Method truncate

cranelift/entity/src/list.rs:600–626

Shortens the list down to `len` elements. Does nothing if the list is already shorter than `len`.

(&mut self, new_len: usize, pool: &mut ListPool<T>)

    ///
    /// Does nothing if the list is already shorter than `len`.
    pub fn truncate(&mut self, new_len: usize, pool: &mut ListPool<T>) {
        if new_len == 0 {
            self.clear(pool);
            return;
        }

        match pool.len_of(self) {
            None => return,
            Some(len) => {
                if len <= new_len {
                    return;
                }

                let block;
                let idx = self.index as usize;
                let sclass = sclass_for_length(len);
                let new_sclass = sclass_for_length(new_len);
                if sclass != new_sclass {
                    block = pool.realloc(idx - 1, sclass, new_sclass, new_len + 1);
                    self.index = (block + 1) as u32;
                } else {
                    block = idx - 1;
                }
                pool.data[block] = T::new(new_len);
            }
        }
    }

    /// Grow the list by inserting `count` elements at `index`.
    ///