}
const FRACTION_LENGTH: u32 = 23;
let exponent = get_exponent_f32(x);
// If the exponent is greater than the most negative mantissa
// exponent, then x is already an integer.
if exponent >= FRACTION_LENGTH as i32 {
return x;
}
// If the exponent is such that abs(x) is less than 1, then return 0.
if exponent <= -1 {
return if x.is_sign_negative() { -0.0 } else { 0.0 };
}
const FRACTION_MASK: u32 = (1 << FRACTION_LENGTH) - 1;
let trim_size = FRACTION_LENGTH as i32 - exponent;
let trunc_mantissa =
((x.to_bits() & FRACTION_MASK) >> trim_size).wrapping_shl(trim_size as u32);
let prepared_bits = x.to_bits() & 0xFF800000;
f32::from_bits(prepared_bits | trunc_mantissa)
}
#[inline]
pub const fn trunc(x: f64) -> f64 {
// If x is infinity or NaN, return it.
// If it is zero also we should return it as is, but the logic
// later in this function takes care of it. But not doing a zero
// check, we improve the run time of non-zero values.
if x.is_infinite() || x.is_nan() {
return x;
}
const FRACTION_LENGTH: u32 = 52;
let exponent = get_exponent_f64(x);
// If the exponent is greater than the most negative mantissa
// exponent, then x is already an integer.
if exponent >= FRACTION_LENGTH as i64 {
return x;
}
// If the exponent is such that abs(x) is less than 1, then return 0.
if exponent <= -1 {
return if x.is_sign_negative() { -0.0 } else { 0.0 };
}
const FRACTION_MASK: u64 = (1 << FRACTION_LENGTH) - 1;
let trim_size = FRACTION_LENGTH as i64 - exponent;
let trunc_mantissa =
((x.to_bits() & FRACTION_MASK) >> trim_size).wrapping_shl(trim_size as u32);
let prepared_bits = x.to_bits() & 0xFFF0000000000000;
f64::from_bits(prepared_bits | trunc_mantissa)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_truncf() {
assert_eq!(truncf(-1.0), -1.0);
assert_eq!(truncf(1.0), 1.0);
assert_eq!(truncf(1.234211), 1.0);
assert_eq!(truncf(-1.234211), -1.0);
}
#[test]
fn test_trunc() {
assert_eq!(trunc(-1.0), -1.0);
assert_eq!(trunc(1.0), 1.0);
assert_eq!(trunc(1.234211), 1.0);
assert_eq!(trunc(-1.234211), -1.0);
}
}