Method push

cranelift/entity/src/list.rs:389–418

Appends an element to the back of the list. Returns the index where the element was inserted.

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

    /// Appends an element to the back of the list.
    /// Returns the index where the element was inserted.
    pub fn push(&mut self, element: T, pool: &mut ListPool<T>) -> usize {
        let idx = self.index as usize;
        match pool.len_of(self) {
            None => {
                // This is an empty list. Allocate a block and set length=1.
                debug_assert_eq!(idx, 0, "Invalid pool");
                let block = pool.alloc(sclass_for_length(1));
                pool.data[block] = T::new(1);
                pool.data[block + 1] = element;
                self.index = (block + 1) as u32;
                0
            }
            Some(len) => {
                // Do we need to reallocate?
                let new_len = len + 1;
                let block;
                if is_sclass_min_length(new_len) {
                    // Reallocate, preserving length + all old elements.
                    let sclass = sclass_for_length(len);
                    block = pool.realloc(idx - 1, sclass, sclass + 1, len + 1);
                    self.index = (block + 1) as u32;
                } else {
                    block = idx - 1;
                }
                pool.data[block + new_len] = element;
                pool.data[block] = T::new(new_len);
                len
            }
        }
    }

    /// Grow list by adding `count` reserved-value elements at the end.
    ///