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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, mantissa_f32, mantissa_f64};
#[inline]
pub const fn roundf(x: f32) -> f32 {
// If x is infinity NaN or zero, return it.
if !x.is_normal() {
return x;
}
let exponent = get_exponent_f32(x);
const FRACTION_LENGTH: u32 = 23;
// 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 exponent == -1 {
// Absolute value of x is greater than equal to 0.5 but less than 1.
return if x.is_sign_negative() { -1.0 } else { 1.0 };
}
if exponent <= -2 {
// Absolute value of x is less than 0.5.
return if x.is_sign_negative() { -0.0 } else { 0.0 };
}
let trim_size = (FRACTION_LENGTH as i32).wrapping_sub(exponent);
let half_bit_set = mantissa_f32(x) & (1u32 << (trim_size - 1)) != 0;
let x_u = x.to_bits();
let trunc_u: u32 = (x_u >> trim_size).wrapping_shl(trim_size as u32);
// If x is already an integer, return it.
if trunc_u == x_u {
return x;
}
let trunc_value = f32::from_bits(trunc_u);
if !half_bit_set {
// Franctional part is less than 0.5 so round value is the
// same as the trunc value.
trunc_value
} else if x.is_sign_negative() {
trunc_value - 1.0
} else {
trunc_value + 1.0
}
}
#[inline]
pub const fn round(x: f64) -> f64 {
// If x is infinity NaN or zero, return it.
if !x.is_normal() {
return x;
}
let exponent = get_exponent_f64(x);
const FRACTION_LENGTH: u64 = 52;
// 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 exponent == -1 {
// Absolute value of x is greater than equal to 0.5 but less than 1.
return if x.is_sign_negative() { -1.0 } else { 1.0 };
}
if exponent <= -2 {
// Absolute value of x is less than 0.5.
return if x.is_sign_negative() { -0.0 } else { 0.0 };
}
let trim_size = (FRACTION_LENGTH as i64).wrapping_sub(exponent);
let half_bit_set = mantissa_f64(x) & (1u64 << (trim_size.wrapping_sub(1))) != 0;
let x_u = x.to_bits();
let trunc_u: u64 = (x_u >> trim_size).wrapping_shl(trim_size as u32);
// If x is already an integer, return it.
if trunc_u == x_u {
return x;
}
let trunc_value = f64::from_bits(trunc_u);
if !half_bit_set {
// Franctional part is less than 0.5 so round value is the
// same as the trunc value.
trunc_value
} else if x.is_sign_negative() {
trunc_value - 1.0
} else {
trunc_value + 1.0
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_roundf() {
assert_eq!(roundf(0f32), 0.0f32.round());
assert_eq!(roundf(1f32), 1.0f32.round());
assert_eq!(roundf(1.2f32), 1.2f32.round());
assert_eq!(roundf(-1.2f32), (-1.2f32).round());
assert_eq!(roundf(-1.6f32), (-1.6f32).round());
assert_eq!(roundf(-1.5f32), (-1.5f32).round());
assert_eq!(roundf(1.6f32), 1.6f32.round());
assert_eq!(roundf(1.5f32), 1.5f32.round());
assert_eq!(roundf(2.5f32), 2.5f32.round());
}
#[test]
fn test_round() {
assert_eq!(round(0.), 0.0f64.round());
assert_eq!(round(1.), 1.0f64.round());
assert_eq!(round(1.2), 1.2f64.round());
assert_eq!(round(-1.2), (-1.2f64).round());
assert_eq!(round(-1.6), (-1.6f64).round());
assert_eq!(round(-1.5), (-1.5f64).round());
assert_eq!(round(1.6), 1.6f64.round());
assert_eq!(round(1.5), 1.5f64.round());
assert_eq!(round(2.5), 2.5f64.round());
}
}