Method try_ensure_capacity

cranelift/bitset/src/compound.rs:271–303

(&mut self, n: usize)

    /// allocation failure.
    #[inline]
    pub fn try_ensure_capacity(&mut self, n: usize) -> Result<(), OutOfMemory> {
        // Subtract one from the capacity to get the maximum bit that we might
        // set. If `n` is 0 then nothing need be done as no capacity needs to be
        // allocated.
        let (word, _bit) = Self::word_and_bit(match n.checked_sub(1) {
            None => return Ok(()),
            Some(n) => n,
        });

        if word < self.elems.len() {
            // Already have capacity.
            return Ok(());
        }

        // Need to allocate additional capacity.

        assert!(word < usize::try_from(isize::MAX).unwrap());

        let delta = word - self.elems.len();
        let to_grow = delta + 1;

        // Amortize the cost of growing by at least growing another
        // `self.elems.len()`, so the new length is double the old length.
        let to_grow = cmp::max(to_grow, self.elems.len());
        // Don't make ridiculously small allocations.
        let to_grow = cmp::max(to_grow, 4);

        let mut new_elems = TryVec::from(mem::take(&mut self.elems));
        new_elems.reserve_exact(to_grow)?;
        new_elems.try_extend(iter::repeat(ScalarBitSet::new()).take(to_grow))?;
        self.elems = new_elems.into_boxed_slice()?;
        Ok(())
    }

    /// Insert `i` into this bitset.
    ///