vendor/compiler_builtins/libm/src/math/round.rs

   1 use core::f64;
   2
   3 const TOINT: f64 = 1.0 / f64::EPSILON;
   4
   5 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
   6 pub fn round(mut x: f64) -> f64 {
   7     let i = x.to_bits();
   8     let e: u64 = i >> 52 & 0x7ff;
   9     let mut y: f64;
  10
  11     if e >= 0x3ff + 52 {
  12         return x;
  13     }
  14     if e < 0x3ff - 1 {
  15         // raise inexact if x!=0
  16         force_eval!(x + TOINT);
  17         return 0.0 * x;
  18     }
  19     if i >> 63 != 0 {
  20         x = -x;
  21     }
  22     y = x + TOINT - TOINT - x;
  23     if y > 0.5 {
  24         y = y + x - 1.0;
  25     } else if y <= -0.5 {
  26         y = y + x + 1.0;
  27     } else {
  28         y = y + x;
  29     }
  30
  31     if i >> 63 != 0 {
  32         -y
  33     } else {
  34         y
  35     }
  36 }
  37
  38 #[cfg(test)]
  39 mod tests {
  40     use super::round;
  41
  42     #[test]
  43     fn negative_zero() {
  44         assert_eq!(round(-0.0_f64).to_bits(), (-0.0_f64).to_bits());
  45     }
  46 }