Method next_back

arrow-array/src/run_iterator.rs:129–160

(&mut self)

    <&'a V as ArrayAccessor>::Item: Default,
{
    fn next_back(&mut self) -> Option<Self::Item> {
        if self.current_back_logical == self.current_front_logical {
            return None;
        }

        self.current_back_logical -= 1;

        let run_ends = self.array.run_ends().values();
        if self.current_back_physical > 0
            && self.current_back_logical < run_ends[self.current_back_physical - 1].as_usize()
        {
            // As the run_ends is expected to be strictly increasing, there
            // should be at least one logical entry in one physical entry. Because of this
            // reason the next value can be accessed by decrementing physical index once.
            self.current_back_physical -= 1;
        }
        Some(if self.array.values().is_null(self.current_back_physical) {
            None
        } else {
            // Safety:
            // The check `self.current_end_physical > 0` ensures the value will not underflow.
            // Also self.current_end_physical starts with array.len() and
            // decrements based on the bounds of self.current_end_logical.
            unsafe {
                Some(
                    self.array
                        .values()
                        .value_unchecked(self.current_back_physical),
                )
            }
        })
    }
}

/// all arrays have known size.