vendor/rustc-rayon/src/math.rs

   1 use std::ops::{Bound, Range, RangeBounds};
   2
   3 /// Divide `n` by `divisor`, and round up to the nearest integer
   4 /// if not evenly divisable.
   5 #[inline]
   6 pub(super) fn div_round_up(n: usize, divisor: usize) -> usize {
   7     debug_assert!(divisor != 0, "Division by zero!");
   8     if n == 0 {
   9         0
  10     } else {
  11         (n - 1) / divisor + 1
  12     }
  13 }
  14
  15 /// Normalize arbitrary `RangeBounds` to a `Range`
  16 pub(super) fn simplify_range(range: impl RangeBounds<usize>, len: usize) -> Range<usize> {
  17     let start = match range.start_bound() {
  18         Bound::Unbounded => 0,
  19         Bound::Included(&i) if i <= len => i,
  20         Bound::Excluded(&i) if i < len => i + 1,
  21         bound => panic!("range start {:?} should be <= length {}", bound, len),
  22     };
  23     let end = match range.end_bound() {
  24         Bound::Unbounded => len,
  25         Bound::Excluded(&i) if i <= len => i,
  26         Bound::Included(&i) if i < len => i + 1,
  27         bound => panic!("range end {:?} should be <= length {}", bound, len),
  28     };
  29     if start > end {
  30         panic!(
  31             "range start {:?} should be <= range end {:?}",
  32             range.start_bound(),
  33             range.end_bound()
  34         );
  35     }
  36     start..end
  37 }
  38
  39 #[cfg(test)]
  40 mod tests {
  41     use super::*;
  42
  43     #[test]
  44     fn check_div_round_up() {
  45         assert_eq!(0, div_round_up(0, 5));
  46         assert_eq!(1, div_round_up(5, 5));
  47         assert_eq!(1, div_round_up(1, 5));
  48         assert_eq!(2, div_round_up(3, 2));
  49         assert_eq!(
  50             usize::max_value() / 2 + 1,
  51             div_round_up(usize::max_value(), 2)
  52         );
  53     }
  54 }